Re: [CAD_CAM_EDM_DRO] Orbicut CNC Head

Hi Zafar:
I went through a fair bit of this question set when I bought a Hansvedt
sinker last summer and wanted orbiting capability.
My intentions were to build my own, and to that end I enlisted the generous
help of a fellow group member who lives in my corner of the world.
I aborted the build-yourself approach when a used Gromax unit became
available but I will give you as much info as I can.
The Gromax unit, (and I suspect most others as well) uses a set of canned
cycles that do not involve g code or any other machine instruction.
There are a set of control pushbuttons that will set up pulse trains
directly to the steppers, and the only thing the onboard microprocessor
seems to do is to calculate the magnitude of the axes movements by setting
the number of pulses and coordinating them so a precanned orbit path will
end up the right size while maintaining its intended shape.
In addition, there is a circuit that seems to simply interrupt the pulse
train when the spark gap resistance drops below a definable threshold and
resume when the gap resistance rises again. (This capability is selected
when you want to burn sideways...for roughing the orbiter simply follows its
canned path without spark gap feedback and the ram controls the gap)
My friend and I cudgelled our brains forever, trying to figure out a way to
make it back up along the same path that it just travelled, but I'm not sure
that the commercial ones do this either.
It sure doesn't look like it when I do a side burn on the Gromax.

The "how to do this" is way out of my league...my knowledge of electronics
is worse than just dangerous...but a starting place might be the article on
how to build an EDM by Robert Langlois in Home Shop Machinist.
He describes a stepper driven sinker (Z axis only) that operates much as I
have described for the Gromax.

You'd need to come up with a suitable microprocessor for the canning of the
cycles...but they're all very simple.
A circle, a square, individual axis movement, and a 45 degree vector into
the corners are all that's needed.
Anything else is overkill for all but the most complex burns, and if you're
in that league, do yourself a favour and buy a proper CNC sinker!

So...find a smart buddy as I did, and roll up your sleeves.
Let us know how you make out and don't hesitate if you need more info from
me.
(Just don't ask me anything that requires a knowledge of electronics or
motion control)

Cheers

Marcus

----- Original Message -----
From: "Zafar Salam" <zafar@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, September 06, 2002 8:00 PM
Subject: [CAD_CAM_EDM_DRO] Orbicut CNC Head


> Hi all,
> I have this Orbicut CNC head removed from a sinker EDM. It's pics and
details are on http://www.geocities.com/zafarsa/. Since I am a newbie with
CNC, I was wondering where to start from to make this thing work. It has two
8 wire steppers (50 mm size) and two limit switches with each slide (I guess
for making the home position). Which drivers, power supplies, software etc.
would you suggest for it.
>
> Regards,
> Zafar
>
>
> [Non-text portions of this message have been removed]
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this as a
sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
>
> Post messages: CAD_CAM_EDM_DRO@yahoogroups.com
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> Moderator: jmelson@... timg@... [Moderator]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> bill,
> List Mom
> List Owner
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>