Specializing in CNC and Manual Precision Machine Tools
On most modern Machine Tools, the ball screw on the X, Y, and Z axis is pre-tensioned or "stretched" when installed to minimize changes in axis positioning due to "thermal growth" of the screw from ambient to normal operating temperature. When the axes are moved, heat is generated by the recirculating balls in the ball nut. The ball screw is therefore subject to "GROWTH" or thermal length deformation, by the coefficient of thermal expansion for steel of 6.5 parts per million per degree Fahrenheit (11.7 ppm/° Celsius)
The average temperature rise of a cold ball screw is 5.4 to 7.2° Fahrenheit (3 to 4° Celsius). Pre-tensioning places a cold ball screw in a state of tensile stress. This stress decreases or normalizes as the screw expands toward its normal operating temperature, minimizing axis position deviation. During normal operation, tension may become relaxed, causing possible end play and positioning error; requiring re-tensioning of the ball screw.
If the ball screw preload (tension) has been relaxed for any reason, follow this general procedure for pre-tensioning the ball screw.
We have many years of HANDS-ON experience with ball screw issues, from evaluation only to removal, replacement, and Laser Calibration – sometimes called Alignment; we have even undertaken the On-Site repair of our customers' ball screws. We can help with yours.