RE: [CAD_CAM_EDM_DRO] Re: EMC - M codes pause motion?

I have drawn up a little circuit that uses the spindle and
brake signals from the parallel port to check for positive
spindle rotation.

In cnc router apps that don't have programmable spindle speed
I find a nasty and often encountered crash mode is when the
spindle stalls from too agressive feed rate programming or
a dull or damaged cutting tool. The drive motors just keep pushing,
sometimes with very large forces. Enough to break things.

This little circuit just checks that the speed is ABOVE a certain
value with a little hall sensor, quad NAND gate and a couple other
inexpensive components. If the speed crosses that threshold a logic
high is sent to estop.

For this to work I use the brake/spindle on timer built into EMC.
But I use the BRAKE to start the spindle and the MOTOR ON to enable
after a wind-up delay.

If anyone wants I can put it on the web site after I get a chance to
build it up an test it.

Les

Leslie M.Watts
L M Watts Furniture
Tiger Georgia USA
http://home.alltel.net/leswatts/wf.html
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