Re: RTLinux lessons, and EDM's

Brad Heuver wrote:

>
> Jon Elson mentioned having EMC monitor the spark current and advance
> the electrode into the work. THis is essentially what the stepper
> control in the HSM design does. Maybe we could have the actual current
> monitoring done as was shown there, and have emc accept motion inputs
> off of a card or calculatd in a small code generating program.? (I
> really don't know where this was going, but it does seem like if the
> board designed by R.Langolis can move a stepper based off the current, a
> part of that board could be made to talk to EMC to drive the Z axis,
> allowing the idea Jon put forward to work.

A very interesting idea. Once EMC has been updated to accept jog commands
from a manual encoder, we could set it up so that the encoder signals came from
a stepper drive chip. Then the R. Langlois board could drive it.
Otherwise, signals from the current sensor could drive some other electronic
circuits that give direction and a pulse train signal to a counter chip that makes
AB quadrature signals.

But, a better way would be to have something wired into the user interface
so you could specify a parameter that mapped EDM current to feed rate, and
then could move whatever axis was specified in a move command at a rate
determined by the EDM current, but the direction and distance would be
programmed by G-codes. Currently, the UI (user interface) can send
a speed modifier of 0-100% to the motion control code, but it can't make it
back up. If we could get -100 to +100% feed override to be accepted by the
motion code, then we could have the UI handle updating the velocity and
backing off when a short develops. Of course, a special version of the
motion control software would make the response much quicker.

Jon