Shaft Critical Speed Demonstration

This clip demonstrates an ACME screw shaft with simple end support on a CNC mill reaching critical speed where vibration sets in. The end of the clip shows the same shaft after the end support is changed from simple to fixed support. Critical speed is not reached with the fixed support.

Category:

Science & Technology

Tags:

• CNC
• Mill
• DIY

[bassman2914]

Fixed support means there are double bearing supports at one or both ends of the screw making flexing require more force which increases critical speed. You described screw pre-tensioning which is also a very good method to increase critical speed and column loading. Mine has (or will have) fixed screw supports on both sides and has a pre-tenioned screw even though it's not all that long. This post is old but i felt like adding my 2 cents.

[rumblfmp]

I guess "fixed support" means that you now have angular contact bearings on both sides, putting tension on the ballscrew?

It's strange, most ballscrews I found have only 1 end with a thread to mount a fixed bearing. I built a machine with a 2m (75") ballscrew, it came with only one threaded end but to go faster than a few hundred RPM you really need two fixed sides and pre-tension the whole thing (which was also stated in the tech-specs of the screw ...)