Wednesday, 8 January 2014

axCut Laser Cutter - Y dual stepper homing and z axis drives

Have uploaded a quick overview video of the completed homing system for the dual Y stepper arrangement:

It uses a normal microswitch on one side (the Y2 side) and a linear hall effect sensor on the other (Y side).  Have updated my fork of the Marlin firmware to support this homing technique.  Calibration parameter is modified using M666 command (and M667 to read), values stored in EEPROM.

Homing algorithm:

  1. Home Y as per normal
  2. Disable Y2 stepper, disable endstops
  3. Measure hall reading and compare to calibration target
  4. If error big, move Y one step towards correct position and goto 3
  5. Enable Y2 stepper, enable endstops
I'm currently using 32x oversampling on the hall reading, with 5ms delay between reads, but there's still a load of sensor noise.  Doesn't help that the sensor is next to two stepper motors!  Works ok, just takes a few iterations to converge.  Will do for now.

Z axis drives fitted (uses Mendel90 z-couplings) and ready for wiring tonight.

1 comment:

  1. Question for you Damian. Where did you get your stepper motors. In one of your videos you said you purchased 10 of them from china. I have been studying your site extensively and I am going to to build a Laser Cutter.

    Is that info on github? Did I just miss it?
    Thanks for your time,