So a few months back ive got myself a budget 3d printer. I knew the basics of how to use them as we had them back at my old college. we used maker bot printers. ive learnt a hell of a lot over the past months and overcome many problems myself but im stuck with one problem that i cant seem to fix.

i had a lot of success with a lot of prints but all of a sudden my printer started under extruding. ive been using PLA and ABS, both in a controlled environment, (IKEA lack enclosure). I found that the plastic tensioner on the MK8 extruder had cracked. so i ordered an aluminium one. this fixed some of the problems i was having with extruding. but there was still some problems when the prints got 20+ layers high at 0.2 layer height. it was still under extruding. so i changed some settings in slicer for extrusion widths. ive changed heat settings for PLA between 90 and 230. ive cleaned the extruder nozzle and feed holes. ive adjusted spring tension and ive changed the potentiometer on the driver for the extruder stepper motor. everything seems to be working smoother now but the only problem i have is with white PLA ive tried 2 different brands. Geetechs own and some unbranded one. the issue im having with the white PLA is that when using it the stepper motor is jumping back and forth. even on high heat it seams not to be pushing it through but when i feed it by hand it runs through fine. anyone come across a problem like this or am i just missing something so simple? any suggestions would be greatly appreciated.