Third Color for Dual Extrusion Printers Testing

[yyh1002 60]

I did some testing on creating the third color with dual extruder, inspired by Tim Kuipers’ greyscale printing research and the effect on prime tower https://ultimaker.com/learn/3d-hatching-grayscale-printing-on-the-ultimaker-3 [gr5 fixed link]

Interlacing two colors can create third color on vertical surface quite consistantly as long as the two nozzles are properly calibrated. 

 

I then tested the idea with an astronaut model by BZH1 meant for 3-4 color (https://www.thingiverse.com/thing:2609610). I prepared the model with Rhino, manually cut the third color into slices, and imported into Cura together with the other two colors. Surprisingly, Cura was able to hollow out the third color instead of printing it as a solid piece. 

 

The print came out has a nice tone thanks to the additional color. It is showing mixing inconsistancy possibly because of heated bed shape change or one of the magnets on my mark2 coming loose during the print. 

 

It would be nice if CURA can add a third color choice and slice the part with half tone treatment as an experimental feature. 

 

[ahoeben 1,948]

Nice result! Note that the research you reference is actually by Tim Kuipers (@bagel-orb). Matt just wrote the blog article on it.

[pbackx 11]

6 hours ago, yyh1002 said:

manually cut the third color into slices

This is a great result.

 

How did you manually slice that third color? Did you use the CuraEngine branch by Tim or some other trick?

 

[yyh1002 60]

44 minutes ago, ahoeben said:

Nice result! Note that the research you reference is actually by Tim Kuipers (@bagel-orb). Matt just wrote the blog article on it.

Oops, my appologies to Tim. It’s been too long since I read the article so I just jumped in and refered to the author. Thanks for correcting me. 

 

34 minutes ago, pbackx said:

This is a great result.

 

How did you manually slice that third color? Did you use the CuraEngine branch by Tim or some other trick?

 

I didn’t try the CuraEngine branch by Tim. I literally cut the objects in disks in modeling software. 

[bagel-orb 61]

You don't need to cut the model into layers, Cura already automatically does that for you by default!

Just load the part where you want to alternate color twice and set one instance to the one nozzle and the other instance to the other nozzle.

Make sure Remove Mesh Intersection and Alternate Mesh Removal are both enabled and also verify that Top Layers and Bottom Layers are even numbers to prevent them becoming solid. Verify these settings for both nozzles.

Here's what the layer view looks like for a model similar to https://www.thingiverse.com/thing:1421443

The eyes are in both colors.

[ahoeben 1,948]

Cool! Do you need to set the flow to 50%?

[bagel-orb 61]

Nono, the layers are automatically made non-overlapping due to the Remove Mesh Intersection setting.

[yyh1002 60]

48 minutes ago, bagel-orb said:

You don't need to cut the model into layers, Cura already automatically does that for you by default!

Just load the part where you want to alternate color twice and set one instance to the one nozzle and the other instance to the other nozzle.

Make sure Remove Mesh Intersection and Alternate Mesh Removal are both enabled and also verify that Top Layers and Bottom Layers are even numbers to prevent them becoming solid. Verify these settings for both nozzles.

Here's what the layer view looks like for a model similar to https://www.thingiverse.com/thing:1421443

The eyes are in both colors.

I tried this earlier. It works most of the time but the interlace is not as consistant as manual cut. Sometime the part shows same color for a few millimeters. It would be awesome if the feature is more reliable. 

[bagel-orb 61]

I cannot reproduce your problem in Cura 3.4.1.
I tried making the whole body in both colors and there were no layers where the color wasn't swapped to the other color.

If it keeps persisting in your model you can try setting the Horizontal Expansion of one of the extruders to -0.01mm.

[yyh1002 60]

24 minutes ago, bagel-orb said:

I cannot reproduce your problem in Cura 3.4.1.
I tried making the whole body in both colors and there were no layers where the color wasn't swapped to the other color.

If it keeps persisting in your model you can try setting the Horizontal Expansion of one of the extruders to -0.01mm.

Thanks for clarifying this. In this case I think it was because I export the overlapping geometry together with each color and the mesh possibly turned out slightly different. I tried export the overlap geometry by itself and the interlacing seem to work just fine. 

Edited July 11, 2018 by yyh1002

[bagel-orb 61]

Hmm. It should work better when you have the gray regions as part of the 1 mesh for white and the 1 mesh for black. If you keep just 2 meshes there will be less boundaries on the inside of the mesh.

If you use my method to model the gray region as a separate mesh you will get wall lines between the gray and the white or black regions. That's a waste of material.

[bagel-orb 61]

[bagel-orb 61]

The layer below shows how the black is receding where the back of the helmet should be white: (In blue so that you can see the black)

[yyh1002 60]

I tried export just two meshes again. I needed to transfer the model into mesh before export to make sure the overlapping part has the exact same mesh so the auto generated interlacing works perfect.

I printed another one at 70% scale and 0.1mm layer, with fuzzy skin of 0.1 thickness and 0.2 distance. The skin finish is almost injection mould quality. The randomness of fuzzy skin makes the color mixing a bit messy. Is there a way to make fuzzy skin more regular with constant zigzags shifting every layer?

Edited July 11, 2018 by yyh1002

[bagel-orb 61]

7 hours ago, yyh1002 said:

Is there a way to make fuzzy skin more regular with constant zigzags shifting every layer?

No. Sadly not. Implementing regularity across layers with different geometry is rather difficult.

[MobyDisk 4]

This is amazing!  I have red PLA and blue PLA and I wanted to try printing something purple, so I used bagel-orb's suggestion.  Unfortunately it fills the entire thing solid, even if I have an even number of top and bottom layers on both extruders, as you described.  My only solution was to make 0 top and bottom layers for both of them.  This should work for this model since it is very round and it pretty much closes at the top anyway.  If I set the layers to

 

Is this officially supported in Cura?  If so, is there a reliable way to fix the top/bottom problem so that it doesn't fill the model solid?  If I could tell Cura to use different settings for different layers like Slic3r can, then I would tell it to use top/bottom layers for just a few specific layers and that would fix it.

 

[MobyDisk 4]

This is the result with 0.1mm layers.  The blue pattern you see is not a slicing error, the printer really did alternate rows.  I suspect that the blue extruded a bit more or the red extruded a bit less, so the blue sticks out more.  The blue PLA is Inland PLA from Micro Center which was literally 1/4 the price.  It would be interesting to repeat the experiment with Ultimaker PLA in both.  Or to try this with something that can be vapor smoothed it.