A ball screw repair lead screw is nearly frictionless in operation. The load between the screw and nut is carried by ball bearings which provide the only contact between the nut and screw superior ball screw repair. The ball screw assembly will operate with either the nut rotating around the screw or the screw rotating through the nut. A simple check for running may be made in your plant:
1. Make sure the screw is clean and lightly oiled.
2. Rotate the nut around fixed screw by hand. The nut should rotate smoothly with no sticking or hang up. Sticking should not be confused with the balls being squeezed as they enter the raceway going under load between the nut and screw from the return system. Sticking or hang-up (keystoning) causes the balls to skid, wearing flat spots on the balls, and the nut will ultimately lock up. In severe cases, skidding balls will damage screw raceways beyond repair.
Torque and Preload
The ball screw repair to drive the load is as important as all other factors related to the design of a ball screw. These factors are inter-related at the original design layout. High preload provides higher positioning accuracy and high system stiffness, but increases drag torque. Higher than required preload increases drag torque more rapidly than stiffness and results in loss of screw life. A high preload can cause inaccurate positioning. A high preload will also contribute to electrical malfunctions. Low preload gives low system stiffness and low drag torque, resulting in poor system accuracy.
Ball Screw Alignment, Misalignment and Load Application
Close alignment of the ball screw repair journal mounting with the ball nut is required for long life and positioning accuracy. Radial, bending or overturning loads imposed on the ball screw assembly will reduce the life of the unit and its thrust bearings. Radial ball screw misalignment results in increased torque as the ball nut approaches the bearing mountings. Bending or overturning loads cause rough running and noise. Radial, bending or over-turning loads will have a negative effect on positioning accuracy. Improper adjustment of the following will overload the ball screw and nut assembly, and contribute to ball screw failure and poor positioning accuracy.