1. Introduction
A bearing is a machine element that enables rotational or linear movement, and reduces friction between different parts. Bearings are widely used in our lives today, for example, they are used in skateboards, fidget spinners, electric scooters, metro wagons, airplanes and so on. A study shows that people use at least 200 bearings per day. For example, we use bearing every day on the way to school: metro, cars or bicycles. On the way to our classroom: the escalator or the elevator. Even when we are just sitting and playing computer games, there are bearings running non-stop in our PCs to keep us entertained. The manufacturing process of ball bearings and roller bearings includes several steps that can take a couple of days to finish. This article explains each process in detail, and presents some new technologies in the bearing industry.
Ball bearings can support moderate radial loads and moderate axial loads (thrust load). They can operate at high speeds.
There are four types of ball bearings, they are:
- Deep groove ball bearings
- Angular contact ball bearings
- Self-aligning ball bearings
- Thrust ball bearings
2.2 Deep Groove Ball Bearings
The most common type of ball bearings are the deep groove ball bearings. A deep groove ball bearing is composed of an inner race, an outer race, steel balls that fit between the inner and outer, move along the track called raceway, and a cage that prevents the steel balls from falling out or contact in one another.
2.3 the Manufacturing Process of Deep Groove Ball Bearings
The manufacturing process of a deep groove ball bearing consists of:
1. Preparation of Bearing Materials
2. Forging
3. Turning
4. Heat Treatment
5. Grinding
6. Making of Steel Balls
7. Making of Retainers
6. Assembly
Preparation of Bearing Materials
Preparation of materials is the first step to make ball bearings. The steels are first heated to about 1710 degree Celsius to eliminate as many impurities as possible. Then the components are used to form high carbon chromium bearing steel, which has an extremely high tensile strength. Then it is formed to necessary shapes and sizes for the productions of different types of bearings. They are formed into wires, plates, tubes, bars and so on.
Forging
The steel bar is first heated then cut. It is then pressed by machine and molded into inner and outer ring shapes. The designated shapes are formed by hot forging.
Turning
For the turning of the inner ring, first, the surface on one side is cut, then the other. After that, the bore is cut. Then, it is chamfered. Finally, the raceway is cut, and the turning of the inner ring is completed. The turning of the outer ring is similar to that of the inner ring. The marks are stamped on the side surfaces of the ring indicating the information such as the brand and part number. Nowadays, more manufacturers are using laser marking machines.
Heat Treatment
Because the inner and outer rings work under tremendous pressure and they repeatedly go through rolling motions, they must be extremely rigid and wear-resistant. So, they have to go through quenching, which they are heated between 800 and 860 degrees Celsius, then instantly cooled. To boost wear resistance, they are held at 1450 to 200 degrees for a long period, they cooled slowly. This process is called tempering. Tempering must be done soon after quenching to reduce the risk of cracking.
Grinding
For the grinding of the outer ring, the side surface of the ring is first ground. Then the outer surface is ground so that it is precisely perpendicular to the side surface. Then using the outer surface as a reference, the raceway groove is honed. The same process applies to the inner ring.
Making of Steel Balls
The steel balls are more difficult to make even though their shape is very simple. To make steel balls, the wires are first cut and formed into spherical shapes between dies. Then the balls are continuously rolled to create smoother surfaces. After undergoing heat treatment, they are repeatedly polished with grindstones to improve their surface finish. Then their diameters are measured. They are sorted and delivered to the assembly plant. This entire process takes a few days.
Making of Retainers
The retainers for deep groove ball bearings are typically manufactured by press molding the steel plates.
Assembly
There are slight gaps between the inner and outer rings and the steel balls, which is known as the internal clearance. Different clearances apply to the bearings according to various applications. When a bearing is being assembled, the internal clearance is adjusted by selecting steel balls of different sizes. Nowadays, bearings are assembled by industrial robots. This machine is measuring the raceway dimensions between the inner and outer rings. That measurement determines which ball size is chosen. The machine then places the correct number of steel balls between the two rings. Retainers are placed above and below, and then riveted. The assembled units are cleaned. Then the grease is squeezed evenly into the raceway, then the bearings are sealed if necessary. Many manufacturers test the bearings before they ship out. For example, the durability, performance and noise level.
Roller bearings have high radial load capacity and some designs can accept light axial loading. They operate at moderate-to-high speeds.
There are five types of roller bearings, they are:
1. Tapered roller bearings
2. Cylindrical roller bearings
3. Needle roller bearings
4. Spherical roller bearings
5. Trust roller bearings
The most common type of roller bearings are the tapered roller bearings. Similar to a ball bearing, a tapered roller bearing is composed of an inner race, which is also called a cone, an outer race, which is also known as a cup, and a cage. Instead of steel balls, the rolling elements are the rollers.
3.3 the Manufacturing Process of Tapered Roller Bearings
The manufacturing process of a tapered roller bearing consists of:
1. Preparation of Bearing Materials
2. Forging
3. Turning
4. Heat Treatment
5. Grinding
6. Making of Rollers
7. Making of Retainers
6. Assembly
The manufacturing process of a tapered roller bearing is also very similar to that of a deep groove ball bearing. However, the processes of the cage, the rolling element are different.
Making of Rollers
Steel wires are die cut into cylinders to make the rollers. It then goes through several surface finishing and heat treatment processes.
Making of Retainers
Steel plates are first press cut into circles, then formed into cone shapes, the bottom is then cut. It then goes through a turning process. After that, rectangular sections are cut for the assembly of rollers.
4. New Technologies in the Bearing Industry
The technologies in the bearings industry have been developed in recent years. For example, ceramic ball bearings are made for the use under conditions of high speeds and high temperatures. The third generation of bearing hub units for passenger vehicles are pre-sealed, pre-greased and integrated with ABS for better performances. Another technology is the bearing unit with sensors used on high-speed trains. Such sensors monitor the rotational speed, acceleration and temperatures of the bearings in use, which makes great a contribution to safer transportation.
Augustus.Spencer (Wednesday, 15 April 2020 11:01)
try to build the solid foundation of the bricks that others have taken, life will not be so hard.