So I’ve been standing out in the cold watching Garth cut away. I had 4 cuts in 4 quadrants of a sheet of plywood. Garth is my 6x4 maslow and so when I cut, typically I do half sheet, move and then the other half. There are reasons for this and they won’t change, so it is what it is. I find that I home at a y position of 2’ from the bottom of the frame and an x position of either -2.5 feet or + 2.5 feet and have a comfortable 4x5’ cutting area that is pretty accurate.
The issue I am finding is that I’ll home on the left, cut the upper quadrant, and when complete, the home position will be off by a cm or so. I mark the home position on the workpiece as a matter of habit and often cut a 2 mm deep hole so it can be used. This last time it was off, I reset the chains. Each cut completion has a different variance of how far it is off, might be a mileage thing, but it seems that one of the steppers is losing steps and so my cuts in some places appears like steps.
My run times are about 1-1.5 hours per quadrant and the offest is 1 - 2 cm roughly. Seems cumulative, but I could be way wrong. Using a custom shield with TB6643 chips and modified firmware to support the board.
Has anyone experience this before? My thoughts:
- Initially the right motor was suspect because it was dropped and broke the encoder plastic cover. I taped the cover back on and it seems to work ok AND the offset in the home position is up to the left. (if a longer cut, it is off more). This last one was 4mm left and 3 mm up.
- moved the left cable to ensure it wasn’t an electrical interference thing.
- I thought the sled was rocking because the UHMW thing on the bottom of the sled had twisted and it was not laying flat… fixed that, sled is flat, still have offsets.
- realigned router bit with center of ring to make sure it wasn’t a rotational offset problem
- looking through the settings, the only value that seems suspect is the rotational radius for the sled is 87.4 instead of 140, but I think I measured that.
- The left chain tolerance is 0.02 and the right chain tolerance is 0.979
- I have another gen 1 shield on the way, so I’ll try with that as well and see if the offset persists.
In summary, I’m trying to figure out if it is a hardware or software problem. I don’t like what it is doing to my product and I’m hoping one of you have seen this and fixed it.