Re: emc for wire edm control

[celgo-at-eject.co.za]

----- Original Message -----
From: "Michael Coffey" <mdynac-at-prodigy.net>
To: "Multiple recipients of list" <emc-at-nist.gov>
Sent: Thursday, March 13, 2003 6:43 PM
Subject: Re: emc for wire edm control


>
> Ray Henry 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.
> >
> > One way to achieve the reverse path is to simply record the positions of
each
> > axis for each motion loop.  This is how we ran the first backplotter.
The
> > second plotter does the math to make a vector from a whole series of
points.
> >
> > With a file like this, when the parport pin goes low/high the grapical
> > interface could abort the running program, switch to mdi mode, and
issues
> > each point back in the recorded position file as a g0.  Repeat this
until the
> > pin clears.  Once cleared, we could restart the cut at the activeline
when
> > the short happened unless we crossed position into a previous block of
code.
> > If that happened we would need to decrement the activeline by 1 and
restart
> > there.
> >
> > Cutter comp may cause a few problems but a few tests with the
backplotter
> > should show a good approach here as well.
> >
> > Ray
> >
> >
> > 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
> >>Marcel Gombault
> >>
> >>This email was scanned by the ICL anti-virus solution.
> >
> >
> >
> Not all Wire EDM's "back up" during a shorted condition.
> For example, most Japax wires go into feedhold during short,
> and then continues along the contour after the short is cleared,
> usually by flushing,
> Sensing the voltage at the gap is the best way to achieve this.
> A simple, yet precision comparator/opto circuit works nicely here.
> Setting the circuit to output at, say 20 gap volts, is a good starting
> point. Then tweak it for best performance...
> In my opinion I would get the machine up and burning using this
> approach, then delve into the more complex task of actually making the
> machine backup in a shorted condition.
>
>
> I am currently working on a retrofit for wire/sinking/hole popping EDM's
> Both servos and steppers.....
>
> I have several old 2-axis "blue" Andrew 330's and 630's with servos,
> these macines do backup during short, a DEC PDP8\a is the heart of the
> axis motion on this beauty.
> Does anyone know how to dis-assemble pdp8\a a code???
>
> and an old Japax 4-axis machine with steppers, this machine feedholds
> during short
>
> Hope this helps....
> Michael
>
> The reason for wanting ot reverse the feed is that I have a Chinese made
machine that works that way. This machine I set the cutting speed according
to the voltage I dont think the speed changes with any voltage fluctuation.
Maybe one can  stop the feed if the voltage go below a certain point if need
be.

Regards Marcel
>
> This email was scanned by the ICL anti-virus solution.
>
>

This email was scanned by the ICL anti-virus solution.