Re: [CAD_CAM_EDM_DRO] Re: home switches

In a message dated 3/24/2004 12:22:34 PM Eastern Standard Time,
ballendo@... writes:
The short answer is: Microswitches of the proper type--and even some
relative cheapies-- are far more repeatable than is often imagined.

Second, if you AND a single slot index wheel with your microswitch,
and use an optointerrupter for reading the index wheel slot, you can
get even better repeatability. This is the standard technique used in
commercial cnc machines; where they just use the existing servo
encoder's index pulse AND'd with a mechanical switch.

Hope this helps,

Ballendo
Ballendo:

This is the way almost all of the industrial machines set up their Zero/Home
functions. And, I have found that the mechanical limit switches, such as
those mfd. by Telemecaniqe or Square D (they happen to be the same company now)
tend to be most reliable in this application. Some of the industrial machines
on which I work do use the proximity sensors but they tend to fail more often
than do the mechanical switches. I believe this to be cause most of the time
by the harmonic vibrations that are created by the high speed spindle speeds
and any slight balance problem with the tool in the spindle. Keep in mind that
most of the machines on which I work are for woodworking and spindle speeds
are frequently as high as 24,000 rpm. You can't have much of a balance issue at
those speeds.

But, I digress, in my opinion, the mechanical limit switch is the most
reliable way to go, not necessarily the cheapest though.

Randy Abernathy
4626 Old Stilesboro Road NW
Acworth, GA 30101-4066
Phone / Fax: 770-974-5295
Cell: 678-772-4113
E-mail: Cnc002@...

I furnish technical support, repair, and other related services for your
industrial woodworking machinery. My background as Senior Service Engineer for the
SCMI Group for nearly fifteen years with factory training, combines with my
extensive background in electronics, mechanics, pneumatics, electrical and CNC
machinery to offer you needed support for your machinery.


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