10 years of printing on a custom-homemade machine.

Yeah, I've been 'just printing' now for about 5 years straight.
I don't even look at the printer prior to sending it a print wirelessly. I just hit print, and it works.

Always sticks to bed, no failures.

It's about knowing the mechanic's and failure points and knowing how to maintain it properly.


As people have said already this is a somewhat common failure mode, especially when swapping nozzles. This happened to me twice between three nozzle swaps. The first time was a major leak like yours, the other time it was only slight (which I then made worse in my attempt to fix…). I was obviously doing something wrong, but I came fully prepared the second time with video guides for my specific machine and everything but still couldn’t get it perfect.

If you never want to think about this failure mode again (like me) then consider swapping your hotend for a Revo. A Revo nozzle is also the heatbreak, so there’s no possibility of a bad connection between them. The ‘nozzles’ are more expensive but they can be hotswapped (coldswapped, even) by hand with no special tools. Before I did everything in my power to avoid nozzle swaps, so I ended up settling for a jack-of-all-trades (but master of none) nozzle that I would never have to swap. Since moving to Revo however I find myself swapping nozzles way more now that it’s easy and with no chance of destroying my hotend. For instance I have a high-flow 1mm nozzle for quickly doing big structural prints, they print in like one third of the time and are way stronger than equivalent prints on a smaller nozzle. I also have a 0.25mm nozzle for miniature model prints with a better resolution than I could ever get before. I’m still waiting for a high-flow abrasion-resistant Revo nozzle, though.


Thank you for the tip! I’ll look into those for sure. It sounds like they would be a perfect fit with very little downside

rasterweb avatar

If you want it to get worse just change it from a hobby to a business!


Hahaha I’m good there! I’m on month 2 of what should’ve been a 3 day project for a friend. I’m chalking it up to a bad model after this and moving on to a different print to save my sanity

MissJinx, avatar

I’m 2 years in and it’s still the same!


Ah man, but at least you have 2 years of experience under your belt!


Balls. Of steel.

MissJinx, avatar

True! but it’s still very painful! hahaha


I’m guessing you have a nozzle not screwed in fully, or there was filament above the threads preventing it from seating. I’d warm the print head, remove the nozzle, run a bit of filament through without the nozzle, then yank it out, hopefully pulling any globs down and out of the heater block. Reassemble hot and make sure the nozzle seats firmly. Good luck!


Thank you!


It’s worth noting that some but not all combinations of heat break, nozzle, and heater block require re-tightening at the temperature used for printing. Basically, different metals expand different amounts when they’re heated, so if the block expands more than the other two, a gap will open up between them, and melted filament can find its way through.


Good to know. I’ll add that to a check list to go through every now and again


Yes and on some printers, that spot where the Bowden tube meets the nozzle is very problematic. You have to loosen the nozzle a bit, push the Bowden tub up against it, then tighten the nozzle the rest of the way

It was awful on my Ender clone, but haven’t had that issue on my Prusa.


Where is the burned on filament? Is it that grey-ish blob between the box with the little curly q at the bottom and the heatsink looking piece?

My apologies in advance for what is probably a naive question. I don’t have a printer, I’m just “print curious” at this stage, and want to understand more.


No worries! Thats exactly where it is. The burned on stuff goes all the way down the side and around the back.

I’m afraid this bing need to be totally taken apart but i haven’t done much more than investigate and pull at some easy pieces so far.

Keep in mind this is my first printer and I’m new to the hobby so I’m at the why isn’t this working and why did I do this to myself stage. This might not be a problem for more experienced people. Thankfully this community exists because I’d be lost otherwise


Thanks for explaining!

Also, IMO the “why isn’t this working, why did I do this” stage is a right of passage and sign of progress in any new activity! Keep on trucking!


Anytime. Thank you for your words of encouragement!


It will get easier as you learn more and screw up more. You learn what not to do, and then eventually you’ll screw up again as you relax and forget some of the lessons you’ve learned.

But it also gets more fun too. It’s okay to walk away for a while until you’ve got it in you to fix your printer. But repairs will always be a part of this hobby regardless of what printer you have.

I used to brew beer, and that was no different. Experienced brewers are more likely to accidentally ruin a batch of beer because of overconfidence and getting lax about sanitation.

I think any technical hobby is like this.


The problem is I don’t even know what happened or how the pla got around that silicon sleeve. Part of me just wants to say forget it and continue to print with it like this but I feel like this is just a fire waiting to happen.

Thank you for the advice! I think I’m gonna run with it and put the printer in the closet for a bit.


The problem is I don’t even know what happened or how the pla got around that silicon sleeve.

