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INSPECTION & MEASUREMENT Dimensional Inspection in the Digital Age Advanced digital technology has had a significant role in helping shops keep pace with ever increasing customer demands for quality. By Tim Moriarty T oday's machine tool technology allows very high precision parts to be machined consistently and economically with high process stability. Advanced machine tool design and direct CAD-to-machine tool interfaces have reduced many uncertainties that were previously managed by frequent inspection and process adjustment. Likewise, measurement tools have evolved to keep pace with the workfow demands of advanced machining operations. Digital technology has enabled a host of innovations that make today's measuring tools fast, While today's accurate and convenient comparators look to use on the shop foor. similar on the outside as their older counterparts, they are very different on the inside. The Benchmark Optical comparators are the tried-andtrue benchmark for shopfoor measurement. Comparators are hard to beat for economy and ease of use, but are limited in their capability and speed. Customized chart gages and simple DRO controllers make basic comparators too specialized and too slow to keep pace with high volume shop production. However, recent advancements in digital technology have made a dramatic impact on the productivity of these familiar, shop-friendly tools. While today's optical comparators look much the same on the outside as their counterparts from yesteryear, they 32 PRODUCTION MACHINING :: FEBRUARY 2013 :: As an example of the advantages digital technology has brought to dimensional inspection, internal eCAD projection creates virtual chart gages for any magnification. are radically diferent on the inside. Today's comparators use only high intensity LED light sources. Tis lighting provides the brightness needed to measure at higher magnifcations, which in turn makes for more accurate measurements. LED sources also reduce the uncertainty of automatic edge detectors. Te light sources are so stable that edge repeatability as good as 2 microns is routinely possible, compared with 4 to 5 microns with conventional flament or vapor light sources. LED light sources eliminate much of the periodic maintenance needed for a comparator. Teir heat load is easily dissipated using passive heat-sinks, eliminating the need for cooling fans, which add vibration and can blow dirty shop air into the comparator optics. Tey also have a virtually unlimited lifetime, eliminating replacement costs and hazardous disposal issues. LEDs also allow more versatile designs in the light sources. Tey can be arranged in unique confgurations and each LED in an array can be controlled on an individual basis. Tis modular nature allows design of