I am having a little trouble with the motor tuning.  The x and y axis do not seem to hold their calibration settings.  I thought they were calibrated perfectly, then I cut a simple 16" square and one side is almost .125 larger than the other.  Re-calibrated and once again one side is slightly larger than the other.  I first used a standard tape measure to calibrate at several different distances and then after that was dialed in I used a dial indicator for fine tuning.  Any suggestions?

If your calibration keeps changing, you might want to look into the cause of that.

Have you run repeatability tests on each axis to make sure it repeats?
When you ran the repeatability test, did you run across the full travel for each machine?
When you tuned your motors, how much slower from stall did you lower your max speed?
Have you checked if there is any binding on the ballscrews across its full travel (have to spin by hand)?

What have you done to make sure each axis is capable of moving properly?

Chris D

Hi,
I'm a little confused, you say the 'calibration settings', what do you mean? On each motor tuning page there is an entry for 'steps per unit' and that
is what I would call the 'calibration setting'. If it changes then Mach has really lost the plot....shoot it before it escapes and contaminates the world!! LOL

Chris D asks questions which suggest he is thinking as I am that one or more of your axes is losing steps. Is this a new machine? It can take some time
to get things sorted and losing steps is not uncommon until you do.

The first thing is to determine whether its one axis or both. I would recommend writing a small Gcode job just to move your X axis backwards and forwards
at G0 rate, ie rapid rate, several inches multiple times. Then you can remeasure to see if steps have been lost. Its likely that by the time you've got
the settings worked out for the X axis you can use the same settings for the Y axis and solve any problems there too.

Try:
G0 x0y0
x10
x0
x10
x0
x10
x0
x10
x0
x10
x0

should cause your machine to go backward and forwards 10 inches several times but it should stop at the exact same place that you started. If not
then you have a problem. Usually it means that you are trying to drive your steppers too fast or demand that they accelerate faster than they are
capable.

Can you post some numbers for your current settings and the specs of the steppers, power supply and drivers?

Craig