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Hi,if your motor changes direction randomly (in case we are talking about 28BYJ48 and not a NEMA17 type) the most possible issue is wrong connection. Don't rely on the wire colour. Different manufacturers - different wire color order. For me this issue was a little hell as well :) Double check this even on the motor's PCB. Vibration of extruder motor is of course much bigger than other small motors. Setting around 145 steps/mm should be OK. Driver trimmer pot has to be set at higher level than other motors (based on the fact that NEMA17 literally 'consumes more' than 28BYJ48 :) ) How much torque does your extruder motor have anyway? Send us a data about manufacturer and model of your motor if you don't know...FireCrier out.