newbie questions on coupling, screws, nuts....

[fxs]

Hi all. I want to build a linear motion stage, using a stepper motor. The thing is, i'm some confused about the coupling, nuts, screw stuff. Better i ask directly:

- How do you couple the motor shaft to the screw?
- What do you need for converting the rotary motion into linear motion? I know you use some nut, but in some pictures you see one nut, in other two nuts, a bearing between the nuts in others! ... and also it seems mounting flanges nut an other stuff. How is the mounting of all that stuff, and what do you really need for good linear motion? (with 2 millimeter precision at least).

If someone can put pictures of the mounting process, it would be very appreciated . I think it would be ver helpful for other newbies that want understand clearly the linear motion mounting and parts needed. Thanks a lot!

[ahren]

FXS,

It kind of depends on what you're trying to accomplish. For the ultimate in backlash reduction, double ball nuts preloaded against one another work really well, but properly installed single nuts can also work well. Not sure about the bearing between the nuts -- maybe you found a setup where the nut is spinning and the screw is static. This is done for large or long travels.

Since your precision needs are not very demanding, I'd definitely recommend an ACME solution, which is far more affordable than ballscrews. There's a diagram of one approach on my website here:

http://cncrouterparts.com/product_in...products_id=58

You can also download the machine plans from my site for free -- this shows how everything goes together, including linear motion components.

Ahren
www.cncrouterparts.com

[fxs]

thanks a lot, now i get more clear. I haven't see your planes(you need a cad software) yet. But anyway, i have been seen different type of nuts (bronze, plastic, others); if i need a max velocity of maybe 2.5-3 cm/s, and the load is no more than 500-600 gr., is better a plastic nut? (less friction, not heavy load ).