You’re in the middle of a long print and you start hearing a clicking sound and filament stops extruding. Chances are, your printer is experiencing a jam. Jams and clogs happen to every maker and thankfully, they can be fairly easy to fix!
Before we begin, it’s important to define each of the parts we’re talking about as the wording can get a little confusing. We’ll be focusing on extruder assembly which consists of two parts; a hot end and a cold end.
Image from wikimedia
The cold end is what actually pushes the filament forwards. Filament is sandwiched between a gear and a bearing and is forced forwards by a stepper motor. It is fed down into the hot end where it will first pass through a melt zone to liquify the filament until it is deposited out the nozzle.
There are two types of extruders – bowden and direct. A direct drive extruder sits directly above the hot end and forces filament straight through. A bowden extruder is usually attached to the frame of the printer and leads the filament through a thin tube until it reaches the hot end.
When filament get’s stuck, it’s either in the melt zone or nozzle section of the hot end and not at the cold end. Now that we’re clear on what parts of the printer we’re dealing with, let’s take a look at some of the symptoms and causes of a jam.
5 Causes of Jams and Their Fixes!
When your hot end is jammed, you might notice less filament coming out of the nozzle or no filament at all! Here are a few of the more common causes:
1) Heat Creep: It may sound counter-intuitive, but if the hot end isn’t cooled properly, filament starts getting viscous too high up in the hot end and we run into an issue called heat creep. This is when filament liquefies too high up and the extruder has to exert much more force to push it through the nozzle until it eventually becomes unable to and jams up.
The Fix: You’ll generally hear your extruder motor grinding or clicking when filament is jammed and if that’s the case, stop the print and remove the filament. Make sure the cooling fan for your hot end is running properly and ensure that the heat sink and heater block are securely attached. In the case of hot ends like the E3D V6, it helps to apply thermal paste to the threads of the heat break.
2) Hot end temperature is too low: If your hot end temperature is too low, filament can’t be fed through the and this causes the extruder to grind away at the filament, making it even more difficult to extrude.
The Fix: Check the temperature specifications for your specific filament. PLA likes to extrude around 200C and ABS around 245C. If you’re having issues with the listed specifications, try iterating upwards by 5 degrees but make sure not to go above the max temp of your hot end. When switching filaments, make sure all of the previous material is removed before changing temperatures.
3) Nozzle too close to bed: If the nozzle is too close to the bed, there’s no room for filament to be extruded out the nozzle and this causes a jam.
The Fix: Make sure you have a properly leveled bed. Check out our Bed Leveling Guide for more info.
Image from Ultimaker
4) Inconsistent Filament Diameter: Most filament manufacturers say their filaments is within 0.05mm of the listed extrusion width (usually 1.75mm or 3mm). If your filament deviates too much from the specification, it can have issues being fed through the hot end.
The Fix: If you suspect this is happening, break out a pair of calipers and measure the filament at several random locations to see if it’s up to spec. If your filament diameter is consistently off, it might be time to consider a new brand.
Image from Simplify3D
5) Dust or particles:Dust or other small particles might decide to hitch a ride on your filament until they reach your hot end and burn causing an unfortunate clog.
The Fix: Unclog your Nozzle Using the Cold Pull Method – see below for a more detailed break down of how this works.
3 Steps to Unclog your Nozzle with the Cold Pull Method
Some articles recommend using a blowtorch or drill to clean your nozzle. For those of us that can’t be trusted with power tools, fire, and chemicals we’re going to cover a safer way to clear out the filament from your nozzle called cold pulling.
The idea behind a cold pull is that you set your hot end to the glass transition temperature of your filament. This is the temperature at which the filament is between both a solid and liquid. This allows you to pull out the filament and take any residue along with it. This works best with Nylon, ABS or PLA.
Before you start: Cold pulls with a bowden tube can be tricky so if you’re using a bowden extruder, remove the tube and any material in the tube before you start. After you are finished the cold pull, put the bowden tube back in.
Step 1: Heat the nozzle to printing temperature and manually feed about 10cm of filament through the hot end (where the bowden tube was). Try and keep the filament as straight as possible. Natural or clear coloured filament works best so you can see the residue when you pull it out. If your hot end is too clogged to get anything out of the hot end, take a thin wire and a pair of plyers and stick it into the tip of the nozzle to clear the blockage.
Step 2: Once you have some filament coming out of the nozzle, bring the nozzle temperature down (120C for ABS, 90C for PLA, and 100-140 for Nylon). Try to use the lowest temperature possible for this step. It should be hot enough that the filament is malleable but not so hot that it is too soft. Be sure to cut any filament off that is dripping from the nozzle before you start the pull.
Step 3: Pull on the top of the filament until you feel it start to slowly give out. If it comes out too easily and there is no residue on the end, lower the temperature. If you have trouble pulling it out, raise the temperature until it does.
You’ll know you’ve done it right when there is a small sharp tip on the end and possibly some residue on the filament (this is most obvious when doing your cold pull with white or transparent filament).
Mkme lab has a great video tutorial on how to do this as well:
You may have to do this several times to get all the residue out. Your last cold pull should leave you with a smooth filament piece that is clean (no dark residue). Once you’re convinced all the blockage is removed, put the bowden tube back and try printing.
By following these tips, you should be able to remove your nozzle jam and hopefully prevent it from happening again. Happy printing!
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