Re: [CAD_CAM_EDM_DRO] EMC Thread Cutting?

Jon Elson wrote:

> Ozzie@... wrote:
>
> > Is it a practical possibility to use a closed loop EMC system to
> > accurately cut threads by putting a rotary encoder on the lathe
> > spindle and feeding that info to the X axis stepper motor controller.
> > I would think that the feed rate and spindle speed should approximate
> > that needed to cut the desired thread and then the exact calculated
> > numbers loaded into the machine .ini; but then it should work; no?
>
> This is done all the time on CNC turning centers. There is some
> question whether
> EMC has all the code set up to make multiple passes when threading, in
> otherwords,
> does it pick up the thread at the same point of rotation, by use of the
> encoder index
> pulse. It has to do this to take multiple passes while threading.
>
> If EMC does not handle this at this time, it should be fairly
> straightforward to
> do this. Apparently a very old version of EMC that ran on an
> experimental
> (and not very successful) Windows NT platform did run a turning center,
> and
> did handle the threading. This feature hasn't been tested in a while,
> from what
> I can determine. The other thing that is nice, but not necessary at
> first, is
> constant surface speed. These are the two things that are not run into
> on
> milling machines.
>
> Jon
>

Indexing the spindle so one starts the thread at the same place would be a first step. To get out of a thread in a half turn or so
(up against a shoulder) would seem to require reasonably fast cross-feed acceleration/speed. Software to sync spindle and carriage
should not be too hard.

Dave

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