Friday 1 July 2011

Layer selective colour 3D printing

After printing coloured and multicoloured things, I wanted to experiment using my Filament joiner to make prints that had different coloured finishing layers (at different heights) on an object.
A business card seemed a suitable object to start with as I could place things and text onto it and vary the height of each object.
This is what I ended up with, below is how it was done - 

First I actually needed to learn Sketchup so I could design it. I had quick go as hacking other peoples parts a few days back but as I wanted the open hardware logo on the card I needed to work out how to do that first.

Download a picture
Import it into Sketchup and turn on Xray
then trace around the image to form a closed path you can extrude

Extrude that to whatever height you like
Then I added text using Sketchup font tool.

The model should turn out like this.

Design the rest of the card
Each text block finishes at a different height from 0.8mm to 3mm

Export and re-scale in Netfabb if required
this is 85 x 55mm

I did a quick test of fonts to see if they would actually print – 
This just showed me that you need it to be an outline without any infill or it will end up messy.
I could have made a better selection of font and size, but not bad for a first print.
I need to work on the font size so Skeinforge produces a tool path that does not try to fill little gaps in the letters.

Then after slicing in Skeinforge you can use the output Gcode and a program like Grep to isolate out the extruded movements for each layer.
Then you can join the sections of filament together the correct length and print !

At each point you decided should have a different colour the layers change and slowly build-up a multicoloured object.
The red text is only two layers high and a little smudged.

It looks good enough to eat!

A few other multicoloured things printed for fun yesterday.

close up, the changes are quite sharp, I initially imagined it would take many layers to change colour.

I had a go at also doing horizontal selective colouring on the base, but it's not easy to see in this picture.

The inside of both bases lines of different colour so with correct filament lengths you can select  both horizontal and vertical colouring.
If you were printing a cylinder for example, with the correct lengths of filament you could colour half of the object in the vertical plane as it was being built up (quite hard to do though).

Fitted together perfectly.

Many thanks to AgeingHippy for sending me some white PLA to try.
And thanks again to Greg Frost for suggesting using Grep for working out lengths of input filament.

I need to get ready for the RepRap weekend now, so thanks for reading (quite a long one this time).



  1. Great job on that! Thanks for sharing.

  2. Thanks.

    I'm at the Reprap master class in Bath at the moment, I will post more details about the filament length calculations when I get back.

  3. Yay! Maybe I can start working on a way to automate the process...

  4. I do this manually on my Cupcake by snipping the ABS right above the MK5 extruder and sending down a new color behind, on the fly, with no shutdown.

    Since it takes something like 100 seconds before the color changes out the other end, you need to predict the right time to snip.

    Only one have I had a problem when the cut was not straight on a piece and it jammed. So be careful to have clean, straight cuts.

    A couple of my early attempts are here:

  5. I've been using a pair of cat nail trimmers to trim filament. It seems to work well for me. Nice straight cuts.

  6. Cool, thanks, I don't have a cat but I'll look out for feline nail trimmers next time I go shopping!


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