This is a Trammel of Archimedes ( http://en.wikipedia.org/wiki/Trammel_of_Archimedes ), drawn from scratch after seeing another printed version, presumably Thing 5103.
Drawn from scratch as an exercise in Alibre, where the '2' designates this is really v2 with filleted corners to make it easier to hold and where the elliptical path just barely misses the guide.
When printing raftless with ABS, if you have it too close to the platform the bottom layer might be flattened to too big to fit into the slot and you'll need to perform surgery to cut it off. The model can be improved to account for this but these are the original STL's I printed.
Motion is very smooth if printed with PLA - see http://www.youtube.com/watch?v=rSmlT-N9rQM
Edit : Updated the slider with a chamfer on the base for raftless prints which I often do.
TrammelArchimedes_Arm2.stl | 727.5KB | |
TrammelArchimedes_Guide2.stl | 60.0KB | |
TrammelArchimedes_Slider2A.stl | 73.3KB |