Re: Limit switches revisited

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Stephen Wille Padnos
<spadnos@s...> wrote:

>
> yet_another_kent wrote:
>
> >I agree, Paul, although I see a lot of examples where the switch is
> >indeed the stop. I was thinking I could use a roller-arm switch
> >attached to the ways that is tripped by a projection on the bed as it
> >passed by to allow for overtravel. My mill will have limited work
> >volume and my steppers will be slow, so I don't envision
> >any "hurtling," but mashing the switches just seems like shoddy
> >engineering to me.
> >
> >The same "en passant" technique could be used for detecting home
> >position with mechanical switches but I'm uncertain how precise and
> >repeatable it would be.
> >
> >
> It depends on what you want to use home position for, really. If you
> expect to have semi-permanently mounted work holding jigs that

reference

> partially machined pieces (ie, you mill 50x the "tops" of something,
> then want to mill the "bottoms"), then homing will be critical. The
> other place where machine home is important is with certain
> toolchangers. You have to know exactly where the head is in

relation to

> a mechanism that's mounted on the machine, and has nothing to do with
> any part you may be cutting. If it's just for determining absolute
> machine limits, then it can be off a little, as long as nothing will
> break if you go over the limit by that same "little".
>

I think there are those of us who do stuff out of whole sheets. you
cut the perimiter of the part. no need for an edge finder.

And, there are those of us who do find the edge and then set zero from
there.

I have machines and processes that do both. Havn't given it much
thought. I always thought it was like using a wrench on one job and a
scew driver on another. just another tool in the box.

Dave