Under normal circumstances, the axial force, cross-sectional tensile, torsional strength, and bending stress caused by the calculation of the installation error of the transverse ball screw of the lathe; the fatigue strength and the safety factor under the combined alternating stress of tension, torsion and tension and bending are obtained. Conclusion: The fracture of the horizontal ball screw has nothing to do with the design, use, installation accuracy and equipment wear; regardless of whether the horizontal ball screw exceeds the service life, the fracture is due to the low stress and brittleness caused by the initial cracks on the surface of the screw and the internal defects of the material. Off.
The service life of the ball screw on a general lathe is stipulated at 10,000 to 15,000 hours. Based on 8 hours of work per day, more than 200 working days per year, it can run for about 5-7 years. However, many lateral ball screws of lathes break before this running time. Some economical lathes have a life span of less than one year.
So no matter the ball screw used in any machinery, please be sure to cherish it! Only in this way can the service life of the ball screw be guaranteed!
(1) Lubrication of ball screw pair
Poor ball screw lubrication can cause errors in multiple feed motions of CNC machine tools at the same time. Therefore, ball screw lubrication is the main content of daily maintenance. The use of lubricant can improve the wear resistance and transmission efficiency of the ball screw. Lubricants can be divided into two categories: lubricating oil and grease.
The lubricating oil is generally used for the total loss system, and the grease can be lithium-based grease. Grease is generally added to the threaded raceway and the housing space where the nut is installed, and the lubricating oil is injected into the space of the nut through the oil hole on the housing. Replace the grease on the ball screw every six months. Clean the old grease on the screw and apply new grease. The ball screw pair lubricated with lubricating oil can be refueled every time before the machine tool works.
(2) Periodic inspection of screw support bearings
Regularly check whether the connection between the screw support and the bed is loose, whether the connecting piece is damaged, and the working condition and lubrication of the screw support bearing
(3) Protection of ball screw pair
The ball screw pair, like other rolling friction transmission devices, should avoid the entry of hard dust or chips and dirt. Therefore, it must be equipped with a protective device. If the ball screw pair is exposed on the machine tool, a closed protective cover should be used, such as a spiral spring steel belt casing, a telescopic casing, and a folding casing. When installing, connect one end of the protective cover to the side of the ball nut, and fix the other end to the support seat of the ball screw. If the ball screw pair is in a hidden position, it can be protected by a sealing ring, which is installed at both ends of the nut.
Analyze the reason for the fracture of the ball screw on the lathe
2021 09/09