Hi there, My machine seems to travel less on one of the Y-axes than the other. I start the gantry at the back of the frame (flush) and by the time it gets to the front, one side has a gap while the other side is flush. There seems to a delta in travel between the two and I have no idea why. It’s throwing my tolerances way off! I initially thought it could do with tensioning of leadscrews but it’s definitely not that. Not sure if something is bent or if it had to do with current input? Totally stuck. Any help would be greatly appreciated.
Did you get this figured out? I have a Chinese 1515 controlled by a Blackbox and have essentially them same issue. If I make the gantry flush with the front of the frame on both sides and run it back (Y+) 1200mm the left side is at 1200mm but the right side is roughly 12mm short around 1188mm. When I run it back -1200mm to the front then both sides are back to flush with the front. I'm not sure if it's slack in the system, a loose wire, or missing steps. Voltage difference between steppers?
Both of these sound like a mismatch in screw pitch, try removing the gantry and calibrate the two columns/Y carriages separately. See if there's a significant difference between the two numbers. Rolled screws can be pretty drastically off from nominal, which is exacerbated by extremely long screws. I know LinuxCNC 2.9 can feed different step rates to Y1 and Y2 thanks to the joint/axis separation, not sure if any other control can. grbl can't because it can only stepgen for three axes. If they're really that far off and you want to stick with grbl/BlackBox, you'll just have to buy new screws until you get two that match. OpenBuilds would probably be a better bet for matching screws.
