Superfinishing process is not only used in the bearing industry, but also in the engine industry. Other precision machinery and instruments are also beginning to use this process.
What is bearing superfine?
Bearing superfinishing process is a kind of finishing process which can realize micro grinding by feeding movement.
The surface before superfinishing is generally subjected to precision turning and grinding.Specifically refers to in good lubrication and cooling conditions, with fine-grained abrasive (stone) to apply very small pressure on the workpiece, and in the direction of vertical dry workpiece rotation, to rotate the workpiece at a certain speed for a fast and short reciprocating oscillation movement of a finishing process method.
What is the role of bearing superfinishing?
In the process of rolling bearing manufacturing, superfinishing is bearing ring processing at the end of the process, to reduce or eliminate grinding legacy of circular deviation, repair the shape of the channel error, refining its surface roughness, improve physical and mechanical properties, surface reduce the vibration of the bearing, noisy, improve the bearing's mission, plays an important role.
Specific can be reflected in the following three aspects
1, can effectively reduce the ripple.In the process of superfinishing, in order to ensure that the stone always acts on the wave peak and does not contact with the wave trough, the arc of contact between the stone and the workpiece is greater than the wavelength of the workpiece surface waviness. In this way, the contact pressure of the wave peak is large, and the convex peak is removed, thus reducing the waviness.
2, improve the groove shape error of ball bearing raceway.Super-finishing can effectively improve the raceway groove error by about 30%.
3. It can produce compressive stress on the surface of the superrefined surface.In the process of superfinishing, the main cold plastic deformation occurs, which leads to the residual compressive stress on the workpiece surface after superfinishing.
4. The contact area of the working surface of the ring can be increased.After superfinishing, the contact bearing area of the ring working surface can be increased from 15%-40% to 80%-95% after grinding.
Bearing superfinishing process:
1. Cutting of bearings
When the grinding stone surface is in contact with the convex peak of the rough raceway surface, because the contact area is small and the force on the unit area is large, under a certain pressure, the grinding stone is first subjected to the "reverse cutting" effect of the bearing workpiece, so that part of the grinding stone surface abrasive particles fall off and fracture, exposing some new sharp abrasive particles and edge.At the same time, the convex peak on the surface of bearing workpiece is rapidly cut, and the convex peak and grinding metamorphism layer on the surface of bearing workpiece are removed through the action of cutting and reverse cutting.This stage is known as the cutting stage, in which most of the metal surplus is removed.
2. Semi-cutting of bearings
As the processing continues, the surface of the bearing workpiece is gradually flattened.At this time, the contact area between the 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 surface of the stone are blocked and the stone is in a half-cut state.This stage is known as the semi-cutting stage of bearing finishing. In the semi-cutting stage, the cutting traces on the surface of bearing workpiece become shallow and have a darker luster.
3, light whole stage
This stage can be divided into two steps: one is the grinding transition stage;The second is the grinding stage after stopping cutting
Transition stage of grinding:
The abrasive particles are reduced, the edge edge of the abrasive particles is flattened, and the chip oxide begins to embed into the gap of the oilstone. The abrasive powder blocks the pores of the oilstone, so that the abrasive particles can only be weakly cut, accompanied by extrusion and polishing. At this time, the surface roughness of the workpiece is quickly reduced, and the surface of the oilstone is attached by black chip oxide.
Stop cutting and grinding stage:
The friction between the oil stone and the workpiece is very smooth, the contact area is greatly increased, the pressure drops, the abrasive particles can not penetrate the oil film and the workpiece contact, when the oil film pressure on the supporting surface and the oil stone pressure balance, the oil stone is floating.During the formation of oil film, then no cutting effect.This stage is specific to superfinishing.