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Color Change Under Extrusion  

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Imitate3D
(@imitate3d)
New Member
Color Change Under Extrusion

I had an issue last year where there was over extrusion on a color change, so the first letter would always come out thicker than the rest. Prusaslicer was updated and I updated the models to the new default settings and this fixed the over extrusion but now there was a under extrusion on the first couple of letters. It meant that the first letter could easily be pealed off with your nail.

I saw that 2.5 was being tested and would be coming out, so I thought I'd leave it as the updated setting might fix the problem. However, I've ran a test and it's still the same on default settings. 

Publié : 09/09/2022 10:49 am
Imitate3D
(@imitate3d)
New Member
Topic starter answered:
RE: Color Change Under Extrusion

So while waiting for an update, I found a reddit post of someone that has identified the issue and surprised that this hasn't been brought up before.

The Prusa Mini/+, while an excellent workhorse, has at least one very reproducible quirk that I have been able to indentify and troubleshot to all heck with Prusa support themselves with no actual fix: The M600 Colour Change command attempts to repressurize just before returning to the print, but it is given too much time to depressurize again naturally before it starts the next line. This leads to poor lines when the print restarts after the change (see here, right side printed first, then left side with the same speed between the two  ).

 

While sometimes covered up by further layers, this is sometimes either not possible or not desirable for the finish on very thin changes. Fortunately, all you need is some clever application of tricking the slicer into thinking you have more than one extruder and making use of the Wipe Tower feature; this acts like a "purge line" between each of your colours and makes sure that each colour you print starts nice and crisp. Please see here, where the only difference from the test above is applying the wipe tower ( )

 

The way this works is that instead of right clicking to add an M600 custom Gcode in the sliced view layer, first apply the settings as below, and then you left click the + ( ), which provides you the option to change extruders instead of simply colour. The printer just dumps all Gcode references to changing tool number by default, so it only ends up running the M600 on the same tool head. From there since you have the wipe tower set up, it's returning to a point that won't be on your print (stops the odd chance of a filament artifact on the print when it first returns to its last printed spot, see first test on the left), and has a chance to clean itself up and pressurize to a level where it is actually printing the line you intended.

 

So, with doing nothing else to the settings except add a wipe tower to repressurize the nozzle, we see a dramatic improvement for laying down colour changes with less failures, and this same tactic applied to multiple "parts" in your model (that make up the individual colours) allows you to even print face to the bed and achieve results like this (the key tag is only about 60mm tall, 2.4mm thick):

As I understand that they have a work around using the wipetower, I do believe there needs to be an update for this or something we can use as a temporary g-code until the repressurize has been resolved.

Publié : 10/09/2022 7:13 pm
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