RE: [CAD_CAM_EDM_DRO] Limit switches revisited

For me, the most important characteristic of a limit switch is overtravel.
The axis it's limiting must be able to continue to move a small distance
beyond the trip point of the switch when it goes hurtling into it at max
rapid speed. Small pushbutton switches make poor mechanical stops!

I'm using 8mm diam inductive prox switches on my small router project, they
have a 2mm sensing range and seem to be quite repeatable...

PK

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of yet_another_kent
Sent: Tuesday, 15 November 2005 11:24 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Limit switches revisited

Folks:

I'm building a small mill and looking at the problem of detecting home
and limit positions. I could rig up a teststand and evaluate various
alternatives, but I've got lots of other things to do too, so I
thought I'd "ask the experts" first.

Aside: Searching the messages of this group, I find that a newbie
asked a relevant question last August but got mostly irrelevant
responses that moved quickly from limit switches the rise and fall of
the American machine tool industry. I'm hoping we can stay on topic
this time.

For small mills, at least, it looks like many folks are using some
variant of what we called a micro or snap switch when I was growing
up. It would seem to me that for detecting the physical limits of the
machine, most any such switch would do. Probably its most important
characteristic would be its physical durability. How about detecting
home position, however. Are there any recommendations for the
make/model of switch? any favorite mechanical arrangement? any data
available on performance in this application, such as reproducibility,
durability, on-off deadband, etc?

I could imagine a mixed system using mechanical switches for detecting
hard limits, while using some other kind of sensor, say an optical
slot sensor triggered by a moving vane, to detect home position. Same
questions about performance data....

You name the physical phenomenon and there's a sensor based on it that
could be used to detect home and limits. Are there any favorites? Same
questions about performance data....

Regards,
Kent








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