Re: [CAD_CAM_EDM_DRO] EDM - Should it have a burned appearance?

Yo Gary;

What frequency range are you using? You might be able to control this
electronicaly, as in an N pole double throw switch function. One side connects
cap N to the work, and the other side discharges it to ground. If the discharge
time is to long to immediately switch the cap back to the work, switch in/out N
other caps, then recycle back to cap one, and continue.....

Bill

On Mon Nov 19 09:40:09 2001, Jon Elson, <elson@...> wrote:

>garyswindell@... wrote:
>
>> I have small EDM that I am doing some experiments with. It uses an
>> RC type oscillator. 42 Volts 1Amp. Petroleum based dielectric fluid.
>>
>> The general question to those who have actually seen these work
>> is...Does the area being cut end up looking slightly burnt? Two
>> possible answers:
>>
>> 1) You are using electrical sparks to cut something and these are
>> quite hot so naturally there is some burning
>>
>> OR
>>
>> 2) It should not look burnt and the only reason it does is because
>> you are getting some arcing.
>
>There is no difference between arcing and EDM. In either case, some
>amount of workpiece metal is vaporized, and condenses out as extremely
>microscopic particles. There may also be breakdown of the EDM
>dielectric, laving some free carbon if it is a hydrocarbon-type fluid.
>I think this is unavoidable. I have only used EDM to burn out
>broken taps, but the result looks like this. It is not actually burning
>of the workpiece, rather it is STAINING by the black fluid that results.
>I know this, because if the fluid spatters, anything it touches gets
>turned deeply black.
>
>The RC EDM may be partly the culprit, as it takes a while for the
>cap to discharge, leaving the arc going for a moment. During this
>time, probably more EDM fluid is broken down than if an electronic
>switch shut down the discharge after a short interval.
>
>Probably, a fluid flushing system with filters, or going to distilled
>water might fix the problem. Clearly it would eliminate breakdown
>of the fluid into carbon.
>
>Jon
>
>
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