Engineering">
PFC 13406046 Rafael Bobo Garcia
PFC 13406046 Rafael Bobo Garcia
PFC 13406046 Rafael Bobo Garcia
CÁTEDRA DE PROYECTOS
MEMORIA
Universidad Politécnica
de Lappeenranta
Entre los años 1950 y 1960 el gobierno Finlandés hizo planes para ubicar la
Universidad Este de Finlandia en Lappeenranta, pero
finalmente dicha universidad fue descentralizada en tres
ciudades, Lappeenranta, Kuopio y Joensuu. Por aquellos años
solo los departamentos de ingeniería se habían construido, por
lo que permaneció así hasta 1991, cuando se añadió también el
departamento de “Business Administration”
Los anteriores títulos se pueden obtener mediante las tres facultades principales,
y colaborando con los diferentes centros de investigación:
• Facultad de Tecnología:
o Departamento de Tecnología Química
o Departamento de Ingeniería Eléctrica
o Departamento de Tecnología Energética
o Departamento de Ingeniería Mecánica
o Departamento de Ingeniería, Física y Matemáticas
o Departamento de Ingeniería medioambiental
• Facultad de Tecnología de Gestión:
o Departamento de Organización Industrial
o Departamento de Tecnología de la Información
• Escuela de Negocios:
o Contabilidad
o Derecho de empresas
o Finanzas
o Marketing Internacional
o Tecnología y Gestión de la Innovación Internacional
o Organización del conocimiento
o Gestión y Organizaciones
o Investigación Estratégica
o Gestión Logística
• Institutos de Investigación:
o Centre for Separation Technology (CST)
o Technology Business Research Center (TBRC)
o Northern Dimension Research Centre (NORDI)
o Carelian Drives and Motor Centre (CDMC)
o FiberLaboratory
o Centre of Computational Engineering and Integrated Design (CEID)
Además, una de las claves es concentrar las investigaciones en el uso de los más
modernos procesos de producción, con gran integración de toda la tecnología digital. Por
otro lado el departamento tiene como principio el ser accesible, y establecer vínculos con
la sociedad local, permitiendo crear una gran interacción con las diferentes empresas así
como generando un entorno inspirador y actual.
Por último, destacar que los títulos de Grado y Máster en Ingeniería Mecánica
obtenidos mediante el departamento están internacionalmente acreditados por EUR-ACE
y ASIIN. Esto garantiza una enseñanza de alta calidad, enfoque internacional y continua
mejora.
Prefacio 5
PREFACIO
La memoria de este proyecto está formada por diferentes partes. En primer lugar
se encuentra un resumen en español de la memoria original en inglés. Dicho resumen
está elaborado a partir de una traducción al español de la memoria completa, pero
eliminando ciertas partes, con el objetivo de sintetizar el texto así como añadiendo
algunos comentarios aclaratorios.
Capítulos 14 y 15 se mencionan las contribuciones técnicas más relevantes así como los
posibles futuros trabajos.
ÍNDICE
Universidad Politécnica de Lappeenranta ............................................................................. 2
LUT MECHANICAL ENGINEERING........................................................................................... 4
PREFACIO ............................................................................................................................... 5
ÍNDICE .................................................................................................................................... 7
LISTA DE FIGURAS ................................................................................................................ 14
LISTA DE TABLAS .................................................................................................................. 19
RESUMEN ............................................................................................................................. 21
PARTE I: INTRODUCCIÓN ..................................................................................................... 22
Capítulo 1. Antecedentes ......................................................................................... 22
1.1 IMPRESIÓN 3D .............................................................................................. 22
1.2 HISTORIA DE LA IMPRESIÓN 3D ................................................................... 23
1.3 EL PROYECTO REPRAP .................................................................................. 25
1.4 DESARROLLO DE LA IMPRESIÓN 3D ............................................................. 26
1.5 IMPRESIÓN 3D COMO NEGOCIO.................................................................. 26
1.5.1 Impresoras Hobby: ............................................................................... 26
1.5.2 Impresoras Industriales ....................................................................... 27
1.6 VENTAJAS COMPETITIVAS ............................................................................ 29
1.6.1 Fabricación económicamente eficiente ............................................ 29
1.6.2 Producción rápida ............................................................................. 29
1.6.3 Ahorro de material ............................................................................ 29
1.6.4 Alta calidad y nuevos perfiles............................................................ 29
1.6.5 Económica ......................................................................................... 30
1.7 DESVENTAJAS DE LA IMPRESION 3D ............................................................ 30
1.7.1 Material ............................................................................................. 30
1.7.2 Estructura .......................................................................................... 30
1.7.3 Tamaño del producto impreso .......................................................... 31
1.7.4 Productividad .................................................................................... 31
PARTE II: LA IMPRESORA 3D: DISEÑO GENERAL.................................................................. 32
Capítulo 2. Objetivos del proyecto ............................................................................. 32
Capítulo 3. Partes principales, problemas de diseño y posibles mejoras .................. 32
Índice 8
LISTA DE FIGURAS
Fig. 1 Sistema de impresión 3D ................................................................................ 23
Fig. 2 FDM ................................................................................................................ 24
Fig. 3 Impresora autoreplicante ............................................................................... 25
Fig. 4 AM Landscape ................................................................................................ 27
Fig. 5 Infografía Mercado impresoras 3D [41] ......................................................... 28
Fig. 6 Ejemplo de pieza de formas complejas .......................................................... 29
Fig. 7 Rollos de ABS .................................................................................................. 30
Fig. 8 Estructura de soporte ..................................................................................... 30
Fig. 9 Esquema de componentes de una impresora 3D .......................................... 32
Fig. 10 Extrusor dentado .......................................................................................... 33
Fig. 11 Sistema de extrusión .................................................................................... 33
Fig. 12 Extrusor de Ed Bowden ................................................................................ 35
Fig. 13 Bloque de estrusor Wade ............................................................................. 36
Fig. 14 Bloque de alojamiento Wade ....................................................................... 37
Fig. 15 Rueda Wade 1 .............................................................................................. 37
Fig. 16 Rueda Wade 2 .............................................................................................. 37
Fig. 17 Tornillo perfilado .......................................................................................... 38
Fig. 18 Barras y cojinetes ......................................................................................... 40
Fig. 20 Robot delta ................................................................................................... 40
Fig. 19 Railes perfilados............................................................................................ 40
Fig. 21 Boquilla ......................................................................................................... 41
Fig. 22 Bloque de boquilla ........................................................................................ 41
Fig. 23 Tipos de boquilla .......................................................................................... 41
Fig. 24 X-crossed nozzles .......................................................................................... 42
Fig. 25 Cross crossed nozzles ................................................................................... 42
Fig. 26 Linear Y nozzles............................................................................................. 42
Fig. 27 Linear X nozzles ............................................................................................ 43
Fig. 28 Impresora Cartesio ....................................................................................... 43
Fig. 29 Movimiento relativo cama-cabezal .............................................................. 45
Fig. 30 Montaje modular.......................................................................................... 50
Fig. 31 Impresora printrbot ...................................................................................... 51
Fig. 32 Croquis de distribución de las boquillas ....................................................... 52
Fig. 33 Diseño completo en fase alfa ....................................................................... 54
Fig. 34 Nema 17 ....................................................................................................... 55
Fig. 35 Rueda dentada pequeña .............................................................................. 56
Fig. 36 Rueda dentada grande ................................................................................. 56
Fig. 37 Extrusor diseñado ......................................................................................... 58
Fig. 38 Cama térmica simple .................................................................................... 59
Fig. 39 Conexión entre bloques de camas ............................................................... 59
Lista de Figuras 15
LISTA DE TABLAS
Table. 1 Extrusor dentado. Componentes impresos [25] ........................................ 37
Table. 2 Extrusor dentado. Componentes no impresos [25] ................................... 38
Table. 3 Comparaciones de motores de pasos ........................................................ 38
Table. 4 Comparación de extrusores ....................................................................... 39
Table. 5 Comparacion de sistemas cinemáticos ...................................................... 40
Table. 6 Distribución de boquillas ............................................................................ 43
Table. 7 Requerimientos y soluciones ..................................................................... 46
Table. 8 Comparativa de diseños mediante factores .............................................. 47
Table. 9 Diseño 1 ...................................................................................................... 50
Table. 10 Diseño 2 .................................................................................................... 52
Table. 11 Especificaciones Nema 17 ........................................................................ 55
Table. 12 Especificaciones Nema 17-2 ..................................................................... 56
Table. 13 Tabla resumen del extrusor ..................................................................... 58
Table. 14 Resúmen de diseño de la cama térmica .................................................. 60
Table. 15 Resumen de diseño de las boquillas ........................................................ 67
Table. 16 Resumen de diseño de la coordenada X .................................................. 71
Table. 17 Resumen de diseño de la coordenada Y .................................................. 73
Table. 18 Resumen de diseño de la coordenada Z .................................................. 76
PARTE I: INTRODUCCIÓN
El objetivo de este proyecto es explicar en detalle todo el proceso de diseño de
una “Impresora 3D capaz de crear múltiples objetos simultáneamente”.
Capítulo 1. Antecedentes
1.1 IMPRESIÓN 3D
En primer lugar, ¿qué es imprimir? Una definición sencilla podría ser “marcar en
papel u otro substrato con letras o cualquier otro carácter gráfico”. La diferencia entre
imprimir y la impresión 3D reside en que en el segundo caso se logra un producto
tridimensional.
1
Creative Commons es una organizacion no lucrativa, con sede en Mountain View, en el estado de
California. Esta organización fue creada para usar y compartir la creatividad y el conocimiento mediante una
serie de mecanismos jurídicos que lo permiten realizar de forma gratuita. [40]
Capítulo 1. Antecedentes 23
importante cantidad de limitaciones; pero con el paso de los años han pasado a ser más
baratas, fiables y de tamaño reducido.
Cabe destacar que en esta memoria se hará especial mención al proyecto RepRap.
Esto es debido a que sabiendo que actualmente hay diferentes páginas y comunidades de
impresores, en un primer momento este proyecto fue el que realizó la gran labor de
unificar a la comunidad de desarrolladores inicial. Además sentó las bases de las
diferentes ideas de impresión 3D y estableció las diferentes metas. Es también
importante mencionar de nuevo el uso de licencias creative commons y código abierto.
Capítulo 1. Antecedentes 25
RepRap basa sus orígenes en una impresora gratuita, capaz de imprimir objetos
plásticos. Debido a que muchas de las piezas de una RepRap están hechas de plástico, y la
máquina puede a su vez imprimir esas piezas, se considera que es auto-replicante pues
pude crearse a sí misma, crear un kit que cualquiera puede
ensamblar con el debido tiempo y herramientas. Esto además
significa que si una persona posee una RepRap, puede
imprimir gran cantidad de objetos así como imprimir otra
RepRap para un amigo.
Es importante realizar una diferenciación entre las típicas “hobby printers” y las
“impresoras industriales”.
Empezando desde las típicas impresoras 3D de tipo “hobby” que cualquiera puede
construir, hasta diseños más avanzados, cabe destacar un importante mercado
emergente.
Fig. 4 AM Landscape
• Forbes Magazine: “3D Printing Industry Will Reach $3.1 Billion Worldwide by
2016.” [15]
• BBC News: “3D printer could help millions walk, say researchers.” [16]
• 3Ders: “Singapore to invest $500 million in 3D printing” [17]
Capítulo 1. Antecedentes 28
Basándose en los mismos principios que el anterior punto, con esta tecnología es
posible construir, relativamente rápido, diferentes piezas. Esta puede ser una
competencia realmente interesante por ejemplo para una empresa que fabrique
pequeñas series de piezas pero de gran variedad, o para empresas de producción bajo
demanda. [19]
1.6.5 Económica
Al igual que con las ventajas, es importante mencionar también las limitaciones
que esta tecnología posee. Muchas de estas desventajas serán tratadas con más detalle
en capítulos posteriores, especialmente haciendo hincapié en como solventarlas.
1.7.1 Material
1.7.2 Estructura
1.7.4 Productividad
Esta podría ser una de las razones principales que han llevado a la realización de
este proyecto. Se ha mencionado el hecho de que se puede considerar a estas impresoras
como de “producción rápida”, pero es importante ser consciente de que este valor es solo
en términos generales. La impresión 3D puede hacer que todo un proceso de fabricación
completo sea más breve, pero el tiempo de impresión en si mismo suele ser alto, siendo
de varias horas en piezas grandes y complejas.
