Tool Design
Tool Design
Tool Design
The field of Tool Engineering takes participation in the refinementof product design and the
design of machinery and also machine toolsgauges etc.
Industreis utilize millions of men,production tools,machines,processes,material handling
devices, buildings,other related facilities and millions of rupeesin order to shape and
produce materials to meet the needs of mankind.
The competitive system forces a methodical selection and utilization of the factors of
production in the manufacture of high quality products of low cost.
The many alternative processes available to change the size and shape of materials
requirecomplementary toolling. Ingenuity is required in the design of this tooling to
facilitatescheduled and economic machining, casting, joining and press working of the many
Engineeringmaterials. The field of tool and manufacturing engineering encompasses a wide
varity of industries.It is concerned with the manufacture of airplanes, food handling
equipments, glassware,refrigerators, communication equipments, textiles,electronic
equipments, sewing machines, sporting goods, automobiles,machine tools, furniture,
packaging equipments, missiles, farmequipments, space capsules, stores and soon.
The field of tool and manufacturing is a necessary function in unit or high volume
productionand in large or small enterprises. The tool and manufacturing engineer articulates
in an environment which requires a through understanding of scientific and engineering
principles.The tool manufacturing engineers must understand the broad manufacturing
aspects of the industryin which he is employed and he must also be able to design specific
production tooling.
TOOL ENGINEERING COURSE:
Today many Engineering coruses are available for studying such as MechanicalEngineering,
Electrical and Electronics Engineering, Textile Engineering, Civil Engineering,Automobile
Engineering, Aeronautical Engineering, Marine Engineering etc..
Tool Engineering is one of part of the Mechanical Engineering. It is a Diploma course.It is
very valuable and usuable course. This course is available in Government and
Privatepolytechnic colleges.
After completion of this courses, students have a good job. And also they haveopportunities
in foreign countries. Some other's to start own industries. After completion ofthis course
students are positioning for the following jobs in different industries.Tool and Die maker
post, Supervisor, Quality control department, Tool Room Manager, ProductionManager, Tool
designer etc..
In Tool Engineering course, students have known Tool manufacturing processes and Tool
designing principles. And also have knowledge on machines such as Lathe, Milling
machine,Grinding machine, shaping and planner machine, Drilling machine, power hack saw
cutting machineand some CNC machines.
Educational Qualification: 10th standard with good percentage of marks.
Introduction:
Metal forming is a process of forming the metal into the required shape. In thisprocess no
chips removed from the metal. The metal is formed into shape by applying force on
themetal.
A press woring operation, generally completed by a single application of pressure
oftenresults in the production of a finished part in less than one second. Press working
forces are setup, guided and controlled in a machine referred to as PRESS. Metal is formed
in two different stages such as 1.Cold working 2.Hot working.
Cold working
In this process metal is formed in the cold condition. In cold woring the metalis pressed or
cut, to get the required shape. The metal is stretched beyond its elastic limit.cold working
can be done only on ductile metals. The machine used for pressing the metal in cold
working is called a "cold formingpress".
Hot working:
In this process metal can also be formed in hot condition. Here the metal is heatedto a
temperature, so that recrystalysation takes place. At this hot condition the metal ispressed
to get the required shape. The machine used for pressing the metal in hot working is called
"hot working press"
PRESS TOOLS
The tool which is used on press machines with punch and die is known as press tool.
Punch is the male part of the tool, which is fastened to the ram and forced into the die.
Die is the female part of the tool,which is rigidly held on the bed of the press machine.Die
has an opening in perfect alignment with the punch.
Types of Dies:
1.Based on the operations
1.Shearing, 2.Blanking, 3.Piercing, 4.Punching, 5.Cutting off, 6.Parting off, 7.Notching,
8.Slitting, 9.Lancing, 10.Bending (angle bending and edge bending), 11.Curling,
12.Forming, 13.Drawing or cupping, 14.Plunging, 15.Squeezing, 16.Coining, 17.Embossing,
18.Deep drawing, 19.Flatening or planishing, 20.Trimming.
