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Extruder idler tensioner issue  

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Mike01Hu
(@mike01hu)
Active Member
Extruder idler tensioner issue

Recently, I updated my Mk3 to Mk3s and after 100's of hours faultless work with the Mk3 the Mk3S has performed better until today. Printing with PLA I experienced some extruder skipping and a jam, so I undid the idler bracket to clear the jam brushed out the cavity and reassembled. In do this, I noticed the screw was a little less easy to screw in but not severely so and continued with the print. The extruder started skipping immediately, so started to remove the idler bracket but the screw would not undo and the force required spun the nut in its housing; this required destructive work using a Dremel saw to cut through the nut. Investigation showed that there was PLA dust on the thread and this had got into the screw/nut joint then welded the two together. It's not an uncommon problem and I have had this happen before with a mechanical assembly using PLA parts. In the Mk3S the screw is almost immediately underneath the idler unlike in the Mk3, so filament dust can easily collect on the screw and, as some will know, blowing out the cavity will not remove dust adhering to convoluted surfaces like a thread. Needless to say, printing has come to a halt as I need a new idler bracket and have no printer to print it!!! PLA is the culprit here as polycarbonate filaments are less likely to produce fine dust. I have not thought of a mechanical solution but I advise anyone removing the tensioner screw washes it and the spring in IPA or acetone before refitting.

This topic was modified 2 years ago by Mike01Hu
Posted : 27/07/2019 10:13 pm
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(@)
Illustrious Member
RE: Extruder idler tensioner issue

A dab of grease on the screw will also keep PLA from sticking.

Posted : 27/07/2019 11:33 pm
clipper.tradewind
(@clipper-tradewind)
New Member
RE: Extruder idler tensioner issue

I had the same experience... with brand new printer. Have yet to complete a successful print with it.

Repeated problems with jammed hot end/extruder skipping resulted in multiple occasions of removing idler tension screw. After a while it jammed.

Was able to remove it by pushing out the bolt til the nut protruded from the bracket, then putting a 5.5mm socket wrench on it. This resulted in breaking the bolt with the nut still frozen on it, which I was able to replace from spare parts.

Have no idea how tight the idler tensioner is supposed to be... it seems it has to be overly tight to feed PLA at all. On every print I've tried so far, the feed fails before it completes. It was necessary to turn off the filament detector to get it to start printing at all.

I hope this turns out to be a good printer. So far I'm not seeing it.

Posted : 30/07/2019 1:36 am
Dave Avery
(@dave-avery)
Honorable Member
RE: Extruder idler tensioner issue

it should be roughly with the end of the flush with the surface of the idler door.   I expect you are experiencing the all to common extruder jam problems . there are a long list of possible causes depending on the situation and environment. search the forum for "extruder jam" and read up on some of the many causes 

Posted : 30/07/2019 2:06 am
Mike01Hu
(@mike01hu)
Active Member
Topic starter answered:
RE: Extruder idler tensioner issue

As I have been a 3D printer user as a design Engineer for almost 10 years and Prusa user for about 2 of those and I am ok with the operation and setup. What I have done here is draw attention to a design issue that could be addressed in a future design and avoided by a simple application of lubricant in the meantime (hindsight being a perfect science😉).

Posted : 30/07/2019 8:23 am
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