¿No sería magnífico poder reducir estos tiempos? ¿Qué ocurriría si pudiéramos
obtener dos, cuatro o incluso diez veces el número de piezas en el mismo tiempo? Esto
implicaría una clara mejora de la productividad y una importante reducción de costes.
Capítulo 2. Objetivos del proyecto 32
Aparte
arte de ello, en las próximas páginas
páginas también aparecerán algunas ideas para
resolver los diferentes problemas encontrados. Se definirán desde nuevas aplicaciones
hasta combinaciones de ideas previas enfocadas de una manera diferente. De cualquier
forma, ambos
bos métodos finalmente proporcionarán una buena muestra de posibles
diseños, por lo que con el fin de llegar a una conclusión lo más clara posible, estas
diferentes opciones serán clasificadas, cuando sea posible, mediante tablas o cuadros.
Además, aplicandodo diferentes métodos de comparación
comparación como por ejemplo el cálculo
mediante factores, algunas ideas serán descartadas y otras serán consideradas como de
más valor.
3.2 EXTRUSOR
Cabe destacar que el extrusor debe ser capaz de proporcionar la fuerza necesaria
para extrudir la fibra a través de la boquilla, la que siempre tiene una sección menor
(normalmente alrededor de 0.4 y 0.5 mm para filamentos de alrededor de 1,75 y 3 mm).
Además, esta extrusión se debe realizar a la velocidad adecuada. [21], [22]
• Peso.
• Control y cableado.
• Precio: motor.
• Vibraciones.
• Deslizamientos en el filamento.
Además, mencionar que como una pieza más que es, cada extrusor significa más
objetos, más peso y la necesidad de un motor que a su vez requiere ser cableado.
Teniendo en cuenta el lema “lo simple es lo mejor”, aparece la idea de intentar reducir al
máximo las piezas, con el fin de reducir estos costes. [22]
Mediante el uso de un extrusor remoto se puede concluir que hay una reducción
en el número de piezas que deben estar en constante movimiento, lo que se traduce en
no tener que mover una cierta masa. Además con menos extrusores, menos piezas son
requeridas en total, lo que también implica una reducción de coste. [23]
diseño solo se debe considerar la diferencia de precio de cada pieza, pero no los gastos en
la energía para mover esa masa. De cualquier forma, este aspecto del diseño será tratado
nuevamente en el epígrafe dedicado al substrato o “cama térmica”.
Fig. 14 Bloque de
alojamiento Wade
Montaje
M3×10 tornillos Pernos 0.5 1 3
3 M3 arandelas Pernos 0.5 0.4 1.2
1 M3 prisionero Pernos 0.5 1 1
1 M3 tuerca Pernos 0.1 0.3 0.3
2 M4×20 tornillos Pernos 0.2 2.7 5.4
2 M4 tuercas Pernos 0.2 1 2
2 M4 arandelas Pernos 0.2 0.45 0.9
Total 181.48 g
Table. 2 Extrusor dentado. Componentes no impresos [25]
El motor es quizá el componente principal del extrusor. Éste motor debe ser capaz
de proporcionar el par necesario para mover la rueda dentada que a su vez gira el tornillo
perfilado. Existe un gran catalogo de motores aptos para esta función. En la tabla a
continuación se presentan los ejemplos más habituales. [26] [27] [28]
Unidad Coste por Coste por 4 Peso por Peso para cuatro
unidad (USD $) unidades (USD $) unidad (g) unidades(g)
Motor de Pololu 1 Kg- 52 560
pasos cm
Pololu Hybrid 20 350
3.17 Kg-cm
Unidad de control del 10 40 10 40
motor A4988
Total 30 92 360 600
Table. 3 Comparaciones de motores de pasos
Como se puede ver, la tabla esta diferenciada entre el uso de una y cuatro
unidades. La diferencia reside en que en el caso de usar solo un único motor, este tiene
que ser el más potente, Poulu Hybrid 3.17, para garantizar la extrusión de los cuatro
filamentos. En el caso de usar cuatro motores diferentes si es suficiente con utilizar unos
menos potentes
Este es quizá el diseño más barato y el más fiel a la filosofía reprap de reducción
de coste y uso de piezas imprimibles. Destacar que siempre son necesarias el uso de dos
barras paralelas ya que si solo se usara una, el motor podría girar sobre sí mismo y
convertir el sistema en inestable.
Más bien a modo do testimonial, se presenta aquí un sistema menos habitual pero
con algunas ventajas relevantes. La diferencia principalal de este diseño es que no está
basado puramente en el movimiento en coordenadas
coordenadas ortogonales X-Y,
X sino que de hecho
se basa en un movimiento mediante brazos y coordenadas en paralelogramos [29]. Es una
tecnología muy interesante y aún
aún en desarrollo, pero su ventaja principal es la eficiencia
en los movimientos.
ientos. Por otro lado supone algunas dificultades adicionales en la
calibración y en la programación de los movimientos. [30] [31]
3.4 BOQUILLA
2
Un termistor es un tipo de resistor cuya resistencia varía significativamente con las variaciones de
temperatura del mismo.
Capítulo 3. Partes principales, problemas de diseño y posibles mejoras 42
Por último, en la siguiente tabla aparece una comparativa sobre cómo distribuir en
el espacio las diferentes boquillas de la manera más eficiente. En los croquis, el color rosa
representa el substrato o cama y en negro el volumen de los cabezales y su área de
trabajo. [25]
• Rigidez de la cama.
• Adherencia de la cama.
• Planicidad.
Capítulo 3. Partes principales, problemas de diseño y posibles mejoras 44
Durante este capítulo se presentan una serie de tablas que contraponen las
diferentes opciones de diseño analizadas en esta primera etapa del proyecto, intentando
contrastar las ventajas e inconvenientes para alcanzar el diseño óptimo.
Factor
Otras
Precio Energía Ensamblaje Disponibilidad Precisión consideraci Valor
ones total
Diseño
(menos
Coeficiente es mejor)
1 1 0,8 1 1 0,8
Valor otorgado multiplicado por el coeficiente
Un extrusor
1 1 1 1 1,5 1 5,1
remoto
Dos
extrusores 2 2 1,5 1,3 1 0,8 6,14
remotos
Cuatro
extrusores 3 2,5 2,5 3 1,5 1,5 10,2
remotos
Cuatro
extrusores
2,5 3 3 3 1,2 0,8 10,24
sobre el
cabezal
Sistema de
1 1 0,8 2 1,5 1 5,94
poleas
Guiado
mediante 1 1 1 1 1 0 3,8
tornillo
Tornillos y
1 1 2 1,5 1 0 5,1
cojinetes
Raíl
2 1,5 1 1,1 1 0 4,4
perfilado
Cama
termina 2 1,5 3 2 1,5 0 7,4
artesanal
Cama
térmica 3 1 1 1,5 1 0 4,3
premontada
Lámina de
1 2 2,5 2 2 0 8
aluminio
Diseño
1 1 3 3 2 1 9,2
modular
Robot Delta 3 1 3 3 1 0 7,4
Mediante las tablas de comparación utilizadas ha sido posible derivar en una serie
de condiciones que pueden ser buenos criterios para un diseño optimo, pero la realidad
es que las diferentes relaciones existentes entre cada componente convierten la decisión
del diseño optimo en algo más complicado de lo esperado, y siempre difícil de clasificar
por lo que en muchos casos la decisión final es el sentido común.
En las siguientes páginas los considerados como los dos diseños más interesantes
son presentados, comparando las diferentes ventajas e inconvenientes de cada uno.
Los dos extrusores independientes dan al sistema la ventaja de poder imprimir dos
sets de piezas independientes (o por ejemplo cuatro piezas pero en dos colores). Esto
otorga una mayor flexibilidad, pero por otro lado tiene el inconveniente de que un
mínimo de dos sets de control para el motor son necesarios.
Dado que este diseño se basa en la ventaja competitiva de imprimir dos sets de
piezas independientes, podría ser aun una mayor ventaja si mediante la mencionada
construcción modular se pudieran añadir bloques para aumentar el número de sets
consecutivamente. Debido a que una de las limitaciones de la impresora a diseñar es que
la misma debe ser transportable a través de una puerta normal (en torno a 800mm de
ancho) siendo como mucho parcialmente desmontada, el diseño no puede desarrollarse
modularmente en anchura, pero si podría hacerlo en altura. Surge entonces la idea de
unos módulos apilables verticalmente, fáciles de ensamblar y que cada uno permita
obtener dos piezas más.
Capítulo 5. Concretando el diseño definitivo 50
Por otro lado, para este diseño basado en la modularidad, podría ser una gran idea
el uso de raíles estandarizados y perfilados. La industria que fabrica estos raíles ha tenido
unas buenas cuotas de mercado precisamente porque es un sistema relativamente
barato pero de alta utilidad ya que el raíl tiene un doble uso: servir como guía para los
desplazamientos y a su vez como estructura base de la máquina. Además su relativa
estandarización permite el uso de diferentes componentes y accesorios de gran utilidad y
a un precio asequible.
Diseño 1 Flexibilidad
Nuevo concepto Ventaja adicional
Dos extrusores independientes Diferentes sets de piezas
Construcción modular Flexibilidad, facilidad de uso y buen almacenaje
Formato apilable Eficiencia en el uso de espacios
Complejo sistema de conexiones Fácil ensamblaje
Sistema de poleas Ligero y flexible en alcance de altura
Raíl perfilado Mejores propiedades estructurales y facilidad de montaje
Table. 9 Diseño 1
Su ventaja técnica principal será el hecho de que en este caso sólo el cabezal es la
pieza que está en movimiento, mientas que la cama térmica permanece estática.
Mediante esto, habrá un ahorro de energía en dicho movimiento (importante ya que tal y
como se ha mostrado la cama es una de las piezas más pesadas) pero por otro lado será
necesario diseñar un sistema de raíles y carros adecuado. Es por ello y por los
requerimientos estructurales por lo que se decide utilizar raíles perfilados.
Además, otro importante requisito de este diseño va a ser un buen acabado visual
así como una zona de trabajo de aspecto limpio y accesible, sin marcos que dificulten la
manipulación de la pieza [38].
Por tanto, los conceptos principales de este diseño se pueden resumir como:
Destacar también que debido a que para cada problema pueden aparecer diversas
posibles soluciones, para resumir, al finalizar el epígrafe perteneciente a cada parte de la
impresora, se presentara un cuadro que sintetizará las decisiones tomadas al respecto. En
algunas ocasiones estas decisiones finales pueden venir acompañadas de algunos cálculos
en los casos en que sean necesarios.
Debido a que este proyecto puede ser leído de diferentes formas, desde un lector
que lo lee de la página inicial a la final, hasta otro lector que solo quiere consultar algunos
epígrafes para comprobar ciertos aspectos del diseño. Es por ello, que para ayudar a
contextualizar a los lectores del primer tipo, a continuación se presenta una imagen del
resultado de la primera etapa del diseño CAD, la cual permita desarrollar mejor el
imaginario de la máquina y entender correctamente el diseño, su funcionamiento y las
diferentes decisiones tomadas. De cualquier forma esta imagen no debe ser considerada
como un resultado final, ya que el mismo se presenta en la última parte de la memoria.
3
SolidWorks es un programa de diseño 3D mecánico (CAD, Computer aided design) el cual se
ejecuta bajo el sistema operativo de Microsoft Windows y ha sido diseñado por Dassault Systemes
Solidworks Corp., filial de Dassault Systemes. SolidWorks tiene actualmente una comunidad de alrededor de
2 millones de usuarios a lo largo de más de 165.000 compañías en todo el mundo. En el año 2011 los
ingresos de SolidWorks fueron de más de 483 millones de dólares.
Capítulo 6. Visión general del proceso de diseño 54
Además, una de las definiciones iniciales de la impresora es que la misma debe ser
capaz de ser transportada a través de una puerta estándar de 800x200 mm sin tener que
ser desmontada más allá de algunos componentes.
Respecto a las piezas resultantes, esta impresora será capaz de crear objetos con
un tamaño de hasta 290x290x500 mm. En el ámbito de las impresoras 3D de ABS esto
podría ser considerado como una de las de mayor formato.
