having trouble getting straight acme rod

So I just received my second order from mcmaster the other day and my acme rod arrived practically bent in a u. I got it swapped and this new one is bent too, just a whole lot less. Is there a better source out there? Do I have to spend money on the precision acme rod to get a straight one? It seems a bit much that a product, designed for exact linear motion, would arrive in any way other than perfectly straight.

Is there some straightening procedure I'm not aware of?

I am using this for a z axis on a 3d printer so any little bend ends up causing a z wobble in the print.