Why is my CAD file the wrong size?
It’s not unusual for new users to load an STL file and find that the size is off by a bunch. When this happens, it’s usually off by a factor of 25.4, a clear tipoff that it’s an inch/mm problem.
Many of the high-end CAD programs, like Solidworks, Inventor, or Pro-E, will save STL files scaled for units that might be different than the file that produced them. The STL format provides no information about the units or scale so MeshCAM has to rely on you clicking “Inch” or “MM” when you load the file.
This is the reason that the overall dimensions are show when a file is being opened- so that you have some way to confirm that the overall scale is correct.
If your STL file is in the wrong units you have two options- pick the units that match the file when you load it or change the STL settings in your CAD program.
You’ll have no problems if you have to load a file as metric when you use an inch mill (or inch when you have a metric mill). MeshCAM will handle the conversion to the units used by your mill automatically.
If you choose the fix the output units of your CAD program then you should look for an “Options” or “Settings” button when saving your STL. Change it to whatever units you prefer and you’ll be fixed for good.