Capítulo 7. Extrusor y rollos de filamento 55
7.1 MOTOR
Fig. 34 Nema 17
Propiedad Especificación
Ángulo de paso 1.8 grados
Precisión de ángulo de paso ±5% (por paso, sin carga)
Precisión de resistencia ±10%
Precisión de inductancia ±20%
Incremento de temperatura 80.C Max
Temperatura ambiente -20.C~+50.C
Resistencia aislante 100MΩMin. ,500VDC
Fuerza dieléctrica 500VAC para un minuto
Velocidad máxima 300 rpm
Table. 12 Especificaciones Nema 17-2
Estas ruedas están también basadas en las estándar del extrusor Wade. El
principio operativo del extrusor, motor y ruedas dentadas mediante tornillo perfilado ya
ha sido explicado, por lo que aquí solo se comentan algunos detalles. Como se ha dicho el
sistema de ruedas dentadas se utiliza para conseguir una relación de transmisión
adecuada y un movimiento preciso. Estas ruedas pueden ser fácilmente obtenidas
mediante otra impresora 3D, resultando:
Zଵ 11
= = 0.28205
Zଶ 39
grados
1.8 ∗ 0.28205 = 0.50769
paso
݉݉
2ߨ = ݎ2ߨ ∗ 4.875 = 30.631
݃݅ݎ
30.631 ݉݉
∗ 0.50769 = 0.0432
360 ݏܽ
ܸ݈݀ଵ = ݎߨ = ݈݀ܣଶ ݈݀
ߩ = 1020 ݇݃/݉ଷ
1020
= ݏݏܽܯ ∗ 0.4156 = 4.239 ∗ 10ି ݇݃/ = ݏܽ4.239 ∗ 10ିସ ݃/ݏܽ
1000000000
0.4156
= 0.529 ݉݉/ݏܽ
4 ∗ ߨ ∗ 0.25ଶ
300 ∗ 360 ݀݁݃ ݏ݁݁ݎ1000 ݏݏܽ
= 1800 =
60 ݏ ݏ
ݏܽ
1000 ∗ 0.28205 = 282.05
ݏ
Velocidad máxima de extrusión por cada boquilla:
݉݉
0.529 ∗ 282.05 = 149.25
ݏ
Capítulo 7. Extrusor y rollos de filamento 58
Además, dicho cabezal también es una pieza relevante debido a que marcará la
precisión con la que la impresora trabaja. Se deberá llegar a una solución de compromiso
entre un material barato pero suficientemente rígido, que permita alcanzar el tamaño
deseado pero sin grandes vibraciones.
A modo de ejemplo se definen con algo más de detalle los pasos necesarios para
realizar el estudio mecánico de este caso, por ser el primero. Por razones de brevedad
dichos pasos se omitirán en la memoria en posteriores estudios.
Fig. 47 Von-Mises
Fig. 48 Deformación
Capítulo 9. Cabezal y bloque de sujeción de las boquillas 64
Como se puede ver, las tensiones no son en ningún caso críticas pero si las
deformaciones, que alcanzan los 0,72 mm en el extremo. Tal y como se ha mencionado
este valor excede el límite establecido, por lo que el diseño debe ser optimizado.
Para ello se produce una iteración en los cálculos, probando diferentes modelos,
intentando aligerar la estructura y fortalecer la parte con mayor deformación mediante el
uso de nervios. Tras algunas pruebas e intentos de modificar la sección e incrementar el
ángulo de la barra de soporte se comprueba que las deformaciones siguen siendo muy
elevadas. También se valora la idea de introducir una pieza interior de acero que rigidice,
pero se descarta por el peso añadido que implicaría.
Tal y como se puede apreciar en este caso la deformación es de tan solo 0.02 mm
en el peor de los escenarios. Se concluye pues que el diseño es válido.
Capítulo 9. Cabezal y bloque de sujeción de las boquillas 65
Fig. 58 Boquilla
Fig. 65 Carro
Movimiento a lo Compra de
largo de la carro
coordenada estandarizado
por 80/20
Topes de final
de carrera de
goma
Motor y
transmisión por
correa
Fig. 72 Movimiento en Y
Capítulo 11. Raíles perfilados 73
Fig. 74 Final Y
Fig. 77 Brazo Z
Sistema de tornillo
sin fin colocado en la
posición correcta
Fig. 80 Final Z
Tras haber definido con el mayor detalle posible todas las especificaciones de la
impresora así como realizado un diseño completo en CAD, sigue a continuación un breve
análisis de las posibles vibraciones y deformaciones que sufrirían los brazos de la misma.
Pese a que ya se han realizado estudios mecánicos en los anteriores epígrafes, la idea de
realizar un nuevo análisis independiente reside en la importancia de los mismos.
Otra de las funciones de este capítulo es servir también a título de ejemplo del uso
de este software, para que pueda ser utilizado en la comprobación de diferentes
variantes de la impresora diseñada o de otros modelos. Por supuesto es importante
mantener una visión de conjunto y comprender que este test debe ir asociado a otras
comprobaciones y al correcto diseño de todas las piezas.
Para poder obtener la carga máxima a soportar por el brazo sin superar la máxima
deformación permisible, es necesario introducir una serie de parámetros, que se pueden
resumir en los siguientes:
PARTE V: CONCLUSIONES
Capítulo 13. Resultados
El resultado de este proyecto podría resumirse como la creación del modelo de
una impresora 3D casi lista para funcionar. Por supuesto, considerando que este proyecto
tiene una orientación académica, hay que mencionar que ciertos aspectos no han podido
ser detallados en profundidad, con la idea de en su lugar poder abarcar un conocimiento
más amplio y genérico.
b) Los análisis mecánicos de las diferentes partes. Estos análisis dan una
buena base para asegurar cuando un diseño es fiable.
e) El contexto y los antecedentes. Son un buen resumen para todo aquel que
quiera conocer brevemente la historia de la impresión 3D y sus tecnologías
básicas.
h) Los diferentes costes y datos sobre masas de piezas, útiles para todo aquel
que quiera sentar las bases de un nuevo modelo.
i) La lista de materiales, que en unas pocas páginas resume todas las partes
de la impresora, concretando materiales, precios y algunas referencias.
Chapter 15. Futuros trabajos 83
Design of a 3D printer
capable of creating
multiple objects
simultaneously
PART I: INTRODUCTION
The goal of this project is to explain the complete design process of a 3D printer
capable of creating multiple objects simultaneously.
Besides that, it is not the main point of this project to explain how a 3D printer is
made or how it works, because as said, the project will be focused into the competitive
advantage of multiple objects, even though, there will be also some general explanations
and background.
Chapter 1. Background
1.1 3D PRINTING
First of all, “what it is to print?” One simple definition could be “to mark in paper
or in other substrate with letters or any other graphic character”. The difference between
printing and 3D printing is that in the second case a three-dimensional product is made.
3D printing is based on the additive process technologies.
With this technology is possible to make different solid pieces from a digital model
and without using the traditional machining techniques like cutting or removing material.
Furthermore one of the main advantages of this technology is the ability to create almost
any shape. Also it is important to mention the capability of result in a real object, ready to
use, directly from a computerized 3D model made by the designer. [1]
Several different 3D printing processes have been invented and continue into
development since the late 1970s. Like in a lot of modern technologies as for example
computer science, these machines were, at the beginning, large, expensive and with a lot
of limitations; but time by time those have switched into cheaper, more reliable and
smaller machines.
However, it is possible to assert that the first 3D printer appears around the year
1984 when a technology called “stereolithography4” was invented by Charles Hull. This
technology was used to create a 3D model from a picture and allowed the users to test a
design before investing in a real manufacturing program. [2]
After this, the next milestone on 3D printing development happens in 1987 with
the invention of the Selective Laser Sintering: Selective Laser Sintering (SLS) was also
developed and commercialized in 1987 by DTM (now a subsidiary of B.F. Goodrich), a
process that involves laser melting powder like substances to create an object. [3]
Fig. 86 FDM
After all, in 1996 starts the term 3D printing and the self-replicating printers with
the RepRap project [5].
In this project there will be a special mention for the whole RepRap project. This is
because knowing that nowadays there are a lot of different webpages and communities,
at the beginning this project did a great job unifying a whole community of developers
and settled down the basic ideas of 3D printing and the future goals. It is also important
to mention again the idea of creative commons5 and open-source system that they used.
The basic ideas of RepRap project are completely explained on the document that
the creators, D. Holland, G. O’Donnell and G. Bennett published: Open Design and the
Reprap Project. [6], [7]
5
Creative Commons is an non-profit organization, which main office is in Mountain View, in the
state of California. This organization is created to use and share creativity and knowledge with a number of
juridical mechanisms which are for free. [40]
Chapter 1. Background 91
However, the best place to find all the information is the wiki-based website that
was created [5]. On this website, they defined RepRap as:
RepRap takes the form of a free desktop 3D printer capable of printing plastic
objects. Since many parts of RepRap are made from plastic and RepRap prints those parts,
RepRap self-replicates by making a kit of itself - a kit that anyone can assemble given time
and materials. It also means that - if you've got a RepRap - you can print lots of useful
stuff, and you can print another RepRap for a friend…
It is important to mention also other related pages for the whole community of 3D
printing as for example Thinginverse. [8] On this website anybody can find a huge
directory of pieces to be printed with any 3D printer. All these pieces are for free and
publicly available.
It could be now a good classification to separate into just typical hobby printers
and industrial printers.
Many more can be found searching into RepRap and in other repositiories like blogs
and forums. [13]
From only the typical hobby 3D printers which almost everybody could build, and
based on RepRap principles; there is an emergent and growing market of different
specialized printers, each one with their differences.
6
These different parts will be explained properly during the whole document.
Chapter 1. Background 93
Also different enterprises are growing in this market. One simple example could
be the “Rapid Product Development Association of South Africa”. It was founded in 1999
as the representative organization for RP industry and community within South Africa.
According to RAPDASA, since the first 3D Systems SLA 250 was sold in 1991 the market
has grown rapidly and in 2011 there were approximately 268 machines sold. Statistics
from 2009/2010 shows Stratasys (through mainly Dimension/Uprint sales) had the
majority of 3D printer market in South Africa, around 47%, and 3D Systems is in the 2nd
place. [14]
Fig. 88 AM Landscape
However, going even further it is easy to find a lot of articles in magazines and
newspapers explaining these technologies and all the possible uses. Sometimes it is
important to be realistic and do not trust in everything that they propone, which in a few
cases are only exotic examples just for calling the attention of the reader. Anyhow it is
clear that the market is having a good response and hopefully this will continue growing
up.
• Forbes Magazine: “3D Printing Industry Will Reach $3.1 Billion Worldwide by
2016.” [15]
• BBC News: “3D printer could help millions walk, say researchers.” [16]
• 3Ders: “Singapore to invest $500 million in 3D printing” [17]
Chapter 1. Background 94
During the background some of the improvements or maybe the bases of possible
advantages of the 3D printing technology have appeared, but to summarize a little bit
here come the most important points.
On 3D printing there is less human resource participating into the different stages.
For example only one designer can make a piece with his CAD program and directly print
it by a connected printer. With this he can make a prototype which everyone can see and
touch to check different aspects. In this way, designer can obtain feedback, refine design
and iterate until everything is correct. [18]
Based on the same principles than the previous point, with this technology it is
possible to make, relatively fast, different pieces. This could be really interesting for
manufacturing pieces by a small enterprise which does not have huge demand of pieces
or for example online on-demand manufacturing. [19]
1.6.5 Affordability
This project is based on hobby 3D printers which have the explained principles of
self-replicant and being really cheap, but even industrial printers can be really cheap
comparing with other machines and the possibilities those give. [20]
Like with the advantages, here come some of the most important general
limitations of 3D printing. Of course these drawbacks will be treated and studied deeply
on later chapters and during the whole CAD design stage.
1.7.1 Material
1.7.2 Structural
1.7.3 Size
Because of different limitations of the printer like the size of the bed or the
structure of the kinematic system, these printers are a little bit limited about the size of
the piece which can print. It is usual to find heated beds with a size about 300x300 mm.
Chapter 1. Background 97
Of course there are some exceptions and printers made for making wider pieces but
however those are not the common ones.
1.7.4 Productivity
This could be one of the reasons for making this project. Mentioned above it is
possible to find as an advantage the “quick production” (1.6.2) and “cheap
manufacturing”(1.6.1) that these printers provides. But these ideas should be considered
into a relative manner. 3D printing can make the whole manufacturing process fast, or be
a quick solution for a strange piece, but indeed 3D printing is not a rapid process. It takes
a lot of time, hours, to print a piece.
