Y axis skips during very long print

Hi everyone,

I’ve been running a very long print, ~20 hours, in PLA, and after a few computer related failures (a windows update and a crash) I had a successful print of the entire part, however there are three large skips in the y-axis of the print about 2/3rds of the way through. This print is from an SD card, so the skips can’t be due to a computer issue. I’m trying to figure out what the cause of these could be so I can fix it.

I’ve looked at the x and y belts, and the tension is identical and doesn’t appear to be too loose. I can’t see any rubbing of the belts on any parts of the printer, and the x and y motion is smooth when I push the bed and carriage by hand. The skips are 10, 4 and 8mm in the y direction, respectively, and at 3 and 2.5mm spacings in the z direction, and seem to occur at a single layer, not gradually.

Could this be an issue with motor drivers overheating, or an interrupted power supply? I can’t identify any mechanical issues that would be causing this, especially ones that would allow the print to continue after the print. Anyone have any similar issues?

How fast was the print speed settings? Mind including the gcode file used?

Your Y belt is probably too lose for that much mass and skipped, or the pulley set screw has backed out on the Y axis pulley. I’d install a belt tensioner module and tighten the pulley.