|Most mold makers are proficient in
EDMing steel. If the same parameter settings are used on copper alloys, slow cutting
speeds and high electrode wear will result..The advantage that our MoldStar alloys offer
(rapid dispersion of heat) actually becomes a disadvantage when EDMing them. Taking this
into account, certain settings can be selected that will offer the highest efficiency
possible when EDMing with both graphite and copper electrodes.
In recent years
we have found that the EDM machine tool is THE single most sigificant influence when EDM
We found that Sodick EDM machines utilizing LINEAR MOTION,
combined with the Sodick Power Supply capabilities, as well as a complete Library of
settings for copper alloy workpiece/ graphite electrode selection, which offers cutting
speeds 5 times faster than the nearest competitor and eletrode consumption rates that are
comparable to EDMing steel.
If you are considering updating EDM equipment we would suggest you investigate
the Sodick machine as a solution.
If you do NOT have access to the Sodick technology, TALK TO GRAPHITE
MANUFACTURERS AND YOUR MACHINE MAKER BEFORE MAKING ELECTRODES...
IT WILL SAVE YOU TIME AND MONEY........
OTHER GENERAL GUIDELINES
GRAPHITE ELECTRODES: The best grade of premium graphite or
copper-graphite is the best material to use. Any low or mid-range grade of graphite
will result in much higher electrode consumption, usually three times the wear rate
compared to premium graphites.
COPPER ELECTRODES: Copper can be an effective electrode.
However, the only option available to further reduce the wear factor is to move up to
copper-tungsten. This results in higher material cost along with electrode machining
ELECTRODE WEAR RATES: Reports from customers, machine manufacturers
and graphite manufacturers put electrode wear rates at between 11% -18%, under the best
conditions. For this reason it is advisable to use conventional machining practices over
EDM, whenever possible.
POLARITY: Electrode polarity is usually positive when EDMing
coppers alloys with any electrode material. This translates to "normal"
or "standard" polarity on older machines.
"Reverse" polarity cutting is highly inefficient, is cause for DC arcs and
should not be considered unless recommended by your specific machine manufacturer.
AMPERAGE: This is where disappointing results may often
There seems to be two distinct levels of performance:
- 30 amps and under
- 50 to 60 amps
It appears that the lower amperage cuts are not as effective due to the high thermal
conductivity factor of copper alloys. Heat generated by the EDM spark is quickly
dispersed, thus causing an inefficient cut.
The higher amperage settings seem to overpower the thermal conductivity factor of the
material and are much more efficient. Conclusion - don't be shy with the amperage
Surface finish results will be 30% better when EDMing copper alloys compared to steel
at the same power settings. This makes a good case for using the higher amperage,
CHECK WITH YOUR MACHINE MANUFACTURER Because of the
increase in copper alloy use in mold manufacturing in recent years, most EDM machine
manufacturers now offer definitve information for EDMing copper alloys. Check with their
HELP IS ALSO AVAILABLE FROM POCO GRAPHITE by calling 1-940-627-2121
Poco has technical data sheets available with the latest information in EDM of our Copper
Alloys. Poco online information is available at www.poco.com