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Geometry inspection represents a critical activity throughout the development process of a new vehicle model because it guarantees that individual vehicle parts can be assembled correctly. Volvo Cars Ghent and Metris cooperated on a long-term development project focusing on innovative optical 3D inspection of car components and virtual assembly of scanned components. The results of the project show that optical 3D technology offers the means to revolutionize automotive inspection in terms of measurement throughput and reporting transparency, overall translating into major development time and cost savings.
“The components that make up a vehicle must fit perfectly,” says Alfons Van Den Bergh, Head of Geometry Department at Volvo Cars in Ghent, Belgium. “Dimensionally-stable components ultimately determine the production quality level of a car. In case assembled components do not match 100%, the driver may experience a variety of annoying discomforts, such as leak, squeak and rattle. To avoid “side effects” of this nature, quality engineering must form an integral part of the entire development process.”
| The geometry of parts must be inspected thoroughly from the earliest development stages up to pre-production, long before a new model goes into production. Quality control executed during the final production phase provides verification that the assembly process is implemented correctly. This illustrates the importance of the activities conducted by the Geometry Inspection department of Volvo Cars Ghent, which operates mainly during the engineering of production processes for new vehicle prototypes. Until recently, the department used traditional inspection tools for 3D geometry inspection. Tactile probes installed on Coordinate Measurement Machines (CMMs) were used to verify the 3D geometry of components. The assembly of pre-production vehicle series was “physically simulated” by means of |
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complex moulds, cubings and fixtures. This way of working represents a time-consuming and material-expensive procedure. Another drawback of tactile point measurement concerns the interpretation of geometry results, which is rather difficult. Tactile probe measurements only yield a limited amount of geometry data that is listed anonymously in data tables, making results interpretation a real challenge.
| To streamline inspection processes, Volvo Cars and Metris joined forces in replacing the previous inspection process with optical inspection technologies that support the creation of virtual assemblies. Volvo Cars implemented 3D laser scanning for the inspection of individual components as well as entire vehicles. 3D laser scanners acquire thousands of measurement points per second and visualize these points using a so-called 3D point cloud, a complete digital representation of the surface of the scanned object. The point cloud from the 3D scan is then aligned to and compared with the original CAD data, resulting in an error color chart that reflects local out-of-tolerance geometry deviations. As these graphic 3D reports speak for themselves, they facilitate and speed up analysis work |
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and decision making considerably. Volvo Cars Ghent also uses point cloud data to virtually assembly vehicles by connecting geometry data with representations of other components, for example CAD models or other scanned parts. As such, 3D laser scanners not only provide more precise geometry data, they also offer the potential to realize huge time savings.
The cooperation between Volvo Cars Ghent and Metris already goes back a number of years. The company deployed a Metris XC50-LS laser scanner for feature inspection, mounted on a horizontal-arm CMM. Compared with complex tactile probe programming, the programming of scan paths for CMM-mounted laser scanners is straightforward and can be executed quickly. CMM-mounted laser scanners only perform a series of linear movements when scanning a surface.
Another co-development achievement concerned the K-Scan handheld laser scanner for mobile inspection tasks. While the XC50 laser scanner targets automated CMM inspection purposes, the handheld K-Scan system is 100% mobile. The ultimate proof of a well-implemented quality process is provided during the quality control of finished cars. At this time, the new K-Scan is used to verify correct gap and step between trunk and car body, for example. During start-up and production of the Volvo C30, the new mobile K-Scan measurement probe – along with the virtual assembly approach – were implemented and evaluated for the first time. In parallel, Volvo Cars performed traditional tactile verification methods to set benchmarks in terms to inspection precision and throughput.
Based on the outcome of the project, Van Den Bergh concludes that the deployment of new geometry scanning methods potentially compresses the rollout of the entire assembly process by up to 10 weeks. Moreover, laser scanning facilitates the inspection of incoming components from different suppliers. Complete and clear graphic 3D reports help Volvo Cars to efficiently communicate with suppliers, when product quality issues become apparent in visualization. Volvo Cars strongly believes that 3D scanning has a great future in the car industry sector. “Also in other production environments, where components are inspected for optimal assembly, optical laser technologies will undoubtedly gain importance in combination with tactile inspection methods,” Van Den Bergh stated.
Download: Volvo Cars uses Metris laser scanners for innovative optical inspection (PDF file)
Download: Volvo Cars verwendet Metris Laserscanner für innovative optische Messungen (PDF file)
Download: Volvo utilise le scanner laser Metris pour un contrôle géométrique innovant (PDF file)
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