Does your nozzle get blocked?

So the print starts fine. First layer goes well and maybe even few more layers print really nice. And then you find that your 3d print has stopped mid way and no filament is coming out.

You pull the nozzle out, clean it out and try again. Your 3d printer behaves the same way. You take another roll and it works fine.

Sounds familiar? Is it the printer, is it the filament or is it something else? you lost and ready to give up.

There are few potential causes for that.

First of all good starting point would be to reduce the retraction settings to 0 to check if it is the cause of the problem. Do not get scared – the print will look ugly with all sorts of the stringing and blobbing. This exercise is to check if this is the cause of the problem. The cause of this is that the 3d printer filament gets stretched out of the nozzle into the heatbreak. Once the same length is fed back into the nozzle fresh filament that is not molten rams into the molten filament that potentially has slightly expanded in the thermal break due to slight oversize (and we are talking about the heathbreak being 1.9-2mm rather than same size as the filament of 1.75mm).

This “rivet” effect causes what it appears to be lockup and blockage of nozzle. Because of this you might find that when cleaning the nozzle you find nothing wrong with the nozzle and/or filament. This issue is most common with PLA and PPLA (PLA+) 3d printer filament. Most other plastics do not exhibit the same symptoms.

If the reduction of the retraction helps to resolve the issue start dialling up the retraction until you are happy with the oozing of the filament.

The second most common problem is old PTFE tube inside the hotend. This is not an issue if the hotend is all metal. Please don’t rush to change it to all metal. All metal hotends are only useful with high temperature filament and mostly PETG. It is not performing as well when printing with PLA. PTFE is good to be used up to around 240C. After that the degrading of the tube is very fast. Below that temperature PTFE is degrading slower, but still doesn’t last forever. From prolonged usage the tube starts to shrink and prevent filament from passing through.

It is advisable to replace the tube as preventative maintenance. In most of the cases when the setup is bowden – the tube goes all the way to the nozzle. Thus the whole tube is replaced at once the size of the tube is 4mm OD and 2mm ID (Outside diameter and inside diameter). In the case of the direct drive extruders the tube is inside the thermal break and most common size if 3mm OD and 2mm ID. The tubes are usually sold by most of the 3D printer suppliers in 1m length. No need to look for precut tubes since it would be not economic at all.

Third common problem is the overheating of the 3D print hotend heatsink. This is usually caused by the degrading cooling capability of the fan. This might be caused by a wearing out fan that is either poor quality or is getting tired from a long life. The heatsink is not cooled enough and the heatsink heats up and the filament melts inside it. This causes the filament to get jammed and the print fails. Replace the fan and that should fix the issue.

You can find PTFE in these links