2.Based on construction
1.Simple die, 2.Progressive die, 3.Compound die, 4.Combination die, 5.Inverted die
BLANKING:
Blanking is the operation of cutting a flat shape from sheetmetal . The part
punched out from the metal strip is called “blank”, and it is the required product of
the operations. It is usually the first step of series of operations. After blank the
metal strip called as scrap.
CUTTING OFF:
PARTING OFF:
Notching is the cutting operation by which metal pieces are cut from the edge of a
sheet.
SLITTING:
LANCING:
PEFORATING:
In this process,multiple holes are produced, which are
very small and close together are cut in flat work material.
BENDING:
During the bending operation, the outer surface of the metal is in tension and the
inside surface is in compression. The strain in the bent material increases with
decreasing radius of curvature. The stretching of the bend causes the neutral axis
of the section to move towards the inner surface.
EDGE BENDING
In edge bending, a flat punch forces the metal against the vertical face of the die.
The bend axis is parallel to the edge of the die and the stock is subjected to
cantilever loading. In this bending, a pressure pad is used, for prevent the
movement of the stock during operations.
SHAVING
TRIMMING
Curling is the operation of rolling the edges of the sheet metal to a small circular
form. Curling is done to strengthen the edges. By curling, the sharp edges of the
metal is avoided.
The lower die held stationary. The upper die has got a curved form at its end.
When it moves down,the edge of the work is curled into a circle. Curling is used in
making sheet metal vessals and containers
FORMING
COINING
Coining is the operation of squeezing the metal between two dies. A blank of
correct size is placed between the lower and upper die.Both dies are engraved to
have the required pattern and shape.
Both the dies press the metal blank with very high force. The blank metal flows in
the cold state and fills up the cavity between the dies. The pattern on the two dies
are transferred to the component.The movement of the die is guided by a guide
plate.These operations producing coins,metal and other similar parts.
EMBOSSING
PLUNGING
Plunging is the operation of localized bending around a hole in the sheet metal.
Plunging is done in two stages. First the hole is pierced in the work at the required
position using piercing punch and die. Then the hole in the sheet metal is plunged
The plunged hole will take the shape of the punch and die. Plunging is done to
received a screw head or rod through the holes. Plungingaremade asCountersunk,
burred or dimpled holes.Plunging operation is also called as Hole flanging or
Extruding.
FLATTENING OR PLANISHING
This is the operation of straightening a bent or curved sheet metal. The planishing
punch has small projections on its face. The projections are spaced equally. The
die has a flat plain surface.The sheet metal having bent is placed over the flat die.
The punch presses the sheet metal with high pressure.The bends on the sheet
metal are removed.
DRAWING OR CUPPING
Drawing is the operation of producing cup shaped parts from the sheet metal
blanks. The blank is placed over the forming die. The stripper plate is hold the
blank on the die. When the punch moves down, the blank is pushed into the
dieopening. A pressure pad is placed inside the die opening, which is used for
uniform drawing operation.Plastic deformation takes place in the blank. The metal
is drawn over the surface of the die opening. Sufficient clearance is given between
the punch and die.A cup shaped components are produced by drawing
operation,this process is calledCupping.
DEEP DRAWING
Deep drawing is the operation of producing cup shaped components having more
depth. Here the depth of the component produced is more than its diameter.
Deep drawing is done in different stages,by using different sets of punch and dies.
After each stage of drawing, the blank surface gets hardened. So to avoid rupture
and failure, the blank is annealed before the next stage of drawing operations.
Sharp specially shaped blades are used in die cutting. The blade is bent into the
desired shape and mounted to a strong backing. The result is known as a die. The
material being cut is placed on a flat surface with a supportive backing, and
the dieis pressed onto the material to cut it. Depending on what is being made, a
single die might cut one piece of material, or it might be designed to slice through
multiple layers, generating a stack of blanks.
