Hobbymat BFE65 Conversion - Gearing my Steppers?

I'm busy converting a BFE65 head with an unknown XY table + stand. It's coming along well - but I'm a little stuck with gearing the table/head...

I'm using 3Nm SY60 steppers with a microstepping PM542 driver. It's driving 16mm x 5mm lead linearmotionbearing ballscrews. Any idea what factors I should be using to calculate my pulley ratios?

Should I be basing it on what I want the jog speed to be, or max torque or pulses per inch? 50% torque on my motor is at 1650rpm (5.5k pps)

Any advice would be most appreciated - thanks!

Attachment 4472

This spreadsheet is a good start:

http://www.mycncuk.com/forums/showth...otor-do-I-need.

You'll need to measure (or guess) the coefficient of friction of the slides ideally. Fairly easily done with a mass on string plus pulley arrangement, or better a force meter.