[mrsa]

It is imposible to do direct coupling in y and z axis i will use timing belt pulley.
Pulley that will be mounted on y axis ballscrew can be maximum 100mm diameter to fit.
Which type pulley-belt is best for this case that has very low backlash?
htd5m htd3m gt3mm gt5mm at5 or something other better?

[joeavaerage]

Hi,
mostly I direct couple servos or use servo reducers. On those few occasions where I've used pulleys and belts, and I doing exactly that combination right now, I have
used HTD5mm pulleys of 16mm width, appropriate by manufacturers recommendation for a 15mm wide belt. This is for a 750W servo. I think its adequate, but for
a higher torque servo maybe 25mm wide would be better.

The pulleys I've used are 30 teeth ie 150mm circumference (diametrical pitch), or about 50mm diameter. That would be as small as I would like to go for this power. The smaller the diameter the more force
is applied to fewer and fewer teeth. I have not encountered any problems with this arrangement....but then I've done no experimenting to establish the limits before failures occur.

Craig

[mactec54]

It is imposible to do direct coupling in y and z axis i will use timing belt pulley.
Pulley that will be mounted on y axis ballscrew can be maximum 100mm diameter to fit.
Which type pulley-belt is best for this case that has very low backlash?
htd5m htd3m gt3mm gt5mm at5 or something other better?

If you have the GT Profile available, then that is the best you can use, each Timing Belt Profile have a minimum pulley diameter you can use for the motor torque being used, once you decide on what Profile you want / can use, you can check the Gates Powergrip GT3 Design Manual and find your minimum pulley diameter.

To give you an idea of size a 24/ 48 2:1 the 24 is 37.1 Diameter and the 48 is 75.3 Diameter what plays a big part of your smallest Timing Pulley is the Motor Shaft that it is fitted on.