Originally Posted by bradyfb Dennis, I'am new to this cnc stuff; and may not be asking this question the right way. the nut will be mounted to the bridge or gantry, which the ballscrew will be turning inside the nut. the screw will be mounted to the motor by a belt drive. and I'am sure that there is a limit to what diameter screw i can use with my 850 oz/inch torque servo motor before I risk burning the motor up, because I'm trying to turn to much weight/load... I do think that I have big motors or am I wrong? |
Hi. Your 850 oz-in motors are not tiny by any means. And your belt and pulley arrangement between the motor and screw will work to your advantage: you will likely have a speed reduction of 3:1, 4:1, or more. If you reduce the motor speed at the screw by a factor N you boost the torque at the screw by the same amount. For example, a 4:1 reduction would make the screw think it was being driven by a 4 x 850 or 3400 oz-in motor. Plenty strong!
More important than the screw diameter is the threads-per-inch or lead. That will determine how much of the load (gantry, etc) is "seen" by the motor. I've got two 1" and two 1.125" diameter screws, all over 60" long and all having 5 threads per inch-a 1000 oz-in stepping motor directly coupled has no problem spinning any of them. I haven't done any testing to see how hard it can push the nut, but I'd guess it could handle any reasonable gantry without breaking a sweat.
Look at
Roton's site for more information with respect to screws.
Good luck!