3MF: the 3D printing file that knows its size.
3MF is the 3D printing format that says its unit and keeps colours and parts. Open a 3MF in your browser, nothing uploaded and no slicer needed.
By Suraj Kumar4 min read
3MF was made by the 3MF Consortium as a better STL for 3D printing. Where STL holds only triangles, a 3MF says what unit it is in, keeps several parts and their colours, and is packed in a ZIP. Slicers save their projects as 3MF too.
What a 3MF holds.
A 3MF is a ZIP of XML files: the model's triangles, the unit they are in (millimetres unless it says otherwise), the parts and where they sit on the build plate, and often colours and settings.
Because it says its unit, and its rules ask for every part to be a closed shape, a 3MF is less often printed at the wrong size than an STL.
Open one without a slicer.
Open the 3MF viewer and drop the file on it. It is shown at the size it says, standing as it does on the printer's bed, with its parts listed by name.
Measure it, cut through it and see whether each part is a closed shape. Slicer settings inside the file are not read.
3MF or STL?
Most printers and slicers take both. STL is older and everywhere; 3MF carries more and needs no guessing about size. Either can be turned into the other under Change the format.
Further reading
Topics: what is a 3mf file · open 3mf file · 3mf viewer · 3mf vs stl · 3mf viewer online · 3mf file
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