My 3D printer keeps stopping part way up the print

[dpgtaylor 0]

I had recently been printing a run of the same 3D print file - and need to print a large amount more for a deadline. Unfortunately the printer stopped extruding part way through one of the prints. I went on to unblock the nozzle but noticed the coupler was completely blocked (as pictured). I then ordered a replacement coupler and installed it. I then proceeded to carry out 11 atomic pulls as pictured until it came out clear.

This seemed to work and the first print I did yesterday since the atomic pulls came out clear. I removed the print and went to print the file again, when I came back to it the print had failed (as pictured and there was a blob of pla on the outside of the nozzle. I have only used pla on this nozzle. Any suggestions as I really want to make this deadline, cheers.

 

 

[Smithy 1,144]

Check if the middle fan (on the back) is working. This fan is responsible to keep the cold zone of the print head cool. This fan should work as soon as the nozzle heats up over 40°C.

[dpgtaylor 0]

Yes the middle fan is working, no issues with it 

[Smithy 1,144]

Do you print PLA?

How fast and how hot do you print?

 

I don't think that we find the root cause here, otherwise your first print would also fail, but who knows.

[dpgtaylor 0]

Yes I print PLA at 210 and at 60mm/s I believe 

 

[robinmdh 100]

not sure if this helps but my atomic/cold pull's do look different, way less stringy, this might allow gunk to stay on the sides of the nozzle.

The whole tip should be straight and not thin immediately behind the nozzle, I suggest you wait a bit longer before you pull back to allow the temperature to stabilize or do the pull a bit colder untill it comes out like this.

or review https://support.ultimaker.com/hc/en-us/articles/360011620800-How-to-perform-a-hot-and-cold-pull again.

 

Alternatively if you have polycarbonate filament on hand, use that, the temps are a bit higher but it sticks a bit better to the whole mess, and is a bit stronger so it can more easily handle the cold pull forces.

Edited July 22, 2020 by robinmdh
added polycarbonate suggestion

[dpgtaylor 0]

Thanks - I have dropped the temperature when doing the cold pulls and its giving me a better looking tip. 

I performed 11 cold pulls and tried to perform a print - it completed the print but under extrusion meant it snapped and was messy. I tried to print again and it was massively under extruding. 

 

I have performed another 10 cold pulls and this is what the tip is looking like. It shouldn't take so many pulls + it shouldn't look this bad after 10. Its not smooth at all - I know a new nozzle would solve this but not keen to just buy another and need the printer today.

 

Any suggestions for cleaning it out properly? Im worried there is some abs in there from prints I did ages ago - or just some really stubborn PLA

[Smithy 1,144]

I am not sure if it is the nozzle, could be, the tip is not very beautiful, but it doesn't explain why you can print one object before you run into troubles. 

 

Have you double checked the coupler? Everything installed as it should be? 

 

When I look at the last picture, I can see that the filament gots the form of the upper end of the coupler, which should not happen. So I would say, that you have too much heat there and the filament gets soft in the area of the coupler, especially above. But you said that the middle fan is working, this is normally the main problem.  

 

Very strange .....

[geert_2 557]

I think that "ring" on your last cold pull pic should probably not be there? (See the very left border of the pic.) Long ago I have seen a short video of a coupler that did not fit well, and molten filament came in-between nozzle and coupler, pushing the coupler up like a hydraulic cylinder. I don't remember the cause, but this could happen if there is burned residue sitting between nozzle and coupler, so there is a gap. You might want to check that?

 

But I also think you should double-check if the third fan keeps running well while printing. Worn-out or dirty fans might start well, and then slow down or stop, or vice-versa. Not saying this is the cause, but I would double-check it.

 

For nozzle-cleaning, I also think you should wait *much* longer for the nozzle to cool down, so that the inner core of the filament totally solidifies and comes back to room temp. Then wiggle and try to rotate *gently*, before pulling. This helps dislodging dirt from the nozzle. Then I reheat the nozzle to about 75°C (for PLA), while *gently* pulling and rotating the filament, until it comes out. I never use brute force, only very gentle wiggling, rotating and pulling. And longer waiting cycles.

 

See my very old manual on atomic pulls here (I should update it...):

https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/

 

Typically my cold pulls look like these below. The bottom orange one is best. For the top one, I did not wait long enough, the core wasn't totally solid yet.

 

If there is burned residu on the walls of the nozzle that I can't get out with pulls, then I *very gently* scrape the inner core with an M3 threaded rod, with rounded end to not damage the core. Never use steel: this is too hard for brass nozzles.

 

Very gently scraping; this is on an UM2. Not sure if this is a good idea on other printer models though... Also note that this is not an official method, just my own thing; I am not related to the Ultimaker-company and not an official spokesperson.

