Stepper motor tune-up aid by jpnurro

Last crawled date: 3 years ago

I ran in to the issue with 3DBenchy. The cabin walls got the diagonal stripes with 0.1 &0.05 mm accuracy. (You'll find the phenomenon called as 'Zebra stripes' or 'Moire')
The reason is that our stepper motors aren't rotating full steps but electronically created fraction of the steps, (microsteps) e.g. 1/16. These are not accurate especially near the motor's full step area. Holding in to those depends about the current feeding in to the motor.
The phenomenon is visible when motor needs to do micro movements. The surface is on the low angel '__----' towards axis so these steps comes visible.
Here is the test piece I made. X-axis (ends) & Y-axis (middle two) surfaces are 5 & 10 degree off the angels. (In the picture on the front 10 degree and back 5 degree Y-axis off-set angle)
During the printing I tuned up the motor drivers current to find out the optimum settings for the both axis. (There are small trimmers on the motor drivers e.g. in A4988 Stepper Motor Driver)
On the left the my original setting and right end the optimized result. (when the current goes too low or high the steps are missed - gaps in the picture)
I DO RECOMMEND TO USE CAUTION WHEN TOUCHING THE LIVE ELECTRONICS !!!
Use non-conductive screwdriver with tuning the trimmers (or very steady hand :-)
Avoid static electricity, don't use synthetic clothing. Earth yourself e.g. touching the water tab before the work.
The Z-axis shouldn't be the issue. E.g M8 tread has 1.25mm progress/rotation (pitch). The Nima17 motor has 200 steps/rotation -> 0.2 layer the motor turns 32 full step and 0.5 gives 8 steps, these are good, no microstepping.
If you'd like to use e.g. 1/100in layer height you'd get the rotation 6 1/4 steps, in this case you might have a issue.