One common problem is that the nozzle is completely or partially clogged, which contributes to poor or no plastic being extruded at all. (Learn more about troubleshooting poor extrusion here.). This can be because dust and/or other particles have followed filament down to the nozzle and got stuck there. It may also be plastic (PLA) which, during long periods of time without extrusion, can carbonize on the inside of the nozzle.
One way to solve this without having to disassemble the extruder is to do a so-called. "Cold Pull", which means feeding plastic into the extruder and then allowing the temperature to drop so much that the plastic changes from melt to soft / solid form. The plastic is then pulled by hand and the plastic will take away any debris and coating from the inside of the nozzle. You will then repeat this until the plastic you pull out is clean and free from debris
We recommend using a Cold Pull kit for best results.
- Start by moving the extruder so it is not in the middle of an axis. This because the rods should get damafed when applying pressure on the filament while feeding it in hotend.
- Heat the extruder to about 240 ° C with "preheat" and then feed the filament. Continue feeding until plastic is coming out of the nozzle.
- If the nozzle is completely blocked and there is no plastic coming out at all, take a steel brush and cut a straw. Using a pliers, you can insert the thread into the nozzle. This way you can easily clean the nozzle to get enough plastic thru to get even if just a little flow. There is a video describing the approach here.
- Then let the temperature drop (apply a slight pressure on the thread until no plastic comes out of the nozzle) to somewhere between 120-140 ° C.
- Pull up the plastic (not too slowly) and inspect. Then repeat this a few times to the plastic that is pulled out is clean and free from old plastic residues.