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CRITICAL MEASUREMENTS


he replied. “This is true not just for our devices, but any system that employs 3D optical technology.”


Esthetics and Measurements


Polytec’s TopMap Pro.Surf+, the latest generation of 3D surface metrology solution capable of measuring form and fi nish.


growth in additive manufacturing, where the surfaces need to be precisely characterized. “Still, there are many applications where a stylus system is best,” he noted. While still a useful device in a quality lab “our technique allows us to deliver systems that sit next to grinders and other manufacturing systems on the production fl oor, and while they are doing a tool change-out or some other operation, they can measure the parts to ensure the production method is optimal,” explained Schmidt. One example is the new Nomad portable optical profi ler. He noted that these ‘hardened’ systems are near-line produc- tion systems, employing statistical process con- trol rather than 100% inspection. While automo- tive is the primary market he serves, Schmidt went on to note that Zygo serves a number of other industries, including paper, medical, den- tal, and semiconductor manufacturing. These instruments are essentially micro- scopes and fundamentally simple to use, but like any advanced technology, it is fair to ex- pect that users need some education in using white light or coherent scanning interferometry. “Probably the most diffi cult thing for our cus- tomers is determining the right set of measure- ment and analysis parameters that are neces- sary for optimal quality and process control.”


72 AdvancedManufacturing.org | June 2016


Measurement of s urfaces in terms of engineering quantities like Ra is not the only application of non- contact optical metrology devices. “We deliver sys- tems that measure surface defects for esthetics,” ex- plained KR Srinivas, business manager, 3D scanning for Carl Zeiss Industrial Metrology (Plymouth, MI). The surface quality of a product—particularly in the auto industry—is important for customer acceptance. Poor esthetics can mean poor perception of quality of the overall vehicle. Small errors undetectable to the eye may cause defects such as dents, bumps, or sink marks that can pop into plain view after painting. “After that, it is too late to fi x it,” he said. He terms this an Esoteric measurement and con- trasts it with the more common Discrete measure- ments. Discrete measurements can be compared to a numerical ‘perfection’ such as a CAD model or surface roughness call out. With Esoteric measurements everything is relative—such as automotive Class A bodies-in-white. There is no practical way to relate surface measurements to a CAD model or other nominal fi gure, according to Srinivas. “Run your hand over a smooth surface until it feels a bump. Why is the bump there? Because all around it there is no bump. You feel the bump because it is higher relative to the surrounding


The objective of the ABIS inspection system from Zeiss is to identify esthetic surface defects in visible surfaces, like automotive Class A, that could mar the perception of quality in a product.


Photo courtesy of Polytec


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