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"Lumps" in final filament.


I am making PLA filament from recycled printed parts and have success to some extent but also I am fighting one particular issue: filament every few meters develops some lumps (!AmzyylHZBP6ulqptF-_hps3FNpOwhw?e=cDTsHa)   It is not any foreign material and it is building after nozzle exit and in one moment it is pulled down.  I greatly reduced occasion by changing the nozzle to 3mm but still, sometimes it happens. 
What can affect it? speed? cooling?

BTW: this is printed with 100% recycled PLA 
(!AmzyylHZBP6ulqthaW3bLtbk6Hk-Zw?e=Tc5eBD!AmzyylHZBP6ulqtg_uGUjUx6tx7-Sg?e=yGdUhX )

PS: it would be really great to be able to upload photos to the post.

Topic starter Posted : 30/09/2020 12:53 pm
timo liked
Member Admin

Hi Rado @hunterius_prime,

What settings were you using here? This problem is often caused when the nozzle is too cold, which solidifies the material partially, causing the buildup. The first thing to check is if the nozzle is covered properly with the insulation wool and the nozzle plate, like in the attached picture.

The fan cooling also cools down the nozzle, so reducing this cooling could also fix the issue. If none of the above help, probably the temperature of heater#1 has to be increased a bit. Also, is the material feeding in properly? With recycled flakes this can sometimes be problematic, causing inconsistent flow (which can also cause the effect you described). If you can send over a datalog (, I can help analyse the data and perhaps get some useful insights.

Very awesome prints by the way! They look really nice :) hopefully you will be able to produce much more.

About the uploading of pictures, did the attach file button not work? I will ask my colleague from IT what is going on here.


Best regards,


Posted : 01/10/2020 9:33 am