How to 3D print a photo in colour on a single-colour printer

You don't need a multi-colour printer. Print the photo flat, in thin layers of a few filaments, and change filament at a few set heights. Thin plastic lets light through, so the colours mix into the shades of the photo.

How it works

The darkest filament is printed first, as a solid base. Each lighter filament starts a little higher, and only where the photo is lighter does the model rise into it. Where the photo is dark you see the base, where it is light you look at the top filament, and in between you see the colours mixed through a few thin layers.

How much a filament lets through is its TD (transmission distance): the thickness at which you can no longer see the colour below it. Light colours have a higher TD than dark ones. The height each colour gets should be at least its TD, or the colour below shows through.

Step by step

1. Open Photo to STL and choose a photo with clear light and dark parts: a portrait, a pet or a landscape.
2. Choose the shape and width, and crop the photo.
3. Choose Layered colours and the number of filaments (2 to 8). Pick the colours you have, or let the maker take them from your photo. If your filament brand lists a TD value, fill it in.
4. Choose your nozzle and layer height. The preview shows what the print will look like with your filaments.
5. Download the 3MF and the filament plan. The plan lists the layer and height of every filament change.

Adding the filament changes in your slicer

• PrusaSlicer opens the 3MF with the layer height, the colours and the filament changes already in place. Check the first layer height and slice.
• Bambu Studio and OrcaSlicer: slice, then in the preview move the layer slider to each height in the plan, right-click the slider and add a pause or a filament change.
• Cura: use Extensions › Post Processing › Modify G-Code, add the Filament Change script once per change and fill in the layer from the plan. Check in the preview that the change lands where the plan says.

When the printer pauses, load the next filament, purge until the new colour comes out clean, and resume.

Print settings

• 100% infill, so no infill pattern shows through the thin layers.
• The first layer height and layer height the maker gives you: the changes are counted from them.
• Print it flat, picture up. No supports.

Other makers that print this way

The same filament-change method is used by the photo wall clock, the photo coasters, the photo puzzle and the pixel art maker.