You could have a similar issue as the DRV8825 drivers. Due to the nature of their operation, and how 3D printers actually run, the microstepping is actually causing problems. How accurately do think it is really operating making those 1/256 steps? It is most likely not making some, and other times making a few too many.
Some of these stepper motors really need to be run at 24V and decent amperage to get the best microstepping control.
1:256 microstepping is just WAY too much for an 8 bit AVR to process.
I believe the best mix is to get 0.9* motors and stick with 1:16 or 1:32 microstepping max (well, maybe experiment at 1:64 and 1:128 with 32 bit electronics). Oh, and switch over to 32 bit, especially for delta printers.
When running the DRV8825 at 24V and lower amps (I get more than enough holding torque under the max rating), the mixed mode causes microstepping issues. I had to hack them to run in fast decay mode to rectify the problem.
My future printer upgrades include a 32 bit controller and 0.9* steppers.
Some of these stepper motors really need to be run at 24V and decent amperage to get the best microstepping control.
1:256 microstepping is just WAY too much for an 8 bit AVR to process.
I believe the best mix is to get 0.9* motors and stick with 1:16 or 1:32 microstepping max (well, maybe experiment at 1:64 and 1:128 with 32 bit electronics). Oh, and switch over to 32 bit, especially for delta printers.
When running the DRV8825 at 24V and lower amps (I get more than enough holding torque under the max rating), the mixed mode causes microstepping issues. I had to hack them to run in fast decay mode to rectify the problem.
My future printer upgrades include a 32 bit controller and 0.9* steppers.