A350 3D print head grenaded on first attempt

So I sent a work request for replacement Y rails and now the 3D print head and that is in the course of 24 hours. I followed the calibration tutorials and the print was running smoothly for ~3 hours before I went to bed. Woke up to the SM2 still thinking everything is fine while dragging the melted remnants of the print from the extruder. Further inspection showed the filament impacted so badly it cleaved the two exposed wires nears the hot end off and the heat of the filament melted the protective rubber (?) away.

Has anyone else had this happen?


Never seen it this bad. Someone was showing a melted Silicon boot but that was it iirc.
you said the thermistor got ripped out, or atleast that what the two wires look like that are sticking out into the black plastic. Or was it removed from the nozzle as you took away the black remnants?

Yea I agree - the thermistor could likely be carefully cleaned and reinserted - but this is probably a lost cause, just get a new hotend installed.

I’ve also never seen anything this bad. I don’t understand the rectangular blob and how that possibly could form, unless that was part of the print that lifted off the bed.

I’m not 100% it didn’t occur when when taking the print off but there was no way to remove it besides how I did it without some kind of solvent. The situation would have been funnier watching it mindlessly trying to print dragging the plastic corpse if it wasn’t so upsetting to see my investment breaking lol.

I was printing the ultimate test file from thingiverse to see how it performed and it was about a 4" square base it builds upon. I’m guessing it picked up the base somehow and kept extruding until everything in the cavity was just a molten hot blob. Rest in pieces, homie.

Something like that? https://www.thingiverse.com/thing:4459658

Oof, yea, that’s a super difficult print. Definitely watch prints like that if it’s the first time you’ve done that. That particular one looks close to impossible to print successfully, the question is where is it going to fail.

Good to know going forward! I should have lookup it up before I said ultimate because that’s definitely the one I took the name from but the one I ended up trying was this one:

Either way, can’t do any more damage until I hear back from the company so I guess it’s time to try out the CNC. lol

Yea, that one will also fail at some point - there’s just not enough cooling to do an 80 degree overhang. And those long bridges will be problematic too. I’ve played around with the Cura experimental bridging settings and they help a lot. Even better than Simplify3D’s bridging where there’s short lead in/out.

It really doesn’t look too bad honestly - the toolbox should’ve come with a spare hotend you can swap out, and I think they sell them on the website for $20 or so. But nothing in there looks particularly damaged.

The silicone being torn and melted doesn’t really affect too much - mostly how much energy has to go into the hot end to keep it hot, it’s just a thermal blanket. And the thermistor popping out happens sometimes, that’s also not a huge deal. If you can clean it off by carefully nibbling it it with clippers or something then it should still work. I have vats of DCM that could dissolve all of that, but that’s like super cancerous, generally wouldn’t recommend, requires training to do safely.

Good luck!

Also for a test print I recommend the one from kikstarter, I feel it is a better representation of what the printer is capable of then any other test print (as there are clear instructions on how to evaluate and score the print) also it is what all3dp uses. So you can compare your results to a bunch of other printers.

@Atom, had a quick look through the kickstarter pages, but was unable to find the model you’re describing. Do you have a link, or is it somewhere else?

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That was one of my first prints! It printed without a hitch, I don’t know how. Both the overhang and bridges look great

Although, looking at other parts of the model, I suspect I had not calibrated my E and I was underextruding


@Atom, it’s just occurred to me that you might be talking about the Autodesk model, rather than a SM provided model.

This one:


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You are correct, that is the one I am referring to. It was a collaboration between autodesk and kickstarter.

I just purchased an A250 printer from an individual. The hot end looked just like this just not quite so bad. I’m sure it would have gotten to this point had I not replaced the hot end. If you remove the hot end you will note that the blob of filament is squeezing out between the feeder tube and the block. I had a similar issue with my original Snapmaker. The issue was caused by the nozzle coming loose or being loosened with filament in the head. The problem is that it’s impossible to properly tighten the nozzle if there is filament in it. So if you need to replace the nozzle; extract the filament, remove the hot end from the head, and replace the nozzle. Make sure the plastic core is pushed all the way into the silver tube and that both the tube and nozzle are tight.
Hope this helps.