My mk3 cnc machine has just has an upgrade from single to twin X ballscrew. Now that I can jog the machine around it is clear that there is significant run-out from the new ballscrew - it's very bent!

The runout is enough to cause a kind of cyclic loading on the angular contact bearings which makes the stepper and ballscrew run quite rough. I suspect it was bent in transit from China at it is a 1605 at 1300mm long and arrived in lots of bubble wrap and tape, but no solid box.

The original X ballscrew is not perfectly straight either but is significantly better. This one was much more expensive and was UK sourced (motioncontrolproducts). I'm guessing it is still China sourced but was sent over in bulk in some kind of crate.

I've made a few enquiries and found a ballscrew specialist company slightly north of Derby who will straighten them using a 60 ton press to a claimed 0.05mm runout. Cost £45 / ballscrew. My concern is that the straightening could chase the bend into the threaded/plain shaft end. They do offer a grind, plate, re-grind service to cover this but no figure on that.

So this weekend the worst ballscrew will be sent out for the basic £45 straightening and next weekend I should be able to report back on whether it runs better in the machine.

Depending upon how this goes I might also send the other one out. I'll report back here with the results as I'm sure I'm not the only one using bent ballscrews.