Journal of Physics: Conference Series

PAPER • OPEN ACCESS

Design of a high precision mechanical linear system for the study of the
variables involved in the gas metal arc welding process
To cite this article: J L Lázaro Plata et al 2020 J. Phys.: Conf. Ser. 1587 012034

View the article online for updates and enhancements.

This content was downloaded from IP address 190.90.37.4 on 05/08/2020 at 17:17

6th International Week of Science, Technology and Innovation (6th IWSTI) IOP Publishing
Journal of Physics: Conference Series 1587 (2020) 012034 doi:10.1088/1742-6596/1587/1/012034

Design of a high precision mechanical linear system for the

study of the variables involved in the gas metal arc welding
process

J L Lázaro Plata1, C S Sánchez Rincón1, and F J Regino Ubarnes1

1
Grupo de Investigación en Ingenierías Aplicadas para la Innovación, Gestión y
Desarrollo, Universidad Francisco de Paula Santander, Seccional Ocaña, Colombia

E-mail: jllazarop@ufpso.edu.co, cssanchezri@ufpso.edu.co

Abstract. The gas metal arc welding process is studied because of its high productivity and low
cost. One of the drawbacks of this process is achieving repeatability of the welding seams. This
article shows the design of a linear mechanical system that provided a high precision in the
trajectory of the base platform. Three important factors were investigated such as platform speed,
the main stresses present and the manufacturing material. A descriptive type methodology was
used which consisted of conducting the study as a discrete particle system. The optimum
conditions for the efficiency of its operation were a linear velocity of 1.44 mm/s, maximum shear
stress in the power screw of 283.57 kPa, which was calculated by means of static analysis to
determine as the material of medium carbon steel of type AISI 1040, which due to its ductility,
facilitated the machining of the power screw. This provided a mechanical efficiency of 30.9%.
The kinematic calculations of the system were made with standardized elements found on the
market.

1. Introduction
Gas metal arc welding (GMAW) is a very complex process that uses many scientific and engineering
disciplines to study techniques that can lead to the best possible mechanical properties of the resulting
part. The GMAW process is widely used because of its low cost and productivity, and other processes.
Despite these advantages, the quality obtained by human work in a repetitive and prolonged process
tends to suffer variations [1], which requires a high precision inspection to achieve the desired physical
and mechanical properties. Today, the use of automated welding, as is the case with industrial robots, is
one of the main signs of contemporary welding [2].
A truly mechanical welding frame should have three main parts: sensors, which identify the status
of the welding procedure; a process model, which provides the relationship between the welding factors
and the geometry of the weld seam; a control frame, which evaluates the sensor information and changes
the welding procedure factors using the relationship in the process model [3-6].
The GMAW process is influenced by some variables, such as: welding current, arc voltage, welding
speed, electrode extension (stick-out), welding torch inclination, joint type, electrode diameter, gas
protection and wire feed speed, [7]. It is important to emphasize that knowledge and control of these
variables are essential to obtain satisfactory quality welds. These variables are not completely
independent and changes in one of them require changes in one or more of the others to produce the
desired results [8]. One of the elementary components for the development of such processes is the

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution
of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Published under licence by IOP Publishing Ltd 1
6th International Week of Science, Technology and Innovation (6th IWSTI) IOP Publishing
Journal of Physics: Conference Series 1587 (2020) 012034 doi:10.1088/1742-6596/1587/1/012034

power screw, which is used to provide a smooth and uniform linear movement. It mainly contains a
worm and screw gear assembly, a pinion and bevel gear, a bronze screw and nut and a drive motor [9].
In the same way, physics and mathematics play an important role in development because of the
complexity of the problems, since their intervention in the engineering discipline is fundamental [10].
So, the physical principles that developed the equations to perform the static and dynamic analysis
present in the power screw are used. Therefore, the objective of this research is to design a high
production precision machine using the equations that associated the physical principles to perform the
kinematic and static stress analysis in the power screw.

2. Methodology
The type of research is descriptive and aims to define the design of a linear mechanical system for the
study of the mechanical properties of the joints welded by the GMAW welding process, which can
obtain control of the geometry of the weld seam with precision and repeatability.
The deposition of a weld bead is defined by the process and by a mechanical component that allows
for straight-line displacement. This displacement is carried out by means of a power screw. This article
takes as a reference the analysis of the loads and stresses acting on the screw, being one of the main
working elements in the development of the research. Therefore, it is studied as a discrete system of
particles, which relates to physical principles such as Newton's second law, with the development of the
equations to perform the static and dynamic analyses present in the power screw. The kinematic
calculations of the system are with standardized elements found in the market. In addition, this process
was developed in the environment of computer aided design (CAD) programs.

