Re: know your limits

["William Scalione" <wscalione-at-nc.rr.com>]

Ian,

I had the same question about this when I first hooked up my home switches

When you home in EMC each axis is homed separately, and yes, you must
either use the offset function or move that axis off the switch to home any
other
axis. I believe you can also use one of the limit switches as a home switch
although I have not done this.

Once an axis is homed, then the software limits work well. Suppose you
set up an axis with 10" of total travel, with zero at one end of that
travel.
 If you now move to 5" and set that point to zero you will be able to move
-5" to +5". It will not let you move to +6"

Bill



> Hi,
>
> Having now got bits of mechanism moving back and forth under EMC control,
I
> am turning my attention to adding switches to the axes etc.
>
> What use are home and limit switches using the EMC program? I can't work
out
> in my own mind how three home or limit switches in series can possibly
give
> any usable output. Presumably the first to trip will just bring the
machine
> to a complete stop and, since it would be physically impossible to get all
> three to trip at the same instant, this would mean that two axes will be
at
> an unpredicatable position. If you use the 'home offset' feature, does
this
> mean that the first axis will close its switch, back off by the offset
> amount and then stop, and that the second axis will then continue to move
> until its switch closes and then back off and stop to allow the third to
do
> likewise? I had considered just relying on the software 'maximum distance'
> option to limit travel but, if you reset zero along the way, this
presumably
> becomes ineffective. Any advice would be appreciated. Thanks,
>
> Ian
> --
> Ian W. Wright
> Sheffield  UK
> www.iw63.freeserve.co.uk
>
>