Creating dies is meticulous work. The die must be designed so that it efficiently
cuts the desired material with minimal waste. Most factories which
use die cutting as part of their manufacturing process have techniques for
recycling material left over from die cutting, but they want to avoid excess if
possible. Often, multiple dies are fitted together on one mount, nestled with each
other for maximum efficiency. Material left over from the die cutting process may
be melted down and reused, or reworked into other components.
Common examples of die cut items include keys, paper products, and flat plastic
pieces which can be snapped together. Die cutting is limited, because it can only
really be used to produce flat objects. For more dimensional shapes, other
manufacturing techniques such as molds need to employed. Dies can also range
widely in size from cookie cutters to massive machines designed to cut out ship
components. With large dies, it is important to observe safety precautions
while die cutting, as an industrial die designed to slice through metal can also
remove a limb without difficulty.
In conventional stamping the material will bend away from the punch, causing the
part to fracture.In Fine blanking, the material is held in constraint In many
situations, "impingement" is added to the clamp action to stop material from
flowing away from the punch. The final element is counter force. An additional die
element is added which mirrors the shape of the punch. Pressure is applied to this
element throughout the process. This keeps the part from bowing away from the
punch resulting in an extremely flat piece.
Fine blanking
Typical fine blanking press cross section figure
A typical compound fine blanking press includes a hardened punch (male), the
hardened blanking die (female), and a guide plate of similar shape/size to the
blanking die. The guide plate is the first applied to the material, impinging the
material with a sharp protrusion or stinger around the perimeter of the die
opening. Next a counter pressure is applied opposite the punch, and finally the die
punch forces the material through the die opening. Since the guide plate holds the
material so tightly, and since the counter pressure is applied, the material is cut in
a manner more like extrusion than typical punching.
Mechanical properties of the cut benefit similarly with a hardened layer at the cut
edge from the cold working of the part Because the material is so tightly held and
controlled in this setup, part flatness remains very true, distortion is nearly
eliminated, and edge burr is minimal.
Clearances between the die and punch are generally around 1% of the cut
material thickness, which typically varies between 0.5–13 mm (0.020–0.51 in).
Currently parts as thick as 19 mm (0.75 in) can be cut using fine blanking.
Tolerances between ±0.0003–0.002 in (0.0076–0.051 mm) are possible based on
material thickness & tensile strength, and part layout.With standard compound
fine blanking processes, multiple parts can often be completed in a single
operation. Parts can be pierced,partially pierced, offset (up to 75°), embossed, or
coined, often in a single operation. Some combinations may require progressive
fine blanking operations, in which multiple operations are performed at the same
pressing station.
CENTRE OF PRESSURE
CENTRE OF PRESSURE
When the shape of blank to be cut is irregular, the summation of shear forces
about the centre line of press ram may not be symmetrical. Due to this, bending
moments will be introduced in the press ram, producing misalignment and
undesirable deflections. To avoid this the “centre of pressure” of the shearing
action of the die must be found and while laying out the punch position on the
punch holder, it should be ensured that the centre line of press ram passes exactly
through the centre of pressure of the blank. This “centre of pressure” is the
centroid of the line perimeter of the blank. It should be noted that it is not the
centroid of the area of the blank.
3.The outline of the piece part is divided into convenient line elements. These are
numbered as 1,2,3 and so on.
6.The distance of the centroids from the X and Y axes is determined. Let
x1,x2,x3etc. and y1,y2,y3 etc. be the distance of centroids of line elements l1,l2,l3
etc, from the X and Y axes respectively.
7.The distance of the centre of pressure from each axis is determined by the
method of centroids. i.e.,
X =l1x1+l2x2+l3x3+………/l1+l2+l3+………………..
And
Y = l1y1+l2y2+l3y3+……/ l1+l2+l3+……………..
