Valkovia

I know this is a little late for a reply, but it ranks high in SEO and people might click looking for answers (like I did) If you are using inventor. there is no need for any form of plug ins. open your .ipt file that is set in inches. go to TOOLS -> Document settings under the units tab set "length" to mm (at this point all inches in inventor will be converted to mm) To export File -> Export -> CAD Format Set save type to .stl, then click options, make sure the units read millimeters Export .stl and you're good to go. if you tend to be on the paranoid side. Cura will give the overall Length width and height if a part, you can open up a drawing and measure your .ipt in mm to double check the sizing is correct in Cura.