Identifying when you need to Cold-Pull a clogged Nozzle

The fact that your 3D Printed takes an (usually) exposed roll of plastic and drag it through pipers and gears to end up in a funnel, pushing molten plastic out of a tiny hole is a recipe for disaster. No, really. It’s very easy to get particles down the pipe and end up partially clogging your nozzle The best way to solve it is by making a cold-pull clogged nozzle.

A clogged nozzle can be fully and partially clogged. A partially clogged nozzle will sometimes make your drive gear to skip steps and dig into the filament, as if you had too much pressure. But a partial clog will almost always curl your filament around the nozzle when extruding filament over the print bed.

A fully clogged nozzle can be identified when you cant extrude filament and you can’t manually push filament down and out of a hot extruder.

300w, 768w, 1024w, 624w" data-sizes="(max-width: 2184px) 100vw, 2184px" data-was-processed="true" />Clogging a nozzle can also happen when you use filaments of different brands, colors and types all the time. Some of them tend to leave a bit of residue that other plastic types might not bond and melt with. You end up with a hard part that clogs your nozzle.

Replacing a nozzle all the time is expensive and time-consuming, not to mention the fact that you could end up snapping wires and need to re-calibrate the build plate.

Before we start. I do recommend doing something that’s more of a “hot-pull” since it’s less stressful for the mechanics in your 3D Printer. I’ll guide you through that procedure first, if it fails, We’ll move over to Cold-Pull.

Step 1.

300w, 768w, 1024w, 624w" data-sizes="(max-width: 2367px) 100vw, 2367px" data-was-processed="true" />Unload your filament and make sure you have good access to you hotend. For bowden typ extruders, this might mean that you need to unplug the guide-tube.

Step 2.

300w, 768w, 1024w, 624w" data-sizes="(max-width: 2395px) 100vw, 2395px" data-was-processed="true" />
Heat the nozzle to around 200-220C. Make sure you start of cold, and as low as 190C for PLA-only printers.

Step 3.

300w, 768w, 1024w, 624w" data-sizes="(max-width: 2407px) 100vw, 2407px" data-was-processed="true" />
Insert a piece of white/bright nylon or a strong filament. Push it down for 5-15 seconds or if you push filament out of the partially clogged nozzle.

Step 4.

300w, 768w, 1024w, 624w" data-sizes="(max-width: 2365px) 100vw, 2365px" data-was-processed="true" />
Pull back the filament out of the hot end and inspect the semi-molten end. This should have some dirt and gunk on it. Usually some black dots and filament.

Step 5.
300w, 768w, 1024w, 624w" data-sizes="(max-width: 1279px) 100vw, 1279px" data-was-processed="true" />Cut away the dirty part of the filament and repeat from step 3 until your filament comes out clean.

After around 5-20 repetitions you should now have a unclogged nozzle. Please note that sometimes this isn’t enough, and we have to do a severe cold pull, that puts more stress on the printer. The Cold-pull helps clean harder particles lodged and the end of the extruder.

To do a full cold-pull procedure, follow these steps instead:

• Step 1.
  Make sure you have good access to you hot-end. For bowden typ extruders, this might mean that you need to unplug the guide-tube.
• Step 2.
  Heat the nozzle to around 240-260C. If you’ve only printed with PLA, go to 220C.
• Step 3.
  Insert a piece of white/bright nylon or a strong filament. Push it down as hard as possible (by hand). Is there filament coming out? then stop.
• Step 4.
  Stop the heater and let the printer cool down to around 90C for PLA and 160C for ABS. Try to keep pressure on the filament during cooldown.
• Step 4.5,
  When the printer reaches the colder temperature mentioned in step 4, Pull back the filament quick and hard out of the hot end and inspect the semi-molten end. This should have some dirt and gunk on it. Usually some black dots and filament.
• Step 5. Cut away the dirty part of the filament and repeat from step 2 until your filament comes out clean and you can feed filament without it curling up on the sides.

You are now free of clogs! Congratulations!

Special thanks to https://www.antonmansson.com/how-to-cold-pull-clogged-nozzle/