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

Leslie M. Watts wrote:

>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.
>
>
>

I have a VFD on my mill, and it has a fault relay. I used the NC (when
everything
is OK) contacts on that relay in series with the estop chain on my system
to do the same. If the motor stalls (pretty unlikely, but it can happen)
the VFD will fault, and cause an estop.

Jon