I want to DIY.. some questions please!

[Jonathan]

1) Ballscrews have far greater efficiency - about 90% vs 50% and significantly lower, but not zero, backlash however unlike leadscrews due to the use of rolling not sliding friction they can be preloaded to obtain practically zero backlash.
2) Extremely important. An unsupported rail will bend significantly more when a force is applied, ultimately leading to tool deflection and thus poorer accuracy. Supported rails are supported along the entire length, hence the force is largely transmitted to the frame which is significantly stronger than the rail and therefore deflects less. Does depend on the orientation, but either way a 12mm supported rail is probably stronger than a 25mm supported... huge difference.
3) Motors, driver voltage, ballscrew pitch, ballscrew diameter, drive ratio, mass of moving parts, type of rails used, preload of rails ... etc. You can estimate it using this calculator:

http://www.google.com/url?q=http://w...zkjSyaojkuQQKA

[Tenson]

Thanks for the info Jonathan.

Could somebody please explain to me what is meant by 'fixed side' and 'supported side' with reference to ballscrews?

I don't understand why the same simple bearing can't be used on each end.

[Robin Hewitt]

I don't understand why the same simple bearing can't be used on each end.

The ballscrew is going to push axially (lengthwise). It needs something to push against so one bearing must be fixed axially.

If you fix both ends axially you have to wonder what will happen when it expands and contracts due to temperature change.

Fixing at both ends is good if you can hold it in tension with springs, otherwise you have to let one end free to slide.

[JAZZCNC]

Thanks for the info Jonathan.

Could somebody please explain to me what is meant by 'fixed side' and 'supported side' with reference to ballscrews?

Robin explains it very well but a picture paints a thousand words.!!

Pics below show ballscrew with fixed end on right and a floating end on left, you will see fixed end as threads on ballscrew and the block is wider than the floating end because it has 2 angular contact bearings working togehter to handle the axial loads. The fixed end has just a normal bearing which is allowed to move inside the mounting block if any thermal expansion happens, it is still attached to the ballscrew via a small circlip so it can't fall off.

Simplizzz really.!!