STL import scale change

Rhino Rhino for Windows
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1

I see mentions of this issue back in 2015…

tool-R8-STL import
tool-R8-STL import978×1121 257 KB

When i export to STL in Rhino7 and then import the STL file back into the .3dm file there is no scale change. However doing same in Rhino8, results in a scale change. Is there a fix?

2

Check your units… looks like maybe cm<>Inch scale 2.54… STL files do not have a unit system.

3

The issue is that STL stinks.

There’s no “issue” with Rhino here, it has no way of knowing what the units in an STL file are, the information is just not there, you simply exported from a Rhino file using a certain unit and opened it with a template file that was in another unit.

4

Thanks

I always work in mm. Not finding a units setting related to cm or inch.

Is there some other units setting that you are referring to?

units setting
units setting595×469 36.5 KB

5

Not understanding the difference in how Rhino7 maintains the scale and Rhino8 doesn’t.

6

Do you see this dialog when you import the STL?

image
image563×368 20.3 KB

7

Only difference is, “Current Rhino units : Printer point

8

So that’s the units in the Rhino file/template you’re importing it into.

9

1 printer point = ~0.353mm

So going from one system to the other the model will either decrease in size to about 1/3 or increase in size by a factor of around three, depending in the direction of export/import. Looks consistent with your first image, exported from a printer point unit file and imported into a mm file.

10

Got it—Thanks