Re: Threading under EMC

[Chris Stratton <stratton-at-mdc.net>]

> 
> Chris Stratton wrote:
> 
> >
> >
> > I wasn't going to bother with an index pulse, since I don't think the
> > LS7266 (dro.c) code supports it very well. But it could be used as a
> > sanity check to see if the encoder is reliable.
> 
> Speaking of sanity checks....one does want the spindle going the correct
> way.  Also, without the index pulse how do you get the single point to
> start the thread in the same place on successive passes?
> 

Seems the program or operator would have to get the spindle going the
right way first.  There are lots of ways to shoot yourself in the foot
(or drill a hole in your fixture/table) with a CNC machine, why should
this be any different?  

You don't need an index pulse if you keep tracking the spindle encoder
all the time.  EMC uses a 32 bit counter.  Even with a high count
encoder, it takes several hours (potentially days) to roll over.  We'd
simply have to zero the counter at the start of the part, or use an
encoder with a power of two cycles per revolution, which will wrap
cleanly.

Chris

-- 
Christopher C. Stratton, stratton-at-mdc.net
Instrument Maker, Horn Player & Engineer
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