(2) Half cutting of bearings. Because as the processing continues, the surface of the thin-walled bearing workpiece is gradually ground flat. At this point, the contact area between the grinding stone and the workpiece surface increases, the pressure per unit area begins to decrease, the cutting depth gradually decreases, and the cutting ability also weakens. Moreover, the pores on the surface of the grinding stone are blocked, and the grinding stone is in a semi cutting state. During the half cutting stage, the cutting marks on the surface of the bearing workpiece become lighter and a darker luster appears.

(3) Finishing stage. This stage is a step in the ultra precision machining of bearings. Because as the surface of the workpiece is gradually flattened, the contact area between the grinding stone and the workpiece surface further increases, and the surface of the grinding stone and the thin-walled bearing workpiece is gradually isolated by a lubricating oil film, the pressure per unit area is very small, the cutting effect is reduced, and cutting automatically stops afterwards. During the polishing stage, there are no cutting marks on the surface of the workpiece, and the bearings exhibit a bright finished product luster.

2. Processing difficulties

(1) In the forging process, for thin-walled bearing rings with large dimensions and small aspect ratios, two or more pieces are forged together for production. After the rough grinding process, the rings are separated by wire cutting to reduce the machining difficulty of the forging process, reduce ring deformation and end face machining allowance, save raw materials, and improve production efficiency.

(2) In the machining process, the main factors affecting machining accuracy are clamping, excessive cutting force, unreasonable fixture design, cutting thermal deformation, and vibration during the cutting process. To reduce deformation caused by excessive machining stress, rough turning is carried out using steel soft claw clamping collars with large envelope contact areas and without quenching, such as using multi-point clamping chucks (twelve point clamps or twenty-four point clamps); Change the clamping scheme (change the radial clamping to the end face pressing method); Adjust process parameters (such as high-speed cutting, small back draft, larger tool deviation angle, smaller tool tip arc radius, reasonable selection of cutting fluid, etc.). Add an additional tempering after rough turning to eliminate stress. Afterwards, soft grind the end face and perform precision turning on the collar.

(3) During the heat treatment, the internal structure of the ferrule undergoes phase transformation, mainly from austenite to martensite, the density decreases, the volume expands, and the structural stress is generated; In addition, the ferrule rapidly quenches and cools from the expansion state of high temperature (usually 830-845 ℃ for thin-walled products), generating thermal stress. When these two types of internal stresses exceed the material yield limit, the material will undergo plastic deformation. Usually, mold quenching is used to control deformation. When there is no condition for mold quenching and the outer diameter deformation of the ring exceeds the process requirements after quenching, a comprehensive shaping and tempering method is used to correct it, so as to control it within the range of process requirements.

(4) The main task in grinding is to choose appropriate grinding equipment, processing methods, and grinding process parameters. If using a method with reinforcing rings and a "one drag two" structure for processing; Grinding the outer diameter surface using multiple fine adjustments of the machine tool; Add tempering stabilization treatment during the process to ensure that the grinding quality of the ring meets the process requirements.

1. The bearing environment meets the requirements. During installation and use, it is important to keep the surrounding environment of the bearings clean, tidy, and dry. Many small dust particles are invisible to the naked eye, but if they enter our bearings, they will increase wear and noise.

2. Install with reasonable force. When installing, it is important to be careful and careful. Thin walled bearings have high precision and are not suitable for strong stamping. It is also not advisable to directly hit the bearings with a hammer, which can affect their service life and, in more severe cases, directly damage the bearings. In addition, attention should be paid during installation to avoid using fabrics and short fibers, as these fibers can easily leave debris and bring unnecessary pressure to the bearing operation, which can seriously damage the bearing life.

3. Do a good job in rust prevention. If installing bearings in summer, rust prevention work should be done well. Due to the high amount of hand sweat in summer, directly taking it by hand may cause external rust on the bearings, leading to the failure of thin-walled bearings. Rust can also directly affect the service life of thin-walled bearings. It is recommended to wear gloves or thoroughly wash the sweat on your hands, and apply mineral oil before proceeding with the installation operation.