Hi!

I have a cnc converted micro lathe, with an index on the spindle and relays to turn it on an switch direction.

I control the lathe’s original motor by pwm, and I have spindle feedback to mach3 by the index signal.

I have just changed the original 2:1 (from 4.000 RPM to 2.000 RPM) pulleys by a new double pulley set. One of the sets reduces the speed to  6:1, so I get max speed of aprox. 650 RPM, for higher torque when threading

The strange thing is, in this pulley set (6:1),  when I command mach3 to S300 and then M3, it takes aprox. 25 seconds to get from 0 to 300RPM stable.

If I turn off the spindle control by mach3, and control it manually by the original potentiometer, it takes less time to get to the desired speed.


When I use the original ratio pulleys (2:1) I get to any speed very quickly.

I use a BOB Gecko G540, and PWM settings of 72hz and Min PWM at 1%

My debounce interval for the single index pulse is debounce interval: 600 and index debounce is 10

I use Spindle Feedback in Sync Mode,
Closed Spindle Loop Control and Spindle Speed Averaging

Is it normal in a reduced ratio pulley for the spindle take  so long to get to this 300RPM speed? Is there something I could do to improve it?

Thanks, Rodrigo

Ok, I'll answer myself, so if anyone get's to this post will have the answer.

I had to mess with the adjustments in  the spindle settings in the TAB "Motor Tuning -> Spindle"

I don't know the values, as Velocity and Accel are in mm/min and mm/sec/sec, and the "Steps per" I let at 10 (how it was). The other two I changed until the spindle got faster with smooth acceleration at the desired speed.

So, now it works normally at both pulleys, get's to desired speed normally and faster.

Regards, Rodrigo