View Full Version : bad racking on gantry

Thu 19 September 2019, 22:03
Hey all,

I've recently got my mechmate back up and running after a hiatus. I noticed very quickly my gantry sounds terrible. Can anyone illuminate what is making the noise? I have to stay at the PC to be able to run, or else I'd try to be closer to the motors. I am assuming it's because my gantry is drastically out of square with the machine but I'm not sure. Any advice is greatly appreciated.

Turn down your volume before watching...


Fri 20 September 2019, 04:35
It seems to be happening on the X and the Y, but not the Z. When you are moving in the Y axis, are you ONLY moving the Y, or are you also moving in the X at the same time?

I don't think it is racking. If it is happening on both the X axis and the Y axis (independently), then it's probably something common to the two axis like power supply, BOB, cable from the PC to the BOB, the PC, or the application on the PC. Look at what you have changed since it was running correctly. Did you change your software, PC, cabling, power source, what?

Fri 20 September 2019, 12:46
I've updated to Mach 4, a new PC, and now using a Ethernet smoothstepper. I remember I had this issue before the upgrade, maybe it wasn't as pronounced, I'm not sure as it's been siting for some time (a few years unfortunately).

I'm wondering if my motor tuning is way off, I don't remember the math behind my values so I will check that next, but I need to find the formula's again. Haven't checked that in 8 years! If anyone knows where the formulas are let me know please.

Fri 20 September 2019, 14:27
Looks like it was an issue with my steps and motor tuning. In mach 3 I think it was in mm, in Mach 4 its in units (which I believe I have set to inches).

My steps per unit were 636.626 which seems super odd so I went and did some math. My motors are 1.8 so its 200 steps per rev. My pinion is 20 degree, and 20 teeth, and my micro stepping is 10x.

200 x 10 / (20/20) = 2000, which is much better value. Still have to work on acceleration and max speed but the grinding has almost all but gone away.