Where,
X = x distance to centre of pressure
Y = y distance to centre of pressure
1 10 5 0 50 0
∑l = 37.5
∑lx = 159.375
∑ly = 98.437
Successful deep drawing depends on many factors. Ignoring even one of them
during die design and build can prove disastrous. However, regardless of the many
factors involved, the most important element to a successful deep drawing
operation is initiating metal flow. The following are key elements affecting metal
flow, and each of them should be considered when designing, building, or
troubleshooting deep drawing stamping dies:
1. Material type
2. Material thickness
3. N and R values
4. Blank size and shape
5. Part geometry
6. Press speed (ram speed)
7. Draw radii
8. Draw ratio
9. Die surface finish
10. Die temperature
11. Lubricant
12. Draw bead height and shape
13. Binder pressure
14. Binder deflection
15. Standoff height
Because thicker materials are stiffer, they hold together better during deep
drawing. Thicker materials also have more volume, so they can stretch longer
distances.
The N value, also called the work hardening exponent,
describes the ability of a steel to stretch. The R value—the plastic strain ratio—
refers to the ability of a material to flow or draw. Blank sizes and shapes that are
too large can restrict metal flow, and the geometry of parts affects the ability of
metal to flow. Press speeds must allow time for materials to flow.
Die surface finishes and lubricants are important because they can reduce the
coefficient of friction, allowing materials to slide through tools more easily. Die
temperatures can affect the viscosity of lubricants.
As a controller of metal flow, draw bead height and shape can cause materials to
bend and unbend to create restrictive forces going into a tool. Increasing binder
pressure exerts more force on a material, creating more restraint on material
going into the tool.
The remaining key elements affecting metal flow are examined in more detail in
the remainder of this article. To illustrate the principles of metal flow, this article
examines two basic draw shapes, round and square. All deformation modes that
occur in any given part shape are present in one of these common shapes.
Figure 1
In the illustration of incorrect draw ratio (L), the too-small post would cause
metal to thin to the point of failure, while the correct draw ratio (R) will result in a
successfully deep drawn part.
The draw ratio is among the most important elements to be considered when
attempting to deep draw a round cup. The draw ratio is the relationship between
the size of the draw post and the size of the blank. The draw ratio must fall within
acceptable limits to allow metal to flow.
When a very tall small-diameter part is being processed, draw reductions likely
will be necessary (see Figure 2). A draw reduction is a process in which a part is
first formed within acceptable draw ratio limits and then is progressively reduced
or reshaped to a desired shape and profile.
Figure 2
Reduction percentages for various thicknesses of draw-quality steel.
The most important factor to remember when performing draw reductions is that
all of the material necessary to make the final part shape must be present in the
first draw. Figure 3 is a reduction chart for the first, second, and third draws with
draw-quality steel. Reduction percentages are based on metal thickness and type.
To determine the post diameter and height of the first draw, the total surface area
of the finished part must be calculated. (If the part is to be trimmed, allow
additional material during this calculation.) The
During draw reductions, the blank diameter should not change after the first
draw.
The primary step in calculating the first draw post diameter is determining the
blank diameter. Multiplying the blank diameter by the percentage given in the
chart, and then subtracting the result from the original blank diameter, yields the
diameter of the first draw post. It is important to remember that all dimensions
are taken through the centerline of the material. The height of the first draw is an
area calculation directly related to the amount of material necessary to make the
finished part.
If a die entry radius is too small, material will not flow easily, resulting in
stretching and, most likely, fracturing of the cup. If a die entry radius is too large,
particularly when deep drawing thin-gauge stock, material begins to wrinkle after
it leaves the pinch point between the draw ring surface and the binder. If
wrinkling is severe, it may restrict flow when the material is pulled through the
die entry radius.
Figure 4
Minimum die entry radii are shown in this chart for round draws involving various
thicknesses of draw-quality steel.
Figure 4 provides general guidelines for die entry radii for round draws of draw-
quality steel ranging in diameters from about 1.5 to 15 inches.
The die entry must be produced accurately in a fashion that makes it true and
complete. It should be hook-free and polished in the direction of flow. High-wear
tool steel should be used for die entry radii.
Binder Pressure
The problem of too much binder pressure can be overcome by using standoffs.
