Thank you peggyb and mastory for the replies, they helped a lot and now the UMO is back to work! It was a feeder-related problem: sometimes the bowden pops up, so the file that mastory linked was very useful, thank you so much again.
29 minutes ago, peggyb said:and.... where is the fan?
The fan was temporarely removed when we disassembled the hot end the first time, now it's back to its place 😉
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peggyb 171
this could be a lot of things, test the everything from feeder to nozzle:
Check if the little black wheel inside the feeder is rotating freely, and if the tension is right. When closed, try to pull at the filament if it slips. https://ultimaker.com/en/resources/240-cleaning-the-feeder. Look at the marks on the filament, are they overall the same? Deep or shallow? Are there bite marks?
Take the print head apart by starting with the Bowden clip and remove the Bowden tube. Heat the nozzle and push the filament through by hand. Also perform a 'cold pull'. Cool the nozzle down to 90 degrees with filament inserted, and with the print head in one corner, pull out the filament. Check what the end looks like: is it dirty, is it thicker than normal? You can do this a couple of times.
Take the printhead further apart and look at the white teflon coupler. When it is brown, it should be replaced.
Remove the nozzle and clean it, clean the heater block and put everything back together, tight (not over tight). Check the assembly manual for instructions https://ultimaker.com/en/resources/235-assembly
Take a piece of filament and push it in from above the printhead and feel if there are any obstructions.
Put the bowden tube back on, heat the nozzle and load some filament. Turn the feeder wheel and look at the extruded filament, is it a nice consistent flow?
Start a print....
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mastory 44
On the early UMO's, I don't think there was a teflon coupler. The Bowden had to be cut very accurately and the end of the tube was jammed down against the brass tube that passed from the nozzle thru the heater block and into the PEEK insulator. Heat migration up the brass tube would cause deformation of the end of the bowden, and cause a bottleneck for feeding filament. Also the brass tube tended to have a very long melt zone which was prone to clogging. Do not leave your machine with the hot end at printing temp for more than a few minutes when not printing. Another problem was retaining the end of the bowden against the hot end. The extrusion forces will tend to pop the bowden out of the hot end. Once it pops a couple times, the retainer clip will not bite into the bowden well and the bowden will need shortening to grip. There are a couple printable user developed add-ons that remedy this. Owens bowden clamp is one
My recommendation is to upgrade both the hot end and the feeder to something aftermarket. I found the original hardware for the filament delivery to be problematic and unreliable. After cleaning my nozzle out 3-4 times, replacing it once, I upgraded the nozzle. This is exacerbated by the fact that the hot end is not easy to disassemble and reassemble. Personally, I went with a Geohagan extruder (outdated or hard to find parts for now) and a home built hot end. There are much better and inexpensive options out there today. You will probably need to alter your firmware and possibly machine wiring for a different hot end.
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peggyb 171
and.... where is the fan?
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