2.1. Weld bead deposition

As a pre-welding test, the technical indices are set as a basis for making a productivity comparison
between the different welding processes [11]. One of these factors is: The deposited material M! is a
key factor for the calculation of welding costs and is defined as the quantity of filler material required
to complete a given joint. A DR of 108 Kg/h, a t "#$ of 0.39 minutes was considered, the deposited
material was calculated from Equation (1).

D% ∙ t "#$
M! = . (1)
60

Where, M! is the material deposited (Kg), DR is the deposition rate (Kg/h), t "#$ is welding time
(minutes). This rectilinear displacement is transferred to a welding working deck by GMAW deposition.
For greater accuracy with the load data that the shaft will support, the weight of the weld deposition was
calculated taking into account the ER70S-6 welding feed material for a linear bead of 15 cm, and a
welding speed of 1.44 mm/s. In addition, the weight of the plates was added to the calculations. The
physical properties are shown in Table 1.
On the other hand, to avoid damage to the linear table, either by current leakage or by excessive
heating during the welding process, a Bakelite plate was necessary, a copper plate to facilitate rapid heat
distribution and return of welding current, this allows electrical and thermal insulation, the parts are
shown in Figure 1.

Table 1. Physical properties of materials.

Dim (b∙h∙l) (cm) V (cm3) ρ (g/cm3) Mass (g) Weight (N)
Weld bead ER70S-6 x∙x∙15 x 7.83 12.27 0.12
Plate AISI 1020 5∙0.635∙20 63.50 7.87 500.00 4.90
Plate Cu 30∙0.5∙25 375.00 8.96 3360.00 32.96
Plate bakelite 30∙0.5∙25 375.00 1.30 487.50 4.78
Plate Al 30∙0.5∙25 375.00 2.71 1012.50 9.93

2
6th International Week of Science, Technology and Innovation (6th IWSTI) IOP Publishing
Journal of Physics: Conference Series 1587 (2020) 012034 doi:10.1088/1742-6596/1587/1/012034

Figure 1. Loads on the power screw.

2.2. Power screw force and torque analysis

Power screws are mechanical devices that change a rotation or angular displacement in a straight line,
transmitting force and mechanical power. In practice, power screws are provided by specialized supplies
that offer technical literature that includes all the data necessary for their selection. Two common types
of thread are shown in Figure 2. Screwed joints can only transmit limited alternating stresses due to the
notch stresses resulting from the functional design of a screw [12].
The square chord shown in Figure 2(a) provides the highest efficiencies and strengths; it also
eliminates the radial force components between the bolt and nut. However, Acme chord is a common
selection for power screws that must carry loads in both directions. The Acme cord, shown in Figure
2(b), has an included angle of 29°, which makes it easier to fabricate and also allows the use of a split
nut that is tightened radially against the bolt to reduce wear. Most bolts are manufactured with only one
cord (1 boot) [13].

(a) (b)
Figure 2. Power screw with (a) square thread and (b)
Acme thread.

2.2.1. Coefficient of friction. The coefficient of friction must be greater than the tangent of the feed
angle. For a static coefficient of friction on the screw flank of 0.15, the maximum corresponding feed
angle should be 8.8°. In this case the coefficient of friction was maintained, and the feed angle was
calculated [14]. When choosing one of the steps used commercially by the Acme threads, it is verified
that it met the previous condition. The pitch diameter Dp of the thread is obtained from Table 2, being
a single strand, the feed L is equal to the pitch p.

Table 2. Preferred steps for ACME thread.

p, in 1/14 1/12 1/10 1/8 1/6 1/6 1/5
Dp, in 5/16 3/8 1/2 5/8 3/4 7/8 1

3
6th International Week of Science, Technology and Innovation (6th IWSTI) IOP Publishing
Journal of Physics: Conference Series 1587 (2020) 012034 doi:10.1088/1742-6596/1587/1/012034

2.2.2. Torque. The movement of the platform is defined by the angular movement of the power
screw, which in turn requires the action of a torque. The motor to be used on the table can be step-by-
step, which is capable of directly controlling the axis by a pulse train and can be configured from 200
pulses per turn to 10000 pulses. The torque is applied to move the load on the power screw and is
calculated with Equation (2).

