So, after a long spell away from my GUS I'm back on getting this to work even though I wimped out and bought an off the shelf cartasian printer (CTC).
I managed to find myself an Anubis hotend from a gent I met at one of the 3D printer meetups at Hackney Hackspace which now means my arms don't get near the singularity and collapse. My geometry now is probably very close to the norm.
I've fixed a few firmware settings such as setting my minimums to 0. Before that following a home command my printer would think it was well into the negatives and even a small positive move would result in the arms shooting out of bounds .
I'm still struggling with the bed levelling calibration in Segmentise. Firstly my co-ordinates were throwing up 'maths domain error' but now I have better values the g-code generated for some reason is in the negative domain. Running the unchanged, downloaded segmentise gives the right sort of movement but as you would expect not necessarily near the printer bed. A cheeky cheat I discovered to test values one by one for the maths errors is that even though segmentise expects 6 minimum values you can re-use the same value more than once. I used this trick to swap out readings one by one until I found the ones that broke the maths.
I do have a problem with my Y motor. Sometimes I can hear a rythmic light ticking which sometimes manifests as slight movement. If the arm is trying to move when this is happening it affects the movement causing moves to be disrupted, possibly what was causing my innacurate readings before the problem became bad enough to notice. On a related note I may well need a chipset fan as the thermal glue that holds the heatsinks on my stepper drivers liquefies.
At the moment I am using the GUS as a simple teaching delta robot building gcode routines by hand in Repetier. I am planning on using a model hotend file to make a number of tools such as hooks and stamp holders so the kids can use GUS to programme simple tasks like moving parts from point A-B and using stamps to mass produce X-mas cards