Would not be great to do it faster? What if we get two, four or ten times the
amount of pieces into the same processing time? Of course this would mean a really
important cost reduction and a better productivity.
Chapter 2. Goal of the project 98
In the last chapter it has been mentioned the productivity of the printers. To
increase this productivity is the real goal. Of course there could different ways to achieve
that, but the selected is to build four objects in the time that a printer usually only would
make one. For this the solution is clear: use one printer but with four nozzles that prints
four copies.
On the next pages there are descriptions of the different possible parts which a 3D
printer could use.
Furthermore, after the description or even during that, several discussions are
showed in order to contrast different ideas to reach the optimal generic design for a 3D
printer. Of course on each part or property there are different criteria but in overall the
main goals are like in all typical Engineering products: A really working design, reliable
and trustworthy, good looking and cheap.
Chapter 3. Main parts, design issues and improvements 99
Besides that, there will be also some new ideas to solve the different issues. There
could be new applications or even combinations of older ideas ideas into a different way.
However, both methods finally give a lot of possible designs so, in order to t have a final
decision
cision as clearly as possible,
possible these different options are going to be classified, whenever
it might be, into charts. Applying different comparison methods as for example giving
factors some ideas will be dismissed and some other will be taken into deep
consideration.
After this comparison and description stage, in Chapter five,, the considered as the
two most interesting designs will be showed up.
3.2 EXTRUDER
Furthermore, the extruder needs a certain strength to be able to force the raw
material through the extrusion width, (usually between 1.75 and 3 mm for the filament
and 0.5 or 0.4 mm for the nozzle); and also with enough speed. [21], [22]
• Weight.
• Control and wires.
• Price: Motor.
• Vibrations.
• Grip to the filament.
Furthermore, as any other part, each extruder means more pieces, more weight
and the need of a motor, which also demands wires and a control system. Keeping in
mind our lemma “the simpler it is the better” again appears the idea of avoid or reduce
all these parts somehow. [22]
At the moment that the project requires to use four filaments to be delivered to
four nozzles, it is necessary to decide how to do that as the simplest way.
a) One remote extruder: With this unique extruder the design somehow should
manage to pull of four filaments.
b) Four remote extruders: In this case each extruder has to take care only about
one filament. This is the most commonly used design, basically because almost all the
printers use only one fiber.
c) Four non-remote extruders, over the nozzle: This design is almost like the
previous one but now each extruder is placed over each nozzle. With this idea is possible
to avoid the typical problems of Ed´s Bowden extruder but of course it translates into the
requirement that each one should be moved. In other words, less printing speed and
more energy demanded.
Chapter 3. Main parts, design issues and improvements 101
For example, designers of Bowden extruders talk about hysteresis. For every
extruder there is a compression effect in the filament, but if this is long, such effect will
be multiplied, leading into springiness. They provided a solution which is using encoders
in every filament, but of course this implies an extra cost and more assembling problems.
[23]
In the case that there is a bed moving in one axis and the header is moving in the
other two, the weight of the nozzle still has influence. But when the nozzle is not moving
at all and the bed is making all the motion, the mass of the header must not be
considered as an energy factor. In this second case designer only should take into account
the price. However this aspect of the design will be mentioned deeply at the design stage
of the heated bed.
Chapter 3. Main parts, design issues and improvements 102
Anyhow, a Bowden extruder also needs a path for the filament. This path should
be different on each design but basically it consists of two main parts:
• Different fix points which mark and guide the path of the filament, avoiding
collisions and knots.
• A tube or sleeve for guiding the filament. This tube should be stiff enough
but also it should bend at least into a minimal radius. Usual
recommendation is to use a simple Teflon tube. It is really affordable, with
good elasticity and also the coefficient of friction of PTFE (Teflon) with ABS
is low enough to not losing much energy. In addition, all these tubes are
standardized and can be easily found in almost every hardware store or
even on the internet. [24], [23]
Besides all the previous ideas, the best for making a general decision is to study
the needed parts of an extruder, and consider how much money and energy could be
saved using only one extruder for the four filaments. For that here follows a classification
of the different parts of a typical extruder. Of course all these parts may defer on every
design but it might be a good approximation. Moreover, it will be divided into printed
parts and bought parts.
The main advantage of these parts has already been mentioned, but anyways
based on the self-replicant idea is possible to get all this pieces by another 3D printer, so
the cost can be only the raw material. That means that the price is assumed only
multiplying the weight by the price of the ABS.
For the weight of printed parts, using the 3D model in SolidWorks and considering
ABS´s density about 1.02 g/cm3.
For the price, estimated ABS at 30$/Kg (see bill of materials, item 67).
Non printed parts are the ones that cannot be made using 3D printing process.
This group includes fasteners, bearings, and some structural elements. As they are mass
produced parts, their prices are rather low. Also sometimes this pieces offer several
competitive advantages or properties that ABS printed parts cannot reach.
Stepper motor can be considered as the most important part of the extruder. This
motor provides the needed torque to move the gear which then moves the rod. There is a
wide catalogue of stepper motors. Here follows an example of a possible one which is
provided by the brand Poulu. [26] [27] [28]
Unit Cost per unit Cost per four Weight per Weight per
(USD $) units (USD $) unit (g) four units (g)
Stepper Pololu 1 Kg-cm 52 560
motor Pololu Hybrid 20 350
3.17 Kg-cm
Steper motor driver carrier 10 40 10 40
A4988
Total 30 92 360 600
Table. 22 Stepper motor comparison
The difference is that in the case of using only one stepper motor, the more
powerful one, Poulu Hybrid with 3.17 Kg-cm torque should be used to guarantee the
extrusion of four filaments. Other option could be using a smaller motor with another
gear for a different transmission ratio, but in that case, the velocity of the extrusion
becomes a new problem.
Anyways, a good design of the piece in which the stepper motor is placed is
important, and it should allow a good movement of the filament with the idler.
Moreover, in the case of using one motor, the diameter and the position of the four fibers
should be taken into account.
After stepper motor, the hobbed bolt is other of the pieces which has an extra
relevance on the extruder. Basically it consists of a typical bolt (it is possible to use
different sizes, for example in this case M8x50). This bolt will be hobbed or modified to
Chapter 3. Main parts, design issues and improvements 106
adapt itself properly to the shape of the filament. In other words, with for example a drill,
a tangential drilling is made to the bolt. [25]
There are several ways for making the hobbed bolt, so one of these methods could
be used just with the change of making four slots instead of only one. Finally the decision
was not to make four slots, but to make only one but bigger. Also the space where the
bolt is sheltered should be reconsidered.
Note that in the case of using only one extruder we save 100 USD $ and also there
is no need to assemble the same thing four times, so assembling time is saved.
Furthermore, with this unique extruder 594 grams are moved instead of 1577
when there are four extruders over the nozzle (not considered the nozzles which are
always there).
Knowing the basic way of work of a 3D printer it is clear that it needs some kind of
kinematics. Later on this project the different options for these movements are going to
be explained, but however a motion system is a mandatory requirement for printing.
Basically in this field there are two main types of solution for achieving this
movement: Linear motion slider based on a single profiled rail and linear slider based on
two smooth bars and bearings.
Chapter 3. Main parts, design issues and improvements 107
It is the cheapest design and also follows the philosophy of reprap cost effective
printers, because it is easy to build and not so many parts are used. As a design
requirement two smooth bars are needed because in other case, the motor could turn
around the bar and be unstable.
The main difference of this system is that it is not purely based on a typical X-Y
coordinate system; actually the key feature is that it uses parallelograms in the arms, [29].
Delta robot is an interesting technology and also still in development, but its main goal is
the efficiency of its movements, [30]. On the other hand it also has several drawbacks as
for example it is harder to program and should be properly calibrated before starting to
work. [31]
3.4 NOZZLE
As nozzle is possible to define the whole composition which has these two main
functions:
For example the temperature should be monitored and controlled, so for that a good
solution is to use thermistors7. Besides that, the whole nozzle system needs to be
properly placed somewhere where the motion happens. In other words it should be
connected to the header and well fixed to avoid vibrations, [32]. There are some
discussions about these topics on different communities.
through the nozzle and raises the fixation part (which is Fig. 107 Nozzle types
made by plastic) or even worse, starts melting or
warping the fiber before it raises the hot end. For that, some maker have utilized and
developed designs trying to avoid that this heat goes up. Typical are the use of fans and
fins to achieve a higher dissipation on the upper part.
However, in the field of nozzles there could be a lot of improvements, but not so
much related with the productivity which is the main goal of the printer of this project so
there will not be further investigation about that except how to combine and distribute
four nozzles. [25]
7
A thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard
resistors. The word is a portmanteauof thermal and resistor. Thermistors are widely used as inrush current limiters,
temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements.
Chapter 3. Main parts, design issues and improvements 110
Talking about printing always goes hand in hand with talking about substrates. In
3D printing there is no substrate, only the board or table where the extruded material
lays. This one is a really important part of 3D printers.
The main function of the heated bed is to prevent warping. Basically, when the
extruded plastic cools down it shrinks slightly. This is not a problem if under the new layer
there is an older one which is still cool down, but when this shrinking process does not
occur through a printed part, the result could be a warped part. It is easy to find this
warping by examining the corners being lifted off of the bed. By printing on the heated
bed it is possible to maintain the printed part warm during the whole printing process.
[33], [34]
However, it is easy to think about using only a simple board of some flat and
smooth material as a heated bed, but indeed much more considerations should be made:
Table should be properly calibrated and the distance to the hot end of the nozzle
has to be constant during the whole printing process [35]. As the bed is never perfectly
flat, the tolerance for the flatness is roughly not more than half of the thinnest layer the
printer is supposed to produce.
Also calibrations for this parameter are needed. In the case of some instability or
imbalance, a deformed piece could be the result. Also even the whole surface where the
printer is placed might not be flat.
A non-properly prepared bed can result in a bad adherence of the plastic to the
base, and also the possibility of a “bubbling” effect exists. Typical problems could be the
existence of dust or finger print grease on the surface.
Chapter 3. Main parts, design issues and improvements 112
The bed should be stable and made by a material which is stiff enough. In case of
movable bed, the quality of linear bearings and the stiffness of guide rails affect the
distance between the bed and the nozzle during operation. This affects the quality of
produced parts.
There are basic limitations about the maximum size of the heated bed. This
limitations mainly come from the energy that is required to heat the bed and also
because the thermal losses. Even more, depending on the material of the bed, there
could be some dilatations, so it is better if the table is not so big [33], [36], or it could
warp under the thermal load. Another limitation is achieving tight flatness tolerances for
large surfaces.
Apparently the best system should be the one which only moves the header,
because the movement of the heated bed (which is heavier) is avoided, but indeed this
system has an important limitation. At the time that movement in one axis is transmitted,
the other motor should be free of motion in the opposite coordinate, sliding over some
rails, as seen on Fig. 113.
Chapter 3. Main parts, design issues and improvements 113
As shown in the drawn, motors should be able to run over the red rails. If for
example Motor Y is transmitting movement to the header, the whole set of Motor X and
it transmission should move over the rail as the blue arrows indicate.
After all, the technology typically used is a mixture of two movements. With one
motor the X coordinate of the header is moved and with another motor the Y-coordinate
of the table is moved (or vice versa). In this case both motors are independent so no need
of these rails structure.
A different discussion starts about the movement on the Z axis. For these motion
also two solutions can be adopted, movement of the header o movement of the heated
bed.
Chapter 3. Main parts, design issues and improvements 114
Formerly it has been explained the paths of the movement, or in other words, how
the different moving work but, how to transmit this movement? Designer should be able
to go from the movement of the shaft of the stepper motor to a lineal one.
For that, the most common used way is to connect a belt to the carriage. Of
course this is only one of the possible ways, which could be chains, cables or even directly
by a screw8.
Also here appears a new interesting design which is the use of winches. Basically it
will consist of a stepper motor connected to a cable which is also connected over a rail or
some kind of sledging system. It could be compared with a typical belt system but only
with cables and for vertical forces.9
Once again the best criterion for decision is to check the number of pieces, weight
and cost of one typical heated bed, and see which change could worth.
With the data from above, it is shown that moving the header means moving 594
grams in the best case (only one extruder), 1577 grams when there are for extruders, plus
the four nozzles weight; and by the other hand the motion of the four heated beds results
on moving at least 2871 grams.