Standoffs maintain a given space between the draw ring surface and the binder,
and they should be set at 110 percent of the metal thickness to allow for
compressive thickening. If the standoff gap is too small, the material will be
pinched tightly between the draw ring and the binder surface, reducing its ability
to flow freely. If the standoff gap is too large, the material will wrinkle during
circumferential compression.
Square Draws
Figure 5
Square draws are similar to round draws because they contain four 90-degree
profile radii. Because of the radial corner profile, material flowing toward the
corners is forced into compression. The straight sections of the square are simply
being bent and unbent. Considerably less flow restriction takes place in the
straight walls of a square draw than in the corners (see Figure 5).
Increasing the profile radius of the draw greatly increases the ability to draw
deeper in a single operation (see Figure 6)because a larger-profile radius reduces
compression. Too much compression in a corner restricts metal flow, resulting in
fracture.
Increasing the profile radius and reducing the blank size reduce forming severity.
Mitering the corners of the blank also can help to reduce compression.
To help balance metal flow conditions during square draws involving heavy
metals, it may be necessary to draw spot the corner areas of the binder or draw
ring face with respect to the increasing material thickness. This process allows
metal to thicken in corners without being pinched excessively between the draw
ring and the binder.
Figure 6
If a proper draw spot is achieved, blank holding force is evenly distributed through
the perimeter of the drawn shell. When thin metal is used, draw spotting the
corners may cause undesirable wrinkling in the relieved areas. This results
primarily from a lack of control of the metal flow and the inability of thin stock to
resist wrinkling.
If the square drawn shell is too tall to be drawn in a single operation, it must
undergo a draw reduction. As with round draws, all material necessary to make
the final part must be present in the first draw. Draw reductions for square shells
are achieved by increasing the profile radius to acceptable compression limits and
increasing the width and length to obtain the necessary surface area of the
finished part.
Thin press work. Above is a lighting louver stamping produced at A & R Engineering Ltd.
Click here, for the lighting louver department, and more information on these type of
products.
PERCENTAGE OF UTILIZATION
Width of strip W = H + 2B
= 20 + 2 X 1.5 =23mm
C =l + B = 10+1.5 =11.5mm
Posted by TOOL ENGINEERING UPDATES at 6:36 AM 3 comments:
In blanking:
blank die opening size = part size – elastic recovery
= 30 – 0.05
= 29.95mm.
blank punch size = die opening size – 2C
= 29.95 – 2 X 0.05
= 29.85mm.
In piercing:
piercing punch size = part hole size + elastic recovery
= 10 +0.05
= 10.05mm.
piercing die opening size = punch size + 2C
= 10.05 + 2 X 0.05
= 10.15mm
----------------------------------------------------------------------
Solution:
Cutting clearance = material thickness X cutting allowance
=1.5 X 6%
=0.09mm preside.
Here, elastic recovery taken as 0.05mm.
BACKUP PLATE:
Backup plate or pressure plate placed between the
top plate and punch holder plate.It is a hardened one.
It is used to prevent the punch making any impression
on the soft top plate.
The plate distributes the pressure over a wide area
and the intensity of pressure on the punch holder is reduced
to avoid crushing.Backup plates are made from OHNS
materials and carbon steels(C45) and it is hardened and
ground parallel.
(OHNS-Oil hardened non-shrinkage steel)
The thickness of the backup plate depends upon
the stock thickness.
STRIPPER PLATE:
This plate is mounted on the die plate.It is called
as fixed stripper plate. A channel is provided in this plate
for feeding the metal strip.It is used to stripout the strip
from the punch during the return stroke of the press.
It is also helps to correctly guide the punch into the
dieopening. In some cases, it is mounted to the punch
assembly. It is called as spring loaded stripper.
2.COMPOUND DIES:
In compound dies,two or more cutting operations
may be performed at one station by one stroke of the press.
Compound dies are more accurate and economical in mass
production as compared to single operartion dies.
For example, a washer component is made by one
stroke of the press in compound die. The washer is produced
by simultaneous blanking and Piercing operations.
