Re: [CAD_CAM_EDM_DRO] Tap burning EDM? Need it Quick and Dirty ;-)

Hi,

You really need the solenoid to push the electrode towards the work and for
a spring to pull it away. Then you use the contacting / sparking of the
electrode to short out the solenoid (perhaps through a transistor circuit).
The first EDM I built used a stepper motor driving a screw which held the
electrode. The stepper was driven by an SAA1027 chip and the shorting of the
electrode as it was driven down reversed the 'direction' pin to the chip -
so, the free-running stepper drove the electrode down, it touched the work
and shorted out, this took the direction pin to 0 and the stepper wound the
screw and electrode up again until current stopped flowing because the
sparking stopped. This 'cleared the short' setting the direction pin to 1
again and the electrode started on its downward journey again to repeat the
sequence.

Best wishes,
Ian
--

Ian W. Wright
Sheffield, UK


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----- Original Message -----
From: <egroupscdh@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, November 06, 2002 5:02 PM
Subject: RE: [CAD_CAM_EDM_DRO] Tap burning EDM? Need it Quick and Dirty ;-)


> > From: Jerry Kimberlin [mailto:kimberln@...]
> >
> > jmkasunich wrote:
> >
> > > It seems that anything simple that I can come up with will
> > > require manual electrode feed. Is it practical to use
> > > manual feed to burn out about 3/8" of a #8 tap? Or is slow,
> > > smooth advance of the electrode too difficult to do?
> >
> > I don't think you could do it easily by hand in this lifetime
> > :-). A more practical way might be to use a hand held vibratory
> > engraving tool with an insulater chucked in it that can hold the
> > electrode. Most of the big tap burners (and some small ones) are
> > just a vibration device that sits there and jiggles. In your
> > one-off tribulation, you could hand feed that into the tap. You
> > could duct tape the engraving tool to a rod chucked into your
> > drill press to hold it all steady. Kind of rube goldberg but it
> > should work once and hopefully you'll not break another tap :-).
> >
> > JerryK
>
> Would it work to use a solenoid or relay coil with the electrode attached
to
> the armature and feed the coil through the electrode? Contact would
engage
> the coil pulling the electrode away, breaking the connection which would
> cause the electrode to drop making connection, etc. etc. With perhaps a
> light-bulb ballast ...
>
> All you'd have to do is feed slowly listening to the sound of the
mechanism
> to adjust for maximum cutting rate.
>
> I may try this next time I get into a jamb ...
>
> Cheers,
>
> Chuck Hackett
> Omaha, Nebraska, USA
> 7.5" gauge UP Northern 844
>
>
>
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