8
This will be explained later on Chapter 11
9
More details on Part III: New Designs
Chapter 4. Comparison of different designs 115
Here comes a table which compares the different options analyzed on this first
stage of the project, looking for basic advantages and drawbacks.
Factor
Others
Price Energy Assembly Availability Accuracy Total value
issues
Design (less is
Coefficient
better)
1 1 0,8 1 1 0,8
Given value multiplied by the coefficient
One remote
1 1 1 1 1,5 1 5,1
extruder
Two remote
2 2 1,5 1,3 1 0,8 6,14
extruders
Four remote
3 2,5 2,5 3 1,5 1,5 10,2
extruders
For over the
2,5 3 3 3 1,2 0,8 10,24
nozzle
Winch system 1 1 0,8 2 1,5 1 5,94
Screw drive 1 1 1 1 1 0 3,8
Steel guides with
1 1 2 1,5 1 0 5,1
rods
Single profiled rail 2 1,5 1 1,1 1 0 4,4
Rubber
2 1,5 3 2 1,5 0 7,4
handmade HB
Ready PCB
3 1 1 1,5 1 0 4,3
heated bed
Aluminium sheet 1 2 2,5 2 2 0 8
Modular (top
1 1 3 3 2 1 9,2
over top)
Delta robot
3 1 3 3 1 0 7,4
design
Table. 28 Designs comparison
• One remote extruder is the lightest and cheaper way to deliver the
filament, but it should be well designed.
• Moving only the header could be good in energy terms but indeed is not
always used because of a quite difficult design.
• Two different motors on each side seems to be the best choice for the Z-
coordinate.
• The nozzle position should be well balanced.
• Already built heated beds are easier to use.
It is important to mention that in these first conclusions there are not all the
results of the project. In other words, these are only the first ideas which appeared and
were considered as basics of the design. Further solutions and even some decisions which
might look contradictory to these basis will be considered later.
Chapter 5. Focusing the design 117
Consist of two independent extruders, with two nozzles per each. By placing one
header in the top of the other, a modular system is created. Also a winch system for the Z
coordinate is used as a new improvement.
The two independent extruders system gives the advantage of printing two
different set of pieces (or the same four but in two colors). This gives more flexibility to
the system but of course, on the other hand it has the drawback of two more motor set
needed.
As the point that this design is minded to print two different sets, it could be a
great idea if the printer is made in a modular construction that allows even further the
chance of adding parts to get another set. Considering that one of the conditions of the
printer is to be portable through a medium sized door (800 mm width) without many
assembly operations, the design cannot be expanded in X or Y coordinate, but it could be
expanded in height.
The idea of modular assembly technologies can be found in so many fields and it
has been always a good idea to increase the productivity and cost efficiency. By the other
hand, this modular construction requires a well thought design and must be able to
assembled and disassembled fast.
About the winch system, it is possible to find several examples and also in progress
designs on different forums and in reprap.org. It could be really interesting to continue
searching on this and seizing the ability of winches to raise a big mass with a relatively
small power.
Chapter 5. Focusing the design 118
Moreover, for this design, based on modularity will be a great idea the use of
profiled rails. The utilization of these has been growing in industry mainly because it is a
comparatively cheap way and besides that, the rail makes two functions: a path for sliding
and a structural component able to hold weight and be assembled in many ways.
Furthermore, the different companies provide a lot of useful components and accessories
for these rails for an acceptable price.
Design 1 Flexibility
New idea Extra advantage
2 Independent extruders Different sets
Modular construction Flexibility, easy to handle, better storage
Pile format Space efficient
Connection system (to be designed) Easy assembling
Winch system Lighter and flexible in height
Profiled rail Better structural properties and easier to assemble
Table. 29 Design 1
Based on “printrbot” distribution of the pieces, starting with the idea of “simple is
better” but clarifying the fact that sometimes is important to expend something else in
quality and reliability, here is going to be presented the main points of the design that
later is going to be fully studied in this project.
The main technical advantage of this design will be the fact that only the header is
in movement, instead the header and the bed. With this, there will be an energy saving
on moving the bed (heavy compared with other parts, as shown in the previous chapters)
but on the other hand a well carriage system has to be designed. For that, standardized
profiled rails are going to be used.
Also one important requirement of this design is a good visual aspect, specifically
related with an open working area, which allow more flexibility and a better handling of
the printed parts. This fact in combination with the non moving bed gives to the design
the possibility of for example work over the parts while it is still printing [38].
After proposing the two designs, it has been decided to focus only in one choice
which will be the “Second design”. This decision is made to get the best results and to be
able to go into a deep study and real conclusions. However, the main concept of the “First
design” which is the modularity is a really powerful idea which stays for future studies.
Chapter 6. Overview of the design process 121
Like in most of the designing processes, few issues are going to turn up and the
possible solutions and decisions will make sometimes a redundant routine with several
iterations. In order to describe the system as clear as possible, the design is going to be
divided into different milestones based on the main parts of the 3D printer. Furthermore,
going into that, several points and conditions of the design are mentioned.
During the design process, solutions to the different processes will be proposed,
and finally there will be a summary, by description or by a chart which shows the last
decision. Sometimes this final decision might be presented along with several calculations
in the needed cases which help to justify it.
Apart from all the previous information here comes a small image of the result of
the first stage of the CAD design. This project can be read in different ways, for example
from the beginning to the end or just checking some chapter to understand the design.
For those who are reading this step by step this first picture will clarify a little bit how the
printer should be and work. Of course this image must not be considered as a final result
for anyone.
10
SolidWorks is a 3D mechanical CAD (computer-aided design) program that runs on Microsoft
Windows and is being developed by Dassault Systèmes SolidWorks Corp., a subsidiary of Dassault Systèmes,
S. A. (Vélizy, France). SolidWorks is currently used by over 2 million engineers and designers at more than
165,000 companies worldwide. FY2011 revenue for SolidWorks was 483 million dollars. [Wikipedia]
Chapter 6. Overview of the design process 122
One of the limitations where is possible to optimize is on the size of the 3D printer.
During the whole design, size has to be a keystone into the decision making. Furthermore
this maximum size will be the reference for the rest of the pieces. Under the limitation
inflicted by the maximum dimensions of the heated bed because of thermal dilatations
and other issues (see 3.5.5) no printed piece can be bigger than this limit.
Besides that, the whole assembly of the printer should be handled and carried
through a typical door of 800x2000 mm.
About the resulting pieces, this printer will be able to create items with a size
about 290x290x500 mm. On the hobby 3D printer market, this printer can be considered
as one of the biggest.
Chapter 7. Extruder and filament rolls 123
The first part to mention in an extruder is the stepper motor. Such motor provides
the power which will move the filaments. The typical stepper motor is a Nema 17 (see bill
of materials, item 6). This motor has the following properties:
Item Specifications
Step Angle 1.8 degree
Step Angle Accuracy ±5% (full step, no load)
Resistance Accuracy ±10%
Inductance Accuracy ±20%
Temperature Rise 80.C Max
Ambient Temperature -20.C~+50.C
Insulation Resistance 100MΩMin. ,500VDC
Dielectric Strength 500VAC for one minute
Shaft Radial Play 0.02Max. (450 g-load)
Shaft Axial Play 0.08Max. (450 g-load)
Max. radial force 28N (20mm from flange)
Max. axial force 10N
Max speed 300 rpm
Table. 32 Nema 17 specifications 2
These wheels are also based on the typical ones from wade´s extruder. The
operating system of the extruder and the stepper motor has been explained before so
here just come a few details of it. As mentioned the design will need two geared wheels
able to transmit the movement from the shaft of the motor to the hobbed rod which is
spinning against bearings and in contact with the filaments. These wheels can be easily
printed in ABS. In this design these will be with the following aspect:
Besides all the properties, here turns up an important question: Will the torque of
the motor or the transmission ratio be enough to move the filaments properly?
It is possible to check that the transmission ratio between each other gear is:
Zଵ 11
= = 0.28205
Zଶ 39
Chapter 7. Extruder and filament rolls 125
In this case it could be necessary to use a more powerful motor, but after some
design iterations and considering that a reduction by gears is going to be used, the
decision is to maintain the Nema 17. This decision is based on the volume of filament
which has to be moved, which is succinctly calculated as:
Considering a radius of 0.875 mm, the design is using a Nema 17 which has an
accuracy of 1.8 degrees each step. By the transmission ratio it means:
degrees
1.8 ∗ 0.28205 = 0.50769
step
Assuming an average radius of 4 mm on the part of the hobbed rod where the
filament contacts and adding the radius of the filament it is possible to assume a linear
movement of:
݉݉
2ߨ = ݎ2ߨ ∗ 4.875 = 30.631
݊ݎݑݐ
30.631 ݉݉
∗ 0.50769 = 0.0432
360 ݁ݐݏ
Now it is known the length that the filament should move each step.
Knowing that there are four filaments with a circular section of 1.75 mm of
diameter it is possible to calculate now the volume of plastic moved by the motor each
step
ܸ݈݀ଵ = ݎߨ = ݈݀ܣଶ ݈݀
So now with all the data, substituting the differential of length for the linear
movement of each step, the volume that the motor moves each step is
ߩ = 1020 ݇݃/݉ଷ
1020
= ݏݏܽܯ ∗ 0.4156 = 4.239 ∗ 10ି ݇݃/ = ݁ݐݏ4.239 ∗ 10ିସ ݃/݁ݐݏ
1000000000
Chapter 7. Extruder and filament rolls 126
One important restriction for printing speed, apart from the aforementioned like
moving masses or accuracy, is the amount of filament that the extruder can move
through the nozzle hole. Assuming a nozzle of 0.5 mm diameter and with all the previous
data:
is the volume extruded considering the four filaments. Each one has to go through
a nozzle of 0.5 mm of diameter:
0.4156
= 0.529 ݉݉/݁ݐݏ
4 ∗ ߨ ∗ 0.25ଶ
Assuming a maximum speed of 300 rpm for the motor:
ݏ݁ݐݏ
1000 ∗ 0.28205 = 282.05
ݏ
This means that the maximum extrusion speed per nozzle is:
݉݉
0.529 ∗ 282.05 = 149.25
ݏ
Also the extruder should be placed and designed considering the orientation and
position of the filament rolls, even more in this case where there are four different
filaments.
Chapter 7. Extruder and filament rolls 127
Here comes a small chart to summarize the main points and solutions of the
design of the extruder
From the articles and conditions of the desired design of the printer, it needs a
heated bed. Taking into account the aforementioned problems of heated bed with
dilatations and maximum size, four interconnected heated bed were the final decision. It
means that some structure to joint and hold the four independent heated beds is needed.
In other words, the two main parts are:
As said in the point 4.2, the best choice is to buy a standardized heated bed
instead of creating one. In this case the selected is: see bill of materials, item num. 23.
For the heated beds connector starts a small design. The main requirements are
the ability of holding the heated bed and to connect between each other and the base. In
the decided design the bed are static so there is no need for any kinematic structure, but
anyways it would be a good idea to keep in mind a possible connection to a profiled rail.
Also, in this part it is really important the conduction of the different materials.
Since the bed is heated, there will be dilatations and thermal losses. These losses should
be minimized with a good design.
However a good criterion for this part is, like always, try to make it easy to build,
easy to assembly and also as lighter as possible.
c) At this point, the design tries to reduce the mass of the piece, but of course
considering the minimal requirements of stiffness. However, this part is going
to be placed over the main base of the printer, so buckling is not a problem.
Chapter 8. Heated bed 129
d) As mentioned, the idea is to connect four heated beds, so for that the
connector has to be a big structure. Since it is printed, no structure can be
bigger than the size of the typical heated bed. That means one thing:
connector will be made of two or more parts.
e) Knowing that, the design is divided into parts and prepared for connection.
Finally, the joint between different holders is made by using a simple M6 bolt.
f) This joint it is not strictly necessary for the operating condition of the printer
and it could be skipped over, because during the assembly you could just
attach each bed supporter directly to the base; but on the other hand it has an
advantage: By this connection, the distance and relative position between
each bed is always the same, so there is no need for extra calibration. It also is
based on the idea of a possible modular design, where you could attach even
more heated beds if it is necessary.
g) A hole on each corner will allow the assembly with the beds and the base. For
this, a standardized M6 bolt is enough.
This is one of the most important parts of this project because it really sets the
difference with other 3D printers. At the moment that the decision of using one moving
header, able to hold four nozzles, was taken, the basic idea of this part was set.
