Trouble with TPU

[Teds455 1]

Hello! First post, glad to be here...

I've been printing a fairly complex design with TPU on my Ultimaker 2+.

 

The design takes about 24 hours to print, as there is a TON of support material required. While the first 3 have printed without a hitch, now the material already layed down appears to get stuck to the nozzle with each pass at times, ruining any possiblity of the print being finished. Luckily I've descovered this early on during the print job.

 

I've already checked the bed height, and do this frequently, and performed a calibration as neccessary.

It appears the nozzle is loaded with the TPU material and perhaps this is what the print gets stuck on during the pass. I'm still using the original nozzle that probably has a couple hundred hours of printing various materials.

While I haved been greasing and oiling the moving parts, I have done nothing with the orignal nozzle already installed when purchased. There is another nozzle that came with the printer, but I'm not sure if it is the same and if it's suitable to use with TPU.

 

Is there a way to clean the existing nozzle? Any help would be appriciated, as I have about another 4 days of printing to do with this design.

Thanks in advance!

Ted

[gr5 2,099]

TPU is more hygroscopic than ABS or PLA and I suspect you need to dry your filament. It only takes a few days in typical (40-60%) humidity for many materials to be "ruined".  This definitely includes PVA and NYlon but I'm not sure about TPU.  Likely it's a problem for TPU.

 

Check where your TPU softens and goes to a clay like material by heating up the bed to say 80C and putting a few cm of TPU on it and with a towel over it for about 1 minute and then squish it to see if it bounces back or not.  If it does then I would uncoil enough TPU for your print and put that all on the bed and the spool on top and heat the bed to 75C and put a towel over all of that and let it sit overnight to get most of the water out.

[gr5 2,099]

Now to answer your question more directly about cleaning the nozzle, look up "cold pull".  Either for UM2 or really any printer.  Read about the process and try to do that.  That will clean the inside of the nozzle.  I'd try it at least 5 times.  The tip of the filament should look exactly like the inside of the nozzle including the thin section at the end (I assume 0.4mm).

 

You can do the cold pull with TPU but I'd do it with nylon or pla.

 

To clean the outside of the nozzle, just heat it up and wipe with a paper napkin.

[Teds455 1]

I wound up changing the nozzle and it corrected the problem. I could not simply wipe off the excess material from the old nozzle... Plus when i removed it and manually cleaned it, I could not load filament after re-installing... It would not extrude the TPU through, even after multiple tries.

 

Installed the new nozzle and I'm back in action.