Robots are critical to the speed and efficiency of automotive production lines. They help control costs and ensure the quality of today’s automobiles by quickly and reproducibly performing repetitive tasks such as part handling and welding. But to ensure the quality of the end product, every aspect of every part—planes, slots, holes, gaps, studs, etc.—has to be correctly sized and precisely located. There was a time when testing and measuring of those features could be done manually, but to keep up with today’s robotic assembly lines, measurement too has had to be automated. Bolts and studs welded to sheet metal have been a particular challenge. Their absence, typically due to improper welds, can cause problems further down the line. Similarly, if they are misplaced by even a small amount, parts won’t line up properly, affecting the vehicle’s fit and finish. And improper angle of attachment will cause difficulty when attaching adjacent components. The speed and repeatability of robotic assembly makes it an ideal application for optical measurement. However, optical technology has to address several challenges. First, material—copper, steel, or aluminum for example— affects a bolt’s optical properties, which fortunately is somewhat consistent. More critical is the fact that manufacturing processes can create unanticipated changes in the bolt’s surface and appearance. Welding can leave dark soot and raised spots on the surface. Small defects in the bolt itself can change surface reflectivity as can stress marks, grease, or other foreign materials. Any measuring technology, laser or otherwise, that relies on reflection from the bolt itself will be negatively influenced by these varying characteristics. A new alternative, one that eliminates these problems completely, has been introduced and patented by ZEISS Automated Inspection. It uses angled non-laser light to project shadows of the bolt onto the sub-surface and measures those instead. Obviously, if the bolt is missing there will be no shadow, and if the bolt is incorrectly positioned or improperly angled the shadows will indicate this. By using two light sources from different angles, this approach accurately measures a bolt’s position in three dimensions. An algorithm collects and analyzes the data, working much like a GPS to “triangulate” precise position and orientation and compare it to CAD specifications. This solution easily identifies any unacceptable variation ensuring a more robust and trouble free process control. Inspection is completed with the Coded Bolt Sense specially developed for optical inline measurements. This technology projects laser lines, not for direct measurement of the bolt or stud but simply to generate a reference plane. The data from the angled lights and camera are then used for the actual measurement of the bolt or stud. A robot moves the lights and camera into position over each bolt in turn, requiring just over three seconds per bolt for the entire process including robot movement. The actual optical measurement takes just milliseconds. The technology works with most robotic systems and can be integrated into virtually any assembly process. The robot and laser sensor can also collect data for other features such as flush and gap, hole locations, slots, etc. Because shadows are unaffected by the condition of a part’s surface, the technology is virtually foolproof, catching any flaw and generating no false positives. It works on any bolt or stud, either threaded or unthreaded, and can measure accurately to +/- 0.2mm. Viewing two different shadows of the same object provides immunity from reflectivity variables, and collecting the data through a single camera reduces cycle time. For more information please contact Gerrit deGlee, Product Sales Manager, at 1-800-327-9735 or firstname.lastname@example.org. ZEISS Automated Inspection www.zeiss-ai.com U.S. Locations and Metrology Information www.zeiss.com/metrology 1-800-327-9735
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