Re: [CAD_CAM_EDM_DRO] Re: Software for wire EDM control?

Alan,

You are right. We use the taper cutting options for plastic mold relief and
sometimes sheet metal blanking dies back relief too. I had shot a video for
the machine's operation sometime ago. Have converted it to mpg too. I guess
a few shots from that and a few stills would help. I'll try to post them in
the files section or if the space is limiting then I'll put them on my web
page. You'll have to wait for a couple of days for that.

Have a nice day.

Zafar

----- Original Message -----
From: "Alan Marconett KM6VV" <KM6VV@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, July 31, 2003 12:06 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Software for wire EDM control?


> Hi Zafar,
>
> Thanks for the excellent descriptions! I take it the tapers it can do
> are somewhat limited. If watching an ampere meter is enough to get the
> feed right, that could simplify a hobby WEDM design. A "feed rate
> override" might suffice in this case.
>
> Three axis calculations are done (3D)? Then are the UV moves just
> calculated from the taper information and the XY tool path? I suppose
> what kind of parts are being made. This may be all that's needed for
> mold relief.
>
> And yes, a pix would be welcome!
>
> Alan KM6VV
> SherlineCNC
>
> Zafar Salam wrote:
> >
> > Hi everybody,
> >
> > I've been following this thread with great interest because I own a
chinese
> > wire edm for the last eight years. The chinese machines mostly run on
> > molybdenum wires of dia .15 to .20 mm. We normally tie a 200 m piece of
wire
> > on it's drum which moves back and forth between two hardened v-section
> > pulleys. This length of wire lasts about 24 hours after which it weekens
and
> > breaks up. Typical cutting speeds are 25 mm per hour in a 25 mm thick
steel.
> > For thicker or thinner sections speeds vary proportionally. Speeds on
> > Aluminium are the fastest and carbides cut the slowest. Surface finish
> > improves a little with lower currents. The 0.18 mm wire, which is most
> > widely used, can withstand a current upto 2.5 amperes in contineous
> > operation.
> >
> > It uses 3B code. I've seen newer models of this machine which use G
codes
> > too. It is a 4 axis machine. Work is clamped on the table which moves in
X-Y
> > direction. Lower end of the wire passes through a pulley which is
> > stationary. Upper end's pulley is attached to another small two axis
drive
> > U-V. Taper is controlled through the movement of both X-Y and U-V. The
3B
> > code doesn't have options for 4 axes. We can only put the amount of
taper
> > required in the machine with the height of the workpiece and the
controller
> > figures out which axis to move. With newer machines running on G-code,
top
> > and bottom different shapes machining is also possible.
> >
> > It doesn't trace back automatically when a short circuit between wire
and
> > work piece happens. It just halts there. There is a button on the
controller
> > which manually backs the table on the cutting path. So if the short
circuit
> > persists then we have to press that button to clear it. Normally short
> > circuit doesn't happen if we have set the machine parameters correctly.
Ther
> > is a knob on the controller which control the stability of cut. What
this
> > knob does is control the speed of the steppers. If we set it to a higher
> > speed than the material removal rate then a short circuit happens.
Slower
> > speeds result in an unstable current on the ammeter.
> >
> > I am a mechanical engineer, so can't explain all this in the ee terms.
Also
> > excuse me for using the metric units. We are taught to use metric units
from
> > elementary school. It's hard to even think in imperial units :).
> >
> > I hope all the geniuses out there can figure out a simple plan for
building
> > and controlling a wedm at home. I would sure like to give it a try
myself.
> >
> > Regards,
> > Zafar
> >
> > P.S. I can post videos of my machine's operation if anyone is
interested.