Solution (in-theory… going for proof of concept at 1200 today):
Open parts using guidance from here:
Copying and modifying parts
(as found on FarmBot website)
RMB on item I want to download, select “Hide other instances”
Use “Select and Export” function in the toolbar at the bottom of the screen.
Save as STL - (Make sure saving the isolated part and not the whole assembly!)
Import to MeshMixer.
Under the “analysis tab” select “Units/Dimensions”.
Here’s the fun part…
I needed to confirm one true dimension. MeshMixer will auto-snap the other dimensions in accordance with the ratio aspect of the drawing.
To confirm the dimensions I did this:
Use the “Display Orientation Navigator” (I made that name up!!) in the top right hand of screen to orient the drawing to the most useful view. I used Isometric view with Z as the horizontal axis. Looked like this.