Many equipments need to be precise, so they are valuable. However, when the ball screw is in operation, the high temperature will affect the accuracy of the equipment, especially some high-precision machinery. And which factors will increase the temperature of the ball screw?
The elements of temperature rise are basically these three types: 1. Pre-pressure 2. Smooth 3. Pre-tensioning
1. The influence of pre-pressure
In order to prevent any loss of step of the mechanical transmission system, it is important to improve the rigidity of the nut. However, to improve the rigidity of the nut, it is necessary to make the preload of the nut reach a certain level. Applying pre-pressure to the nut will increase the conflicting torque of the screw and increase the temperature rise during operation.
HIWIN advocates that the medium and heavy preload is 8% of the dynamic load; the medium preload is 6% to 8%; the medium and light preload is 4% to 6%; the light preload is below 4%, and the heaviest preload should not exceed 10% The dynamic load to obtain the best life span and lower temperature rise effect.
2. The effect of smoothness
The selection of smooth oil directly affects the temperature rise of the ball screw. HIWIN ball screw must be smoothed with oil or grease. Generally, it is recommended to use bearing lubricating oil as ball screw lubricating oil, and for grease, it is recommended to use lithium soap-based grease. The choice of oil viscosity is based on operating speed, operating temperature and load conditions.
It is best to choose low-viscosity oil when the working condition is high speed and low load; when low speed and high load, it is recommended to use high viscosity oil. Generally speaking, it is recommended to use the viscosity index scale of 32～68 cSt (ISO VG 32～68) (DIN 51519) when the lubricating oil is 40℃; Compensation is done by pre-pulling; and the target value of pre-pulling compensation is the negative T value indicated on the drawing. Excessive pretension will burn the support bearing, so HIWIN advocates using a pretension value of less than 5℃, but it is not suitable for pretension if the screw diameter exceeds 50mm; a large screw diameter requires a large pretension force, which leads to support The bearing is overheated and burned out.
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