RE: [CAD_CAM_EDM_DRO] Re: Safe Spindle Control

Keith,

A lot depends on how you've wired your system. Simplistically, (assuming
here that you are not using a VFD), any type of switch in the coil circuit
of the spindle starter (contactor) will allow you to turn the spindle off.
It could be a toggle, start/stop station (using the starter's auxiliary
contact to latch), or a relay contact. Your E-Stop button should (among
other things like killing the power to your stepper/servo drives
appropriately) break the coil circuit to the spindle's starter. This in
turn will accomplish the same thing as trying to add a switch in series with
the three phase legs to the motor.

MACH2/3 does support a circuit known as a "charge pump" which will send a
signal to let the system know if MACH is trying to move the tool, but
personally, I opted for depending on a hardware solution instead. My coil
is wired to a normally open contact of my ENABLE relay. This in turn cannot
be actuated until MACH is activated. It's sort of a failsafe. If the
software isn't running, nothing works. If the software is running, an
E-Stop kills all moving motors. Independently, I can turn the spindle
on/off, but only if the other conditions are met.

Hope this helps,
Jeff



This is something I have worried about ever since I rebuilt my CNC
Bridgeport. Each time I change a tool, I wonder if the spindle could
somehow start up. Is this really a possibility? The tool change is
usually done during an M6 command and the computer is waiting for
cycle start button to be pushed.

Where would the best place be to place a switch to disable the spindle
motor? I assume it would be on the 3 legs of the 3phase power as it
comes into the motor? There would have to be a second switch for the
AC 110 that would disable the power to the DC powersupply that runs
the stepper motors too. I imagine opening the normally closed switch
during a tool change, then closing it before proceeding. Would I have
to have 2 separate switches or is there a way to use just one?

Thanks guys for bringing this up!

Keith Clark