PART DESIGN
What
are the primary differences between a stamped metal part and a machined
part?
A machined part can have a
relatively lower initial investment in tools and tooling. The parts
produced can be very precise with machined edges and better surface finish
on the edges.
Machined parts are slower to produce and economies of scale are
dramatically less. Tools must be resharpened or replaced and the parts
must be checked constantly to assure constant results.
A metal stamping has higher initial tooling costs and the part
produced has tapered edges and tapered holes.
Once the tooling is complete, parts can be produced quickly and
economically with very low variation from part to part even in runs of
10,000 pieces or more.
Metal stampings can have secondary operations performed such as reaming or
milling to produce a more precise part.
A COMPARISON OF MACHINED
AND METAL STAMPED PARTS
| |
Machined
Parts |
Metal
Stamped Parts |
| Production
Speed |
slower |
fast |
| Initial
Investment |
lower |
higher |
| Economies
of Scale |
lower |
higher |
| Tool
Maintenance |
periodic
resharpening & replacement |
TO
BE ADDED |
| Advantages |
-
Very precise parts.
- Machined edges.
- Good surface finish. |
-
Very large part
runs (10,000+)
possible.
- Very low variation
between parts. |
| Disadvantages |
Parts
must be checked constantly to assure consistent results. |
TO
BE ADDED |
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What can I do to
make my part less expensive to produce?
Every part has a unique set of
requirements and characteristics.
Here are examples of typical things to consider to reduce the cost of your
parts:
- Substitute materials that are less
expensive and/or easier to process.
- Reduce tolerances that will not affect
the part’s function
- Replace complex bends with simple
bends.
- Avoiding heat treating by modifying
the design to accommodate the final material specification.
- Redesigning the part to make it easier
to manufacture.
Bandel’s
engineers can help you design your parts to function well and be less
expensive to produce. Please call
to find out more about Bandel’s Design For Manufacture services.
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DIES
What is a punch press?
A punch press is a machine that consists
of a fixed (bolster) plate and a moving head (ram). A die set is mounted to the bolster plate
and the punch is mounted to the ram.
The press starts in the idle position in which the ram holds the punch
above the die. Material is advanced into the die. During the work cycle,
the ram brings the punch down into the die and blanks or forms the
material in the die and then returns to the idle position. The material is
then advanced and the cycle is repeated.
There are may types of punch presses. Some can use more than one punch and
die at a time and some are computer controlled.
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of Page
What is a die?
In metal stamping, a die is a tool that
runs in a punch press.
There are four main types of dies: blanking, compound draw, form
and progressive. The selection of the die type depends upon the
part being made.
- Blanking dies
are
like cookie cutters and can put one or more holes in a part or make a
single part with no holes.
- A Compound die can blank, form
and put holes into a part in one hit but not all parts are suitable
for this type of die. Compound dies can be difficult to maintain.
- Draw dies
force
a flat blank of material into a cavity of the required shape. The die
confines the metal between the drawing surfaces that change the flat
blank into a cup or shell of the desired shape. One or more draw dies
may be required to form the part into the final shape.
- A Form die can put one or more
bends or forms into a part blank.
- A Progressive die can perform
many different operations with a single die. In a progressive die the
material is advanced by a fixed amount (the progression) through each
station in the die. Each station can perform either a blanking or
forming operation. The number of stations in a die is limited by the
size and power of the punch press.
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Can I use the same
tooling for different thicknesses and types of material?
Dies are usually designed to give the
best result for one type and thickness of material. The use of different
thickesses and types of material by the same die is possible.
BLANKING DIES
In general, a blanking die can be designed to blank the same type
of materials that vary in thickness by up to 100%.
The die can be made to blank different types of materials too. However it
is important to inform the die designer of the range of thicknesses and
materials to be used. In this way, the designer can optimize the die for
the range of materials and thicknesses rather than a single material.
FORM DIES
Form dies are more sensitive to varying thicknesses and types of
materials, however in some cases the same die can be used. Discussion with
the die designer is highly recommended.
Always discuss your
material and thickness requirements with your die designer before
the die is built.
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Can a single die
produce more than one part?
If two different parts are used in an
assembly and made of the same type and thickness of material, it may be
economical to produce both parts in the same die.
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TOOL MAKING
What is a tool?
Tool or tooling refers to a device
capable of cutting or forming a workpiece, which is usually used in a
machine such as a lathe, mill or punch press. (The tooling for a punch
press is a die.)
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How long will our
tool last?
Because of the many factors involved, it
is difficult to predict the actual life of a tool.
However, if one knows the total number of parts needed over the life of
the product, suitable materials can be selected. It is not uncommon for a
die to produce 500,000 pieces or more over its life time when properly
maintained.
Remember to give the die maker an estimate of the
number of parts you expect to produce.
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METAL STAMPING
What size press will
I need for my die?
The press tonnage can be predicted by
multiplying the length of cut, or the sum of the perimeters times the
thickness of material times the shear strength of the material.
Example
To make a two inch square part with a one inch hole in the center in 16
gauge 6061-T6 aluminum, we'd use the following calculation:
Perimeter of square: 4 *
2.00 = 8.000 inches
Perimeter of circle: pi * 1.000 = 3.142 inches
Total of perimeters: 8.000 +
3.142 = 11.142 inches
Material Specifications:
Thickness of Aluminum: 0.060
inch
Shear strength of Aluminum:
13.5 tons / sq. in
Tonnage Required:
11.142 in. x 0.060 in. x 13.5 tons/sq. in. = 9 tons
The minimum press tonnage would be 9 tons
but practically speaking a press of at least 12 tons should be used.
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