gr5

When you said 6+ years ABS and recently printing at 260C I was like "change the teflon part". But you got it working for now. Still you should order 1 or 2. They will go out of stock some day as UM doesn't officially support UM2 series printers anymore so I assume (I could be wrong!!) that they will run out at some point. I see that fbrc8 still has them: https://fbrc8.com/collections/ultimaker-2/products/tfm-isolator-coupler-um2-um2-go-ext-plus Anyway the problem isn't usually so much the "char" as that the teflon gets much softer and more flexible at that end such that when it is compressed inside the print head, this teflon part squeezes the filament. Quite hard. You can remove only the nozzle and with the print head cold you can pass filament through the print head and feel the resistance. Deburring or really making the hole slightly larger (just 0.1mm is often enough) can make a huge difference. If you widen the teflon too much the filament can expand in that space and get stuck when it goes solid again. If it's working I'd just order 2 spares and not worry about it until you start getting underextrusion again.

UM2 series printers are a special case where you control temp on the printer under the material settings. On the printer itself in it's little menu screen. To be able to control temp in Cura for a UM2 you have to make some changes: Go to left side of screen in PREPARE mode. Click on your printer, then do "manage printers" then "machine settings". Now change it from "Ultimaker 2" to "Marlin". Now you can do all kinds of temperature tweaks. Other things will change: filament diameter, bed temp, flow rate, fan speed settings are now all controlled in cura only. If previously you had one gcode program for PLA and Nylon prints, now you will have to slice those separately. Different slice for each material type.

@J_Wills - you should start over. How many printers do you have. How old. Which ones have the problem. What version of software. Do you have tinkerMarlin or regular Marlin? What is the symptom - does it give an error? Does it power cycle (there are many cases where the printer power cycles in the middle of a print but if you aren't around it isn't obvious) and it just ends up on the normal startup screen? The thing that most people are talking about here is where the screen freezes but the print continues just fine to the end so you just power cycle the printer after the print is complete.

This is just basic underextrusion. I don't think it has anything to do with where it happens - those are more subtle reasons related to changes in speed, retractions, etc. Ignore all that for now. The basic problem is underextrusion pure and simple. 1) Were you printing ABS with no troubles for a while and then after something like 50 or 200 hours of printing it slowly got worse? If so it's probably related to the teflon part. If it has always been a problem then let's ignore this for now. 2) What is your nozzle temp? And what is your printing speed? You probably want around 240C to 245C. If you go too hot it can quickly turn into a gum like substance after a few minutes. If you go too cold it's too thick (viscous) and you get underextrusion. There is no magic temperature as you are always too viscous or too dangerously hot but I like around 240-245. 0.2mm layer and 40mm/sec is a good starting volume/sec for a 0.4mm nozzle. 3) ABS is a very difficult material and I recommend you pick something else. It's going to be a weaker material for the most case until you become an expert (so the first 100 prints or so are likely to be weaker than PLA). You can ask me about how to make ABS parts stronger but really - it's best not to use ABS. If you want higher temp materials maybe you should go for something easier and stronger like Nylon or PETG. If you want something strong, well you probably picked the wrong material as best case you might be able to match the strength of petg or pla and never as tough as nylon. Did you pick ABS for strength? For temperature resistance? Oh and ABS smells awful. After you answer these 5 questions I'll help you diagnose the problem some more. I have a list of about 30 causes for underextrusion.

See http://gr5.org/unbricking/

Desiccant is great but use a LOT. A fist sized amount. And if it's not fresh out of the original packaging, you need to recharge it. I used to recharge my desiccant by microwaving it - steam would come out and it would change back to the original color but using the humidity monitor I realized I was only getting the dessicant down to 30% humidity. Now I strive for 10 to 20%. Typically around 15%. Not sure if that's enough but it's better than 30% as that was definitely not enough. Other people say 10% makes the nylon print like a dream but then the parts are stiff and brittle for a few weeks until the parts absorb a little water.

@Manfred_Schwarz - I think you misunderstood. Me also. The support is doing something - it is supporting that super tiny ledge near the top of the tallest part. I changed the support overhang angle from 45 to 60 and now it doesn't support that tiny ledge. That's all you need to do. I thought you found some new bug. You should close that issue over on github. You could also use a support blocker. Really only one of the 4 parts need support and I see you put support blocker in that tiny hole which is smart. You could have used a support blocker on the tall piece as well. It doesn't need any support.

rats.

TinkerGnome has his own version of Marlin called "tinkermarlin" and it's wonderful and it has something called "geek mode" which is default and when you are printing it shows like 20 parameters on a single screen. He crammed everything onto one tiny screen. It has dozens of other wonder features like "continue failed print" and many more firmware settings that can be changed in the interface such as steps/mm and I think current for each axis and many many more. https://github.com/TinkerGnome/Ultimaker2Marlin/releases

Oh. Well then post the first 30 or so lines of gcode from each file labelling which works and which one hangs. It should be obvious once I see the gcodes.

