I am building a HICTOP prusa i3 printer but the z axis wobble a lot, so I decided to get the threaded screws straight https://www.youtube.com/watch?v=dy64oB7fG-k but this was not enough, the operation was not smooth. The final solution was to replace the whole z axis with leadscrews and bronze nuts.

Besides that, I added some pegs to firmly hold the linear bearings.