Exporting STL automatically rescales my file

For whatever reason when I go to export a file into an STL, it is exported to the wrong size - it is no longer 1-to-1. I drew a box and made it 10’x5’x3’ and exported it into an STL. When I loaded the file in my slicer, it was 120mm X 36mm X 60mm. In the past when I exported a file, it was the same size when I opened it up in my slicer, so the 10’x5’x3’ would still hold true. Why is SketchUp now resizing my exports?

Check the export options, the options button on the export dialog.

The export options are the same as they always have been. I’ve used “Model Units” and “Binary” forever. But now it scales down my models when I export them. never did that in 2017 or 2018. I’ve even install SketchUp Make 2017 and it is doing the same thing - rescaling my models.

STL files by their nature are unitless. You have to select the appropriate units in the slicer software as you are importing the STL.

10 feet be 5 feet by 3 feet is pretty big for 3d printing.

Never had to do that before. I drew everything in inches, exported it, opened it in slicer and it was the same scale as what I created it in. Something in SketchUp has changed. I still have the original STL file I exported a few months ago from SketchUp 2018 and it is the same scale and the original drawing. If I change the units of the drawing to mm and import them in my slicer, the units are the same, but they used to stay the same if I drew them in inches. I’m definitely not going to create architectural drawings in metric. So why is SketchUp changing the scale when exporting STL’s?

Yes, but that was to test my theory. When I export the file, I will rescale it in the slicer to right size. The best way for me to get the print to the largest size that I will be able to fit on my print bed is to scale it down in that fashion. That way I’ll have a scale factor I can use to scale the rest of the drawing. For instance, this house I printed needed to be scaled down to 1.85% of the original size. When I went to make the furniture for the house, I scaled them down 1.85% and everything will be to scale with each other. With this new problem, when I went to print the furniture, the scale was way off and I just threw away a whole lot of time and money for a friend of mine who was helping me out because everything is half he size it should be. If I could get SketchUp to export 1-to-1 I will then be able to properly scale everything else down to fit.

Looks as if either SU or your slicer software is confusing inches and mm.

10’ is 120" and coming over as 120mm. One or other end of the exchange isn’t setting units or interpreting them correctly between US Customary and metric units.

THe 2019 Export to STL Options dialogue includes the option to set the units for scaling:

Maybe you set it so long ago in 2018 you’ve never thought to need to revisit this setting in 2019?

When I export the file, I select “Model Units.” Then I open up a new workspace in SketchUp and import the file that I just exported, and the scale is reduced dramatically. It’s something in SketchUp that is not retaining the correct scale, otherwise the imported file should be the same size as what was exported.

Upload your SKP file so we can see it.

Have you checked the import units.

Just to be clear, as has been said before, .stl is a unitless format. When you export as Model Units it as the numbers and with a nod to the units of your model.
If you then import that into a model and specify feet it will see those numbers as feet, if you do it as inches they’ll be inches, millimeters and so on.
So your slicer must recognise a unit, if that unit isn’t the same as your export then you’ll get an issue.

I just noticed that. SketchUp defaults to millimeters when importing stl’s. Odd, but ok - I understand why it is importing the file at a different scale. But it doesn’t explain why it would export it in a different scale if I have “Model Units” selected. The slicer should still see it in it’s original size. This is the original file that I exported into an stl back in January using 2018 version. if you import it into a slice (I’m using IdeaMaker) you’ll see that it is in the original scale and for it to fit on a 300mmx300mm bed, it has to be reduced to 1.85%.New walls-win.stl (1.4 MB)

Here’s proof of what I am saying, I switched units on the SketchUp file just to show that the dimensions between the two programs somewhat match.

One of us is missing the point here, does your slicer work in Millimeters?
What happens if you export your model as millimeters or cm or m?
Then import it into your slicer.

Yes, if I switch the export units of my model to mm, then it will export with those dimensions and import to the slicer with the same dimensions. However, that’s not the point, I never has to do that before. I’ve always export my sketchup model in “model units” and when importing into my slicer, the dimensions remained the same. It does not do that now. What happened between 2018 to 2019 and caused the exportation dimensions to shift is beyond me. It’s an annoyance that can be manipulated to work but it is something that sketchup needs to look into. Patching an old tire will work temporally but eventually the whole tire will give out. A fault in the programming might not seem like a big issue but who knows what other problems this fault may cause down the road.