The second main point of this part has been also mentioned before: vibrations.
With these two main points in mind here comes several design decisions:
As said, the linear distribution of the nozzles on the X coordinate could be less
space efficiency but provides a really open workspace. On this printer the comfort of this
open workspace is more valued than only the space efficiency because it is one of the
main competitive advantages. This makes the requirement of a big nozzles holder.
300 ∗ 4 = 1200 mm
for the printing space is needed. This could be reached by a nozzles holder made of a
bought material and assembled, but continuing with the idea of make the printer as much
self-replicant as possible; and like it happened with the heated bed connector, the
decision is to make it by assembling two or more ABS pieces.
After all, and once the assembly started, the design was rethought again to reduce
even more the weight, so unnecessary parts were removed. Finally after the mechanical
testing (see point 9.2.4) the decision was to change the material into aluminum to reduce
the deformation.
Chapter 9. Header and nozzles holder 133
During the former design process it has been possible to see that this is an
important part of the printer. Even more, is the one which is in care about holding the
nozzle. This nozzle has to have really accurate movements so no big vibrations are
allowed into the header. Furthermore nozzles are made of brass and other relatively
heavy materials which could be an extra reason for buckling. Also the design is trying to
do the header as lighter as possible, so playing with these limits are dangerous. For that
here come some mechanical checking made by SolidWorks.
This is the first mechanical calculation, so the whole process will be fully detailed.
For next calculations these explanations will be omitted. Anyways, it is possible to find all
the information, properly detailed in the annex of Mechanical calculations.
Based on the calculated weight of the nozzles the main force to input should be
the gravity. Also, it is important to remember that the printer will be on movement, so
there will be some accelerations. These accelerations will also act as forces, in this case
especially when the printer moves into Z coordinate. Other accelerations can be ignored
now.
Assuming 80 grams of weight for each nozzle and applying a factor of 1.25 for the
acceleration, the input for each one will be
100
∗ 9.8 = 0.98 ܰ
1000
So the input will be 1N per nozzle.
Furthermore it is important to mention than the critical deflection for the nozzle
into the vertical coordinate will be 0.05 mm. All values over that will mean a non
functional printer.
For other pieces this deformation could be considered also as the maximum unless
certain considerations change it on each case.
Chapter 9. Header and nozzles holder 135
Here the program output two important results: Von Mises´s tension and the
Deformation.
It is possible to check that the tensions are not critical, but the deflection is about
0.72 mm. This deflection exceeds the maximum established, so the design must be
optimized.
For that, here comes an iteration of these calculations. The design of the header
will be enlighted a little bit more, especially around the central part and then it will be
checked again. In addition, it is necessary to include some other modifications to reduce
the deformation and increase the stiffness of the arm.
After trying some designs, specially modifying the cross section and increasing the
angle of the support bar, the results of the calculations were almost the same: only a little
reduction of the deflection, but not enough to be lower than 0.05 mm. Also the ideas of
adding an extra piece or a steel rod inside were discarded.
The final solution was to change the material of this header. The decision after
several considerations was to use an aluminum alloy. Of course this means an important
cost increase and also the need of manufacture this piece somehow, with different
techniques. With this material, the results were:
It is possible to check now that the deformation is only 0.02 mm in the worst case.
With these results it is possible to conclude that the design is stiff enough and no critical
vibrations will happened.
Chapter 9. Header and nozzles holder 137
Following the same way of thinking that with other pieces, here comes a small
summary of the design process
As seen, there are a lot of possible improvements on the field of nozzles, but these
are not the main goal of this project. Furthermore this design does not have special
requirements for nozzles apart from good stability and to be much lighter as possible.
Besides that no extra fans, insulator or special holders are going to be used.
The nozzle for this design can be bought to some supplier via internet as for
example the one which is shown on point 19 of the bill of materials, and for the CAD
design a regular model of brass is going to be used.
Only one curiosity to mention is that in this design the nozzles are interchangeable
between each other (for example in the case of using different colors, if the nozzle has
some blurs) and also are easy to replace. For that, those are going to be connected by
four bolts to each head of the nozzle holder.
The design is also made to leave a small gap between the nozzle and the nozzle
holder to avoid thermal distortion.
There is a huge market of profiled rails, with different kinds of sizes and materials.
These systems are becoming more popular because the flexibility and reliability that they
provide. Also nowadays some people like to build their own designs, which is really easy
with all the equipment that these enterprises supply. The following picture gives some of
the typical examples of the main brands.
As shown, all these brands provides a standardized sizes and also all the related
equipment as connectors, carriages, etc.
For this entire project the selected profile is from the brand 80/20 Inc. and in
particular the type “Metric 25 series”. The decision of this brand is mainly made because
in their website they provide a lot of services for costumer, as CAD models, video
explanation and also a program for calculating buckling and vibrations. Also the prices
seems to be quite good comparing with other brands.
In the following pages the design of the movement into the different coordinates
is explained. Each coordinate has different properties as for example requirements in
accuracy or torque. In this project the X coordinate is the lightest (the motor does not
have to carry with other profiled rails, only with the header) but on the other hand it has
to move precisely.
Once the general ideas of the kinematics and disposition of the pieces have been
decided, it is time to go deeply to the study of certain details. However, once the
movement is a requirement, the different pieces become harder to design.
It is clear that the movement is based on profiled rails and carriages, but how to
place these carriages? How to connect one rail with another? How to hold the whole
structure?
First of all it is possible to assume a length of 400 mm. The heated bed is 350 mm
width so this should be the minimum length, but also some extra space is needed in order
to place the stepper motor, the joints, and extra pieces. However, the idea is to try to
minimize this length which translates into a mass reduction, but finally and with some
iterations on the CAD design, the selected length is
500 mm.
On the bottom side of the rail, the carriage with the nozzles holder is going to be
attached. This carriage can move over almost all the rail until certain limits on the sides
(made by t-nuts drilled on the rail and some endings).
For this coordinate the carriage is made by a pair of pieces, with two wheels each
one and connected by a piece which design is standardized by 80/20 (but in this case is
going to be printed, so it is lighter and cheaper). It could be possible to use more wheels
or even two different carriages connected somehow (as for example the alternative
explained on chapter 9.1), but those ideas do not provide any significative advantage
which could worth the extra requirement of pieces.
Chapter 11. Profiled rails 144
The formerly showed fixation should be placed properly. Probably the first idea is
just to put it in the middle of the X-rail, but the best option is to place it a little bit off
center in order to play with the mass center of the piece. It is possible to use SolidWorks
for these calculations, but indeed the easiest way to do it is when the printer is
assembled. This piece is attached to the rail with bolts and t-nuts that can slide over it so
a proper balance can be reached.
After the last paragraph now comes the mechanical test for the carriage
connector. This piece has been shown in Fig. 151 Profiled rail connector, and mainly the
test focus in showing that it will not bend so much. The input weight will be the
calculated for the set header plus nozzles and increased for security margin.
ଶ
ଵ
∗ 9.8 = 25.48 ܰ
The design is based on a belt system for the movement, so there will not be any
extra change on that, but now it is important to think where to place this belt and the
related stepper motor. There are different ways and
positions.
The final decision is to place the stepper motor on the side of the rail. This means
an important weight on the end of the rail which is bad for deflection, but on the other
hand with this disposition the rail is shorter. Furthermore the transmission of the
movement is made by a simple belt connected with the nozzles holder.
For the explained movement, there will be a bearing with a screw to tension the
belt, mainly moving the bearing over the coordinate and also tightening up the belt to the
header. Here again could be different options and orientations of the belt. Finally, a
printed part made of ABS with the mentioned bearing and placed on the opposite side of
the profiled rail is the chosen option. This piece is easy to assemble and with some
adjustment can be properly placed and hold the necessary tension of the belt.
However, after some design overview is possible to check that piece, which has to
hold the stepper motor could suffer critical tensions or deformations. For that, here again
comes a mechanical test.
This is the analysis of the motor holder. Stepper motor is hanged by this piece, so
the first force will be the gravity affecting to the motor. Also, this piece has to be in a little
Chapter 11. Profiled rails 146
tension with the belt, so this will be the second force, in the X coordinate. The detailed
calculation is in the annex.
The results are really good. About the security factor there is no problem (this is
the first time than it could be a real problem, because all the forces are affecting and
concentrated in only one point), but indeed the result is a factor of 17 in the worst case.
On the other hand the deformation is higher than in other pieces, about 0.2 mm.
This deformation do not affect directly to the position of the nozzle, so it could be higher.
This value of 0.2 mm is admissible.
Stepper motor
About this axis here come several explanations and details about the design, but
keeping in mind that all the basics are the same that in the X-coordinate.
Following the same argument that with the X coordinate, it is possible to assume a
length of 600 mm which provides enough space for the movement of the carriage and
also it is the shortest trying to reduce unnecessary masses.
In this case the movement it is also reflected into a carriage sliding over the rail.
This carriage is build by two standardized pair of wheels and also connected by a printed
part.
As happened with X coordinate, here again some top ends will be placed.
Like in X coordinate, this profiled rail has to be connected somehow to another rail
in order to move over Z-coordinate. In this case the design became a little bit harder
comparing with the previous one, because the different orientations of the rails made it
difficult to fit. As mentioned before, the design tries to give the maximum movement with
the smallest and shortest rail, so these connections should be well designed in order to
use the minimum space over the rail.
First of all, the design were made for connect only the Y-coordinate rail with the Z-
coordinate rail by a drilled piece which is joined to a carriage that slides over the Z-rail.
But after that, it was possible to see that the design was not stable enough. This problem
is going to be show in later points of this project by proper calculations, but however, the
final decision was to attach an extra rail for Z-coordinate on the other side.
Also, once again it is important to fix the piece which connects both profiles in a
proper place in order to get a good balance and also seize to the maximum the usability
of the rail.
Chapter 11. Profiled rails 151
Stepper motor: In this case the motor can be placed directly over the sliding rail of
the profile because two main reasons:
The connection with the Z-coordinate uses some space of the rail in one side, this
means that the carriage cannot roll over it, so it can be used without consequences over
the other face. A similar thing happens on the other extreme of the rail. The nozzles
holder is a little bit eccentric and projecting so the carriage cannot roll until the edge of
the rail or otherwise it could hit the Z-coordinate rail.
About the orientation of the shaft, in this case it can be placed vertically using the
same belt system that with X axis. The attachment of the belt to the carriage is made by
to printed parts connected also to the piece which holds the X-axis.
Apart from the Z axis system, which will be explained in the next chapter, it is
possible to remind how is the general design of the printer going. For that, here is a
second overview of the CAD model fully assembled.
Just knowing now some of the weights as for example the header or nozzle, and
realizing that all these masses are hanging from the Y axis arm, appears the idea of
instability. Probably the whole header system is too heavy and the arm will bend.
there will be a mechanical simulation to check if the displacement of the cantilever is high
or low.
Basically, the idea is to simulate the worst situation. For that, the fixations will be
totally placed in one side of the rail and all the force, equivalent to the action of gravity
will be on the other side. It would be a good approximation because in the real case the
forces are near one to each other but on the other hand other efforts appear.
Like other mechanical tests, this is explained deeply into the annex, but however,
the result is a deformation higher than 0.05 mm. To solve that, and avoid any other
vibrations, the decision is to add an extra column into the opposite side. This eliminates
the cantilever.
Chapter 11. Profiled rails 153
The motion over this coordinate has been an interesting point during the whole
design. As mentioned in the Part 1 where the main stages and aspects of the design were
defined, especially the use of screw driving, instead of other kind of system with belts or
winches. But when the real implementation of the ideas comes, it appears a lot of
unexpected issues: vibrations, buckling, difficulties placing the stepper motor, etc.
For this problem the solution were to switch the orientation of the nut and his
holder. In this position it will not fall and also will work while the arm goes up.
A good solution for this is just similar with the former case. If the stepper motor is
on the top of the Z profiled rail the whole arm is suspended, affecting only with tension
and no compression to the screw. This means no buckling problem.
The solution adopted in the former paragraph has a drawback. Now it is necessary
to place the stepper motor on the top, which in this 3D printer could be a problem
because there are as less as possible upper frames or places where to join it. In other
words, now a new piece is required for that.
After several iterations, the design finally achieves an assumable low deflection, as
shown in the next figure.
