Ballscrew whip

[lgalla]

Being researching ballscrew Whip it all evening and came to the conclusion DEVO was into ballscrews.Here are some lyrics:
When a problem comes along you must whip it
Now whip it - into shape
Shape it up, get straight
Go forward, move ahead
Try to detect it - it's not too late
To whip it, whip it good

How does one calculate ballscrew whip?
I saw a 5X10 Thermwood with at least 2" screws and there was a lot of whip like a skipping rope.Is this hard on the ballnuts and end support bearings?
Larry

[Edster]

you sure it's not bent!

[ger21]

Originally Posted by lgalla How does one calculate ballscrew whip?

Go to www.nookind.com and use their critical speed chart.

[Jan de Ruyter]

Many moons ago I saw a crane with a 15m long screw drive. The crane was about 100 years old. It had supports that held the screw at the correct height and eliminated whipping. It consisted of two 1/2 nuts mounted on backets that alowed the crane to move over the supports. As it passed, it knocked the one half nut down which in turn raised the second half nut. Somebody with CAD should make us a proper drawing as it should be a common solution looking for a problem.

[lgalla]

Update,
I called the guy with the router for more info.He was just showing off with 1000ipm rapids.The machine has something similar to what Jan described.Spring loaded plastic supports which swing out of the way as the ballscrew passes.The screws are near 11 feet long to accommodate the tool changer.Conclusion,If you expect high rapids on over 10ft you will need huge screws and probably a machine weight over 10,000lbs to tolerate the forces generated.
Driven nut looks good to me.
Larry

[jderou]

We have a machine with 12' travel and 1500 ipm travels. The reason the screw doesn't whip is because it is stationary, the nut turns. It is also 3 to 4 inches in diameter.

[Glacern]

Komo routers are in the 2000 ipm range for moving gantry routers, and 3000 ipm for moving table routers. They use helical R&P.