Innovative roller bearings impress with their low rolling resistance, long service life and lightweight design. Roller bearings offer various advantages, including the ability to significantly reduce fuel consumption and CO2 emissions. The individual components must be precisely coordinated with one other to minimize the rolling friction between the rolling bodies and the inner and outer ring. Managing complex measuring tasks is part of the quality control process for this very reason - roughness parameters for the track, the outer and inner diameter, and the bore holes all need to be recorded. The straightness at the outside diameter, in the bore holes and at the sealing surfaces is measured in order to distinguish the contours of the bearing, and the round angle of the inner and outer diameter is determined. The accuracy with which the round angle (taper angle) is measured influences the load capacity and service life of a bearing; optimal surface roughness is in turn a prerequisite for a high level of running accuracy and low level of rolling friction.

With the HOMMEL-ETAMIC nanoscan, the Jenoptik Industrial Metrology division is offering a machine that has been developed to take combined measurements of the roughness and contours of roller bearings in single measuring run. Depending on length of the probe arm, the machine can measure the most subtle surface roughness at a resolution of 0.6 to 1.2 nm. With a measuring stroke of between 24-48 mm, all measuring tasks for checking the surface can be completed with a single measuring device. Given that individual bearing types and components differ considerably in their design, size and shape, bearing manufacturers expect maximum precision and flexibility from the range of applications offered by metrology equipment.

A clamping device is generally used to secure both the inner and outer rings and the rolling bodies to be measured in the measuring machine in order to hold the parts in the precise position required. The probe arms can then move over the parts repeatedly with the utmost accuracy each time. However, several clamping devices are necessary when the measuring machine is working on different parts and component sizes.

Making Use of Gravity

To phase out the need for complex and inflexible machine conversions, the Jenoptik Industrial Metrology division has enlisted the help of one particular manufacturer of high-performance bearing units in order to put an unusual metrology concept into practice: The device was assembled on a block of granite that features a surface incline of 20 degrees. This is advantageous because by using gravity and arranging the contact surface for the component at an angle, the part can be inserted, easily positioned with a single prism and firmly supported at the same time. Clamping devices can be completely omitted.

Just like the contact surface, the measuring column on the HOMMEL-ETAMIC nanoscan is positioned at the same angle in order to create a short measuring path to the part. The reliability of the metrology concept on this globally unique design has been thoroughly tested and verified in laboratories.

The measurement is conducted fully automatically once the part is loaded. For a new component, only the new parameters, such as the measuring characteristics, measuring positions and target limits, need to be entered into the database along with the permissible tolerances. The measuring conditions such as the measuring speed and range are also defined in advance.

Probe arms featuring double stylus tips also move in both scanning directions as well as up and down in a single measuring run. Where previously several single measurements and evaluations were necessary, the HOMMEL-ETAMIC nanoscan now conducts complex measuring sequences in one go and evaluates them for you. The round angle so crucial for the precision of a bearing can also be determined at the same time via the top and bottom measurements.

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