RE: [CAD_CAM_EDM_DRO] Threading on a lathe with EMC

Is the problem that the hobby machines do not have a proper spindle encoder?

Has anyone done a feed per revolution for EMC?

Ethan

-----Original Message-----
From: ccs@... [SMTP:ccs@...]
Sent: Monday, October 29, 2001 12:26 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Threading on a lathe with EMC

> Sorry if this has been asked before, but can this be done, and if so, how?

Not yet. Several people (myself included) have though about the problem,
but not one has actually done the work yet.

The problem I faced in trying to do it was that EMC assumes it can
slave the real world to its internal clock, wheras in threading you
need to slave the motion to the real world spindle rotation.

Acutally, there is a way to thread with EMC as it currently exists.
You need a spindle drive that can be tightly servoed in position, not
just velocity. In hobby scale machines, folks have talked about using
something like one of the Geckodrive step-servo modules to run
something like a 3/4hp DC motor for the spindle. With this kind of
setup you would simply program a spindle-axis movement coordinated
with your Z axis movement. It should not be too hard to modify EMC so
that the spindle control M-codes run it at a fixed speed for normal
turning. Or even to accomplish constant surface speed as diameter
varies.

Chris


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