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Extruder jamming very often. Also leaking. Help? :)

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Hey, so I'm new to the Ultimaker, but a veteran of the 3D Printing scene. Been around a while, and (had) a reprap mendel, and still have an Up, and a BFB 3D Touch at work. Plus the Ultimaker now. So I know my way around a printer.

I have to first say DAMN am I ever impressed with the mechanical build of the Ultimaker. It's resolution and print quality blow away EVERYTHING else that I've tried.

But... (here comes the issues) I'm having a hard time with the extruder. (and reading through here I'm seeing it's fairly common). I know this is just like anything else... Will take some time to tune/tweak/adjust. So just looking for tips/pointers/help solving this issue.

My Problem:

The extruder is jamming... Often... Like I can't finish most prints without it jamming to the point that I can't push filament through it. (if I heat it to 220 and push from the extruder drive end (with the gear disengaged) it will not extrude at all, but I can retract it fine). If I retract it, snip off the last couple inches, and re-load it, it extrudes fine again for a bit. But jams again shortly after that.

Also, I'm getting leakage. (I was getting it above the aluminum block, between it and the PEEK. now I'm getting it between the nozzle and the aluminum block). It's fairly minor, but irritating (long prints get lots of burnt spots in them from the oozing leaked plastic). Small prints are unaffected.

I'm extruding at 210C for my first layer and 200C for all other layers. I tried 10 degrees higher than this, and it oozed horribly. (I'm used to extruding at 185C on my other printers for PLA). So I dropped it lower. When at 185 or 190 it seems to have a hard time with adhesion and extruding fast. So I raised it back up to 210/200 and this seems to flow fine.

Also I notice a lot of "give" in the extrusion. (if I click extrude in pronterface, and I hear the motor warm up, it extrudes "late". There is a half second delay from when the motor starts turning and when the extrusion comes out, then it comes out for a half second longer after the motor stops, plus it then oozes RAPIDLY for another 1-2 seconds after that.). This seems to be contributing to stringing a lot.

What I've Tried:

Initially I assumed the jamming and the leakage between the PEEK and the aluminum block was the result of a poor seal in the PEEK. So I disassembled the extruder fully, cleaned up the threads as much as I could (I didn't mean to seperate the nozzle and the tube, but the nozzle unthreaded and the tube was jammed in the aluminum and peek, had to heat it up and unscrew it at 200C to get it out due to plastic jamming the threads). I cleaned it up the best I could, and re-assembled all of it, this time adding half-width plumbers tape into the threads above the aluminum block (before threading into the PEEK). I also ensured the brass was exactly flush with the lip at the top of the PEEK. Then I inserted the bowden tube and ensured it had solid contact with the lip and left a gap, then tightened it all up. So I know that's sealed good. That solved the leak up there, but now a leak started between the nozzle and the aluminum block (which were tool-tightened together nicely with no gap)

In addition I've tested different temperatures (+/- 10C) and different speeds. And it still seems to jam almost every print.

thin-wall (vase style prints) seem to extrude fine.

I'm using KISSlicer right now so my extrusion speeds are variable, but none of them are over 100mm/s (all should be under 75mm/s right now for infill, and under 50mm/s for perimiter loops).

Can anyone offer up any suggestions?

If I'm missing any details that will help eliminate the cause, please let me know and I'll provide whatever other details will help.


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I don't think it's possible to jam between the peek and the alu. Because the alu block is hot, and will always melt any blockage. Normal blockage seems to happen between the bowden tupe and the PEEK. This happens if the tube doesn't connect perfectly with the PEEK. Then molten PLA can creep in there and block your printer head.

Remove the end of the hotend, so you can see the end of the tube. Make sure it's atleast 9mm extended from the wooden part (guide says 8, but it's not always enough I think), and perfectly straight cut.

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I went through the troublshooting on the wiki for it. The tube is plenty extended (as I said it's hitting the lip inside the PEEK and there is plenty of gap once the bolts are tightened down solid (a good 1mm+ gap between alu plate and the wood)

I didn't confirm 100% if it was perfectly flat, but it did appear to be so. And as I said the leak was coming out between the PEEK and Aluminum block. It may have been leaking higher up, but then it went down through all the thread to leak out between peek and alu block.

Either way it's no longer leaking there at all. It's now leaking between the nozzle and the aluminum block.


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Sorry that was worded funny... lol I was replying about the leak, but yes you're right the most likely place for it to jam is between the PEEK and the bowden tube. I can doublecheck that tonight. But as I said it's got plenty of contact. The only possible option would be if it's cut crooked. Even then when I back it out, it backs out clean down to the nozzle (you can see the pointed/melted tip like on any other 3d printer, once it's backed out). And there are no crazy parts that would be grabbing in a hold (like the "flange" effect I've seen posted here).