Those lines with the semicolon at the bottom - that shows us that you aren't missing anything. Those are comments that are ignored by the printer (and tell you what settings you overrode). I'm not coming up with any good theories. Go here: support.ultimaker.com and click "submit a request" in the top right corner. Maybe they've seen this before and know exactly what it is. Is that what you already did?

I got something similar to this. It seems to work fine. https://www.ebay.com/itm/203963346074

I've always been able to read older project files with newer versions of Cura but if you go the other way around sometimes it knows there are conflicts so it won't let you open the project file (it will only let you open the models). there's no way for older cura to predict what newer cura settings will exist. Yes some new feature in cura may default wrong but that is unlikely. Very unlikely. Most new features either default off, or they are just so unarguably wonderful that it's okay if you get the new feature by default.

The nice thing about printing over wifi is that it copies the entire gcode file to the "hard drive" on the um3. Before it starts printing. So if there are read errors, presumably you find out about them during that copy step. I would hope. Did you open the "bad" gcode files and go to the end of the file? There should be comments at the end - that's a clue that there isn't anything missing.

I had a question. I put it over on github

You want to get the humidity incredibly low - around 15%. I don't think most of those storing stations get that low. Personally I use a combination of rechargable desiccant and the heated bed method I mention. I bought a liter of desiccant and use about a 1/2 cup of it in a 2 gallon (mixing metric and imperial, lol) ziplock which is big enough to hold the container of desiccant and a spool of filament. I also use a humidity sensor which is crucial as before I started using the sensor I realized I was only getting the humidity down to 30% which wasn't enough. I dry the desiccant in the microwave. 30% humidity is much too high and gives me horrible results. The desiccant is only used to maintain dryness. To dry the filament I use the heated bed. It's all a bit of a process but necessary for PVA and Nylon.

This sounds like a new bug. Please post it on github to be sure you get the attention of the cura developers. Post the 3mf file but don't post the ufp file. After you create the issue, post a link to the github issue here and I'll add a comment over on github to help it get attention. Unfortunately you have to create a github account if you don't already have one but it's free. https://github.com/Ultimaker/Cura/issues

My 2 cents... I never edit profiles. Never. I got burned early on and went a different process and it seems to work better as people complain about profile bugs and issues all the time but never the way I go. I use "projects" the way most people use "profiles". They are 2 ways to achieve the same goal which is to be able to pull up settings that worked for you in the past. Everytime (every time!) I save a gcode file I also save the project file (menu "file" "save project..."). Later when I am going to slice something else I find the project file that has the settings I want and load that. It loads up cura just the way I want it. For example if I do my first ever glass-filled-nylon print and I get the settings just the way I want it and say the first thing I ever printed was some x-clip. Then a week later I want to print a bracket and I just load up the x-clip project, load in the STL and slice. I don't know if this will help you or not. The other thing I want to point out is that there is this wonderful plugin in cura called "printer settings" and more importantly "material settings". There are many many more settings there than you can normally see. To install a plugin click "marketplace" in the upper right corner of cura, make sure it's on the "plugins" tab (not the materials tab) and these 2 plugins are blue. Install the plugin and then restart cura.

When printing the Z stepper is pretty silent? It just makes a quick "blip" between layers. Can you make a 5 second video showing the problem?

Thermal pad? The bed heater? The bed heater is just a PCB. There should be no oils related to that at all. I'd search more carefully for the source of the sticky stuff. Maybe from a transformer?

Does it happen while printing? Or when the printer is idle and supposed to be doing nothing. What does this have to do with the print core breaking at the heat break? Did the core hit something? What is there to hit?

There are 2 common problems with PVA. If you are seeing black gunk and material isn't coming out you may have caramelized it. On the UM3, in the menu system under I think "maintenance" maybe there are instructions for doing hot and cold pulls. Follow those to clean out the nozzle. More likely your problem is due to water absorption. Even just 24 hours at typical (40-60%) humidity can wreck PVA. Restore it by heating your heated bed to 55C. Unspool enough for the prints you will do that day (cura tells you how many meters are needed. Place that on the bed and the spool on top of that (the spools can warp even at 60C but if they are a few mm above the bed it will be fine). Put a towel over all that. Maybe 3 or 4 towels or a blanket or something. Leave it like that for 24 hours (certainly at least 8 hours at 55C, less time needed at say 70C but that will probably cause the PVA to deform - I do this to nylon at about 70C - PLA doesn't need to be dried). The meters of filament you unspooled will now be miraculously just like new.

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.

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.

There's some great stuff here - detailed step by step instructions with photos or videos https://ultimakernasupport.zendesk.com/hc/en-us/categories/115000948826-Installing-Replacement-Parts I think Ultimaker relies on the resellers to help you on things like assembly instructions. Your reseller should know where documents like this exist.