After upgrading optical metrology equipment with a handheld Nikon Metrology ModelMaker D (MMD) scanner for non-contact 3D measurement, PSA radically increased scanning productivity. Featuring a 100 mm laser stripe width and all-digital operation, the MMD enables PSA metrology engineers to complete detailed geometric scans of small to large vehicle body parts in record time. They can take the portable systems to any location or site, set it up and measure parts on the spot. The perfect interaction between localizer, scanner and software speeds up scanning throughput and decreases post-processing and analysis work. Laser scanning also enables PSA to systematically digitize body frames, doors, windshields and other parts, and use the acquired data to validate numerical calculations, ultimately contributing to fewer mechanical prototypes.
A single system that is suitable for many metrology tasks
Europe’s second-largest carmaker has a history with digitizing that dates back to 2001. Since then, PSA has gained significant experience in applying laser scanning to digitize the geometry of vehicle body parts of prototype or early production vehicles. “Dimensional accuracy is of prime importance in vehicle body assembly,” states PSA Poissy’s metrology department. “During the assembly process of a trunk lid, for example, the geometry of the lid slightly changes due to the mechanical interaction between frame, glass, trim, lock, etc. When we prototype vehicle body parts, we closely monitor geometry using the Nikon Metrology MMD to ensure assembled body elements will fit perfectly. The use of a wide variety of materials – including composites and plastics – sets specific manufacturing and measurement challenges, and increases the need for reliable and efficient metrology solutions.”
Physically the largest part that PSA metrology engineers scan using the handheld Nikon Metrology MMD is a body-in-white structure. Positioning the articulated measurement arm at one or two locations is sufficient to digitize a hood or the entire backside of a vehicle body, for example. Metrology engineers at PSA also use the Nikon Metrology MMD to scan interior trim parts, light units and various other parts. To deliver top-quality data for different surface types even under difficult lighting conditions, the Nikon Metrology MMD scanner features ESP (Enhanced Sensor Performance). ESP is an algorithm that automatically adapts camera and laser settings to accommodate varying surface shape, color and reflectivity. This helps PSA engineers accurately deal with sheet metal, composites and plastics – without having to apply spray or other preparation measures. With a laser line that counts as many as 1028 measurement points, the scanner reliably digitizes freeform surfaces as well as the edges of individual features. Another reason why PSA opted for a non-contact scanning solution is the ability to reliably digitize softer trim material, eliminating the risk of scratching fragile components or pressing flexible parts. On finished cars, the system serves as an optical gauge for flush & gap inspection between body panels.
Reducing scanning throughput time and post-processing effort
When scanning a vehicle body part, a PSA engineer operates the laser scanner while the scanned surface takes shape in
real time on the laptop screen. The displayed information provides instant feedback regarding scanning speed, coverage and progress. Scanning takes place at a relentless pace, thanks to the scanner’s extra large laser stripe and fast digital signal processing. “The result of the scan is a cloud of hundreds of thousands or even millions of measured surface points,” explains a PSA scanner user. “After filtering the point cloud to eliminate excess points, we generate a polygon surface mesh and optimize it. The entire process is smoothly managed by Nikon Metrology KUBE software. The tight integration between scanner software and hardware not only streamlines the scanning process, but also cuts the remaining post-processing effort in half compared to the previous scanning solution.”
According to PSA Poissy’s metrology department, the metrology team represents a centralized unit that runs measurements at PSA sites across France to support vehicle development from prototype to release. “Regardless of whether measurements are scheduled to take place in the PSA Poissy facilities, or at PSA sites in Rennes or Sochaux, for example, metrology engineers take the portable system with them and start scanning right away. This pragmatic approach offers maximum measurement flexibility and saves on logistics by reducing transportation of vehicle body (parts) to our metrology laboratory.”
Scanning jobs performed four times faster than before
Besides monitoring the geometric quality of vehicle body parts – Nikon Metrology laser scanning forms an essential step in verifying numerical calculations PSA performs as part of virtual simulation. Metrology engineers at PSA systematically use the Nikon Metrology MMD scanner to acquire digital 3D copies of structural components such as body frames, doors, windshields and other parts. This touch with reality increases simulation accuracy and helps reduce the number of lengthy and costly physical prototype cycles. “Overall, when using the all-digital Nikon Metrology laser scanner with its wide laser stripe, we are able to complete scanning jobs four times faster than before,” says the PSA scanner user. “Productivity improvements of this degree enable us to take on additional metrology assignments and yet increase the level of data quality, all within the current capability of our metrology team.”