MINI loads filament and purges fine but does not print
 
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MINI loads filament and purges fine but does not print  

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papercrane
(@papercrane)
Active Member
MINI loads filament and purges fine but does not print

When I load filament into my MINI it will load fine and purge fine. The new filament will come out. When I try to print something, however, the filament will extrude for a short time, then stops coming out. I've tried recalibrating the Z value and nothing helps. Within the first layer of any print the filament will come out slowly and then stop entirely. If I load filament and let the printer cool down before starting a print then nothing comes out. In order to get the filament back out I have to heat the hotend to much hotter than the filament normally needs, such as 260 degrees for Prusament PLA. Once I get it out I have to push some filament manually into the hotend with a fair amount of force. A large blob of filament will come out quickly and then normal amounts come out. A print after this ends up the same as when filament is originally loaded, only some comes out before it stops entirely.

Today I took apart the entire hotend, removing the nozzle and the pipe with the PTFE tube. The heat block was fine but the pipe had a blockage near the bottom. I couldn't get it out so I reattached it to the heating block and heated it up, then pressed on the blockage with a small allen key. Eventually a blob of various filaments came out and I put everything back together. Doing a first layer calibration seemed to be extruding fine but the square at the end kept being inconsistent, partly filled and partly not. A test print seemed to start ok but ended up like before, with no filament coming out.

I've completely exhausted all of the possibilities I've found in the knowledge base and I don't know what else to try. My MINI is unusable.

Posted : 28/09/2021 6:38 am
fuchsr
(@fuchsr)
Noble Member

Bought as a kit or semi-assembled? 

Posted : 29/09/2021 12:00 am
papercrane
(@papercrane)
Active Member
Topic starter answered:
kit

Bought as a kit. When I put it together it worked fine for a month or two before this problem started.

Posted : 30/09/2021 3:53 am
cwbullet
(@cwbullet)
Illustrious Member
Idler screw

I have you checked the tension on your idler tension screw?  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 30/09/2021 11:07 am
fuchsr
(@fuchsr)
Noble Member

There have been enough reports of issues with the PTFE tube on the Mini that it's probably worth considering replacing the stock heatbreak with a Bondtech heatbreak.  You can look through the Mini forum here for "heatbreak" and will get quite a few hits. It seems to begin showing issues like the one you described after a while of use, due to shrinkage of the tube. I should say that I personally have not experienced that issue at all with my Minis, and my Bondtech heatbreaks are still sitting idle in my drawer. They're about $15 at Printedsolid or Filastruder etc., so something easy to check.

Another possible culprit you didn't mention is the extruder. If the extruder is not pushing material properly, you may also end up with underextrusion or possibly clogs. Trying to adjust the idler screw is worth trying. If that's the case, you may want to consider upgrading to the Bondtech extruder. About $35 for the Trianglelab clone on Aliexpress. For me, it's the only upgrade I wholeheartedly recommend.

But I'd start with looking into the heatbreak upgrade.

Posted : 30/09/2021 11:09 am
Coyoteran
(@coyoteran)
Active Member
Another vote for the changing the PTFE in the heatbreak

Pull the PTFE tube in the heatbreak and measure the length with a micrometer. My Mini was doing exactly what you described and it turned out the tube was a full mm too short. Maybe overheated and shrank at some point. I installed the spare that came with the kit and it now works fine.

Posted : 30/09/2021 3:12 pm
geekandi liked
cwbullet
(@cwbullet)
Illustrious Member
Just pulled mine

My PTFE was also short.  The purging filament fixed it for 5 prints.  6th failed.  Replace PTFE and no issue so far.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 30/09/2021 4:19 pm
geekandi liked
monteg
(@monteg)
Active Member
im having the same issue

took apart everything still wont work 

Posted : 10/10/2021 4:31 pm
MysDawg
(@mysdawg)
Trusted Member
Simiar Issue and Fix

My PTFE tube was short too. Replaced it and all is well......

Posted by: @coyoteran

Pull the PTFE tube in the heatbreak and measure the length with a micrometer. My Mini was doing exactly what you described and it turned out the tube was a full mm too short. Maybe overheated and shrank at some point. I installed the spare that came with the kit and it now works fine.

 

Posted : 10/10/2021 5:50 pm
cwbullet
(@cwbullet)
Illustrious Member
Ptfe

I wonder is Prusa is cutting them too short?

Posted by: @mysdawg

My PTFE tube was short too. Replaced it and all is well......

Posted by: @coyoteran

Pull the PTFE tube in the heatbreak and measure the length with a micrometer. My Mini was doing exactly what you described and it turned out the tube was a full mm too short. Maybe overheated and shrank at some point. I installed the spare that came with the kit and it now works fine.

 

 

--------------------
Chuck H
3D Printer Review Blog...
Posted : 10/10/2021 5:51 pm
MysDawg
(@mysdawg)
Trusted Member
PTFE Length

Possibly?

Posted by: @cwbullet

I wonder is Prusa is cutting them too short?

Posted by: @mysdawg

My PTFE tube was short too. Replaced it and all is well......

Posted by: @coyoteran

Pull the PTFE tube in the heatbreak and measure the length with a micrometer. My Mini was doing exactly what you described and it turned out the tube was a full mm too short. Maybe overheated and shrank at some point. I installed the spare that came with the kit and it now works fine.

 

 

 

Posted : 10/10/2021 5:54 pm
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