QMT Features: April 2009
Full 3D digital inspection
The latest multi-laser scanner technology from Metris delivers full 3D measurement to provide better insight, more flexibility and up to 20 times higher productivity across a range of applications.


At Control 2009, Metris will launch the XC65D which combines multi-laser technology with fully digital operation. The Cross Scanner’s multi-laser implementation consists of 3 lasers incorporated into a cross-pattern configuration. Compared to a line scanner with a single laser, the XC65D digitizes parts on the basis of 3 laser stripes, each shifted 120 degrees in orientation.


In any scanning direction, the cross pattern of laser stripes guarantees sufficient measurement points on the outer edge of a part or on the contour lines of geometric features, such as holes and slots. By continuously observing parts from 3 different viewpoints, the Cross Scanner obtains a full 3D view of the bore of a hole, or the flanges of a notch. As a result, geometric features can be extracted from the acquired point cloud with higher confidence, increasing the accuracy of feature dimensions obtained through scanning.

As the Cross Scanner creates a full 3D view in a single scan, there is no need for multiple scans of the same feature with different scanner orientations, which requires time consuming re-orientations of the probe head. This saves significant teach in effort and scanning execution time.


A full 3D view is also beneficial when scanning parts with more complex surface shapes. Real 3D measurement capability allows the scanner to capture extremely concave surfaces and the cavity of deep pockets. With laser beams being projected from 3 sides, the XC65D provides maximum surface coverage, avoiding shadow zones that typically occur with a single laser line scanner.


Digitizing any surface without user interaction
Metris’ third-generation Enhanced Sensor Performance (ESP3) effectively scans surfaces with varying colour or high reflectivity. The technology not only provides automatic real-time adjustment of sensor settings between successive laser stripes, but also for each individual point of the laser stripe.


Dynamic point-per-point adoption of laser source intensity enables the XC65D to deal with nearly all sample materials and surface finishes without human interaction. This also includes shiny surfaces and abrupt surface type transitions under any lighting conditions. ESP3 is a key differentiator when scanning similar parts in different manufacturing stages; initially dealing with bare sheet metal parts and finally scanning finished products painted in any colour.


Boosts scanning productivity
The XC65D Cross Scanner boosts productivity  by introducing wider laser stripes, and high-speed CMOS camera technology, which triples scanning frequency compared to its predecessor. Acquiring data at a faster pace enables to drastically increase the velocity of the XC65D scanner during inspection. This increases the number of features that can be scanned in the same time frame, or reduces the inspection cycle time for freeform parts. When digitizing smooth freeform parts, the process can be further accelerated by activating the scanner’s single-stripe mode, which allocates full processing capability to the active laser.


When developing the XC65D, Metris paid special attention to temperature stability, established through intelligent airflow design and software compensation measures. They minimize warm-up time and guarantee reliable accuracy under shop floor conditions. By docking the XC65D in the ACR3 heated rack when not used, the scanner has  zero warm-up time, resulting in maximum productivity.


Up to 15 times faster sheet metal feature inspection
In the automotive industry, features are key in realizing fast and flawless assembly because they are used to connect the different components of a product. Therefore, fast and in-depth inspection of 3D features is essential in speeding up the assembly process and increasing the quality of the final product.


Leading car manufacturers use a Metris Cross Scanner and point cloud processing software to automate the inspection of a so-called “Christmas tree”, a feature that looks like a bolt. Such metal features that are automatically welded on sheet metal surfaces allow parts to be connected to one another using screws. It took the OEM less than one day to set up a vehicle body inspection routine covering approximately 250 Christmas trees.


On average, Metris’ patented cross scanning technology requires roughly 5 seconds to inspect the position of a single Christmas tree feature, with approximately 200 micron positional repeatability. Scanning features instead of tactile measurement saves hours of manually mounting cylindrical extensions on the Christmas trees and removing them after measurement. Besides offering comparable measurement accuracy and repeatability, the Cross Scanner enables the OEM to complete the entire process 15 times faster.


The XC65D offers a scanner-to-part standoff distance of 80 mm, which is sufficient for specimens with somewhat flat geometry. The XC65D-LS scanner variant with a longer standoff distance offers distinct advantages. By capturing geometry up to a distance of 170mm (7.1”), the scanner gains optimum access to cavity surfaces of body-in-white structures or scan over the clamps that hold components in position. For these reasons, the XC65D-LS scanner is used a lot on horizontal-arm CMMs used in the automotive industry.


Complex parts  quickly digitized
The concept of the Cross Scanner together with the high standoff distance and field of view depth results in major time savings when inspecting automotive parts. This greatly simplifies scanner motion when digitizing engine blocks, cylinder heads and gearbox covers. To take a full 3D scan of one side of such a specimen, the Cross Scanner is moved along parallel motion paths without indexing the CMM head.


With such limited CMM overhead, the scanner captures the complete surface, including full 3D characteristics of ribs, holes, flanges and pockets, at record speed. One hour is sufficient to set up and inspect casted driveline parts, whereas detailed tactile inspection easily lasts more than a day. Focus Inspection reports include part-to-CAD comparison charts with colour-coded areas marking local geometry deviation, which can be interactively analyzed using license-free viewer software.


Also on complex parts made of plastic or composite material, the Cross Scanner makes a big difference. Its high speed and eye for detail are always beneficial, regardless whether inspecting prototype samples, pre-production batches or serial produced parts. The XC65D easily traces degrading production mold geometry or digitize the slight shrinkage of a blow molded part. In the aerospace industry, Cross Scanners are used to inspect the geometry of larger milled precision parts made of aluminum or composite.


As applicable to all Metris CMM scanners, the Cross Scanner can be retrofitted on a broad range of CMM brands to boost inspection productivity of existing CMM installations anywhere in the world.

www.metris.com
  
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Rob Tremain Photographer
www.4exposure.co.uk
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