microstep uniformity

[HiltonSteve]

Thanks again Irving. As I willl be using ballscrews with a 5mm pitch, I think that halfstepping at 0.0125mm per half step is perhaps a bit lumpy so I am now looking at using a toothed belt drive for the ballscrews.

Mike.

I have 16mm x 5mm pitch ballscrews on x,y and z on my machine running at 1/4 step, runs very nice and not noticed any lumpyness. Did try them at 1/8th and 1/16th step just to see how they ran but did not seem to make too much difference.

Mine are direct drive but belt driving them will give you more mounting options so definitely worth thinking about.

Just my two-penneth..!

[leadinglights]

I was probably spoiled by the first CNC that I built - based on a Proxxon MF70, it worked it's little heart out to give almost unmeasurable errors, really smooth curves etc.. I would like to get a step resolution of 0.0025mm but would settle on 0.005mm. I am thinking of 2.5:1 (1000 half-steps per leadscrew revolution) with 16T to 40T Syncroflex 2.5mm pitch pulleys and 6mm wide belt - would that work with a 3Nm stepper motor?

[HiltonSteve]

Probably don't have to tell you but remember belt driving at 2.5:1 will increase your resolution but will reduce your max feed rates.

My machine uses 3Nm steppers and I am driving them at 36V 5A, absolute maximum feed I can get without losing steps is 7500mm/min but have reduced it to 5,000mm/min so that I am not pushing it to the limit all the time and this is driving the screws direct without any belt reduction.

So 5,000mm/min divided by 2.5 will only give you 2,000. Does depend on voltage's, driver type etc but I would say that 2,000mm/min may not be enough.