 

Other puls: the white one shows a totally worn-out teflon coupler (UM2), indicated by the thick blob or "ring". This does cause underextrusion too, and needs replacement. If there would have been a gap between coupler and nozzle, the "ring" would have been where the dark line now is on the white one. On an UM2, then the whole nozzle would need to be disassembled to clean that (I don't know about other models).

 

 

 

 

[dpgtaylor 0]

Hi thanks Geert_2 your advice is very helpful. I have double checked the fan and it carries on running at full speed. I think the issue lies with the nozzle more than anything. Before trying anymore cold pulls I disassembled the print head and looked at the olsson block. There is a large amount of burnt black residue (as pictured) on the screw threads of both components. The coupler is completely fine as it is new. There is a large build up of residue inside the nozzle with some fairly big parts in there. I wonder if it is worth trying to clear the nozzle as it appears to be in a pretty bad state inside, or just ordering a new one? Is it normal for the thread of both components to become so blackened? I have attached some photos, although it is difficult to get a clear shot inside the nozzle using just a phone camera.

 

[Torgeir 242]

Hi @dpgtaylor,

You got lots of good advice here for sure.

I'll just want to say that I'll agree very much with @Smithy, -you sure have a "hot end cooling" issue.

Even the fact the fan is running, -does not mean your hot end cooling is good!

The heath "somehow" climb through the coupler and create high friction resulting to under extrusion..

There is also another problem, -the nozzle you're using is not in perfect match with the flat surface in the heath block to match (your latest pictures). So this match is leaking and thermoplastic is filling the threads! This cause, less thermal conductivity between nozzle and block as well as leaking filament into the coil surface.

This is information from your last pictures.

Due to this fact, your nozzle do not deliver enough heat and is leaking through the coil reducing heat transfer.

The flange between nozzle and heath block should be very "precise and even" in order to keep the temperature even through the complete heath block.

I'm using copper paste in the treads between the nozzle and the heath block. This improve the thermal contact between block and nozzle! Also it is easier to remove when needed.

It is very important to use "original nozzles" for the type of block used.

 

The flange between nozzle and block is very important to be correct, -not leaking here, -or else old deposit from previous print might make problem collecting up here and ruin your ongoing print.

 

Finally, the wires for the heath block "heating" and heath block "temperature" might cover up the inflow for the cooling radiator. This can reduce your cooling by ~35 %. "There is a small modification to improve this."

 

Anyway, just my opinion.

 

Good luck.

Thanks

Torgeir

 

 

Edited August 13, 2020 by Torgeir

[dpgtaylor 0]

Thanks for your reply. What is the small modification to improve this that you mentioned? Also is there a suggested way to clean the threads of the olsson block and nozzle? I have ordered an official ultimaker nozzle and want to make sure it is going into a clean thread in the heat block.

 

Thanks

[Torgeir 242]

I've wrote a little about this some time ago, you'll find it here:

 

Here's a link to Strawsons design, the Fan Duct spacer (stl file) that's improve the flow through the radiator:

https://github.com/StrawsonDesign/Ultimaker2_Mods/tree/master/Parts/Fan Duct

 

Hope this help.

Regards

Torgeir

 

[Torgeir 242]

Just forgot, I've learned that people use to heat the heat block using a propane burner to clean out stuck filament remains, however I've never done that, but there might be someone here in the forum that can fill in here.

 

Thanks

Torgeir

[geert_2 557]

On 8/13/2020 at 7:58 PM, Torgeir said:

Just forgot, I've learned that people use to heat the heat block using a propane burner to clean out stuck filament remains, however I've never done that, but there might be someone here in the forum that can fill in here.

 

Thanks

Torgeir

 

I never tried burning out a nozzle with a flame.

 

But I did try to burn separate pieces of filament in a metal spoon, in the flame of a bunsen-burner. I let it slowly heat up, and finally catch fire and totally burn up. The results were:

- Both plastics melted into a bubbling pool of hot liquid. The PLA being more liquid than the PET, which stayed more honey-like.

- Ultimaker PLA and colorFabb PLA/PHA filament burned-out into a thin layer of black dust, a bit like coal powder, easy to remove by rubbing.

- PET burned-out into a thick layer of hard, black, glossy varnish. This varnish got glued stuck to the spoon, and was very difficult to remove.

 

So, whether burning residu out works on a nozzle, may depend on which materials were printed. Try this spoon-method first with the same materials, before doing it on a nozzle. Be very sure to stay well below the melting temp of brass, which can be reached easily with a bunsen-burner or similar. Don't go further than the metal glowing dark red. Once into orange and yellow, it starts deforming easily.

 

The use of copper paste seems like a good idea: although the grease will burn-out, the copper particles provide good thermal contact, fill the gaps, reduce leakage, and prevent locking-up.

 

After seeing the last photos, I also think a geometry mismatch between components (due to non-original and non-fitting components, or dirt-accumulation) at least worsens the problem, without ruling-out fan issues.

 

Edited August 16, 2020 by geert_2
corrected typo