Nozzle melts into the purge tower and some loading issues.
 
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Nozzle melts into the purge tower and some loading issues.  

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timo.c
(@timo-c)
Active Member
Nozzle melts into the purge tower and some loading issues.

I just finished my first 2 color print with the mk3s and mmu2s.
There were 2 main problems:
First I had some loading issues which I think come from a not 100% calibrated IR sensor because it simply fails to load and then I do nothing more then loading via the middle MMU button and then continue the print with the right button.
I had some trouble earlier with single color prints regarding this so I will have to look into it but I appreciate any tips going further then the provided info by prusa.

Now regarding the title giving second problem:
Whenever there is a filament change the nozzle parks directly above the purge tower and therefore melts the top layer of the purge tower which curls up. After resuming it then runs into those updent edges making a unpleasant noise but so far everything went fine.
Just before completing the print (which was around 48 hours of total print time) it did not only burn those wholes but it took the whole tower with it and knocked it over.

 

 

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Posted : 02/07/2019 9:33 am
gnat
 gnat
(@gnat)
Noble Member
RE: Nozzle melts into the purge tower and some loading issues.
Posted by: timo.c

I just finished my first 2 color print with the mk3s and mmu2s.
There were 2 main problems:
First I had some loading issues which I think come from a not 100% calibrated IR sensor because it simply fails to load and then I do nothing more then loading via the middle MMU button and then continue the print with the right button.
I had some trouble earlier with single color prints regarding this so I will have to look into it but I appreciate any tips going further then the provided info by prusa.

Check out other threads as getting the IR sensor playing nice is well trodden ground at this point. The "posting out of frustration" thread is a current example of such, but there are plenty of others.

Now regarding the title giving second problem:
Whenever there is a filament change the nozzle parks directly above the purge tower and therefore melts the top layer of the purge tower which curls up. After resuming it then runs into those updent edges making a unpleasant noise but so far everything went fine.
Just before completing the print (which was around 48 hours of total print time) it did not only burn those wholes but it took the whole tower with it and knocked it over.

When you say it "melts" the top layer, is it actually melting it or is it depositing a blob? If it's a blob that could be the IR sensor (which you are already suspect about) or that you need to tweak the extrusion settings for the filaments you are using.

Melting shouldn't happen unless the nozzle stays in the same position for too long (longer than a slow filament change). So if it is melting then I'd guess that the part fan is not working, your nozzle temp is too high, your nozzle is too close to the tower, or it is dwelling too long at that point.

Another possibility, is that your bed is not level and the area where your tower is is higher and thus making collisions possible. This would be a reason for the nozzle being too close and thus contribute to the melting you are seeing. The raised areas from the melting would exacerbate the issue and lead to the dragging and collision.

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Posted : 02/07/2019 2:56 pm
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