Quote Originally Posted by Ricardoco View Post
Cheers Ian, Me too, In fact many of the sites I checked started at 12 teeth.



Thanks Jonathan, I did Intend to use a 10 and 25 tooth pulley to give me the ratio I needed, and going for anything smaller as you say may put too much load on the reduced number of meshed teeth. So 10 and 25 then.

So the pulleys will be as above.

For those people that are not aware of why I would like to use pulleys then let me explain.

:confused:Using 1605 ballscrews will give me a pitch of 5mm, that is to say 360 degrees in 1 rotation of spindle will advance the axis 5mm.

If i use a direct coupling stepper to screw,

The stepper will give full steps of 1.8 degrees.

360/1.8 will give me 200 steps per revolution.

5mm / 200 will give a resolution of 0.025mm per full step.

This is an odd measurement to use in my head, i have done it though..

Using a ratio of 2.5 to 1 ( 10 and 25 tooth pulleys) will give me a step resolution of 0.001mm per step.

and if i were to use half steps as the stepper is capable of doing, it would be 0.0005mm per step...

thats a fair bit of resolution/accuracy, there are however disadavantages to using pulleys.

its upto the individual who is designing/building and using the machine.

(a special thank you to i2i who educated me on this subject in the first place)

There you go clear as mud!!!!:confused:

Rick
And hurry up moderator.

But you should be using 8 / 10 mirco stepping for best performance of the motors and why are you worried about the interger as it is a cnc'd machine that will be controlling it.

As before i have done it with this machine, 0.001 res is pie in the sky, £200,000 machine tool struggle to get that with direct drive and servo's. 0.025 per step is what i run and gives me 1500mm/min rapid you would be lucky to get 700mm/min as you would be over spinning the motor and have not torque.

resolution and power work againest each other.

here a like to my Thread on cnc zone.

http://www.cnczone.com/forums/bencht...g_machine.html