&∙!! ($*+∅∙-"./01)
T= ($*+∅31-"./)
. (2)
(

Where, T, is the torque required to move the screw, F, is the resulting force due to the torque, Dp, is
the pitch diameter of the thread, λ is the forward angle, μ is the coefficient of static friction on the screw
flank, ∅ is the angle of thread.

2.2.3. Mechanical efficiency. The efficiency in a screw is the same as in any system: the work
entering the system, due to the applied torque (servomotor), is equal to the work leaving, plus the work
of the friction losses on the screw flanks. As the power screw is an Acme thread, the value of the angle
between the flanks is 14.5º. If the friction on the rope is reduced, the efficiency would increase
significantly [15].

2.2.4. Shear force. This effort is what will sustain the mechanism due to the stresses parallel to the
cross section. To calculate the shear stress produced by the torque, it is assumed that the area of the core
is equal to that of a circle with a diameter equal to that of the interior of the screw, so the maximum
shear stress occurs at the periphery of the section and is given by Equation (3).

456
τ= . (3)
78" #

Where, τ, is the shear force, T is the torque, d# is the minor diameter.

2.3. Material
When a structural element or machine component made of brittle material is under uniaxial tension, the
value of the normal stress that causes it to fail is equal to the ultimate strength of the material [16]. A
ductile material, medium carbon steel of type AISI 1040, was considered for this selection. Therefore,
a failure theory, involving the factor of safety and the maximum stress, is applied for the determination
of the Sy. It is calculated with the Equation (4).

;$
τ9": = . (4)
(.

Where, τ9": is the maximum shear, Sy is the yield strength, n is the safety factor.

2.4. Modeling in computer aided design software

The parts are sized according to the conditions of the machine. The vertical structure of 250 mm, with
a space for the welding gun that rests on a base connected to the pair of shafts, and the location of the
motor that will give the torque to the power screw. Figure 3 shows a preview of the design using
SolidWorks software.

4
6th International Week of Science, Technology and Innovation (6th IWSTI) IOP Publishing
Journal of Physics: Conference Series 1587 (2020) 012034 doi:10.1088/1742-6596/1587/1/012034

Figure 3. Structure components.

3. Results

3.1. Design calculations

In the application of the stress equations, the selected values, and the use of the commercial tables of
the materials, allowed finding and calculating the following factors exposed in Table 3.

3.2. Material determined

In accordance with the results of subsection 3.1, the maximum stress on the power screw is 283.57 kPa.
To ensure that the material to be chosen will support the stresses already calculated, the failure theories
were applied, where a safety factor of 1.5 was considered, in order to have a result closer to reality,
providing a considerable service life. When calculating yield stress, based on tables illustrating the types
of materials and the stress resistance they support, the ideal material for the construction of the power
screw was AISI 1040 steel, as it provides sufficient ductility for easy machining, and thus ensures the
accuracy of the thread.

Table 3. Power screw design calculations.

Design factors Value
Angle of travel (λ) 4.04º
Torque (T) 0.08 Nm
Mechanical efficiency (e) 30.90%
Stress under axial load (τ! ) 370.27 kPa
Shear stress (τ) 214.86 kPa
Maximum shear stress (τ"#$ ) 283.57 kPa
Yield strength (Sy) 850.72 Pa

3.3. Material determined

In accordance with the results of subsection 3.1, the maximum stress on the power screw is 283.57 kPa.
To ensure that the material to be chosen will support the stresses already calculated, the failure theories
were applied, where a safety factor of 1.5 was considered, in order to have a result closer to reality,
providing a considerable service life. When calculating yield stress, based on tables illustrating the types
of materials and the stress resistance they support, the ideal material for the construction of the power
screw was AISI 1040 steel, as it provides sufficient ductility for easy machining, and thus ensures the
accuracy of the thread.

3.4. Computer aided design modelling

In the design of the pieces that form part of the mechanism and the modelling of the existing ones, the
optimization of the materials that carry the quality line was considered, in addition it was stipulated as
a biaxial system, emphasizing the automation of the welding speed. Consequently, the system is

5
6th International Week of Science, Technology and Innovation (6th IWSTI) IOP Publishing
Journal of Physics: Conference Series 1587 (2020) 012034 doi:10.1088/1742-6596/1587/1/012034

composed horizontally of a base containing a power screw coupled to a servomotor and a pair of sliders
with their respective blocks, supported on a table; vertically, as shown in Figure 4, it consists of a worm
adapted to the base that holds the welding gun and two additional sliding shafts that provide manually
adjustable freedom of movement.

