Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: BrianW on February 05, 2021, 12:30:14 AM

Title: Odd Problem with 4th Axis movement in one direction
Post by: BrianW on February 05, 2021, 12:30:14 AM
I have configured my 4th axis as linear to control the knee on my milling machine and am having an erratic problem with motion in the negative direction.  (This problem occurred some time ago and has gotten worse.)   Motion upward seems to work fine most of the time, but occasionally will not move at all.  Motion down may not work at all, may go up instead of down and will not stop when reaching the commanded point.  Of interest, these problems do not occur when using incremental motion from the jogging control screen.  I have checked everything I can think of, including testing the connections and continuity of the "DIR" wire from the break out board to the servo.  All other axes work flawlessly.  I have swapped the 4th axis servo for a new one with no change in the problem.  I have tested the servo output on another motor and it shows the same symptoms.  I have concluded the problem is not with the motor, the servo or the wiring back to the ports on the breakout board.  I checked that all chips are firmly seated on the breakout board but have not changed them out.

I should mention that I am running Ethernet Smooth Stepper between Mach3 and the break out board to drive all the axes.  I'm not sure how to test that.

None of the tests I have done can account for why the axis does not stop when the target reading is attained (only going down).  This made me wonder if there is a bug in Mach3 so I reverted to an earlier build but that made no difference.

I have run out of ideas for diagnosis and have found no one else with the same problem on the forum.  I would really appreciate advice from all you wise members.