Anyone with technical 3d printer experience?

It’s kind of a longshot but I figured someone here might know. I did a tmc2208 stepper driver upgrade on an anycubic i3 mega s at home and some prints are now running really slow. All drivers are set to vRef ~.85v. Could undervolting the extruder driver cause long linear print sections to run slow in order to keep pace with extrusion? I’ve heard some people overvolt that one but I haven’t tried it yet.

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Notes from my technical friends:

“I don’t know anything about i3 modding but i would assume the vRef means “reference voltage “. Definitely try tweaking the variable slight up or down and do a timer. Might be that the stepper motor is slightly off. Not sure though :)”

“Might have something to do with the default steps per unit of the oem drivers vs the 2208. Would make it run half speed
You probably have to flash a new marlin firmware to account for the 2208”

“0.85 on a TMC2208 for that printer sounds really high. I run 0.8 on my Voron, but I have better stepper motors.
Undervolting/overvolting generally wont cause long sections to print slow. It will cause miss-steps or overheating. The only time I’ve seen overvolting cause it has been when the power supply for the entire printer is undersized and that slows down the CPU running the gcode. Adding cooling to the CPU can help with that.
Really you need to check the steps per mm in the firmware for the extruder, and check that slicer isn’t doing something funky since they said only some prints do it.”

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No, steppers really can’t run “slow”. They can run in perfect lockstep, or, if their torque capability is ever exceeded for an instant, it stalls and loses its position unrecoverably. Often this appears as a layer shift.

That’s the two cases. Perfect or total failure. And it can’t slow itself down

If it’s still working and not slow because you saw it stalling and reduced the speed/acceleration, then my first question would be whether you got the micro step count correct for the new driver

Turns out it just seemed slower to me because it was quieter lol. I’ve been printing a bunch since then and print times are pretty close to the slicer estimates.