Centroid Community CNC Support Forum

Can someone explain P 78 in practical terms for me? This happens on several lathes for me, so I'm curious as to the behavior why. Here are some conditions:

Set P78 to 1

Goto MDI CYCLE START

Spindle goes to 30 rpm.

Set P78 to 7
Goto MDI CYCLE START

Spindle goes to 55+ rpm, I freak out and stop the spindle.

This happens on two different machines running Oak.
I know that 30 rpm or 55 rpm doesn't seem like much, but on a 88" chuck, that's scary fast.

That certainly does not sound right.

What CNC12 software version(s) are you running?

Do you get correct spindle speed response with P78 = 0?

Does the error (running too fast) happen with P78 = 3? What about with P78 = 5? Perhaps we can narrow down which specific feature is adversely affecting the spindle speed commands.

I set P78 to 0,1,5, etc, but that didn't help much.

I think the issue was that the min/max spindle speed is what determines the 0-10v scale, (in Setup - Motor). I was hoping it was smarter than that. If there's a parameter we can adjust to slave the 0-10v to the encoder pulses, that would be a lot cooler. I also have a problem with the wording on the min/max, since it's relative to high gear. (This particular 100hp machine is certainly capable of spinning its 88" chuck at 500 rpm, but no way would I want to be near it).

So here's a tip for those in the future looking for why this occurs: If your spindle drive has a max RPM setting at 10v, that's exactly what you need to have in the motor setup. It appears that spindle encoders are only used when they are in a slaved operation (like threading).

Rookie mistake, thanks for your help guys.

Spindle encoders are only used to read spindle rpm. Centroid does not use them to control rpm.

post some photos of this machine , sound interesting