Figure 4. Machine modeled in SolidWorks.

4. Conclusions
The study focused on the calculation of the main stresses of the power screw since it is the piece most
exposed to alterations in its movement with loads. The equations used were deduced through the
physical principles of the second law of newton, focusing on the forces present and the kinematics of
torque. In this way, the results of the stress analysis corroborate the hypothesis that the forces involved
in the movement of the power screw will not alter the speed of the process. Furthermore, the material
selected for processing can withstand the stress and move a 53 N load in both directions, from 0 mm to
150 mm at a speed of 1.44 mm/s. Finally, the modeling of the machine determined that the dimensions
were appropriate for this type of application, which provided a preview of its construction.

Acknowledges
To the “Universidad Francisco de Paula Santander, Ocaña, Colombia”, the INGAP research group of
the Mechanical Engineering program and the Research and Extension division for supporting the
exploration of new technological advances.

References
[1] Wang X, Shi Y, Yu G, Liang B, Li Y 2016 Groove-center detection in gas metal arc welding using a
template matching method International Journal of Advanced Manufacturing Technology 86(9-12) 2791
[2] Cui H, Dong J, Hou G, Xiao Z, Chen Y, Zhao Z 2013 Analysis on arc-welding robot visual control tracking
system International Conference on Quality, Reliability, Risk, Maintenance, and Safety Engineering
(QR2MSE) (China: IEEE)
[3] Xue Y, Kym I S, Son J S, Park C E, Kum H H, Sung B S, Kim I J, Kim H J, Kang BY 2005 Fuzzy regression
method for prediction and control the bead width in the robotic arc-welding process Journal of Materials
Processing Technology 164 1134
[4] Chen S B, Qiu T, Lin T, Wu L, Tian J S, Lv W X, Zhang Y 2004 Intelligent technologies for robotic
welding Robotic Welding, Intelligence and Automation ed Tarn T J, Zhou Ch, Chen S B (Berlin: Springer)
pp 123-143
[5] Chen SB, Lv N 2014 Research evolution on intelligentized technologies for arc-welding process J.
Manufacturing Processes 16(1) 109
[6] García E D, Plata J L, Quintero A E 2017 Revisión de técnicas de sistemas de visión artificial para la
inspección de procesos de soldadura tipo GMAW Revista Colombiana de Tecnologías de Avanzada 1(29)
47
[7] Modenesi P J, De Avelar R C 1999 The influence of small variations of wire characteristics on gas metal
arc welding process stability Journal. of Materials Processing Technology 86(1-3) 226

6
6th International Week of Science, Technology and Innovation (6th IWSTI) IOP Publishing
Journal of Physics: Conference Series 1587 (2020) 012034 doi:10.1088/1742-6596/1587/1/012034

[8] Scotti A, Ponomarev V, Lucas W 2012 A scientific application oriented classification for metal transfer
modes in GMA welding Journal. of Materials Processing Technology 212(6) 1406
[9] Golpinath R 2014 Design of a power screw Middle-East Journal of Scientific Research 20(5) 630
[10] Kurmushev E 2003 Basis of Mathematic Methods for Physic and Engineering (Mexico: Limusa)
[11] Garcia C, Conde A, Gesto D, López A 2012 Estudio comparativo de la productividad y calidad obtenidas
en la soldadura de tubos de calidad T9 empleados en el sector petroquímico, mediante los procesos TIG,
HW-TIG y PAW Soldagem & Inspeção 17(3) 264
[12] Kraemer F, Klein M, Oechsner M 2020 Fatigue strength of metric steel screws depending on pre-load and
nut type Engineering Failure Analysis 112 104484
[13] Mott R L, Vavrek E M, Wang Jyhwen 2018 Machine Elements in Mechanical Design 6th edition (New
York: Pearson Prentice Hall) p 647
[14] Budnyas, R G, Nisbett K J 2008 Diseño en Ingeniería Mecánica de Shigley, 8 edición (México: McGraw-
Hill/Interamericana) p 401
[15] Norton R L 2011 Diseño de Máquinas: Un Enfoque Integrado, 4 edición (México: Pearson Educación)
[16] Beer F P, Johnston E R, DeWolf J T, Mazurek D F 2010 Mecánica de Materiales, 5 edición (México:
McGraw-Hill/Interameriana) p 451