The filament does not get chewed up and the and there hasn’t been anything wrong with the temperatures. (I installed my hot end on another printer, and it worked fine) The motor doesn’t seem to have enough strength to push the filament through, it is unable to strip the plastic off the filament. It twitches back and forth when it hits any resistance. The hot end is also completely clear of all plastic debris.
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If the same behavior is occurring with different motors, then the issue is likely not the motors. It could be a physical issue with your controller board such as power delivery or firmware. Also, wiring is always a possibility. “Jerky” sounds like a bad connection, so that may be a good place to start.
It is a modified Prusa i3 printer, the whole extruder assembly is completely clean and free of debris. The two wheels are under the correct tension. The plastic does have the small dimples. When the filament does not extrude, it is not being stripped either, the motor simply twitches back and forth, like it’s too weak to do the job.
Thanks for the reply, I’ve ordered new wiring. I’m not sure it’s the control board, because every other motor works perfectly, and it’s a new board that I had replaced rather recently.
I now know it’s not the hot end, I’ve installed it on another printer and it worked printed fine. I checked the vref, and it seems to be sitting at 0.2. How much would I have to turn the trim pot on the stepper driver to increase this? Or is that just for increasing the current?
Is it a RAMPS board? If so, check to make sure you have all the jumpers in place. Got tripped up by that one more than once. Try swapping out drivers.
The following possible causes come to mind
a) physical connectivity: polarity reversed?
b) firmware needs reflashed
c) hotend temp lying! Thermistor issue? (it it doesn’t extrude, maybe its not hot enough)
Please use the “divide and conquer” technique for troubleshooting
Isolate the faulty / problematic variable. Do this by testing the integrity of each component SEPARATELY. This will include running the stepper motor by itself from a static power source, or plug it into a different port then manually control it to determine if its faulty or healthy. Also, you’ll need to test the port on the controller board with a different motor. When testing it don’t have the motor installed on your extruder. Divide and conquer.
“Twitching” instinctively seems like a physical connectivity issue. A shorting wire that is exposed or something else that is affecting the continuity of the circuit.
EDIT: not enough power to extrude the filament could be just that: a power issue. You need to use a multimeter to check the appropriate power is being delivered all the way from the PSU to the stepper motor’s port.
Can you make a picture of your electronic board (ramp)? So we can check together where the pololus are and I can follw you better in adjusting the value.
We also do need the type of your extruder stepper motor, in order to know the electric features
Feel free to send the picture(s) to d.roncadori@gmail.com
Try upping the current it is receiving.
It is NOT the stepper. They rarely fail, and your testing and subsequent posts imply it is not the stepper.
It is likely the wiring has gone bad. This is common for the stepper wires, which break inside from repeated same movement over and over.
Test a different wire, such as using the one from your y-axis. I’ll bet a dollar you will see the wire is bad.
PS If you have a ptfe liner, replace it now and then, it can cause these issues, but my money is still on the stepper wire.
A whole dollar? 
when steppers fail, it’s usually due to overheating which can warp the core where the windings are wrapped. This will cause the rotor to “hunt” for its index. In my case, the stepper would oscillate back and forth.
Update (Problem has been located):
- I switched the cables around, and there was no change.
- I switched the stepper drivers for the extruder and the z-axis, and the filament started extruding more smoothly than ever before!
- I had switched the drivers before, but with a different motor for the extruder. With the original motor for the printer, and the z-axis driver, it worked.
Thank you to everyone who helped, hopefully when the new driver gets here, there will be no more issues!
2 years later
Does the original stepper have this issue plugged in somewhere else?
This still sounds like a cable issue.