What is the bearing super-precision process? Is it important for bearings to be super precise?
Super-precision technology is not only used in the bearing industry, but is also widely used in engines. Other precision machinery and instruments have also begun to use this technology.
What is bearing super precision?
The bearing super-finishing process is a feed movement to achieve micro-grinding, a finishing method.
The surface before super-finishing is generally precision turned and ground. Specifically, it means that under good lubrication and cooling conditions, fine-grained abrasive tools (whetstones) are used to exert very small pressure on the workpiece, and in the vertical direction of rotation of the workpiece, the workpiece rotates at a certain speed to make fast and short reciprocating oscillations. A finishing method of movement.
What is the function of bearing super precision grinding?
In the manufacturing process of rolling bearings, super-precision is the final process of bearing ring processing. It can reduce or eliminate the circular deviation left by the grinding process, repair the shape error of the groove, refine the surface roughness, and improve the surface physical and mechanical properties. , it plays an important role in reducing the vibration and noise of the bearing and improving the mission of the bearing.
This can be specifically reflected in the following three aspects:
1. Can effectively reduce waviness. During the super-precision grinding process, in order to ensure that the whetstone always acts on the wave crest and does not contact the wave trough, the arc of the contact between the whetstone and the workpiece ≥ the wavelength of the waviness of the workpiece surface. In this way, the contact pressure of the wave crest is large, and the convex peak becomes smaller. are cut away, thereby reducing waviness.
2. Improve the groove error of the ball bearing raceway. Super precision grinding can effectively improve the groove shape error of the raceway by about 30%.
3. It can produce compressive stress on the surface to be super polished. During the super-fine grinding process, cold plastic deformation mainly occurs, resulting in residual compressive stress on the surface of the workpiece after super-fine grinding.
4. It can increase the contact area of the working surface of the ferrule. After super precision grinding, the contact support area of the ferrule working surface can be increased from 15% to 40% after grinding to 80% to 95%.
Bearing super-precision process:
1. Bearing cutting
When the surface of the grinding stone comes into contact with the convex peaks on the surface of the rough raceway, due to the small contact area, the force per unit area is large. Under a certain pressure, the grinding stone is first subjected to the "reverse cutting" effect of the bearing workpiece, causing Some of the abrasive grains on the surface of the grindstone fall off and fragment, revealing some new sharp abrasive grains and edges. At the same time, the convex peaks on the surface of the bearing workpiece are subject to rapid cutting, and the convex peaks and grinding deterioration layer on the surface of the bearing workpiece are removed through cutting and reverse cutting. This stage is called the cutting stage, where most of the remaining metal is removed.
2. Semi-cutting of bearings
As processing continues, the surface of the bearing workpiece is gradually smoothed. At this time, the contact area between the grindstone and the workpiece surface increases, the pressure per unit area decreases, the cutting depth decreases, and the cutting ability weakens. At the same time, the pores on the surface of the grindstone are blocked, and the grindstone is in a semi-cutting state. This stage is called the half-cutting stage of bearing finishing. In the half-cutting stage, the cutting marks on the surface of the bearing workpiece become lighter and appear darker.
3. Finishing stage
This stage can be divided into two steps: one is the grinding transition stage; the other is the grinding stage after stopping cutting.
Grinding transition stage:
The self-sharpening of the abrasive grains is reduced, the edge of the abrasive grains is ground flat, the chip oxide begins to embed in the gaps of the whetstone, and the abrasive powder blocks the pores of the whetstone, so that the abrasive grains can only cut weakly, accompanied by extrusion and polishing. At this time, the surface of the workpiece The roughness decreases quickly, and black chip oxides adhere to the surface of the whetstone.
Stop the cutting and grinding phase:
The friction between the oil stone and the workpiece has become very smooth, the contact area has greatly increased, the pressure has dropped, and the abrasive particles can no longer penetrate the oil film and contact the workpiece. When the oil film pressure on the supporting surface is balanced with the pressure of the oil stone, the oil stone is floated. An oil film is formed during which the cutting effect is no longer available. This stage is unique to ultra-finishing.
