Why positive polarity is commonly used for tool
electrode during Electro Discharge Machining?
Answers
Answer:
My first problem is the term positive polarity, because it does not indicate which electrode is positive or anodic. Examinating the removals of he anode and the cathode, then we find that the anodic removal for time ranges up to about 1 µs is substantially larger than the cathodic removal. For most metals this turning point (anodic and cathodic removal is equal) between 0.8 and 2 µs. For WC-Co-alloys at this point is 20 µs and higher. WC-Co alloys are therefore machined with anodic workpiece polarity reversal.
The differences between EDM and Micro-EDM are the micromachining is performed exclusively with needle pulses under 2 µs. The same statement applies to the Wire-EDM to.
Therefore, it is incomprehensible to me when working in Papers in Wire-EDM with pulse duration greather than 100 µs. (????)
In the final analysis thus depends on the chosen polarity of processing of the used process energy source (generator).