Wire EDM Machine Operation Chapter 8
Copyright November, 98 Page 8-1 Sodick Inc.
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Now we will discuss taper cutting. We will limit our discussions about taper cutting to
machining die clearance angles. There are other applications for taper cutting, but we feel
that if you understand how to machine taper for die clearance angles, you should be able
to apply what you know to other applications.
The primary use for machining taper is for die clearance. You usually need some form of
clearance angle on the die to allow the blanked slugs from the punched workpiece to fall
easily through the die. There are several different ways to machine this taper, depending
on your requirements for cycle time, clearance angle, and basic personal preferences.
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Do you want Die Land? Die land (also called die life) is an amount of non-tapered area
of the die. The purpose for die land is to allow the die to be sharpened (ground on the top
surface) with absolutely no deviation to the size of the die opening. Depending on the
taper angle, die land may not be necessary. Many companies machine only about .25
degrees (1/4 degree) taper as the angle. If your desired taper angle is this small, and if the
part to be punched is relatively thick, the very small change in die opening size during
sharpening will be minimal. For example, if machining .25 degrees as the taper angle,
when you sharpen the die and remove .007 inch stock from the top surface of the die, the
change in die opening size will only be .0000305 inch (per side). For all intents and
purposes, this small deviation will not affect the performance of the die.
Knowing this, companies can save a great deal of cycle time by tapering right up to the
top of the die with absolutely no land. But remember, as the taper angle grows, the
amount of deviation to the die opening during sharpening will also grow. You can easily
calculate the amount of growth (per side) by applying this formula:
Growth (per side)= TAN of the taper angle times the amount of stock to be removed
per sharpening:
How much die land do you need? Of course, the amount of die land will be directly
related to the life of the die. But you must also be concerned with the ease of the blanked
part removal. You can reference the Machinery’s Handbook to get their recommendation
for amount of die land for various blanked part thickness.
How big do you want the taper angle to be? The taper angle in a die affects the strength
of the die. Generally, you will want the taper angle to be at its smallest acceptable angle
to keep the die strong. The desired taper angle will also affect the best and easiest way to
machine the die. More on this later.
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