Re: emc for wire edm control

[Ray Henry <rehenry-at-up.net>]

On Thursday 13 March 2003 10:48 am, you wrote:
> At 15:53 3/12/2003 -0500, you wrote:
> >Marcel
> >
> >I have done a bit of work here and with Roland Friestad planning for such
> > a retrofit.  He has a two axis Agie wire EDM that is a few years beyond
> > factory service.
> >
> >We had planned to use an analog signal for wire current but your approach
> >also sounds interesting.  This could simply be a voltage up signal
> >optocoupled to a parport pin and read by tkio.
> >
> >-------------------------<snip>-------------------------------------------
> >------
> >
> >On Wednesday 12 March 2003 12:18 pm, Marcel wrote:
> > > Hi
> > > I want to know if its possible to change emc to control a two axis wire
> > > edm machine. A wire edm machine need to be able to go back when the
> > > cutting voltage is low (shorted) and only start to go back to the
> > > cutting direction when voltage is high Regards
>
> ------------------------------------<snip>---------------------------------
>-----
>
> An EDM monitors the operator selected gap voltage to determine cutting
> speed. If the voltage drops the feed rate slows down. Only when there is a
> no-voltage situation will it actually back up. I think you will still need
> to deal with an analog signal to make it work.
>
> -Bob

Bob

I can see this approach also.  It could be implemented in either real time or 
at the interface level.  At the interface level we would just have to scale 
the signal from 0 -100 and put a set command in the tkemc update loop.  

Again at an interface level, if we wrote a separate tickle process like tkio 
we could run that loop much faster if we needed greater response that 0.2 or 
0.1 seconds.  If we needed 0.001 we'd need to get into the real-time 
processes. 

There are several inexpensive analog boards.  I suppose the least cost way to 
get this signal in would be joystick but I can just hear a thundering chorus 
of, "M-i-c-k-e-y-m-o-u-s-e (tm)."  

How much smoothing, averaging, or integrating would it take of a raw voltage 
signal in order to use it this way?  Would you recommend that the smoothing 
and scaling be done in hardware or in the EMC?

Ray