Wire EDM Machine Operation Chapter 7
Copyright November, 98 Page 7-6 Sodick Inc.
necessary. It may seem like a great deal of work to cut test squares for each material,
thickness, and wire diameter you are going to be using, but it is the only way to know
what the results will be.
I
I
N
N
C
C
O
O
R
R
P
P
O
O
R
R
A
A
T
T
I
I
N
N
G
G
D
D
I
I
E
E
C
C
L
L
E
E
A
A
R
R
A
A
N
N
C
C
E
E
W
W
I
I
T
T
H
H
O
O
F
F
F
F
S
S
E
E
T
T
S
S
It is important to cut test squares to attain the exact values for your on size offsets. The on
size offset if used will make the part come out to the EXACT size that the part
coordinates in the program commanded. As you also know, you can lie to the control
about the values of the offsets to force it to machine the part with clearance.
Once you have determined the amount of clearance that is necessary, you can easily use
wire offsets to create the clearance. To come up with the modified offsets for the shape
that needs clearance, simply SUBTRACT the amount of clearance (per side) from ALL
offsets needed to make the shape on size. By subtracting this amount from all of the on
size offsets, you will be making punches smaller and dies bigger. Here is a detailed
description.
Say you had a punch and die to make and you are going to use .010 diameter wire. You
determine that the punch must be made on size and the die must incorporate .002" die
clearance (per side). You look in the condition manual and have decided that you need to
use three cuts (rough and two trims) to make the part to your finish and accuracy
requirements. Lets assume the book recommends the following offset values.
Rough Pass .0085 inch (H085).
Second pass .0056 inch (H056)
Third pass .0053 inch (H053).
You test the recommended conditions and offsets on a test square and find the results
acceptable.
You would cut the punch with the recommended offsets (H085, H056, and H053). When
you machine the die, you will take the on size offsets and SUBTRACT .002" from all the
offsets to come up with the offsets for a .002 inch die clearance.
The die offsets with the clearance calculated in would be as follows.
Rough Pass .0065 inch (H065).
Second pass .0036 inch (H036)
Third pass .0033 inch (H033).
These offsets will keep the wire .002 closer to the programmed path than the on size
offsets, and correctly form the die clearance.
WHEN CLEARANCE IS LARGER THAN THE OFFSET VALUE
If the clearance is larger than the smallest on size offset, when you subtract the die
clearance from the on size offset, the result will be a negative H number. In this case the
H number can be called up as a negative value EX: G41 H-050 (negative .005 inch
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