Re: Home Switches

At 02:33 AM 12/24/99 -0600, you wrote:

>From: William Scalione <scalione@...>
>
>Anyone know what the best type of switch to use for a home switch?
>I am using mechanical "Cherry" microswitches but they don't always
>actuate at the exact same position, which makes them kind of useless.
>>

DeVlieg, a maker of "tenth" accuracy jig borers uses ("used" perhaps, as
this was many years ago) microswitches in their rod troughs to automaticly
position and home these mills.
Two cautions on how they used them: They didnt use an actuating lever, but
allowed the machine to operate the pin that comes through the body of the
microswitch directly, and they closed on the microswitch at a low and
standard speed.

You can approach the home position in rapid, but you must be in creep to
close on the switch. You can use any switch for this purpose, perhaps with
an override lever, but it must be set far enough from the home switch to
prevent an inertial override of creep.

The method in common use today on encoder equipped machines requires much
less accuracy. It uses a microswitch to stop the machine, then reverses
and creeps out to the index on the encoder. Some encoders have an A and B
channel plus an index channel, often maarked C or Z which occurs only once
per revolution. It is often gated with the A or B channel for even
narrower accuracy.

If you are using stepper moters, you can reverse on switch actuation and
gate the microswitch home with a particular step of the stepper motor.

Ted