Keep centimeter scale when saved to .stl

Rhino Rhino for Windows
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1

I’m new to 3D printing.
Every time I save a file in .stl the scale is changed. I’m working in centimeters in Rhino 6, but when I look at the .stl file I saved, it’s in millimeters.
Does anyone know how to keep in centimeters? Some tutorial on how to set it up.

2

The STL file format has no unit specification, it only contains numbers. They are always assumed to be either mm (most of the world) or inches (US and a few other places). So whatever units you are working with in Rhino will end up being either mm or inches in the exported STL. If it’s centimeters, your models will end up being 10x too small when the printer software imports them, because 1cm will be assumed to be 1mm.

The remedy to this situation is to either

  1. Scale up your model by 10 before exporting, or

  2. Temporarily set the file units to mm (answer “Yes” to the scaling question), export, then undo, or,

  3. Use a script that automatically scales your exported objects from whatever units you are working in to mm and then exports.

Personally, for 3d printing sized objects, I would start modeling in mm in any case, rather than cm.

3

Many thanks for the information and help, Helvetosaur. :grin: