Worm gear screw elevator - what is the effect of temperature rise on the ball screw?
When the ball screw is running, the temperature rise will affect the accuracy of the mechanical transmission system, especially for high-speed and high-precision machinery. The following are the factors that affect the temperature rise of the ball screw
There are basically three factors for temperature rise:
(1) The influence of the preload of the screw elevator: In order to avoid any step out of the mechanical transmission system, it is very important to improve the rigidity of the nut. However, to improve the rigidity of the nut, the preload of the nut must reach a certain level.Applying pre-pressure to the nut will increase the friction torque of the thread and increase the temperature rise during operation.
(2) The influence of the lubrication of the screw elevator: the choice of lubricating oil directly affects the temperature rise of the ball screw. HIWIN ball screws must be lubricated with either oil or grease
When the working conditions are high speed and low load, it is best to use low viscosity oil; when low speed and high load, it is recommended to use high viscosity oil.Generally speaking, it is recommended to use lubricating oil with a viscosity index range of 40 to 32 cSt (ISO VG 68 to 32) (DIN 68) at 51519°C at high speed; while at low speed, it is recommended to use lubricating oil with a viscosity index range of 40°C above 90 cSt (ISO VG 90).When applied to high speed and heavy load, the temperature must be reduced by forced cooling, and the cooling effect can be achieved by feeding cooling oil through the hollow screw.
(3) The influence of the pre-tensioning of the screw lifter: When the temperature of the ball screw lifter rises, the thermal stress effect will elongate the screw and make the length of the screw unstable.Its elongation can be calculated by the M40 formula, and the elongation can be compensated by pre-tension; and the target value of pre-tension compensation is the negative T value indicated on the drawing.Excessive pre-tension will burn the support bearing, so HIWIN recommends a pre-tension value less than 5°C, but if the screw diameter exceeds 50mm, it is not suitable for pre-tension; a large screw diameter requires a large pre-tension, which leads to support The bearing overheated and burned out. HIWIN recommends a temperature rise of about 3°C as the benchmark for the compensation value T (about -1000~-0.02mm per 0.03mm of screw).Different applications require different T values, please contact HIWIN engineers for questions about T values.