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Ball bearing wiki: Technical information about ball bearings
What is the structure of a ball bearing?
Inner and outer ring:
The suitability of a xiros plastic ball bearing is determined by the materials of the two races. Our low-friction ball bearings are made from high-performance plastics with different material properties, allowing them to be used in a wide range of applications and maximising their service life.
Ball bearing cage:
The cages of our plastic ball bearings are perfectly matched to the materials of the outer and inner rings in terms of chemicaland temperature resistance.
Ball bearing balls:
In addition to stainless steel balls, balls made of glass, plastic or ceramic are also used. Glass balls should be selected if freedom from metal and chemical resistance are important. Plastic balls produce particularly lightweight ball bearings. The stainless steel version is particularly cost-effective and temperature-resistant.
What is a ball bearing?
Without ball bearings, the world wouldn't really turn, would it?
Because we simply see the world as it is. Everything grows and develops, is in motion and is taken for granted. However, people hardly think about such a marvel of technology: the ball bearing. We encounter it every day in our lives, whether we are travelling to work by bike, train, bus or car. Because ball bearings are found in all means of transport, but also in kitchen appliances, training equipment in the gym or at the bowling alley in the evening - we find ball bearings everywhere. But what is a ball bearing anyway? Since the development of the steam engine and the beginning of industrialisation, ball bearings have become an integral part of our everyday lives.
Ball bearings, also known as roller bearings, are bearing components that reduce the frictional resistance caused by rolling bodies between an inner ring and an outer ring. They are used to locate axles and shafts and can absorb radial and/or axial forces, depending on the type. Due to their design, they also allow the shaft or other components that are mounted on an axis, such as a wheel, to rotate.
If there is a blockage due to coarse contamination, it may be possible to rinse or blow out the ball bearing and it can continue to be used. This applies if there is no damage to the bearing rings and balls.
Each customer defines the wear limit for themselves depending on the field of application. For applications that require high precision or positioning accuracy, maintenance intervals should be shorter. For users who utilise xiros conveyor rollers, for example, a higher level of acceptance may apply, as only simple deflection tasks need to be performed.
Our polymer ball bearings have an inherent radial bearing clearance of approximately 0.05 to 0.15 mm. They owe this characteristic to their smooth running and low breakaway torque. The open design also makes them very easy to clean.
Is it actually necessary to lubricate ball bearings?
Metal ball bearings are generally dependent on lubricants. But is it possible without? Our plastic ball bearings are an example of how it can be done without.
In-house test laboratory for plastic ball bearings
Our ball bearings are put through their paces. Years of research work in our test laboratory have resulted in numerous product advantages for our xiros plastic ball bearings compared to their metal counterparts. The expertise gained flows into further developments and innovations that are ideally suited to the most individual applications.
How do I mount ball bearings?
1. mounting (tolerance H7)
2. front side (balls visible)
3. rear side (cage visible)
4. press in the ball bearing with the front side first
5. mount shaft (tolerance h6) with chamfer
6. a locating spigot must be provided
Measuring ball bearings: Tolerances and measurement recommendation
The tolerances for inner and outer diameters depend on the installation size. These are often approx. ±0.05 mm to the nominal dimension. The bearing rings are usually injection moulded and have a certain ovality by nature. For this reason, the caliper is used to measure 90° to the injection moulding point (if present) over the entire width of the bearing. The dimensions and tolerances are designed in such a way that they fulfil an easy press fit by hand when using an H7 holder and h6 shaft. An additional locating spigot using a circlip (shaft) and snap ring (housing) is recommended to prevent axial displacement.
What ball bearing seals are available? Ball bearing open or closed?
Plastic or ceramic ball bearings: open or closed?
These two types of ball bearing are usually only available as open types. The reason for this is that these bearings do not need to be lubricated. The open design has a major advantage with these materials. Any dirt that gets in can easily escape again, or be flushed out or blown out with compressed air. This makes it impossible for lubricants to accumulate dirt. igus® therefore dispenses with the use of suffixes in comparison to their metallic counterparts.
xiros plastic ball bearing with cover disc
In our online shop, customers can choose between different cover disc variants. Not all of them are available for every bearing size, but a cover disc on one side is always available.
- Open type
- One-sided cover disc
- Double-sided labyrinth seal
How do the balls get into the ball bearing?
Ball bearings consist of an inner and outer ring, a cage and rolling elements. The cage is there to separate the rolling elements, in the form of balls, from each other. If the balls were not separated, they would run against each other and overheat. This would have destructive effects at high rotational speeds and friction of the balls. But how do the balls get into the ball bearing?
Possibility 1:
This question is easy to answer when looking at a deep groove ball bearing in accordance with DIN 625, as these have noticeable indentations on the inner and outer ring. If the inner and outer rings are moved towards each other up to the respective recess, the balls can easily be filled into the grooves and fixed with the cage. In this case, the cage takes on the function of preventing the balls from falling out.
Option 2:
Heating the outer ring and cooling the inner ring for smaller metal bearings down to miniature designs is also unusual, but is practised in the industry. The balls and cages can then be easily inserted into the space created between the inner and outer ring. If the materials of the rings contract or expand again, the ball bearing has reached its standard dimensions and all the balls are in place. For igus®, only the first option comes into question, but there are also others, which are illustrated below.
How the balls get into the ball bearing at igus:
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