To print a model in several colours, the file has to say which part of the model is which colour. A 3MF file can carry that information; an STL cannot. This guide shows how to set up a multicolour 3MF in the three free slicers most people use, so that you can upload it for an instant multicolour price.
You do not need a multicolour printer to do any of this. The slicer only needs to know how many filaments there are and which one goes where.
The two ways to add colour
- Parts. The model is made of separate pieces, such as a sign plate and its letters, and each piece is assigned a filament. Best for designs where the colours are separate shapes.
- Painting. You paint colours onto the faces of a single model, a bit like colouring in. Best for figures and organic shapes, where the colours follow the surface.
You can use both in one file.
Bambu Studio and OrcaSlicer
The two programs work the same way here.
Add the filaments. In the filament section on the left, use the plus button to add one filament per colour. The colour you set for each is only for your preview; you choose our actual filaments in the quote.
Colours by part:
- Import all of the pieces at once. When asked whether to load them as a single object with multiple parts, choose Yes. They keep their positions relative to each other.
- In the object list, each part has a filament number next to it. Click it and choose the filament for that part.
- If your model is one piece that should be split, right-click it and choose Split > To parts, then assign each part.
Colours by painting:
- Select the object and open the Color painting tool (shortcut N).
- Choose a filament, then paint faces with the brush, or use the fill tool to colour a whole connected area at once.
Save it: use File > Save Project As to save a .3mf file. Do not export a plain STL; that drops the colours.
PrusaSlicer
PrusaSlicer only shows colour options when the printer profile has more than one extruder or filament slot, so choose a multi-material printer profile first (any one will do).
Colours by part: add the pieces as parts of one object (right-click the object and choose Add part > Load), then right-click each part and choose Change extruder.
Colours by painting: select the object and open the Multimaterial painting tool (shortcut N), choose an extruder and paint.
Save it: use File > Save Project as to save a .3mf file.
Combining separate colour STLs
Many models are shared as one STL per colour, all exported from the same origin so they line up. To make a multicolour 3MF from them:
- In Bambu Studio or OrcaSlicer, import all of the STLs together and choose Yes to load them as a single object with multiple parts.
- Assign a filament to each part.
- Save the project as a 3MF.
If the parts do not line up, they were not exported from the same origin. Ask the designer, or move them into place before saving.
Design tips that save time and money
Each colour change means the printer stops, swaps filament and purges a little of the old colour. On a design where colours change on every layer, that happens hundreds of times. So:
- Stack colours in layers where you can. Raised lettering on a flat sign only changes colour once, where the letters start. The same lettering inlaid through the whole plate changes colour on every layer.
- Keep small colour details near the top or bottom. A few layers of a second colour cost little; a thin stripe running up the whole height costs a lot.
- Use fewer colours. Each extra colour adds changes. Two or three well-chosen colours usually look better anyway.
- Keep details printable. Strokes and features narrower than about 1 mm are hard to print cleanly.
- Remove colours you do not use. Unused filament slots cost nothing, but they add colour pickers to the quote.
Check it before you upload
When you upload, the quote shows one colour picker for each filament in the file, and a 3D preview with every part in the colour you choose. If the colours look wrong, or the quote offers only single-colour printing, the colours were not saved in the file: go back and check each part has its filament and that you saved a project 3MF.
Upload your 3MF for an instant price
Frequently asked questions
Why does my STL not show as multicolour?
STL files store shape only, with no colour. Set up the colours in a slicer and save a 3MF project.
Do I need a multicolour printer to make a multicolour 3MF?
No. Add one filament per colour in the slicer, assign or paint them, and save. We print it on our multicolour printers.
How many colours can a file have?
We print up to 8 colours in one print.
Does the colour I pick in my slicer matter?
Only for your preview. The quote matches each colour to our nearest filament, and you can change any of them before you order.
Can I upload a whole plate of models?
Yes. Everything on the plate is priced, as laid out, up to 400 x 400 x 450 mm for multicolour.
My model is painted. Will the paint work?
Yes. Painted models from Bambu Studio, OrcaSlicer and PrusaSlicer are priced in colour, and the preview shows the painted areas.