What's new
What's new

EDM book

durableoreo

Plastic
Joined
Jun 5, 2020
Is there a good book on EDM?

I'm interested in the electrical details of generating the arc. However, I don't know enough about it to know what I need to know so any suggestions are welcome!

I found Electrical Discharge Machining by EC Jameson. Is that any good?
 
Hi durableoreo:
There are some very good books about how to RUN an EDM and how to BUY an EDM; the EDM Handbook by Bud Guitrau springs to mind.
There is much much less information about how to design the circuitry; this is held like gold by the EDM manufacturers to the point where even schematics of individual machines are very rare.

The basic challenge as I understand it is to create a current and voltage spike super quickly such that the waveform is almost square rather than sinusoidal, that all pulses be equal, that they occur at moderate to highish frequency and that they be responsive to external inputs through a feedback loop that starts with sending gap voltage information to the spark generator side of the control to say when to do it's magic
.
The desired effect is to create and then decay plasma channels in the dielectric fluid between electrode and workpiece such that electrons can flow and do useful work as they transit the gap via the plasma channel.

Over the years, successively more modern devices have been employed to achieve this goal with more precision and consistency while the gap sensing circuitry that dictates the electrode position relative to the workpiece position and therefore the discharge voltage trigger has also improved in responsiveness but also in the range of parameters it can sense (other than just gap voltage).

This in turn has led to improved circuitry to respond to these additional input conditions, so the ram (and electrode) no longer responds only to gap voltage but to "other things" as well.

As you can expect, this is all super top secret proprietary information that the EDM makers jealously guard and try to reverse engineer from each other.

So finding publications that reveal the current state of the art are going to be challenging to uncover.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 
Hi durableoreo:
The desired effect is to create and then decay plasma channels in the dielectric fluid between electrode and workpiece such that electrons can flow and do useful work as they transit the gap via the plasma channel.

Hi Marcus,

I believe this is slightly out of order. It was my understanding that the voltage/electrical potential between the electrode and the workpiece gets high enough that the dielectric ionizes, causing the dielectric break down, which allows a high current discharge, which causes the plasma.
 
Hi pb1:
You may well be correct; my knowledge is no where close to comprehensive on the subject.

When I do a Google search on "EDM discharge mechanism", I get a series of scholarly articles dense with scientific jargon, that propose to explain it in detail.
After the eye watering formulas and all the words I have to look up, I come away with a recognition that my understanding is perhaps good enough to run a machine and to troubleshoot it if it's not performing as I expect, but certainly not enough to design an EDM circuit or compose a treatise on the subject.

However it actually happens, the establishment and subsequent decay of the plasma channels is supposed to be what does the useful work of blowing bits off the workpiece...on that our understanding concurs.
Reading up on the details of that mechanism makes my eyes hurt, and it's not information I can use to help me burn better, so I confess I'm lazy and resistant to digging too deeply into the subject myself.

If you can go there without harming your brain, my hat's off to you!:D

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 
No worries, I can be a bit too pedantic at times. I started as an EDM operator some years ago and then progressed to programming, setup, then applications engineer, and had a meter in the back of the machine more than enough times when something went wrong. I guess I know enough to know that I know nothing. :D
 








 
Back
Top