article is intended to introduce basic tool making knowledge
to beginner toolmakers, die maintenance technicians and press
technicians. We will first define what is a stamping die and
difference type of stamping dies exists in the market. Step
by step introduce die component and it function and application.
It will also discuss some terminologies use in the stamping
industries such as cutting, forming, lancing, ironing operations
Is a Stamping Die?
Basically, Stamping operation is a cold-forming operation,
which mean that, it runs under room temperature and no
heat was introduced to the entire operation intentionally.
However, heat is still generated from friction during
the punching process. As such, proper lubricant needs
to be applied during the stamping operation to reduce
heat and wear rate of die members.
A stamping die is usually consists of a serious of precision
punches and dies that cuts and forms sheet metal into
a desired shape or profile within a specified dimension
zone. The die members (punch and die) are typically made
from special types of hardened tool steel. In some cases,
die members are made of special material called carbide
to prolong tool life and enable it to runs in much higher
speed. ( 800- 1,500 spm in some cases)
typical die set design can be seen on Figure 1.
Name of Tooling components:-
1. Top Die shoe
2. Top thrust plate
3. Punch holder plate or punch plate
5. Stripper backing plate ( some tools without this plate)
6. Stripper plate
7. Die plate
8. Die backing plate
9. Lower Die shoe
10. Guide pillar and bush
The part that the Die produced is called a piece part (see
Figure 2). Usually, a Die can produces 1 part per cycle (
Stroke ) but some Dies can produces more than one piece part
per cycle and runs as fast as 1500 strokes per minute with
close tolerances up to +/- 0.05mm ( 0.0019 inch ).
Types of stamping Die.
There are many kinds of stamping dies exist in the market,
all of which perform a few basic operations, either cutting,
forming, bending, drawing or all of them. The Die can be runs
manually ( manual loading and unloading of piece part ) or
automatically. The automatic Die we called a Progressive Die.
Which consists of many operations within a Die.
Cutting operation is perhaps the most common operation performed
in a stamping die. The component to be cut is placing in between
the punch and die. Desired shape and form is cut after two
members bypass each other. Usually, the Die is bigger than
the punch to allow smooth enter of the punch. The sizes difference
between the punch and die are called the cutting clearance.
Cutting clearances change with respect to the type of cutting
operation being performed, the metal's properties, and the
desired edge condition of the piece part. The cutting clearance
often is expressed as a percentage of the metal's thickness.
Different clearances applied to different material thickness
and different type of material to be punched. The most common
cutting clearance used is about 5 percent per side of the
metal's thickness. In general, the harder the material the
bigger the cutting clearance will be applied.
. A steel sheet of 1mm thickness ( 0.0393 inch ). Cutting
Cutting clearance = 1mm ( 0.0393 inch ) x 0.05 = 0.05mm per
side ( 0.00196 inch )
A Brass sheet of 1 mm thickness ( 0.0393 inch ). Cutting clearance
Cutting clearance = 1mm ( 0.0393 inch ) x 0.04 = 0.04mm per
side ( 0.0015748 inch )
High punching force is needed to perform the cutting operation.
In general, the punching force can be calculated as follow:-
F = A X S
Cutting force = Area ( Perimeter of shape to be cut x thickness
of material ) x Shear strength of material
Note : Shear strength = 80% of the tensile strength.
3 show you a typical example of cutting condition.
1. Roll over : Plastic deformation state of material.
2.Penetration : A shinning cut band at the side of cut edge
and it is usually 1/3 of the total material thickness.
3. Fracture. Break off.
4. Burr edge.
There are still many different cutting operations, each with
a special purpose and application. Some common one are:
Trimming-The outer shape of the piece part is trim
away to give the piece part the desired shape.
In the progressive die, notching is applied on the outer edge
of the strip, unwanted part to be cut away to give the desired
profile. In some cases, notching is applied in the progressive
die to provide a stopper for material feeding. (see Figure
Blanking- The term blanking is a cutting operation
in stamping die to cut out the desired piece part from the
metal strip. The dimension on the die profile is exactly the
dimension of the component wanted. The cutting clearance is
applied on the punch. ( subtract 5% / side from die )
Cutting a hole onto the sheet metal or component. Some time
called perforating. The main difference between piercing and
blanking is that in blanking, the slug is used, and in piercing
the slug is discarded as scrap. The punch's size is exactly
the hole size of component wanted, cutting clearance added
on the die side. (see Figure 7).
lancing, the metal is sliced or slit in an effort to free
up metal without separating it from the strip.
operation is to remove some small material from the component,
usually applied to provide better cut band. (see Figure 9).
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