Missing steps

[sinole]

Hi

I haven’t used my printer in a while but recently started some prints. I noticed thatsome layers shift in my x axis. I serviced the printer, oiled it and everything. Still some layera shift. Crazy thing is they come back and align again. If they didn't shift back I would assume it is a bad stepper motor. If they shift same location i would assume it is the gcode. But since in same print repeated it happens different location I thought maybe it is firmware. Anyone have thoughts?
Still my best guess is bad stepper or bad motor.

[dc42]

@sinole I assume you are referring to the artefact near the top left corner. What I think has happened is that the presence of the holes at that height has caused the slicer to reverse the direction of travel when printing the perimeters of those layers, and this combined with backlash in your motion system has caused the apparent shift. I suggest you check how much backlash your motion system has in the direction that corresponds to the left-right direction of that print.

[sinole]

@dc42 thank you, I dont know much about backlash. but I will research it. never had tio deal with it. that axis has a very short belt and it fairly tight. I also have some Inputshaping setup.

[sinole]

@sinole do you know how I can measure backlash? I saw this link on how we can correct it. it seems that you just count how many milmeter was missed and calculate steps to recover.

[droftarts]

@sinole Check that the belt pulley is not loose and rotating on the stepper motor shaft. If the shaft has a flat, and the grub screw has loosened, it won't completely slip, but will go back and forth depending on the direction of motion, and give you a print exactly as your picture shows.

Ian

[mikeabuilder]

I agree with Ian (Dr-O'farts, I think it might be Irish). A loose grub screw will let the motor move a bit when it switches direction without moving the belt.

[sinole]

@droftarts I did check that before and I always put loctite on those. the problem was the motor. I got weak over the year. I never seen that befor. I did buy the motor very cheap though.