How To Resolve Uneven Wear on A Ball Screw?
Publish Time: 2025-10-16 Origin: Site
1. The typical manifestation of uneven wear and tear
During the operation of the equipment, if scale-like shedding or track depressions are found at specific parts of the ball screw, accompanied by an increase in periodic vibration, it often indicates that uneven wear has entered the mid-stage. A case from a certain CNC machine tool factory shows that the X-axis ball screw developed a wear step of 0.03mm at the midpoint of its travel, causing dimensional errors in the workpieces to exceed the tolerance by 40%.
Vibration spectrum analysis shows that the amplitude of the frequency components corresponding to the wear area is 8-12 dB higher than that of the normal area. Notably, when the reverse clearance suddenly increases to above 0.15 mm, it often indicates that irreversible damage has occurred on the raceway working surface, at which point merely adjusting the preload cannot completely solve the problem.
2. Analysis of the causes of damage
The primary cause of installation eccentricity exceeding limits. In a case study of an automotive welding line, a 0.05mm installation deviation of the screw support resulted in a 200% increase in local contact stress, leading to noticeable grooves after just 800 hours of operation. The second major issue is lubrication failure; when the water content in the grease exceeds 0.3%, its extreme pressure performance decreases by 60%, exacerbating direct metal contact. Material heat treatment defects also cannot be ignored. Metallographic testing revealed that the surface hardness of the screws with abnormal wear fluctuated by HRC3-5, with agglomerations of undissolved carbides appearing in the microstructure. Additionally, operating conditions exceeding the rated load by 15% reduce the elliptical contact area between the balls and the track by 30%, accelerating fatigue failure.
3. Systemic solution method
The first step involves laser alignment calibration to control the straightness error of the lead screw to within 0.02mm/m. A semiconductor equipment manufacturer uses a white light interferometer for detection, improving the concentricity of the support seat to 99.5% and reducing wear by 70%.
The second step involves using nanoscale composite lubricant containing molybdenum disulfide particles with a particle size controlled between 80-100nm, reducing the friction coefficient to 0.008.
The third step recommends using induction hardening to form a hardened layer of 0.8-1.2mm on the raceway surface, with microhardness stabilized at HRC60±1.
The fourth step involves online monitoring by installing vibration acceleration sensors, triggering an alert when the characteristic frequency amplitude exceeds the baseline value by 30%, allowing for the detection of anomalies 120 hours earlier than traditional methods.
4. Maintenance suggestions
Establish a three-level maintenance system: daily inspections focus on listening for unusual noises and monitoring temperature rise, weekly use of a surface roughness tester to check changes in the Rz value of the raceway, and quarterly maintenance requires using a laser distance meter with 25μm precision to recheck lead error. After a certain precision injection molding machine user implemented this system, the screw replacement cycle extended from 12 months to 36 months.
It is recommended to conduct the first comprehensive disassembly inspection after cumulative operation of 2000 hours, with a focus on measuring the diameter dispersion of the balls. When the diameter difference of more than 95% of the balls exceeds 2μm, the entire set must be replaced. Using statistical process control (SPC) methods, keeping the preload force fluctuation within ±5N can effectively slow down the wear rate.