I just added a PWM spindle to my machine (Mach3 > SmoothStepper USB > Gecko G540). Now it runs, but with some very odd symptoms:

  1. The spindle gets up to speed quickly (1sec?), but then slowly drops in speed... from 2500 RPM initially, down to <100, then stall, over the course of 2-3 minutes.
  2. If I check voltage across Ground->Speed pins at the spindle, I can watch it correspondingly drop slowly from 5V down until it stops, in tiny increments.
  3. Power cycling the spindle or Gecko G540 does not fix it.
  4. Stopping and restarting the spindle from in Mach3 does not fix it. In fact, if I stop the spindle, and restart it, it continues at whatever slow speed it was stopped at, and continues it's slow decline to stall.
  5. Changing the spindle acceleration in Motor Tuning of Mach3 has dramatic effects. A setting of 1 gives the "slow decline" behavior above. A setting of 5 causes the spindle to start, then stop within about 1-2 seconds. A setting of 10 causes the spindle to start accelerating and then decelerate to a stop before it even reaches full speed (<1sec), then it will do the same thing when the spindle is stopped in Mach3.
  6. Closing, and restarting Mach3, without turning off or resetting anything else, will reset the problem... resetting the spindle to its full speed, to start a new slow decline.
  7. Also, not sure if this is important, but I'm typing 2500 into the spindle box, Mach3 is showing 2500 in the sVo box, but the RPM box always shows less (~2415).


Anyone have any ideas?