Spent last week tidying up the gantry, fitting flange bearing and reading, mostly about stepper motors:

http://homepage.cs.uiowa.edu/~jones/step/an907a.pdf
https://www.mpja.com/download/18304ms.pdf
http://www.haydonkerk.com/Portals/0/...uators_101.pdf
http://www.selene.co/Blog/2011/08/se...motor-winding/
http://www.micromo.com/microstepping...-and-realities

The aim was to understand how the choice of motor i.e. chopper motors, effects the design of the circuit. Without the depth of knowledge to fully understand everything I have read, there where a number of points I need to carried forward:

(1) Motors can be driven at between 10-24 times there specified voltage. Increasing the multiplier will increase the stiffness of the motor.
(2) A motor is most effective when is it operating within the 'slew' range of the speed torque curve.
(3) Micro-stepping increasing the machines efficiency at the expense of the available holding torque.

The last point is important as it helps limit my expectation of micro-stepping i.e. it won't make up for accuracy lost within the design or the build ) I would imagine this last point is reflected in the 'motorcalcs' spreadsheet, which includes a significant safety factor?