So I chopped off the extruder motor socket and soldered on individual sockets for each of the four wires. Finally, at last, I got a proper response out of the extruder motor. So I ran tests for a few hours and it all seemed to be OK and then the extruder stopped for no obvious reason.
Well the only piece in the whole extrusion chain that I hadn't replaced or repaired was the teflon tube in the filament pre-heater. And sure enough when I extracted it I found it had partially melted to partially fill the filament hole, making proper extrusion impossible. A bit of creative gouging with a small drill bit restored the hole sufficiently to allow filament to pass through.
And finally, after more hours of testing, I have a working 3D printer. I put all the original parts back in and it still worked :).
So I've started trying to catch up on my backlog of needed enclosures. Obviously I don't need a special enclosure for a RUMBA board because I've put the original board back into the enclosure already supplied.
I tried making an enclosure for my Parallella. This required me to re-construct the SolidWorks example on Thingiverse here into a parametric model I could change to suit my requirements, specifically I only had a 40mm x 40mm fan and I wanted to continue using the existing 5V power socket.
Yak-shaving to make a 3D model
I wondered if OpenSCAD was the quickest and easiest open source 3D modelling program. I wasn't prepared to pay the SolidWorks licence fee considering how infrequently I would be likely to use it. I looked at FreeCAD and it seems an interesting parametric design program. Then quite fortuitously I found SolveSpace which has only recently been made open-source but seems much more powerful and capable than FreeCAD. And there is a Mac OS X version as well. The trouble was, for the simple box enclosures I want to make OpenSCAD simply makes better sense to me. I suppose it appeals to my programmer background.
In the meantime, I ordered an enclosure and cooling fan for the Parallella from Ground Electronics just in case I found making a usable enclosure too tedious or too difficult. The Plan B case arrived today and although I was very close to a working enclosure, I couldn't get the correct screws so it seemed easier to use this enclosure and get on with other things.