Holes in sliced file after adding color change option
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[Solved] Holes in sliced file after adding color change option  

Holes in sliced file after adding color change option

Hi, has anyone found a way to solve the holes that appear on a sliced model after adding a color change using the same extruder?

I have these holes appear on the most simple models (a cylinder even). I am extremely confident that the stl files or obj files I am using are not corrupted. I have remade, tried repairing software, remeshed using blender, etc, and always get the same holes when slicing. 

What I have noticed is that if I remove the color change at layer X, then the holes disappear. I assume there is some issue in the slicing instructions when forcing the end of one color and beginning of a second color in the middle of a print. 

I have played around with various prusaSlicer settings to see if I can remove these holes. I have tried switching from arachne to classic, played with arachne settings, played with infill settings, tried adding extra perimeters, increased infill density and layer height - all to no prevail. 



- Using PrusaSlicer 2.5.2

- Prusa MK3S+ with the MMU2S (though not using the mmu2s for this setup, it is simply a passthrough using only the 1st extruder - I have removed the wipe board).

- I attached an example of my slicer file (.3mf)


- I attached the stl model I am trying to print as well. Though one easy way to reproduce this is to use tinkercad and export some letters (T's, V's etc.) Slice those letters and do a color change on a layer in the middle. Holes should appear.


- I attached screenshots of my sliced file with and without the color change showing the holes appearing when adding a color change.

Below is a zoomed in version of holes appearing with a black color change

Screenshot of holes appearing with a black color change, the infill pattern seems to be disconnected at the color change barrier.

Screenshot of no holes when having no color change

Any help will be greatly appreciated. I have suffered from these holes for a long time now and have simply been ignoring them, but as I increase the sizes of my prints, these holes are becoming visible on the finished printed product which I can no longer sell with dignity.


P.S. Yes it is weird that I have a mmu2s and yet am preferring to do a color change through a single extruder. I have found that the color change on the mmu2s is not the most reliable and if I want a single color change at a particular layer, I found it better to do the swap myself (also removing the unnecessary wipe board for this situation).


Posted : 26/11/2023 10:34 pm
Veteran Member Moderator
RE: Holes in sliced file after adding color change option

Good morning, 
I am using the new prusa slicer 2.7.0 and I don't seem to be able to re create this issue. 

Prusa slicer 2.7.0 doesn't seem to allow change by layerheight, in the vertical scroll bar, on the sliced model plater screen, it offers change extruder, instead. 
(I Literally loaded slicer 2.7.0 this morning, so this is the first time I have used it!)

If I change the printer to Mk3S & Mk3S+, I get the change by layer height option. 
SO I would be tempted to use the standard Mk3S profile, and simply load filament to nozzle, on the MMU via the LCD Screen. 
I would step through the wrong printer type warning... and move forward when running the gcode. 

Additionally, I would set a height range modifier to change the last couple of layers to have a single perimeter,  this leaves more space in the fine details, for infill, reducing some of the potential gaps in extrusion. (Having a single perimeter on solid infill sections does not significantly alter the model strength)

you are showing PLA in extruder 1, and extruder temperature of 230C with Bed temperature of 85C. are these the temperatures that you want to use? 
or is it a hangover from previous PETG settings?

When I do a colourchange by layer height, I make the colour change one or more layers higher than the feature start height. this is because the printer returns to the last print position, when it returns to a model, after an M600 colourchange. this last position, is usually outside the features for the new colour, and you often get a blob of the new colour, on the surface of the old colour... 
By delaying the colour change one or more layers, the last print position, is ALWAYS, under where the new colour needs to be... and prevents random blobs.

I suggest that you consider updating your slicer, and trying the methods, above... 

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 27/11/2023 10:25 am
ggaswint liked
Topic starter answered:

Hi Joan,

Thank you so much for the thorough response. I will play with some of those settings you mentioned, update my slicer software, and see if I can fix the holes. This is great information so I very much appreciate it. I did not know I could add a height range modifier, which makes a lot of sense.

I am using PETG, so please ignore the PLA setting 🙂

Also, I have that same single option as you when I click on the plus sign at a particular layer. If you right click where the plus sign is on a layer then you get the color change option for the same extruder, if you wanted to try it out again (not sure if this was the reason you didn't see the option - maybe you already tried that). Here is a screenshot of those options when right clicking.

I actually found a work around where I use the MMU. I import my model and perform a cut at the layer where I want the color change to happen. Then I color the two models separately (bottom using default color in extruder 1 and top using the color from extruder 2). Next I merge the two pieces into a single model again (I found coloring to be easier this way, otherwise the bucket fill doesn't color all the surfaces correctly). When I merge, I make sure to not have the top model extend into the bottom model at all so there are no layer overlaps. 

Slicing the new model with the two colors produces a gcode that has a single color change (using the second extruder for the second color) and does not include any of the artifacts I was seeing when doing a color change for a single extruder. This also has only 1 color change reducing the chances for a potential failure with the MMU. 

I am currently printing this setup. Hopefully it works out well. 

This post was modified 3 months ago by ggaswint
Posted : 27/11/2023 10:02 pm