Question Y-Axis Screws Out of Sync

After completing the build of my ST2-600 a little over a week ago, I have yet to get the "Home All" to work with all 3 axes. I manually adjusted both Gantry Uprights (no belt, no power) to be in exact same position on the Lead Screw Y-axes, but now one is about 3mm ahead of the other. I have loosened, adjusted, then re-tightened til I am blue in the face. The USA distributor is little help (ignores trouble tickets), so this forum is the only help I get (Rory of StoneyCNC has been a great help, even tho not purchased from him. DerRoy, ThomasDBg, Doug, and Woodendonkey have been super).

Hi,

Sounds like the belt can't move both sides of the y-axis. Can you turn both y-axis screws without much force? Are they getting out of sync right away or is there a position where one of the sides gets stuck and only the other one is moving?
You could check that by moving it slowly using the software and checking if you can see that one of the screws stops or move slower at a certain point.

SFDeeJay wrote: I manually adjusted both Gantry Uprights (no belt, no power) to be in exact same position on the Lead Screw Y-axes, but now one is about 3mm ahead of the other. I have loosened, adjusted, then re-tightened til I am blue in the face.

With no belt & no power, manually turn both Y axes using fingers of both hands back to front over the whole drive range to check for resistance/tightness.

Once all is well, I set up the Y axis by driving both lead screws flush with the front end (or equidistant by inserting shims of the same thickness) manually, clamped them against the front plate using quick release G clamps then attached and tensioned the drive belt.

I have never had any issues with misalignment in the Y axis lead screws as you describe.

Good Advice Doug and SiSt. Yes, I had noticed occasional stopping, but hadn't reasoned that one side might be trying to go ahead, causing out-of-sync. Going to try all these good suggestions.

ThomasDbg: You have been helpful, and I was not referring to Erick, who changed the assignment of my ticket to Dan, who responded immediately. As to the Y-Axis screws, think I found a dumb mistake (and will correct right now): One of the bushings appears to have been inserted from inside to out (the other is correctly outside to in). Though a small difference, going to take apart and do it right. Erick is kindly sending a couple of new Drive Pulleys (I mangled one, not realizing how easily the outer "washers" could get bent).