It is possible to see that the deformation is higher than 0.05 mm but on the other
hand the screw will hold part of this deflection, so it is assumable. For further details see
the annex.
About the fixation of the base, at the beginning the decision was to use the same
piece which was used for connecting the arms to the carriages (See point 11.2.3 Carriage
system and connection)
After the first implementation of this piece into the CAD design it was quite easy
to check that it was not stiff enough.
To solve this, a lot of possibilities were considered but finally, the decision was to
use a standardized piece of 80/20 Inc. which fits properly with the profiled rail and is
totally designed for a good fixation. Also this piece is cheap, and with a simple design.
Chapter 11. Profiled rails 158
After adding an extra column, the disposition of the stepper motor should be
reconsidered and also the chance of installing a gear for reduction or a second stepper
motor over the other column in other to get enough torque. Finally this last option is the
chosen one because it provides a more balanced strength distribution and also it gives a
better security factor.
Screw driver
properly placed
After the complete definition of the printer by the CAD model, here follows a
succinct analysis of the possible vibrations, deflection and buckling. There have been a
short analysis for each interesting or critical part, but however as iteration, here comes as
an extra study. Basically, this chapter is only focused into the profiled rails, especially
about the Y one.
For studying this, different software called “TechToolkit” is going to be used. This
software is provided by the company 80/20 Inc. itself. It can be found in their webpage
and it is a powerful tool for ensure that the whole structure will not break or collapse
[39].
Mainly this chapter of the project can be considered as an example, for future
works and to know how to check the results. Also this last mechanical testing is apart
from the previous made because it will be considered like a security check, instead of
being part of the design process itself. Of course, both tests are totally related between
each other and only with good profiled rails the printer cannot work if other parts break.
As shown in the Fig. 180 80/20 Toolbox, with this program, by the input of several
data as for example length or loaded mass it gives calculations for deflection and other
properties.
The best way for get the more precise results is using all the existing tools in this
project. In other words, going back to the 3D CAD design, and setting properly, piece by
piece the material, SolidWorks will give the mass of each part. Indeed, it provides, when
all the data is correct, a useful bill of materials and pieces.
• First of all, designer should select the type of profile which is studying. In
this case, Metric, and especially 25-2550.
• After this, select the deflection method by considering the way that
fixtures are working: In this case, two fixed ends.
• Set the profile length: 600 mm
• The idea of this experiment is calculate the maximum load that this profile
could support without deflect more than 0.05 mm.
• The value to check is the “Deflection X” because of the disposition of the
rail.
• For that, some values will be introduced into the “Profile Load” until reach
0.05 mm on “Deflection X” for centered load.
• The maximum load is 38 Kg
PART V: CONCLUSIONS
Chapter 13. Results
The result of this project could be summarized as an almost ready to work 3D
printer. Of course, knowing that this project is academically orientated, there are some
aspects of the design that have not been completely developed, in order to embrace a
wide range of solutions.
The project starts with a clear objective: Design and build up a 3D printer which
has to be able to create several objects simultaneously. For that, at the PART I is possible
to find a good background about 3D printers, touching themes like history, the current
market and advantages or disadvantages of 3D printer.
After this, in the PART II there is a general overview of a 3D printer. This helps to
settle all the bases for the new design concepts. With these bases, and knowing the most
typical issues and possible improvements during the design of a 3D printer, PART III
concludes showing the two most interesting concept designs to study.
Finally, in PART IV, after choosing a design, this one is fully developed, by the CAD
model and explained with detail. This part is the one which really took almost all the time
of the project. To reach a detailed model and with all the kinematics working properly is
sometimes hard and time consuming. On the other hand, the study of this model gives
really accurate results and is a powerful tool for all designer because shows the real
problems.
Furthermore, this project is not focused into an exact result as for example a
calculation. The project is the whole design process and all the decisions and
discernment which have conducted to the final model, and of course also the model
itself.
Besides, all of this means that is really hard to sum up only explaining by text,
because one of the most important parts, as said is the whole CAD design, which is made
to work over it and play with the movements and the assembly of different pieces.
Anyways, in order to explain here into the best possible manner the model, during the
whole summary of the project there are several pictures and sketches.
Also, apart from the aforementioned ideas, and also focused into the academic
orientation of this project, this document attach several annexes with different
information, as the detailed mechanical analysis, the definition of the different parts from
catalogues or the plans of some interesting parts. Especially this last annex is remarkable
because it is the only way to transmit properly how the designed pieces are without the
use of the CAD model.
Chapter 13. Results 164
In addition, and to sum up the next figure could be presented as the final result of
the CAD model. However, the next two chapters resume the technical contributions of
the project and finally some ideas for future works.
a) The complete CAD model. It allows future designs to begin from this model
instead of starting from zero. In addition, the CAD model includes the use
of all the tools of SolidWorks and other related CAD software.
b) The mechanical analysis of different parts. These analyses provide a good
base to ensure that the design is reliable.
c) The definition of the critical parts. There are parts which have more
importance for the structural design and some other are important just for
the kinematics but the efforts that these have to support are not relevant
d) Comparison tables with factors. These tables could be used for other
designer to compare similar designs but with different detailed properties.
e) Background and analysis of different parts. These chapters are a good
summary for everybody who wants a general and easy overview of 3D
printing technologies.
f) The main ideas of the disposition of the nozzles.
g) The different issues found during the definition of kinematics and all the
related solutions.
h) The cost and weight calculations, useful for anyone who wants to define
the basics of new models and decide between different distributions.
i) The bill of materials, which in only a few pages summarize all the parts of
the printer, specifying the material, price and in any cases giving some
references.
Chapter 14. Technical contributions of the project 167
One good example for future work is the design presented on Chapter 5.1
PROPOSED DESIGN 1, mainly focused into a modular system. This basic idea could be
more than enough to develop a complete project like this.
In addition there are some other aspects of this project which could be farther
developed:
Num. Name Quantity Belong to Material Weight (g) Price (per unit) (€) Reference
35 ISO 4762 M6 x 10 --- 10N 25 Mix Stainles Steel
36 ISO 4762 M6 x 16 --- 16N 6 Mix Stainles Steel
37 ISO 4762 M8 x 45 --- 28N 1 Mix Stainles Steel
38 ISO 4762 M6 x 50 --- 50N 2 Mix Stainles Steel
39 ISO 4762 M6 x 50 --- 24N 6 Mix Stainles Steel
40 ISO 4762 M6 x 40 --- 24N 16 Mix Stainles Steel
41 ISO 4762 M6 x 60 --- 60N 5 Mix Stainles Steel
42 ISO 4762 M6 x 25 --- 25N 2 Mix Stainles Steel
43 ISO 4762 M6 x 12 --- 12N 12 Mix Stainles Steel
44 ISO 4762 M4 x 6 --- 6N 7 Mix Stainles Steel
45 ISO 4762 M3 x 5 --- 5N 16 Mix Stainles Steel
46 ISO 4762 M8 x 55 --- 55N 3 Mix Stainles Steel
47 ISO 4762 M2.5 x 4 --- 4N 4 Mix Stainles Steel
48 ISO 4762 M5 x 50 --- 50N 16 Mix Stainles Steel
49 Connector 1 Profiled Rails Stainles Steel 54,98 80/20
50 Motor Holder 1 Motor ABS 28,86
51 Hexagon Nut ISO - 4034 - M6 - N 1 Mix Stainles Steel
52 Hexagon Nut ISO - 4034 - M8 - N 1 Mix Stainles Steel
53 8020-25-4111_FORx_INVERSE 1 Motor ABS2 28,7 80/20
54 Gear Belt Support 1 Motor ABS 18,3
55 Connector 1 Profiled Rails ABS 15,21 80/20
56 Bed_connector 1 Heated Bed ABS 2072,3
57 Stepper motor drive 4 Motor - 29,75 15 http://goo.gl/GQcht
58 ExtruderaBlock_contra 1 Extruder ABS 30,13
59 Geared Wheel 1 1 Extruder ABS 14,519
60 Geared Wheel 2 1 Extruder ABS 1,0664
Anexo I: Lista de materiales 170
Num. Name Quantity Belong to Material Weight (g) Price (per unit) (€) Reference
61 ExtruderaBlock 1 Extruder ABS 34,12
62 T-nut-Square.14124 11 Mix
63 beltjoint 2 Motor ABS 1,34
64 Belt1 2 Motor BUTYL 20,87 19 http://goo.gl/tYjgu
65 Belt2 1 Motor BUTYL 20,28 19 http://goo.gl/tYjgu
66 Washer ISO 7089 - 8 7 Mix Stainles Steel
67 DIN 914 - M2 x 3-N 1 Mix Stainles Steel
68 motorhanger 1 Motor ABS 35,52
69 Spool Holder 4 Extruder ABS 1030,4 10 http://goo.gl/yAaR4
70 ScrewReceptor 1 Motor ABS 7,2
71 ATX power supply 1 Motor - 1,8606 60 http://goo.gl/Orw5A
72 Controller Board 1 Motor - 16,91 170 http://goo.gl/ZVbBH
73 Base 1 1 Profiled Rails - 689,46
74 Top End 3 Profiled Rails BUTYL 6,77
75 Base 2 1 Profiled Rails 697,83 697,83
76 ABS Roll 4 rolls Extruder http://goo.gl/IIDbA
http://goo.gl/2VqXc
Table. 39 Bill of materials
Anexo II: Referencias 171
• Header 1
• Header 2
• X-Y Connector
• X motor holder
• Y profiled
• Z motor Holder 1
• Z motor holder 2
• Y Rail by toolbox
Simulation of
NozzlesConnector
Date: 17. April 2013
Designer: Rafael Bobo Garcia
Study name: SimulationXpress Study
Analysis type: Static
Table of Contents
Description .......................................... 1
Assumptions ......................................... 2
Model Information .................................. 2
Material Properties ................................. 4
Loads and Fixtures ................................. 4
Mesh Information ................................... 5
Description Study Results ........................................ 7
Deep analysis of the Header or Nozzle-connector. Conclusion ........................................... 9
This document has been partially created by the automatic
report system of Solid Works
Assumptions
Model Analyzed
Original Model
Model Information
Material Properties
Model Reference Properties Components
Name: ABS SolidBody
Model type: Linear Elastic Isotropic 8(Redondeo6)(NozzlesConnec
Default failure Unknown tor)
criterion:
Tensile strength: 3e+007 N/m^2
Fixed-1
Mesh Information
Mesh type Solid Mesh
Mesher Used: Standard mesh
Automatic Transition: Off
Include Mesh Auto Loops: Off
Jacobian points 4 Points
Element Size 8.43772 mm
Tolerance 0.421886 mm
Mesh Quality High
Study Results
NozzlesConnector-SimulationXpress Study-Stress-Stress
NozzlesConnector-SimulationXpress Study-Displacement-Displacement
Name Type
Deformation Deformed Shape
NozzlesConnector-SimulationXpress Study-Displacement-Deformation
Conclusion
The deformation exceeds the maximum allowed. The design must be optimized.
Table of Con
ntents
Description ........................................... 1
Assumptions .......................................... 2
Material Propertiies ................................. 2
Loads and Fixture
es ................................. 3
Mesh Information
n ................................... 4
Study Results ......................................... 6
Description Conclusion ............................................ 9
Second analysis of the header or nozzzles connector. In this
case the main point is the new material: Aluminum.
Assumptions
Modell Analyzed
Original Model
Material Properties
Model Reference Properties Components
Name: 1060 Alloy SolidBody
Model type: Linear Elastic Isotropic 3(Redondeo6)(NozzlesConnec
Default failure Unknown tor)
criterion:
Yield strength: 2.75742e+007 N/m^2
Tensile strength: 6.89356e+007 N/m^2
Fixed-1
Force-1
Mesh Information
Mesh type Solid Mesh
Mesher Used: Standard mesh
Automatic Transition: Off
Include Mesh Auto Loops: Off
Jacobian points 4 Points
Element Size 8.43772 mm
Tolerance 0.421886 mm
Mesh Quality High
Study Results
NozzlessConnector-SimulationXpress Study-Stress-Stress
NozzlesConnecttor-SimulationXpress Study-Displacement-Displaccement
Name Type
Deformation Defformed Shape
NozzlesConnec
ctor-SimulationXpress Study-Displacement-Deform
mation
Conclusion
With this new material the deformattion is really low and of course under 0.05 mm so the header is now fully
functional.
