Occasional Layer Shifting caused by heat?

[Max Pickle]

I'm getting occasional layer shifting with my Voron 0.1

Its been printing Switchwire parts happily all day and now has shifted on a two part piece. Yesterday was similar - a few good prints and then layer shifts repeatedly with a 3 part print until I gave up and went to bed. The quality of the prints is good except for the shifts. I have completed all the setup and Ellis checks and I believe everything to be in good order. Rails feel to be running smooth. Running with Sunlu ABS

I've adjusted my stepper currents to 0.75 based on the following calc.
Phase Current = 1.5A therefore RMS = PC x 0.707 = 1.0605 x 85% = 0.901 x 75% = 0.795

It tends to occur more with multiple parts on the bed than a single part. Speeds are 240mm/s or lower and 300mm/s for non printing moves. Acceleration is 3000mm/s or lower.

Any thoughts on what would cause occasional shifts? I feel like the speeds/accelerations are within norms. Could I afford to push the motors a bit harder? This is a formbot kit.

 

[NoGuru]

You looked at the two areas that I would also look. I think your motor current is good but see if they are hot when printing.

Try and slow down by say 25% and see if it happens.

 

[Max Pickle]

Thanks NoGuru, Good to know I'm not missing the obvious. Reran the two part print this morning - printed fine.

I'll pop the back off and have a feel of the motors next time its up to temp and running. Given how hot my enclosure gets maybe I need more ventilation in the back for the electrics.

 

[Max Pickle]

Only a shortish print today but I took the back off. They are defo warm to the touch and I can seem them getting hotter over extended usage.

Comparing the specs of the Oukeda motors provided in the Formbot kit and the LDO-35STH52-1504AH which seem to be offered for the Voron 0.1/0.2. The former is 50C and the latter 180C. I'm firmly in the stepper motor overheating camp at the moment.

 

[EkanemJoseph]

If you have already checked and adjusted the print settings, you may want to consider the following options: Check the mechanics of your printer, making sure that all fasteners and belts are tight enough, that the Z-axis moves freely, and that all bearings are in place. Try printing at a lower speed and acceleration to reduce the stress on the motors and see if shear is occurring in this case. If you have the option, try changing to a different material and see if shear occurs with it. If there are still problems, you can consider strengthening the motors, but this may increase heat generation and power consumption, so you need to be careful and make sure that the printer can handle these changes.

 

[Max Pickle]

Since leaving the back off I have had no issues. At some point I will upgrade the motors.