On Wednesday 23 January 2013 16:19:10 Gene Heskett did opine:
Message additions Copyright Wednesday 23 January 2013 by Gene Heskett

Ignore me. "Limit" switches are not always used as "Home" switches.

> On Wednesday 23 January 2013 15:59:55 Bruce Klawiter did opine:
> Message additions Copyright Wednesday 23 January 2013 by Gene Heskett
> 
> > I am curious, how does LinuxCNC back off of a limit switch?
> > I have a bridgeport with hand wheels so it is easy for me, just
> > wondering how this is done on the big machines.
> > 
> > Bruce
> 
> As shown in the gfx on the wiki under homing, there is an implicit
> assumption that it is a mechanical switch, with a bit of hysteresis
> space between the close and the open going the other way.  It's fairly
> well explained, but the lack of hysteresis in an electrical contact
> such as I am using, means I cannot set my backlashes for total
> compensations, because the backlash takeup move may reopen the contact,
> and its a show stopper error if the switch is already open when the
> backup move starts.  I have x home working about 90% of the time by
> setting backlash to half a thou in the .ini file for x on my lathe, and
> around 3 thou less than real on my old sloppy z.  When x works, it does
> all the motions in just a few milliseconds once the initial contact has
> been made.  The old Z was the same except for the 300 milliseconds the
> backlash moves of 20 thou take.
> 
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> Cheers, Gene


Cheers, Gene
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