Rolling bearings are essential for the low-friction operation of machines and mechanical components. However, problems with magnetism often occurring, particularly on the rolling bearing rings. High pseudo rejects during eddy current testing and cleanliness problems due to magnetic build-up of particles are well-known consequences. The companies Cestriom and N-Dect in Germany have developed an innovative solution which enables flexible and precise demagnetisation of rolling bearing rings and other ring-shaped components. This leads to improved performance characteristics and forms the basis for reliable eddy current testing.
Rolling bearings are mechanical components that serve to reduce friction between moving parts and thus enable low-friction and low-wear operation of machines and mechanical components. They consist of balls or rollers located between the inner and outer ring of the bearing. These rolling elements minimise direct contact and enable even load distribution, resulting in efficient movement.
Frequent risk
Rolling bearings are used in a wide range of industries, including the automotive industry, mechanical engineering, aerospace, mining, construction, the electrical industry and the food industry. They are used, for example, in motors, gearboxes, conveyor systems, wind turbines, agricultural machinery, machine tools, food processing equipment and medical technology.
Magnetism in rolling bearings is a frequently occurring risk that causes a number of problems. One common phenomenon is the magnetic attraction of ferromagnetic particles, which can occur during production due to abrasion, for example. In this case, the abrasion particles between the rings and the rolling elements lead to increased wear and increased noise. This can result in a shortened bearing service life and an increased risk of failure.
Magnetic spots
Magnetic spots on the bearing rings lead to false detections during eddy current testing, resulting in unnecessary rejection of tested rings. On the other hand, increasing the eddy current error threshold means that errors in the rings are not detected. One consequence of this is reduced bearing performance, which in turn leads to uneven running, vibrations and ultimately failure of the entire bearing.
An efficient and innovative method of neutralising magnetism in rolling bearing rings is electromagnetic demagnetisation by means of a rotating field, as has now been implemented with the first size of the RFS03 rotating field coil system from Cestriom.
Power modules
This innovative device combines three individual coils to form a complete system. Depending on the application, power is supplied via a Cestriom LM14 or LM20 power module. These power modules are the core components for generating the alternating current sequence required in the coils.
The RFS03 rotating field coil system can be operated both manually and automatically. In manual mode, the rings are placed centred on the RFS03 triple unit. Rotating field demagnetisation takes place in seconds at the touch of a button. In automated mode, the parts are placed directly onto the RFS03 coils with the help of robots or grippers. Another way is to demagnetise inline on a conveyor belt during a cyclical advance. Both methods enable optimum integration into the production process.
Processing options
The RFS03 rotating field coil system allows various processing options. One option is to demagnetise the ring on one side with a system consisting of three RFS03 units. This configuration is usually sufficient for rings up to a height of approx. 30 to 40mm. Two systems with three RFS03 modules on each are used for more comprehensive double-sided demagnetisation of larger rings.
The decisive technological advantage of the RFS03 rotating field coil system lies in the generation of a rotating field that flows through the rings in the magnetically optimal direction. This is particularly advantageous for applications with eddy current testing because it reduces the residual magnetism of the rings to very low and uniform values.
Areas of application
The areas of application for the RFS03 rotating field coil system are diverse. In addition to the demagnetisation of rolling bearing rings, other ring-shaped or round parts such as synchroniser rings or discs can also be demagnetised.
The RFS03 system is also available integrated in an N-Dect Flexitest system to flexibly test rotationally symmetrical parts with eddy current. The RFS03 system was developed for this purpose in collaboration with N-Dect GmbH. The demagnetisation process can be used for rolling bearing rings with a diameter range of approx. 100 mm to 300mm.
