z axis scale problems.

I've nearly got my gantry router running reliably, but I keep chasing a problem with the scale on the z axis. I'll start the machine up and go through my homing routine, and then put a dial indicator on the z to make sure my input matches the output. I'll change the gear ratios to reconcile the input to the travel of my z axis, and run my machine for 20 minutes or so. by the end of that 20 minutes, the scale is all wrong again, by as much as 30%.

Any ideas?

Perhaps you could explain the steps you are taking step by step and the results you are getting. Same results at different feed rates for Z? Sure you are not just losing steps?

Rick

I ran through the stepper configuration wizard, and input all of the gear ratios, pin allocations, etc. Then I test ran the machine.

I would move each axis in .100" increments and measure the movement with a dial indicator. I then adjusted the gear ratios in the config wizard to make the output match the input.

What I'm finding is that the z axis was either losing steps when I did this test, or its scale is changing, because I keep having to repeat this adjustment to compensate for either far more or far less travel than I see on the DRO. One minute I'll be getting .100" of movement for .100" on the DRO, and 20 minutes later I'll notice the machine is taking way to heavy a cut, repeat the test, and find I'm getting .130" or .150" of travel for .100" in AXIS.

Thanks,
Paul