Unique in the World: High-Precision Surface Inspection of Bearing Balls using Optical Measurement
The Fraunhofer Institute for Silicate Research ISC is one of the most important centres for materials-based research and development in Germany. Together with the experts from STEMMER IMAGING, the Fraunhofer researchers have developed a fully automated check system for bearing balls that is unique in the world. The sophisticated quality inspection system is based on cutting-edge optical measurement technology.
The task
Engineering support and component selection for a fully automated surface quality check system for bearing balls.
The challenge
One hundred percent inline quality control of the bearing balls – with highly reflective surfaces, various sizes and high operating speeds.
The solution
STEMMER IMAGING designed a vision solution perfectly tailored to the demanding requirements and delivered all the necessary components ensuring their perfect adaptation and interfacing. The result is a fully automated inspection system based on optical measurement technology that is unique in the world.
- High-precision camera systems
- Perfectly tuned illumination
- Maximum processing speed
- 100 % error detection rate
- Flexible inspection of different ball sizes
Reflective surfaces and high operating speed
Manufacturing bearing balls for ceramic high-precision ball bearings requires maximum precision and process reliability: Even the slightest deviation from the optimum shape or the desired surface quality can cause bearing damage and failures in the end customer's application, which can result in liability claims against the manufacturer.
When developing the automated inline inspection system for a well-known bearing ball manufacturer, maximum reliability was mandatory. Particular challenges in this project were, on the one hand, the reflective surface of the balls made of silicon nitride and, on the other hand, the high inspection speed, as the preceding manufacturing speed had to be maintained. In addition, the system had to be designed for the flexible testing of different ball sizes.
"The surfaces to be measured are highly reflective and require a special illumination system that minimises the reflections in order to solve the various measurement tasks. In addition, the system had to be flexible, as various standardised ball sizes with diameters of 3 to 10 mm had to be tested with it. All in all, these were very demanding requirements for a fully automated quality inspection system.“
Dr. Andreas Diegeler, head of CeDeD at the Fraunhofer Institute
The customised solution
A two-stage quality inspection system with high-precision optical measurement technology.
In order to ensure one hundred percent quality inspection despite the high processing speed, the experts at the Fraunhofer Institute worked with STEMMER IMAGING to design a two-stage, robot-assisted inspection system that is perfectly suited to the automated checking of bearing balls.
Thanks to a special illumination system and high-precision optical measurement technology from STEMMER IMAGING, even the slightest deviations from the standardised roundness and surface defects such as scratches, fractures, dents or colour deviations are reliably detected and the corresponding balls are automatically sorted out.
Two machine vision units for maximum reliability
The bearing ball check is completely integrated into the production process and is carried out fully automated at two separate inspection units. In the first step, the components’ roundness is checked in accordance with the standards, followed by quality control of the ball surfaces in the second step. The exact feeding of the bearing balls to the respective testing module, the passing-on of defect-free balls and the ejection of faulty products is carried out by a robot.
High-precision optical measurement technology at the cutting edge
High-precision camera systems with a resolution of 1 µm guarantee a complete, three-dimensional measurement of the balls with an accuracy of 0.3 μm. A precisely tuned special illumination system minimises any reflections.
The solution’s key success factors
As an independent technology provider, STEMMER IMAGING was able to select and optimally match the most suitable components for the application – without supplier lock-in. In this way, a high-precision inspection system was created which, based on optical measurement technology, enables one hundred percent quality control and automatically sorts out defective balls while they are still in the production process.
High-end cameras
The high-precision camera systems have a resolution of 1 µm. They enable a complete three-dimensional measurement of the bearing balls with an accuracy of 0.3 μm.
Perfectly tuned special illumination
A special illumination system developed by a STEMMER IMAGING partner was used to provide reliable measurement results despite highly reflective surfaces.
Maximum processing speeds
STEMMER IMAGING was able to supply all components used, including software, as a package precisely tailored to the given requirements, enabling an inspection speed of 2,000 balls per hour.
„Our partner's comprehensive know-how on all issues arising in the field of machine vision and the excellent quality of the components supplied simply convinced us. We will therefore continue to rely on STEMMER IMAGING's services and products for future systems.“
Dr. Andreas Diegeler, head of CeDeD at the Fraunhofer Institute
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