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PARADIGM SHIFT: CROSS SCANNING

Laser scanners on CMMs capture thousands of points every second and digitize objects with complex surfaces in a rapid and accurate way. The resulting data creates a 3D pointcloud that can be compared to the original CAD model for full part-to-CAD inspection or for reverse engineering purposes.

When it comes to measuring features, a single laser stripe scanner has some limitations compared to traditional touch probes. To accurately measure features, many scanner re-orientations are required to digitize the holes from various directions. One recent technological evolution is the Cross Scanner from Metris, a high-speed, multi-stripe laser sensor that digitizes features from different directions without the need for a C-axis re-orientation. The optimal distribution of measured points enables this multi-stripe laser sensor to efficiently scan features such as holes, slots and gap and step with many more points than a touch probes.

Laser scanners have been proven in first article inspection, off-line inspection and troubleshooting, but fast and accurate inspection of holes, slots, gap and step remains a challenge. The Cross Scanner introduces a patented technical paradigm that measures holes and features in one fast single scan by combining three laser stripe scanners whose planes are rotated by 120 deg and slightly tilted. Each camera has its own laser field and scans in an alternating way. The total throughput speed of the scanner is up to three times 6400 points per second, or 19,200 points per second.

A single laser stripe scanning method measures the intersection of a laser plane with an object from a single view direction. This approach cannot capture information outside areas that are not viewable by both the laser plane and the viewing direction – a characteristic that requires multiple scans to be taken from different directions. Objects having several features require at least three scans to obtain a sufficiently detailed digitized surface.

The patented Cross Sensor introduces a number of breakthrough advantages for laser digitizing. Higher speed and increased flexibilityis obtained for real 3D measurement by avoiding the use of a (expensive) motorized sixth axis (C axis) that can introduce errors. Compared to a traditional laser stripe scanner mounted on a Renishaw PH10, the Cross Sensor has an even higher speed and flexibility, avoiding the discrete repositioning of the sensor head. Another important advantage is the better resolutionof the Cross Scanner since the object is digitized with an optimal density in all directions.

The most important benefit is achieved by having a real 3D measurementresulting in an accurate representation of the measured feature. The cross scanner can look into feature by the three slightly tilted cameras that are distributed over 120 deg. While Cross Scanning technology applies to general digitizing applications, it is particularly suited for feature detection in sheet metal quality control.

For example, a 20 in x 8 in piece of sheet metal from a car is scanned using the Cross Scanner in less than four minutes,resulting in a pointcloud of 1.6 million data points. Using a traditional scanner, the same detailed scanning job would require at least 12 to 15 minutes. The better resolution is clearly visible when zooming in on a detail of the pointcloud.

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Metris, 1577 Star Batt Drive, Rochester Hills, MI 48309, 248-853-6907, Fax: 248-853-6945, www.metris.com.

INSPECTING BLANKS FOR CONTAMINATION

With PartSens, acp – advanced clean production GmbH makes it possible to directly measure and document particulate contamination on component surfaces for the first time ever. A new, enlarged measuring probe significantly expands the applications for this innovative inspection system so that sheet metal blanks and auto body panels can be efficiently scrutinized for particulate cleanliness.

This new measuring probe has a measuring surface of 20 mm x 15 mm for efficient, random sample testing of component surfaces for particulate cleanliness. Inspecting sheet metal blanks before press forming in the field of auto body fabrication is a typical application. One large U.S. automobile manufacturer already uses this system to inspect auto body panels for cleanliness before they're painted. Further applications include the monitoring of systems and production environments, and examining the degree of cleanliness achieved in the cleaning process. Particulate contamination with sizes down to 25 µm can be detected. Measurements can be performed either manually or by means of an automated process.

This inspection system works with direct sidelighting to illuminate the surface being inspected. Using integrated optical filters, the measuring probe generates extremely high contrast to assure reliable inspection of structured surfaces, even under difficult conditions. The measuring probe only needs to be passed over the surface under test in to inspect it for particulate cleanliness. The sidelight image is visualized in real-time at an integrated screen and the number of particles and their size are ascertained and displayed.

Orientation, position and an outline of the particles are represented in a live image for reliable conclusions regarding the number, the size and the size distribution of the particles. Particle assignment and evaluation can be programmed in accordance with customer-specific requirements. Due to the fact that measurement results are available immediately, the user can react without delay to exceeded limit values, and expensive rework and scrap can be avoided.

PartSens is equipped with an integrated thermal report printer for documentation of measurement results. Measured values and live images can also be saved to a USB memory stick with the help of the USB port at the front of the device for documentation and further processing at a PC.

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acp – advanced clean production GmbH, Röntgenstrasse 30, D-73730 Esslingen, Germany, +49 (0)711 687039-0, Fax: +49 (0)711 687039-10, www.acp-micron.com.