Hi guys not sure if anyone as seen this done, I build a z table for a laser cutter, and tried 4 1605 screws with closed loop belt driven by nema24, put all ball nuts to bottom or top rises smooth go back down, but when it comes back up all screws are out 1 will be top but all others out with bigger gaps than others,

There plenty of these table working, so not sure what screws are used, I now these were overkill but I had 2 so just perchased 2 to match lenth,

Thanks guys for any help. Kev