Re: [CAD_CAM_EDM_DRO] Another EDM Approach

vrsculptor@... wrote:

> Just musing, I'm out of my depth here....
>
> I'm also interested in EDM. I had concluded, before the recent posts,
> that useable home EDM was not feasible. Seeing the recent posts I'm
> not so sure. How about simplifying the proposed circuitry by
> offloading most of the control to a PC.

HUH? The pulse on time that someone suggested was 1 - 9 uS.
There's no way you can control pulses that short with the PC parallel
port.

> The parallel port already
> controls my Z axis using a step and direction pin. Could the third
> pin be tied to a one shot circuit to fire the pulse?

The pulser circuit doesn't "fire" the pulse, the EDM action in the small
space between the electrode and the workpiece does the 'firing", and
the pulse control interrupts the discharge, and prevents another one
from starting for a controlled time. This kind of circuit can be built
with a dual timer chip, the LM556, and 2 resistors and 2 capacitors.

> A trim pot with
> knob on the one shot circuit could manually control the pulse length.
> Determining optimal operation (no spark, just right, short) seems
> like a much harder task. It could be done if the EDM interface board
> could post the operational status using some of the remaining
> parallel port pins. The software to drive such an arrangement would
> be trivial.

But, WAAY too slow. Letting the PC control electrode advance (or
other axis movements) and figuring out when to stop is fine, but the
pulse control is just a bit too 'real time' for the parallel port.

Jon