Ballscrew machining problem ?

[Bart]

Hi,
I bought two HIWIN balscrews and asked seller to machine ends. I've put the long ballscrew (1,3m / 4 feet) into bearing blocks (BF12) and it is stable only in one position (which I guess, means that it is either bent or machining is not concentric).


Here what's happens when I hand tighten the bearings (2x 7001A - DF cinfiguration). Bearing Block is moving in a circular fashion. When I press it down so that it cant move, ballscrew becomes hard to rotate





https://www.youtube.com/watch?v=bfo-9KJfJu0


I know that it's not on a perfectly flat surface - is this the reason for it or it is the ballscrew?


I've also measured concentricity as shown on the picture below and TIR is around 0,1mm / 0.004" which, I guess, could also mean that bearings are not concentric.





Any ideas whats wrong?
And, no I cant put it into gantry yet as I still don't have it :/


Best regards
Bart