The superfinishing process is not only used in the bearing industry, but also widely used in engines. Other precision machinery and instruments are also beginning to use this process.

What is bearing superfinishing?

Bearing superfinishing process is a finishing method that uses a feed motion to achieve micro-grinding.

The surface before superfinishing is generally precision turned and ground. Specifically, it refers to a finishing method that uses a fine-grained grinding tool (oil stone) to apply very little pressure to the workpiece under good lubrication and cooling conditions, and performs a fast and short reciprocating oscillation motion on the workpiece rotating at a certain speed in a direction perpendicular to the rotation of the workpiece.

What is the role of bearing superfinishing?

In the manufacturing process of rolling bearings, superfinishing is the final process of bearing ring processing. It plays an important role in reducing or eliminating the circular deviation left by grinding, repairing the shape error of the groove, refining its surface roughness, improving the physical and mechanical properties of the surface, reducing the vibration and noise of the bearing, and improving the mission of the bearing.

It can be reflected in the following three aspects

1. It can effectively reduce the corrugation. In the process of super lapping, in order to ensure that the oilstone always acts on the wave crest and does not contact the wave trough, the arc of contact between the oilstone and the workpiece is ≥ the wavelength of the workpiece surface waviness. In this way, the contact pressure of the wave crest is large, and the convex peak is cut off, thereby reducing the waviness.

2. Improve the groove shape error of the ball bearing raceway. Super lapping can effectively improve the groove shape error of the raceway by about 30%.

3. It can generate compressive stress on the super lapping surface. During the super lapping process, cold plastic deformation is mainly generated, so that residual compressive stress is formed on the workpiece surface after super lapping.

4. It can increase the contact area of the working surface of the ring. After super lapping, the contact support area of the working surface of the ring can be increased from 15% to 40% after grinding to 80% to 95%.

Bearing ultra-finishing process:

1. Bearing cutting

When the grinding stone surface contacts the peaks of the rough raceway surface, due to the small contact area and the large force per unit area, under a certain pressure, the grinding stone is first subjected to the "reverse cutting" effect of the bearing workpiece, causing some abrasive grains on the grinding stone surface to fall off and break, revealing some new sharp abrasive grains and edge edges. At the same time, the surface peaks of the bearing workpiece are rapidly cut, and the peaks and grinding metamorphic layers on the surface of the bearing workpiece are removed by cutting and reverse cutting. This stage is called the cutting stage, in which most of the metal residue is removed.

2. Half-cutting of the bearing

As the processing continues, the surface of the bearing workpiece is gradually smoothed. At this time, the contact area between the grinding stone 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 grinding stone surface are blocked, and the grinding stone is in a semi-cutting state. This stage is called the semi-cutting stage of bearing finishing. In the semi-cutting stage, the cutting marks on the surface of the bearing workpiece become lighter and a darker luster appears.

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 abrasive grains is reduced, the edge of abrasive grains is flattened, the chip oxides begin to embed into the gaps of the oilstone, and the abrasive powder blocks the pores of the oilstone, so that the abrasive grains can only cut weakly, accompanied by extrusion and polishing. At this time, the surface roughness of the workpiece is quickly reduced, and black chip oxides are attached to the surface of the oilstone.

Stop cutting and grinding stage:

The friction between the oilstone and the workpiece is very smooth, the contact area is greatly increased, the pressure is reduced, and the abrasive grains can no longer penetrate the oil film and contact the workpiece. When the oil film pressure on the support surface is balanced with the oilstone pressure, the oilstone is floated. During this period, an oil film is formed, which no longer has a cutting effect. This stage is unique to super finishing.