I is a bit "widened" (as in it's still smooth, but the end that's in the barrel is maybe 3.1mm diameter but rest of the filament is 2.8mm) for about 1-2cm from the molten tip. (on the backed out filament).


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I am having the same issues as Glasswalker about extruding. If I extrude at LOW quality settings in Netfabb the extruder jams quiete often. It ends up grinding away the PLA. I can not push it through. Only when I cut away some filament and re-insert it. But then again, it jams again some time later.

I have no leakeage though.

My guess is that the tension in the bowden cable builds up to much by the pattern in filament caused by the teeth of the bolt. Just a guess though.

I tested the following:

- printed with LOW settings => fast extruding, and waiting for it to jam

- remove the jammed piece of filament

- start another print with fresh filament with ULTRA settings (slow extruding)

- halfway during the print I inserted 8 cm of the last bit of filament that jammed before.

Result: The inserted piece of filament (different color, so I could identify it easily) went through the bowden cable into my print with ease. No problems

Conclusion: The last piece of filament (although weirdly shaped after removing) is no issue.

This does not solve the jamming of the extruder with fast extruding though.

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Yeah I increased my temperature to 220C (230C for first layer) and it doesn't seem to be jamming now. But it's oozing like crazy (and tons of strings). Still working on tweaking it. And of course the leaking is still an issue (dripping into prints)


For a leak from an already assembled heater/extruder

Here's how I do it, others may differ.

1 Turn the UM heater on to just enough heat to make any plastic in the threads soft.

2 Loosen off the 4 main bolts so you can unscrew the peek block.

3 Tighten 2 - 6mm nuts onto the brass tube on the opposite end of the nozzle

4 Turn the top nut clockwise while holding the heater block so the brass tube turns down through the heater block a few turns.

3 Screw the nozzle onto the brass tube firm using PTFE tape (stretch the tape to make it thin) while using the top nut to hold the brass tube still.

4 Turn the nozzle while holding the heater block so the that the brass tube screws back up through the aluminum block all the way till the top flat part of the nozzle tightens up against the bottom of the aluminum block.

5 Remove the top nut and then the bottom nut while holding the block.

6 Tighten down the Peek piece onto the brass tube through the aluminum plate till it meets up against the top of the aluminum block. Make sure you are holding the nozzle with a spanner etc. so that the brass tube does not wind back through the aluminum block and create a gap between the aluminum block and nozzle.

7 Tighten up the the four screws from the top getting the bowden tube end right (See instruction in Wiki) while preferably holding the heater block in the orientation you want it to end up, usually running long wise from front to back with the thermocouple hole on the correct side.


Always hold the heater block when necessary to not put strain on the wires.

You shouldn't need tape between the brass tube and aluminum block but could use a bit if it helps in tightening things up. The real pressure is between the brass tube and nozzle and this is the one to get right.

As the brass tube becomes older it gets softer and is more breakable due to over tightening.

All the best

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Started with a Rapman love the ultimaker.

My two cents (its true worth);

Run hotter go faster

ReplicatorG lets you change the build speed while it is running. You can double the speed during the print. There is also a material multiplier that you change while its running. Besides multiplying you can pull back too.

My jaw dropped when I saw PLA temp at 240 after using 180 on Rapman. Immediately started dropping the temp and having problems.

Went to 235 but the head had to move faster. The PLA gets less chance to ooze.

Something else to try

Hope you find something that works

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Hi... i'm looking at this thread to resolve the head leak issue...

But, i also had jamming issues... I notice the jamming seemed to be more frequent when printing near the rear of the bed.. for me, it seemed to be more that the resistance from the spool and the tube.

I had bound the feed tube with the electrical cables going to the print head... when the print head moved to the rear of the bed it seemed the electricals were interfering with the 'natural' flex of the feed tube... I unbound them so the electrical cables dont interfere.

Conversely, when the print head is farthest away from the spool feed, the angle out of the feed mechanism it too great - i found if i tilt the feed mechanism (by lifting it up and out f the bottom 'hooks' it would feed better at long range. I was going to figure out some king of hinge for the feed mechanism to allow it to follow the pull of the tube somewhat... but in the meantime i tend to print nearer the centre.

Finally, I also noticed that the filament would tighten on the spool... when i make sure the filament is always loose on the spool (i always sit next to it while it's printing... rather it is next to my work station anyway).

I have seen some designs for better spool rigs.. the wooden ones seem to have too much resistance... perhaps some plastic sheet as bushing may free up the rotation...?

hope this may help some one... now back to pulling the head apart to fix the leaking..


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