Question Layershifting due to hot steppermotors?

[bobobolinski]

I started to print parts for the MPCNC and imedietly ran into problems. Before this the prints have been flawless. But now I get layershifts late in the print, as seen in the pictures. The model is about 5x5 cm and has an infill of 45%. When the print finished the x and y motors are so hot you don't want to touch them. Can it be that they become too hot and that causes the layershift? If so, it is strange that it occures exactly where the hole is bridged.
Any suggestions?

 

[endstop]

Is any overhang curling up? Does the print detach and lift up at a corner (use brim to rule that out).
I'd focus my attention on "why does the nozzle run into an obstacle", not so much "why is it lacking force to pull through".

That said, hot steppers have lower torque. Have you checked the configured current to the steppers? It is NOT the maximum current from the datasheet, typically quite a bit lower.
It seems surprising (of course I don't know every printer in existence but my Voron has been running for hours and the XYZ steppers are not even warm to the touch. Only the pancake extruder stepper shows heating, 60°C maybe).

Regardless of the layer skipping, I'd consider backing off the stepper current a little.
I'm assuming you're printing at room temperature but usually they'd need 30° margin for a heated chamber.

 

[NoGuru]

What microsteps are you set to 16,32,64, ect. What run current, have you tuned the motors?
Are you steppers/motors loud when printing?

 

[bobobolinski]

Thank you for youre suggestions!
Overhangs are curling up a little bit, but not much. The motors are also silent.
But when I looked at the run_current its was 0,79, I don´t remember why it was so high.
I decreased it to 0,69 and are now trying 0,65.
Now perfekt sometimes but not always, The shifting has decresed from 0,8mm to 0,1mm, but I prefer it to be 0.
The motors are still hot, but not as hot as before, You can rest your fingers on the hottest part, but far from endstops motors.
I have Klipper TMC Aautotune installed, but I can see in an older thread that you, NoGuru, wasen't so impressed by it.
The microsteps are set to 32.
I will test with fans blowing on the motors to see if that changes anything.

 

[NoGuru]

Autotune is okay, but its like tuning a car. Plug in tuner will gain some HP but a custom tune will net you the most gains.

You might loose some resolution but running at 16 microsteps might help as well.

 

[bobobolinski]

Fans blowing on the motors makes them cool, but it didn't solve the problem.
But lowering the temperature for the filament and lower the printing speed for overhangs did it!
Now at last are my prints as I want them!