EDM capacitor sizing
Posted by
turbulatordude
on 2003-04-01 07:59:56 UTC
Hi All,
I'm going over the Langois book on EDM and he talks about using a
high uF cap (50 to 400uF) for one type of circuit. This would be an
RC that would discharge when the voltage level will jump the dieletic
and spark the work.
The second type of circuit charges a much smaller cap, (1-3uF) and is
fired from a timing circuit.
I will be using a timing cirucit, so the remaining issue is in cap
selection.
figuring that joules is the measurement of work performed, it seems
that a larger cap will deliver a more powerful ZAP and remove metal
faster, while a lower joule rating will give a smoother finish.
In my other reseach, it seems that voltage dictates the distance the
electrode can be away from the part for a spark to occur. so, with
a somwhat constant voltage for either style, it appears that the gap
distance will be about the same which leaves the current of the ZAP.
I found that photo flash caps are around 120uF to 160uF so I have a
leaning to making these work, but the cost of caps is not signifigant
so I'm not tied into anything.
Can anybody offer insights as to the benefits or problems as regards
removing metal or overall cutting speed with either of these concepts?
as a side note, is there a problem of connecting 2 caps in series to
half the uF rating, or in parallel to double it ? since the voltage
ratng is 330v, that is not a problem on a 70VDC circuit.
Dave
I'm going over the Langois book on EDM and he talks about using a
high uF cap (50 to 400uF) for one type of circuit. This would be an
RC that would discharge when the voltage level will jump the dieletic
and spark the work.
The second type of circuit charges a much smaller cap, (1-3uF) and is
fired from a timing circuit.
I will be using a timing cirucit, so the remaining issue is in cap
selection.
figuring that joules is the measurement of work performed, it seems
that a larger cap will deliver a more powerful ZAP and remove metal
faster, while a lower joule rating will give a smoother finish.
In my other reseach, it seems that voltage dictates the distance the
electrode can be away from the part for a spark to occur. so, with
a somwhat constant voltage for either style, it appears that the gap
distance will be about the same which leaves the current of the ZAP.
I found that photo flash caps are around 120uF to 160uF so I have a
leaning to making these work, but the cost of caps is not signifigant
so I'm not tied into anything.
Can anybody offer insights as to the benefits or problems as regards
removing metal or overall cutting speed with either of these concepts?
as a side note, is there a problem of connecting 2 caps in series to
half the uF rating, or in parallel to double it ? since the voltage
ratng is 330v, that is not a problem on a 70VDC circuit.
Dave