This may occur when the resistance for the extruder motor becomes higher than the stepper motor can handle.
This in turn can be due to a number of reasons:
1. Stop or obstruction in the nozzle – May be due to accumulation of debris in or just above the narrow passage of the nozzle or damage to internal parts of the nozzle. Can be fixed by replacing the nozzle/SwiftTool.
2. Too low temperature in the nozzle for selected material. May be due to settings or problems with the temp sensor.
3. Filament too thick or varying diamater. Check that the dimensions are between 1.7-1.8 mm, preferably tighter. Cheap filament may sometimes have “lumps” that make feeding slower or halting there.
4. The nozzle is positioned too low – mainly plays a role for the first layer. Solved by recalibrating the build-plate or the z offset.
5. Too weak extruder motor. May be due to bad or worn motor cables. The stepper motor itself rarely breaks.
6. Too high friction in the feed from the material spool. May be due to some debris getting stuck in the wrong place or the Teflon tubing being folded or damaged. Try feeding the filament manually from the roller to the nozzle. When fed all the way, it should easily move back/forth. if not, there is a problem.
7. Incorrect settings, e.g. too high extrusion factor. Check that the correct profiles are used.
8. Print speed set too high – If the print speed is set too high, the material will not be able to flow most of the time due to cooling of the nozzle. Can in some cases be remedied with a higher extrusion temperature.
9. It gets too hot around the drive gears, so the material starts to soften too high up – Check that the extruder fan works (it is located behind or above the extruder motor). It should start as soon as the nozzle goes over 60 degrees C.
10. A bearing is broken in the anvil wheel or stepper motor – Turn off the printer and check that both the motor shaft and the anvil wheel spin easily without strange noises. The motor should chop when spinning the shaft, due to the motor magnets, but you should not hear metallic squeaks or other strange sounds.