Wire EDM Machine Operation Chapter 7
Copyright November, 98 Page 7-5 Sodick Inc.
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If you are about to cut a part and are unsure about something, it would be FOOLISH to
cut before you test the conditions and offsets to prove that they are correct. For this
reason, we recommend that any time you are unsure about something, you cut a test
square.
A test square is made from the same material and thickness as the workpiece to be
machined. And, of course the same wire diameter will be used to machine the test square
as the actual part. It is preferable to actually use the same piece of material that is going
to be machined as the material for the test square. If machining a die, choose an open area
of the die in which to run the test square. If the part is to be a punch, find another area of
the stock to run the test square so that it will not interfere with the machining of the
punch. In the planning stages, when drilling the start hole for the punch or die, be sure to
plan for a start hole for the test square!
Now, write a program to machine the test square (usually .500 inch square) that will use
the same conditions and offsets to be used to machine the punch or die. After you
machine the test square, you can see the finish and measure the size that the set of
conditions and offsets will generate. If the test square is on size, so will any punch or die
machined with the set of conditions and offsets for this material, thickness, and wire
diameter.
While machining the test square, do not change any of the parameters related to the
condition. If you make changes, another test square must be cut, since you are changing
values that determine part size, accuracy, and finish.
TEST CUTTING TO CONFIRM OFFSETS
If you find that the finish and size of the part is unacceptable, the set of conditions and
offsets must be modified. For beginners, it would be wise to contact Sodick for help. If
the finish is OK but the size of the part is incorrect, you will have to modify ALL offsets
by the amount of error. Here’s an example. Say the test punch was programmed to be
.500 square, but it came out to .4996 square. The test square is .0004 (overall) too small.
In this case, ALL offsets would have to be INCREASED by .0002 inch to correct the
error.
Once a set of conditions and offsets has been proven to give the desired results, they will
continue to be correct. This means that once you know that a set of conditions and offsets
are cutting properly, you can rest assured that they will remain good for the material, part
thickness, and wire diameter for as long as you run the machine.
With a brand new machine, it may seem tedious to machine test squares. However,
depending on the accuracy, finish you expect and operator knowledge, they are
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