Wire EDM Machine Operation Chapter 1
Copyright November, 98 Page 1-4 Sodick Inc.
When finishing, the stress on the wire is very small and therefore the wire speed can be
reduced to conserve wire.
The wire speed can be entered into the cutting condition or into the NC program on
machines with AWT. This overrides the knob. All machines can adjust wire speed
manually on the control panel.
WIRE TENSION
Wire tension is the amount of tension on the wire as it is driven through its cutting
motions. You can think of the wire tension as how much “stretching pressure” is applied
from the tension roller to the wire ejection rollers. Actually, the tension is caused by the
amount of restriction the wire is given by the tension roller at the top of the wire drive
area. The pinch rollers just above the wire disposal bin pull the wire from the wire spool
and can be adjusted to eliminate wire curl. If the pressure between the rollers is decreased
too much, the wire will slip. The tension roller is the rubber roller that the wire is double
wrapped around. Generally, you will want a slightly lower wire tension during roughing
and a higher tension for finishing.
For roughing, this is due to the fact that the wire will be under a great deal of stress due to
the high power for roughing. You don’t want to make this stress excessive by having too
much tension on the wire, causing wire breaks. Set the knob to 8 for .010" wire (1200
grams).
For finishing, the tension can be increased to insure that the wire is as straight as possible
during machining. This insures that the wall of the workpiece will be as straight as
possible. Set the knob to 9 for .010" wire (1600 grams).
The wire tension can be entered into the cutting condition or into the NC program on
machines with AWT. This overrides the knob. All machines can adjust wire tension
manually on the control panel.
WATER RESISTIVITY
The water resistivity affects the EDM process. The water is intended to be a dielectric,
meaning that there should be no electric conductivity in the water. However, in real life
this is impossible to achieve. There is a bottle containing deionization resin hooked up to
the dielectric tank that removes the charged ions from the water thus reducing the
conductivity. While this system works very well, there will be some conductivity in all
water. Note: Resistivity is the opposite of conductivity. Companies with wire EDMs will
use simple tap water for filling the dielectric tank. They depend on the DI bottle to
remove any conductivity from the tap water. However, if tap water is used that contains a
great deal of iron, this will use up the DI bottle quickly. For this reason, companies will
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