SLB y-axis homing accumulating error/overshoot?

SuperLongBoard ❓Question
1

Hi team-

I’m trying to debug an issue with Y-axis homing where Y2 consistently overshoots the end of travel during homing. Y1 (which has a limit switch) seems fine. Presumably the motors should be ganged during all phases of homing as we’re still not using dual-Y homing capability (side note, it’s weird that the Technical Manual says not to plug in a Y2 limit switch, instead of just ignoring it in software if it’s truly not implemented yet?). I assume that every step sent to Y1 should also be being sent to Y2 as well, no?

Firmware 5.0.5b

Steps to repro:

  1. Default homing settings:
    $25, $190, $191, $192 = 4300,
    $24, 180, 181, 182, 183 = 150,
    $26=25,
    $27=1.5
  2. Home the machine
  3. Manually square the y-axis by turning Y2 by hand to match Y1 distance from end stop
  4. Re-home, and Y2 is incrementally closer to the stop than it was last time

Is Y2 losing (gaining?) steps somewhere in the homing routine? Is it losing/gaining steps elsewhere? Should I be changing the microsteps to something other than 32?

If I slow $25 down to 2000mm/min, then things seem to stay in sync. 3000mm/min is marginally better than 4300mm/min, but still accumulates errors.

2

Well this is embarrassing - I guess this was caused by a slight misalignment of the X gantry on the Y stages which caused something to bind during the homing routine enough for I guess one side to stall and the other not. When the machine was out in the middle of the table things appeared to be fine. I loosened up the X gantry, manually squared things up, and tightened it up again and now it seems like this is working.

Is there a timeframe for dual Y homing? Even if the second limit switch isn’t used for actual homing, it would be interesting to have it indicate how much the table has gone out of alignment during the homing process.

Thanks!