Here is an article for all those who want to know why the extruder is slipping or clicking, why they are having under extrusion issues, or printer not printing correctly. This article was written and illustrated by Peter Solomon, founder of Wham Bam.
Most people think it's the extruder, but, although this is possible, it's usually an indication of something jamming further down the line.
Here are the 6 Main causes of extruder clicking and gears slipping:
1. Print speed too high or temperature too low.
Try on-the-fly, during print, to use your control panel to increase heat by 5° -10°C and slow down feed rate, see if either of these alleviates the problem. Frequently recommended print temps are lower than those actually needed.
2. Interference in Bowden tube or pathway.
This is a big one, before breaking down your whole hot end and redoing nozzle, always check your PTFE clearance first!
To test, remove end of tube from hot end (leave other end in extruder) and squeeze your extruder arm to manually push filament or filament past the extruder and through PTFE tube, if it moves smoothly, your problem is elsewhere.
If it is difficult, first look at the end that was in the extruder, is this melted, dirty, deformed? If so, snip a bit off and see if that resolved it.
Also test your PTFE tube separately with your same filament and see if there is any resistance, if so change your tube. If not check the couplings.
Please note I have found the inner diameter of some PTFE tubes including the Capricorn XS to be too tight for many filaments which may have a variance in diameter a bit larger than specified, and would stop my prints making me think there was a clog, when instead it was just the tube.
3. Assembly of hot end and / or Bowden tube too loose.
If there is any play in your Hot End Coupling and the Bowden tube can move up or down, or if there is any gap between the bowden tube and the heat break inside the hot end, or the heat break and the nozzle, or between any fitting, the molten material can get into that gap, swell beyond the diameter of the tube and make it difficult to move. This can cause jams, under extrusion, or full blockage. Inspect your ends of filament when you pull them out of the tube, if they have a bulb on the end this might be the case.
To alleviate make sure to rebuild hot end in the proper order and tightly to avoid any gaps in the passage.
See my previous post concerning the hot end cleaning and assembly for more info.
4. Clogged Hot End.
To test, while hot end is fully heated, try squeezing extruder arm to compress spring, can you push the filament through, does it come out the nozzle? If not, it may be clogged. You can also remove the PTFE tube and manually push filament through your hot end while hot to see if it comes out smoothly.
If you have a clog you must take apart whole hot end assembly.
Loosen the nozzle while at full temp. Let cool and take hot end off of the carriage, remove the thermistor and heater, remove the coupling, unscrew nozzle, unscrew inner collar, clear all parts, you can use a small butane torch to melt the plastic inside if it is too clogged, but be careful.
If the nozzle is badly clogged toss it! get 10 for $10 online.
Re-assemble carefully and following good instructions to ensure that all is snug.
5. Faulty Extruder.
Check to see if the spring puts enough pressure on the hob gear and bearing to squeeze the filament, try manually squeezing the gears together while feeding to test.
Make sure toothed extruder gear teeth are clean, use a wire brush to get them clean.
Make sure the active center of gears and bearing are at the height of the filament path.
6. Nozzle too close to Bed.
If your nozzle is too close to bed you may be choking the flow of filament and preventing the extrusion, you can verify this if your first layer is just too thin or has gaps.
For more information discover my previous article concerning the 7 main factors in getting the perfect 3D printing first layer.
(please note the illustration is a simplified image showing a typical Bowden system, direct drive would be different, there are a variety of extruders and hot ends so use this only as reference)