Table of Contents
Descripción .......................................... 1
Información de modelo ............................ 2
Propiedades de material .......................... 3
Cargas y sujeciones ................................ 3
Información de malla ..............................4
Resultados del estudio ............................. 6
Descripción Conclusión ........................................... 9
Study of the piece which connects the X arm to the Y arm
Cargas y sujeciones
Nombre de
Imagen de sujeción Detalles de sujeción
sujeción
Entidades: 3 cara(s)
Tipo: Geometría fija
Fijo-1
Nombre de
Cargar imagen Detalles de carga
carga
Entidades: 1 cara(s)
Tipo: Aplicar fuerza normal
Valor: -25.48 N
Fuerza-1
8020-25-4111-DEFAULT-SimulationXpress Study-Tensiones-Stress
8020-25-4111-DEFAULT-SimulationXpress Study-Desplazamientos-Displacement
8020-25-4111-DEFAULT-SimulationXpress Study-Desplazamientos-Deformation
Conclusión
The displacement is really low, under 0.05 mm, so the piece is well designed.
Table of Contents
Descripción .......................................... 1
Información de modelo ............................ 2
Propiedades de material .......................... 3
Cargas y sujeciones ................................ 4
Información de malla .............................. 5
Resultados del estudio ............................. 7
Descripción Conclusión ......................................... 10
Simulación de las deformaciones sufridas por la pieza
encargada de mantener el motor de la coordenada X
Información de modelo
Propiedades de material
Referencia de modelo Propiedades Componentes
Nombre: ABS2 Sólido 1(Línea de
Tipo de modelo: Isotrópico elástico partición2)(8020-25-
lineal 4111_FORx_INVERSE)
Criterio de error Desconocido
predeterminado:
Límite elástico: 4.2e+007 N/m^2
Límite de tracción: 3e+007 N/m^2
Cargas y sujeciones
Nombre de
Imagen de sujeción Detalles de sujeción
sujeción
Entidades: 3 cara(s)
Tipo: Geometría fija
Fijo-1
Nombre de
Cargar imagen Detalles de carga
carga
Entidades: 1 cara(s), 1 plano(s)
Referencia: Front Plane
Tipo: Aplicar fuerza
Valores: ---, ---, -2 N
Fuerza-1
Fuerza-2
Información de malla
Tipo de malla Malla sólida
Mallador utilizado: Malla basada en curvatura
Puntos jacobianos 4 Puntos
Tamaño máximo de elemento 0 mm
Tamaño mínimo del elemento 0 mm
Calidad de malla Elementos cuadráticos de alto orden
8020-25-4111_FORx_INVERSE-SimulationXpress Study-Tensiones-Stress
8020-25-4111_FORx_INVERSE-SimulationXpress Study-Desplazamientos-Displacement
Nombre Tipo
Deformation Forma deformada
8020-25-4111_FORx_INVERSE-SimulationXpress Study-Desplazamientos-Deformation
Conclusión
Como se puede ver, no hay riesgo de rotura, pues en el punto más crítico, el factor de seguridad es de 16.
Por otro lado, los desplazamientos superan los 0.05 mm pero este desplazamiento no se traduce
directamente en una deformación sobre la posición del cabezal, sino que se ve amortiguado por la tensión
de la correa. En resumen, el resultado es aceptable.
Table of Contents
Description .......................................... 1
Model Information .................................. 2
Study Properties .................................... 3
Units .................................................. 3
Material Properties ................................. 4
Loads and Fixtures ................................. 5
Description Mesh Information ................................... 6
Simulation of the forces applieds to the Y coordinate arm in Sensor Details ....................................... 7
the worst postulation.
Resultant Forces .................................... 8
Study Results ........................................ 9
Conclusion ......................................... 12
Model Information
Study Properties
Study name Study 1
Analysis type Static
Mesh type Solid Mesh
Thermal Effect: On
Thermal option Include temperature loads
Zero strain temperature 298 Kelvin
Include fluid pressure effects from SolidWorks Off
Flow Simulation
Solver type FFEPlus
Inplane Effect: Off
Soft Spring: Off
Inertial Relief: Off
Incompatible bonding options Automatic
Large displacement Off
Compute free body forces On
Friction Off
Use Adaptive Method: Off
Result folder SolidWorks document
(C:\Users\g0404599\Downloads\3Dprinter_20130417)
Units
Unit system: SI (MKS)
Length/Displacement mm
Temperature Kelvin
Angular velocity Rad/sec
Pressure/Stress N/m^2
Material Properties
Model Reference Properties Components
Name: Alloy Steel SolidBody
Model type: Linear Elastic Isotropic 1(Extrude1)(Railz_Ycoordinat
Default failure Max von Mises Stress e)
criterion:
Yield strength: 6.20422e+008 N/m^2
Tensile strength: 7.23826e+008 N/m^2
Elastic modulus: 2.1e+011 N/m^2
Poisson's ratio: 0.28
Mass density: 7700 kg/m^3
Shear modulus: 7.9e+010 N/m^2
Thermal expansion 1.3e-005 /Kelvin
coefficient:
Curve Data:N/A
Resultant Forces
Components X Y Z Resultant
Reaction force(N) 30.0023 0.00104874 0.00357592 30.0023
Reaction Moment(N-m) 0 0 0 0
Mesh Information
Mesh type Solid Mesh
Mesher Used: Curvature based mesh
Jacobian points 4 Points
Maximum element size 19.3428 mm
Minimum element size 3.86856 mm
Mesh Quality High
Sensor Details
Resultant Forces
Reaction Forces
Selection set Units Sum X Sum Y Sum Z Resultant
Entire Model N 30.0023 0.00104874 0.00357592 30.0023
Reaction Moments
Selection set Units Sum X Sum Y Sum Z Resultant
Entire Model N-m 0 0 0 0
Study Results
Railz_Ycoordinate-Study 1-Stress-Stress1
Railz_Ycoordinate-Study 1-Displacement-Displacement1
Railz_Ycoordinate-Study 1-Strain-Strain1
Name Type
Displacement1{1} Deformed Shape
Railz_Ycoordinate-Study 1-Displacement-Displacement1{1}
Conclusion
This could be considered as the worst situation, because al the force is applied in one side and the fixtures
are all in the opposite side which is not the real situation.
The deformation exceeds the limit so this case could be the border of the design
Tabla de contenidos
Descripción .......................................... 1
Información de modelo ............................ 2
Propiedades de material .......................... 3
Cargas y sujeciones ................................ 4
Información de malla .............................. 5
Resultados del estudio ............................. 7
Descripción Conclusión ......................................... 10
Primer análisis de la pieza encargada de sustentar el motor
de la coordenada Z
Información de modelo
Propiedades de material
Referencia de modelo Propiedades Componentes
Nombre: ABS2 Sólido 1(Línea de
Tipo de modelo: Isotrópico elástico partición1)(motorhanger)
lineal
Criterio de error Tensión máxima de
predeterminado: von Mises
Límite elástico: 4.2e+007 N/m^2
Límite de tracción: 3e+007 N/m^2
Cargas y sujeciones
Nombre de
Imagen de sujeción Detalles de sujeción
sujeción
Entidades: 4 cara(s)
Tipo: Geometría fija
Fijo-3
Nombre de
Cargar imagen Detalles de carga
carga
Entidades: 1 cara(s)
Tipo: Aplicar fuerza normal
Valor: -33.43 N
Fuerza-3
Información de malla
Tipo de malla Malla sólida
Mallador utilizado: Malla estándar
Transición automática: Desactivar
Incluir bucles automáticos de malla: Desactivar
Puntos jacobianos 4 Puntos
Tamaño de elementos 3.26657 mm
Tolerancia 0.163329 mm
Calidad de malla Elementos cuadráticos de alto orden
motorhanger-SimulationXpress Study-Tensiones-Stress
motorhanger-SimulationXpress Study-Desplazamientos-Displacement
Nombre Tipo
Deformation Forma deformada
motorhanger-SimulationXpress Study-Desplazamientos-Deformation
Conclusión
Aunque el factor de seguridad es alto y no hay riesgo de rotura, las deformaciones son demasiado elevadas,
por lo que la pieza debe ser optimizada.
Tabla de contenidos
Descripción .......................................... 1
Información de modelo ............................ 2
Propiedades de material .......................... 3
Cargas y sujeciones ................................ 4
Información de malla .............................. 5
Resultados del estudio ............................. 7
Descripción Conclusión ......................................... 10
Segundo diseño de la pieza que sustenta el motor para la
coordenada Z. Se han incrementado los grosores de algunas
paredes así como añadido ciertos nervios y estructuras de
soporte.
Información de modelo
Propiedades de material
Referencia de modelo Propiedades Componentes
Nombre: ABS2 Sólido 1(Línea de
Tipo de modelo: Isotrópico elástico partición4)(motorhanger)
lineal
Criterio de error Desconocido
predeterminado:
Límite elástico: 4.2e+007 N/m^2
Límite de tracción: 3e+007 N/m^2
Cargas y sujeciones
Nombre de
Imagen de sujeción Detalles de sujeción
sujeción
Entidades: 3 cara(s)
Tipo: Geometría fija
Fijo-1
Entidades: 5 cara(s)
Tipo: Geometría fija
Fijo-2
Nombre de
Cargar imagen Detalles de carga
carga
Entidades: 1 cara(s)
Tipo: Aplicar fuerza normal
Valor: -33.43 N
Fuerza-2
Información de malla
Tipo de malla Malla sólida
Mallador utilizado: Malla estándar
Transición automática: Desactivar
Incluir bucles automáticos de malla: Desactivar
Puntos jacobianos 4 Puntos
Tamaño de elementos 3.26657 mm
Tolerancia 0.163329 mm
Calidad de malla Elementos cuadráticos de alto orden
motorhanger-SimulationXpress Study-Tensiones-Stress
motorhanger-SimulationXpress Study-Desplazamientos-Displacement
Nombre Tipo
Deformation Forma deformada
motorhanger-SimulationXpress Study-Desplazamientos-Deformation
Conclusión
Como se puede ver el factor de seguridad es alto. Por otro lado la deformación alcanza y supera los 0.05
mm, pero es importante mencionar que este valor no se traduce en una deformación directa de la posición
del cabezal. La actuación extra del tornillo adosado al motor rigidiza la pieza de manera que esta
deformación se reduce notablemente, por lo que este valor es totalmente asumible.
2020
23,62 In. 10200000 Lbs. / Sq. In. 0,5509 In.^4 0,5509 In.^4
600 mm 70326,5 N/mm² 22,930189 cm^4 22,930189 cm^4
Deflection X Deflection Y
Deflection X Deflection Y
Deflection X Deflection Y
Copyright© 2010, 80/20® Inc., all rights reserved. 80/20® Inc. S 400 E Columbia City, IN 46725 Ph: 260-248-8030 www.8020.net
UNIVERSIDAD POLITÉCNICA DE MADRID
CÁTEDRA DE PROYECTOS
PRESUPUESTO
V.I INTRODUCCIÓN
En éste anexo se realiza una valoración del coste incurrido en el proyecto. Al ser un
proyecto principalmente teórico, sin haber llegado a realizar un prototipo final de la
máquina, los costes estarán básicamente divididos entre las diferentes fases del proyecto,
desde estudios previos y elaboración del modelo CAD hasta la escritura de la memoria y su
depuración. A su vez, dichas fases constarán de gastos englobados en dos familias:
dedicación temporal de autor del proyecto y el uso de equipos informáticos.
Extracto del presupuesto de los conceptos relacionados con los estudios previos al
desarrollo técnico del modelo de la impresora.
Parte del presupuesto relacionada con la creación y el desarrollo del modelo CAD
completo de la impresora 3D.
V.5 DESGLOSE
Presupuesto resultante en las tres fases principales así como desglosado por el tipo
de concepto (horas o equipos).
V.6 PROTOTIPO
V.7 COMENTARIOS
El coste de las horas de trabajo han sido estimadas con base al sueldo de ingeniero
recién incorporado a una empresa de Nuevas Tecnologías, según convenio unos 1500 €/mes
con un trabajo de 8 horas diarias en 14 pagas y 1 mes de vacaciones. Según convenio la hora
es valorada a 8'75 €/hora.
Con ello se concluye que el coste del prototipo, en caso de fabricarse sería de 1403 €
(mil cuatrocientos tres) y el coste del proyecto asciende a la cantidad de 12538,25 € (doce
mil quinientos treinta y ocho con veinticinco).