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Melted burned pla over the aluminum heater block

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I am having extruding problem since I started printing: sometimes it works great sometimes it under extrudes and some other times, during long prints (more than 5 hours) you can see looking at the final piece that at some moment extrusion wasn't regulare (you see like an horizontal not-good-extrusion line 1-3 mm thick)

I thought the problem was with the feeding, i used to solve not-or-really-under extrusion by removing the filament, cutting the top and let some of it extrude to "clean" the nozzle. Theese times I noticed that the top of the filament had expanded and distorted (so it was really hard to remove it) and I used to think that this was the reason: a sort of a cap preventing extrusion.

I recently noticed that over the aluminum heater block there was creating some melted and burned pla. Here is a pic:


I cleaned that away but don't understand the reason...

By the way is it normal that inserting the filament is so difficult?

i always have to shape the top to make it reach the nozzle or it stops just before it, into that white plastic thing the tube end in.


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Your bowden tube might not be totally inserted into the plastic bit which can cause bends in the PLA causing more friction sometimes.

As for the Gunk on top of your aluminum block, I don't think it's actually PLA. I recently just changed my nozzle to one that came in an extra hot end pack, and I noticed the same thing on mine. All the time I've used it with the older nozzle didn't have this gunk issue. With the new one it seems it's melting off a layer of protective coating off the brass and it's getting everywhere. My first print had some burnt brown gunk deposited in the print and also ontop of the aluminum block like yours.

Not sure if it's harmful or suppose to be there... New to this issue myself too.


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The situation has degenerated really (really) badly...

The last completed print was already not that good, with several horizontal "lines" as in this picture (bottom part, the picture doesn't show them all but trust me they are annoying)



When I went checking my last print the head was destroyed. By destroyed i mean melted and never to use again. Here a pic:


I found the printer still printing, mid air without extruding. the top of the head was all messed up, I think this happened because the feeder kept feeding pla but the printer couldn't extrude. I think that the pla filament might have pushed the melted head and therefore break it and bend it like in the picture. anyway it also caused the tube to go out of place and the thermocouple to disconnect but still no mintemp error and the printer kept worknig... here a pic:


The object i was printing was distorted and melted. It smelled like burned sugar


I am really disappointed with what happened. Really. I am gonna have to spend a lot of money to get the melted pieces (+ shipping) and I am not a rich guy, and it's also gonna couse a big delay on my schedule. Since I don't wanna this to happen EVER again I would like to at least understand how that was possible, and what might have coused it..... Anyone?



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I didn't post earlier because I thought it was clear but what happened (obviously I think) is that the heater block got so hot it melted/softened the PEEK part (that brownish part) which shouldn't happen until way over 250C. Probably around 300C.

The only way this can happen is if the thermocouple is still reading a valid-looking temperature, but the wrong temperature (reading low) which means the heater will keep heating to try to get the aluminum block up to temperature but it never gets there according to the thermocouple. So it's very important to figure out why the thermocouple is reading the wrong value and to calibrate it several times and test it before printing.

For example a quick test is to set the temp to 95C and make sure no water boils on the aluminum block.

The fault could be in the thermocouple or the board that translates the thermocouple into a voltage or in any of the cabling. Or even possibly in the board under the UM.


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Actually, my issue is that melted PLA is coming/overflowing out of the heating block, form both ends. I made sure it was tight, and this is the 2nd heating block/nozzle i've installed after breaking the first one (while handling while it was cold mistakingly). The print has little bits of burnt PLA on it, that seems to be dripping onto the pint.


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See? Not the same problem.

I've heard people say they used teflon plumbers tape to stop leaks. Have you ever used that in plumbing? It's very cheap - its a thin teflon tape that you wrap 2 or 3 times around the threads and then screw it in.

Also other people use ABS to plug leaks.

Ultimaker used to ship a little bit of ABS filament with every UM and you were supposed to use that to plug leaks somehow but I'm not sure what the temperature and procedure is exactly.


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