Michael ... Not sure just what options are available in Aspire itself, but the main problem here is that there are no surfaces to take the frame from. I had a similar problem a few years back when provided with a very nice 'model' of a train wheel. In fact it had a 1024 sided shape for each of the round sections, and when blown up one could see these. The 3D printer software takes a sliced view of the part and build it up, and if one takes 'Tricopter V3 Tilt mechanism' one can see the way they have been sliced to print them, and while milling would introduce it's own facets, it does result at least in flat surfaces where practical. Also much rounder ones where appropriate.
I am currently using Freecad to handle STL files. This allows you to slice the object and produce selected profiles. Drawing Module - FreeCAD Documentation gives you a good handle on just what can be done to take the 3D model and transfer it to 2D for machining.
This is quite a common problem even with the more expensive CAD systems. My neighbour does drawings in both Proengineer and Catia, but they still fall back to Autocad for 2D manufacturing, and I remember early demonstrations of Solidworks where we used to keep hassling the salesman to 'print a drawing' of the part he had just produced. I think Solidworks does a better job of the 'draughting package' these days, but going back from an STL model will never restore the curves exactly as they were drawn. One needs a better modelling format for that.