Need Help!- HOw i calculate length of BallScrews?

[samsagaz]

hey guys, i already purchased some rails steppers and gecko driver, now i need to purchase the ballscrew, the main problem is that i cant figure how calclate the length and how i mount the nema motor into the screw.

My rails are 51 (x) and 48 (y)cm.

Thanks in advance

[stangtjk]

You need to have you basic design worked out first but I can give an example. Lets say your bearing blocks take up 10cm on your shaft so you would then have 41cm of travel for your x-axis. You would need a ballscrew assembly that also had around 41cm of travel to get full use from both. If the ball nut takes up 4cm then you would need a ballscrew with ~45cm of thread+ some length turned on each end for bearing mounts ect. (depends on your design). You can mount the stepper to the screw directly using a coupling or use belts and pulleys its up to you.

[samsagaz]

Originally Posted by stangtjk You need to have you basic design worked out first but I can give an example. Lets say your bearing blocks take up 10cm on your shaft so you would then have 41cm of travel for your x-axis. You would need a ballscrew assembly that also had around 41cm of travel to get full use from both. If the ball nut takes up 4cm then you would need a ballscrew with ~45cm of thread+ some length turned on each end for bearing mounts ect. (depends on your design). You can mount the stepper to the screw directly using a coupling or use belts and pulleys its up to you.

can you show me an picture of the coupling that can be used to mount the nema into the ballscrew? (thanks for your support!)

[hemsworthlad]

Hi, like previous poster said your design will dictate the length to a great degree.
The bearing blocks used will dictate the amount of machineing required on the ballscrew, this in turn will be added to the overall length of the thread portion required, which will usely be just longer than the rails used. . . But again all this will depend on design.
I would suggest you get a firm Idea of the design and dimensions required before you buy screws.?

Here's a few pics showing parts off machine and assembeled on machine.
If you look at pic 1 you can see machined portion on screws.
This is how most bought bearing block/ballscrew arrangments work.

You have a fixed end (pic2) and a floating end (pic4).
The large machined portion on ballscrew match's large bearing block ID and width followed by threaded bit for locknut, this fixs the block to the screw and when block is mounted (fixed end) it stops the ballscrew from floating sideways, then you have short portion for the motor coupler to connect to.

On the other end, which is called the floating end. You have a small machined portion with a circlip grove that just match's the ID of the narrower blocks bearing, the bearing is held on screw with a circlip and the bearing then floats in the bearing block. (pic4)

Motor couplers just mount in between and lock on to both shafts with lock screws or grub screws, depend which type used, I,ve shown 2 types (pic3) and both work equaly good.

Hope this helps.

[samsagaz]

thanks too much for your support!, i get it clear now
!

[samsagaz]

Originally Posted by samsagaz thanks too much for your support!, i get it clear now !

What about Ballscrew Diameter? 16mm is OK= or 32 will be better?

[hemsworthlad]

Yes 16mm will be fine over that length. (Mine are only 20mm and 150cm long).

[samsagaz]

oh, nice