Bearing super-finishing process: why is it the core technology of high-end manufacturing?
In the field of precision machinery manufacturing, bearing super-finishing is recognised as the 'last mile' in improving bearing performance. With 'high precision bearings' and 'low noise bearings' becoming the trend of the industry, the technology of super-fine process is very important to the modern industry.
Bearing super-precision Process: Definition and Core Technology
Bearing super-precision process is the last finishing process in the manufacturing of bearings, through fine-grained abrasives (such as oil stone) in the lubrication and cooling conditions on the surface of the workpiece for high-frequency oscillation and micro-grinding. Its core objective is to:
------ Elimination of grinding residual errors: correction of round deviations and groove errors in the raceways of the rings;
------- Improvement of surface quality: reduction of surface roughness from Ra 0.1 μm to less than Ra 0.008 μm, achieving a 'mirror-grade' finish;
------- Optimisation of physical properties: Residual compressive stress is formed on the surface through cold plastic deformation to enhance fatigue resistance.
The process can be divided into four stages:
1. Intense cutting stage: the abrasive grains quickly remove the surface peaks and remove the grinding deterioration layer;
2. Half-cutting stage: the contact area increases, the cutting force decreases, and the surface is gradually smoothed;
3. Grinding transition stage: the abrasive grain passivation, mainly extrusion polishing, the roughness is significantly reduced;
4. Stop cutting stage: oil film formation, friction to pure polishing, the surface to reach the final finishing.
Why is the super-precision process indispensable?
1. Breakthrough precision limit
The bearing qualification rate of traditional grinding process is only 30%, while the ultra-precision technology through the 'machining trajectory uniform full-envelope shaping principle', the batch qualification rate of the G3 grade bearing ball will be increased to more than 90%, which is used in CNC machine tools, aviation engines and other high-end fields.
2. Reduce noise and vibration, prolong service life
After superfine processing, the contact area of the working surface of the ring increases from 15%-40% to 80%-95%, which significantly reduces the friction and vibration during operation, and the noise is reduced by more than 30%.79 For example, the life span of wind turbine bearings can be increased by 2-3 times after superfine processing.
3. Improvement of Ripple Degree and Groove Shape Error
By controlling the contact wavelength between the oil stone and the workpiece, the super-finishing process can remove more than 70% of the surface corrugation and correct 30% of the raceway groove shape error, ensuring the smoothness of bearing operation.
4. Promoting process innovation and empowering intelligent manufacturing
Combining CNC and CBN grinding wheel technology, the high-speed grinding speed can reach 120m/s, with online automatic measurement and compensation system to achieve fully automated production.
The popular application areas
----- New energy vehicles: high speed motor bearings rely on ultra-precision technology to reduce the noise of the electric drive system5;
----- Precision machine tools: the accuracy of spindle bearings directly determines the micron-level error of machined parts9;
------ aerospace: the roundness overshoot rate of thin-walled bearing rings processed by super-finishing is reduced from 50% to less than 30% to meet the demands of extreme working conditions.
