I am having some strange problems with my second build,I cant calibrate all 3 axis correctly.
I can make it to go exatly 30mm,making circles perfect,repeatability tests all ok but when I make for example 150mm circles it goes 151mm.
OK,then recalibrated all axis,but then goes perfectly to 150mm but when tested the 30mm test it makes 29mm...
I have no backlash that I can mesure.
I am using 12mm x 1,75mm pitch
threaded rods,directly coupled to my 2Nm stepper motors.
Using this drivers:
2/4 phase stepping stepper motor driver 70V/6A - eBay (item 300528146572 end time Apr-20-11 07:56:00 PDT)

and 50V power supply.