17-01-2013, 04:08 PM
Stamping Basics
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Introduction
The Dayton Mission…
It is the mission of Dayton Progress Corporation to continue furnishing
our customers with the highest quality information, metal stamping tools
and precision components. Our over half century of surpassing delivery
performance of the competition is our commitment to the future.
This report defines basic stamping terminology and illustrates basic stamping
functions. We explore the common types of die construction, compare
stripper design options, and analyze common die operations.
Punch Press
Perforation is generally the most severe operation performed in a die. That’s
because the punch press applies forces ranging from a few tons to more
than 1000 tons. Proper press alignment is essential. While die set has some
effect on alignment during operation, it cannot offset poor press alignment.
Simple Die
A simple die typically perforates holes in a part or blanks out the part using
punches in conjunction with mated lower die components (matrixes). Simple
dies also commonly produce basic forms as well as perform notching and
lancing operations.
Simple dies require a press operator to load and unload parts and part
material before and after each press cycle.
Program Objectives
Descrriibe Common Types off Diie
Consttrructtiion..
Comparre Sttrriipperr Desiign Opttiions..
Analyze Common Die Operattions.
Punch Press
Die
Simple Die
Part
Perrfforrattiing Punch
Striipper
• Hand Fed
• One hit operation
• Secondary operations Matrix Matrrix Rettaiiner
2003 Dayton Progress Corporation, All Rights Reserved.
DAYTON PROGRESS CORPORATION
A compound die blanks and perforates a part at the same time in the same
station. In most cases this operation perforates a hole or holes down, while
the part blanks up. This allows slugs from those holes to fall through the
die. This method leaves the part in the die, requiring some means of part
removal.
Compound dies commonly run as single-hit dies. They can run continuously
with a feeder, provided you can remove the part in a timely manner. Open
Back Inclinable (OBI) presses - in the inclined position along with an air blowoff
- aid in part removal.
Advantages of a compound die include:
• Minimal space in the press
• All burrs in one direction
• Superior accuracy between holes and trim edges
• More economical to build than a progressive die
A disadvantage of a compound blank die is its limited space that tends to
leave die components thin and weak. This concentrates the load and shock
on punches and matrixes, resulting in tooling failures.
Progressive Die
Progressive dies provide an effective way to convert raw coil stock into a
finished product with minimal handling. As material feeds from station to
station in the die, it progressively works into a completed part.
Progressive dies usually run from right to left. The part material feeds one
progression for each press cycle. Early stations typically perforate holes that
serve as pilots to locate the stock strip in later stations.
There are many variations of progressive die designs. The design shown
here illustrates some common operations and terminology associated with
progressive dies.
Compound Die
Part Material
Perforating Punch
Part Knockoutt Bllankiing Die
Blanking Punch &
Perforating Matrix
• Washer die Striipper
• Perforating & blanking in one hit
• L e a v e s all burrs in one direction
Finished Partt
Stripper Designs
Stamping dies require some means of stripping the part from the end of the
punch at withdrawal. Common types of strippers for accomplishing this
include Fixed, Urethane and Spring.
Stripping force varies based on part material type and thickness as well as
punch-to-matrix clearance. This force ranges from nearly zero to as much
as 25% of the force required to perforate the initial hole. Most applications
do not exceed 10% of the perforating force.
DAYTON PROGRESS CORPORATION
Fixed Stripper
Fixed strippers go by many names:
• Box • Bridge
• Channel • Positive
• Solid • Tunnel
A fixed stripper is a steel plate with a clearance slot that allows the part
material to pass under it. This plate mounts to the die retainer in a fixed
position. Clearance holes cut through the stripper plate let the punches
extend through without interference. At withdrawal the part material hits
the stripper, preventing it from lifting as punches retract. The part material
strips from the end of the punch.
Fixed strippers have several drawbacks. They do not hold the stock strip flat
and are unable to absorb impact and snap-thru shock. The result is poor
part flatness and premature punch failure.
We generally do not recommend fixed strippers for high-volume or highprecision
jobs. A typical clearance under the stripper is 11⁄2 times the
material thickness - 1/16” to 1/8” is common clearance on the sides of the
stock strip.
Clearance under a fixed stripper is commonly 11⁄2 times the part material.
This allows for variations in part material thickness and for stock strip
deformation.
This deformation allowance under the punch point results in punch point
chipping. That deformation can also cause lateral movement of both part
and punches, resulting in punch point breakage and poor part quality.