[Barefootboy4]

I'm sure this question has been posted in the past but I have not found it as of yet in my search. Could someone please explain when one makes the decision to use pulleys and belts with steppers or simply go to straight coupling to the ballscrew with the motor. Yes I'm building my own CNC and want a robust design for heavy wood routing. I'm hoping for 500IPM or close to it with rapids of 1000IPM. My ballscrews will be 2 start .500 per rev. Looking at the Keling 425oz stepper package. Will be running Mach3 cam. Is this going to be fast or should I be looking at pulleys?? If so what reduction? 2:1, 3:1?? Someone with some knowledge here would be great!!
Thanks
Steve

[ger21]

It's not quite that simple. There are a lot of things to consider. How much weight do you have to move? How fast do you want to accelerate? How much force do you want to have. What resolution are you looking for?

Everything needs to function together - Drives, motors, power supply, screws.

If you want 1000 ipm rapids with ballscrews, you probably want 1-2 inches per turn, not 2 turns per inch. With the 2 turn per inch screw, you'll need to spin the screws at 2000 rpm. Depending on what size they are, and how they are mounted, they may whip badly at that speed.

Also consider that stepper motors lose torque as rpm's increase. Typically, 800-1000 rpm has been considered a maximum useable top speed for steppers, although recently, I've seen posts talking about nearly double that.

[Barefootboy4]

I see what you are talking about. Maybe I'm asking for more than I can get with steppers. I would go with Servo's but keep seeing posts saying he tuning is a pain in the butt. What do you think? Being my first build I don't want to bite off more than I can chew. With all the support from this forum I'm sure I can make it happen.
So going back to my question. If I go with strong servo's and looking for good IPM and .001 resolution. My gantry will be approx 40lbs in sliding weight. I was going to go with 20mm HiWin rails on a 2' x 4' table. Linearmotionbearing2008 ballscrews from China. Maybe you could suggest a good setup of screws, servo and drives. Your help is great!
Steve