Multicolor bleeding - how can I fix this?  

Eminent Member

Hi fellow Prusa owners,

I have a problem with the MMU2S which really annoys me. I get color bleeding in the first layer as seen on the picture. Some sort of black string is mixing through the white. The things I have tried:

- Increase purge block. This seems not to work. 

- Print without a brim. 

- Cleaning the nozzle ( I might think changing the nozzle might work).

- Change the layer height

- I also tried different materials but I am getting the problem over again. 

- There are NO strings, I multiple check on them

Does anybody of you have any suggestions? 

Thanks alot.



This topic was modified 1 year ago by dennis.p8
Posted : 04/12/2019 8:35 pm
Eminent Member

Hi dennis,

from my point of view, the color bleeding might be due to a partial melting of the previous component at the border regions that contact directly with the fresh extruded hot filament.  

One more reason could be, that not only the temperature plays a role, but also the compatibility of the filaments at the border region. So, maybe the transparent is a kind of disolving the black one, when he contacts it at processing temperature. Do you see the same phenomena when combining other pairs of different fillaments?

By the way, I like your prints! 🙂

Posted : 04/12/2019 9:12 pm
Noble Member

You might not be noticing the stringing, but I can't see what else it is. The string it too long, too consistent, and doesn't follow the print paths for it to be a purge issue. Either it is strings coming from the nozzle or the plate wasn't cleaned before printing and they were already on the plate.

I just dealt with some weird stringing issues myself. I couldn't see it with other colors I was using, but after running a bunch of white through I could clearly see that the filament was leaking out between the block and nozzle. When I went to remove the nozzle I found it was so loose I could have removed it with my fingers (except for the 275 degree issue...). Put a new nozzle in, properly tightened it, and now it's back to nice clean prints again.

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Posted : 16/12/2019 7:49 pm

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