On 01/31/2021 07:28 AM, andy pugh wrote:
I have started to play around with EDM. The intention is to make an
EDM "grinder" to profile tool steel and possibly carbide cutting tools
using CNC-turned profiles.
I think that it shows promise, but only partly works.
I am using a 50R resistor and a 1000uF capacitor. I suspect that this
is too high on both counts.
I am working at 40V and it seems that the tool welds to the work too readily.
I suspect that I would get different results if I controlled to the
gap voltage, rather than charging resistor voltage. And probably
better still with some sort of signal processing on that voltage.
What combination of R, C and V would be typical for a servo-controlled
eroder? I imagine it might be different to a "doorbell" style one.
There are a few different systems for EDM. Ben Fleming (who
I met at a couple CNC meetings) has a line of self-published
books out on EDM. He has done LOTS of work with EDM, and is
an expert.
I made a simple EDM for tap burning type jobs a long time
ago. It used something like 36 V DC, 30 Ohm resistor and a
selection of oil-paper capacitors of 1, 2, 4 and 6 uF or
so. It was glacially slow.
See http://pico-systems.com/edm.html
Ben Fleming's pulse EDM, on the other hand is quite fast.
Flushing of the debris is a key requirement. Also, his
pulser recovers quite quickly, and so fires several thousand
discharges per second.
What are you using for dielectric?
Jon
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