This is more for the experts of the group. I designed/built a 5x10 gantry that runs on gear rack with steppers motors, running off a mx4660 4 axis driver and a UC400eth pulsing engine. My issue is that I am gaining steps and having erratic movement because of this. Right now if I move to 6" its exactly 6" 10" is exactly 10" however thats as long as I can measure with my micrometer. When I go out to 36" using a tape measure its off by roughly .25" I've used both UCcnc and mach 3 with somewhat similar results. This only occurs in the y axis from what I can tell, I have been focusing on that axis of movement. Its a slaved axis with individual drivers and wiring. I have even replaced the gear rack and drive gears on both sides and have similar if not identical results ( I am not super accurate with the tape measure). I have squared up the gantry sides with a angle gauge and some 1 2 3 blocks. Ive also noticed that when I cut this specific bracket the outlet and nearly all the bolt holes line up but one. This one bolt hole is cut halfway through the program and the machine returns back to zero exactly so I know I am not losing steps or anything during the cut. Any ideas? I am going to swap to UC100 USB and a different (TB6600HG 4 axis board) to test motion here tomorrow just to confirm, might even try and swap out the laptop. I am not sure what else I can try, just doesn't make sense. Never had an issue like this on any of the other machines I've built however this is the biggest on thus far. Speed is set to 500IPM and 60 accel. I've run the machine at over 2000IPM and 150 accel with smooth motion