Die construction:
Here the blank punch cum piercing die is
mounted on the bottom of the bottom plate which
is bolsted with machine bed. Blank die and piercing
punch are mounted on the top plate which is mounted
on the press ram. A knockout is placed between
blankdie and piercing punch which is used for to
eject the component from the die. A stripper plate is
held with blank punch which is to strip out strip from
the punch after the operation completed.
3.COMBINATION DIES:
In combination dies more than one operations may
be
performed at one station. It is differs from
compound dies.
In combination dies cutting and non- cutting
operations done
at one station by one stroke of the press.
1.BACKUP PLATE 2.PUNCH HOLDER PLATE
3.BLANK PUNCH CUM DRAW DIE 4.KNOCKOUT
5.STRIPPER PLATE 6.DIE PLATE 7.PRESSURE PAD
8.FORMING PUNCH 9.BASE PLATE.
5.TRANSFER DIES:
Unlike the progressive die where the metal stock is fed
progressively from one station to another. But in transfer dies,
the already out blanks are fed mechanically from
station to station.
6.MULTIPLE DIES:
Multiple or gang dies produce two or more
workpieces at each stroke of the press. A gang or number
of simple dies and punches are ganged together to
produce two or more parts at each stroke of the press.
7.INVERTED DIES:
In generally, in punch holder plate punch is held,
which is fastened to the ram. Die is fitted with die holder,
which is held on press bed.
But in inverted dies, the punch and die are to be
interchanged. Punch is held in bed and the die is fastened
to the ram.
Posted by TOOL ENGINEERING UPDATES at 6:29 AM No comments:
Solution:
(a)clearance for soft steel is taken as
C = 5% of t
= 5/100 X 1.5
clearance = 0.075mm/side.
SOLVED EXAMPLE:-2
The strip thickness is 2.0mm and the length of
blank is 10mm and height is 20mm. Strip length is 1.0m.
Find (a) the value for front scrap
(b) the value for scrap bridge
(c) width of strip
(d) length of one part of stock needed to produce
one part.
(e) Number of parts which canbe produced in strip.
(f) Scrap maintaining at the end of strip.
Solution:
A = front scrap ; b = back scrap(bridge thickness)
l = length of part ; h = height of part
T = thickness of part; w = width of scrap
C = distance from part to part
Y = end of scrap; L = total length of scrap
Solution:
Length of part l = 10mm
Height of part h = 20mm
Thickness of part = 2.0mm
Total length of scrap L = 1.0m (= 1000mm)
(a)Front scrap and back scrap
a = t + 0.015h
= 2.0 + 0.015 X 20
= 2.30mm.
(b)Scrap bridge thickness = It is taken as one times
of sheet thickness
= 1 X 2.0
= 2.0mm.
SOLVED EXAMPLE:-3
A washer with a12.7mm hole and an outside
diameter of 25.4mm is to be made from 1.50mm
hickness Of strip of 0.2% carbon steel. The ultimate
shearing Strength of the material is 2800Kg/C
(1) Find the total cutting force if both punches act at
the same time and no shear is applied to either
punch or die.
Solution:
(1)Cutting force F = П(D + d)st
D=25.4mm; d=12.7mm; t=1.5mm
Shear strength S=2800Kg/Cm2 = 28Kg/mm2.
F = П(25.4+12.7)X1.5X28.0
= 5.027 tonnes.
F=ПDst
=П X 25.4 X 28 X 1.5
=3.35 tonnes.
(3) F = t X K X Fmax
KXtXI
K = percentage of penetration = 0.6
I = shear on punch = 1.0mm
Fmax = 5.027 tonnes.
SOLVED EXAMPLE:-4
A hole of 60mm diameter is to be produced in
steel plate 2.5mm thick. The ultimate shear strength
of the material is 45Kg/mm2. If the punching force
is reduced to half of the force using a punch without
shear. Estimate the amount of shear on the punch.
Take % of penetration as 40%.
Solution:
The punching force with non-sheared punch.
Fmax = ПDst
= П X 60 X 45 X 2.5
= 21.20 tonnes.