It’s kinda normal. If the hotend clogs there’s only two places for the plastic to go (or it can stop going into the hotend), the other one is up. And this is both more common and way better than up.

It doesn’t look like it, but the printer pushes the filament with a lot of force. It’s normal for it to just go into some completely unexpected direction that you can’t replicate by hand.

Anyway, if it’s working correctly and what bothers you is the extra plastic, just heat the printer until some 160 °C and pull it away.


Thank you, that did the trick to remove it!

If i were to leave something like that, is there a risk of a fire starting?


I’m not going to say no, however my nozzle has been pretty gross for a long time between cleanings and never been an issue.

The bigger danger is that the thermocouple could fail and allow runaway heating (beyond 300c). But most good print firmware is supposed to prevent that.


Thank you! I that makes me feel better about leaving it print while I’m at work


Not really. Nothing on the printer get hot enough for that.

But there is a large risk of the extruded plastic adhering to it and of it contaminating your print.


Thank you! I’d rather deal with a contaminated print than a fire


Maybe its best to put it away for some time and then come back to it when you feel its time. I mean, its a hoby and it can be frustrating, but its worth IMO. Dont forget its a machine and not a plug-and-play device.

Im in this hoby for 10ish years and I never had a leak. Probbly because I was reading about that even before I got my first printer. I did have many other issues and failures, but they almost never happen anymore. Most of the crap stopped after I got Ultimaker 2, but I believe experience is the main reason.

Like others said, your nozzle wasnt sealed (tightened) against the heat brake properly. You have to heat up your hotend before tightening, but dont use full strength or you might break your nozzle.

Now you can clean it up or just replace heatbrake and nozzle, at least parts are available everywhere


Thank you! I gave it a clean and fingers crossed it works put tomorrow when I’ve got some more time to mess with a test print

FuglyDuck, avatar
Okay, using a microswiss hot end for an example, and that’s a clean photo. They’re all usually about the same anyhow. What’s going on here is a very common mistake to make. the immediate cause is that the heat break (red arrow in the picture) is not screwed on to the heater block tightly enough, and some filament is oozing out the top rather than getting forced out the nozzle.

The solution is to heat it up, clean everything up with a brass brush or something similar. Then remove the nozzle and run filament through while it’s hot, clearing out any gunk that’s built up.

Now, to get it on there tight enough, what you need to do is heat up the nozzle to higher than you normally print at, then tighten it down as tight as it can go while trying very hard to not burn yourself.

You can get the same problem with the nozzle oozing, out (blue arrow) as well, so while you’re running hot, go ahead and put the nozzle back in and get it as tight as you can, too. once it’s done, you can loosen the set screw above the heat break (green arrow. the set screw holds the heat break in place.) and turn the block so it’s more or less aligned with the printer. Let it cool back down and bring it up to temperature and check for leaks again.

and just for the record. everyone here has probably had this happen. I just want to make that clear. please don’t give up. You’ll reach a point where it all makes sense. If you need to step away for a bit, that’s okay, but also, don’t be afraid to come back to it.


Thank you for your advice and encouragement! Its comforting to know that its happened to everyone and its a common error.

After everything is cleaned up should i reseat the heat block before i remove the nozzle to clear the gunk or after?

FuglyDuck, avatar

I would suggest removing the nozzle, and clearing it if there’s a jam first, then seating the heat block to the break. Then the nozzle. Both the best break and the nozzle need to be hot as you’re doing the final tightening. I don’t know that the order really matters … it’s just how i do it. I do recommend being systematic about how you go through things. It’s helpful to have a process.

Systematic processes help you to not forget things, like forgetting to reconnect the BLtouch cable when doing stuff with the hot end. (Ooops.)

I’d also recommend keeping some of the more interesting failed prints as “art”. I may be weird but sometimes the spaghetti monsters look cool


Thank you! Unfortunately i didnt get a cool spaghetti monster this time, but I like the idea of keeping them to see how far youve come

dual_sport_dork, avatar

while trying very hard to not burn yourself.

Those otherwise stupid silicone oven gloves are just about perfect for this task, at least on your non-wrench holding hand.

FuglyDuck, avatar

I always laugh at those stickers on the hotend cowlings “Caution Hot.” On one hand… thank you captain OBVIOUS… on the other hand… eh… hehe.


Hey I’ve been there. Take it apart carefully and inspect it as you go. Do lots of reading, clean it up, put it back together and hopefully it won’t happen again - but know that it might if you don’t find a cause. Sometimes things have to get worse before a cause becomes obvious.

I’ve got a Prusa, but I’ve had to replace many different parts on it, sometimes multiple times. Some of that was factory issues. Some of that was my fault. Some of it was just bad luck.

I still love the hobby, but it sure as Hell isn’t trouble free.

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