Production Machining

FEB 2013

Production Machining - Your access to the precision machining industrial buyer.

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Inspection in the Digital Age highly efcient oblique surface lighting, where the direction, angle and intensity of the light can be controlled to highlight part features at an angle with respect to the part's surface. Well designed oblique lighting makes it possible to see and measure small chamfers, beveled edges and other angled features that would not focus sharply with only square-on surface light. CAD Driven Comparators Digital technology has also enabled another game changer for optical comparators—the digital chart gage. A high resolution digital projection system inside the comparator projects a CAD drawing with tolerance bands onto the comparator screen. Te part image can be easily compared with the CAD drawing, just as one would do with a traditional overlay chart. Te eCAD system from Certifed Comparator Products, for example, automatically scales a part's CAD drawing to the comparator screen based on the magnifcation lens being used. Color-coded tolerance bands make it easy to judge if a part is in tolerance. When the comparator stages are moved, the coupled CAD image and tolerance zones move with the image automatically. Tis capability is important because it allows larger parts to be conveniently inspected on a smaller screen at higher magnifcation, assuring better accuracy. Direct CAD projection is a vital time-saver in a high-mix environment, enabling new digital chart gages to be produced instantly. Unlike Mylar or glass charts, digital charts don't need to be stored, handled, cleaned or re-calibrated. Best of all, the digital chart gage is re-scaled automatically when a diferent magnifcation lens is selected. Imagine being able to zoom from 10× to 50× for a closer look and have the chart gage automatically resize in an instant. Using a part's CAD fle as the basis of the inspection process can be taken one step further with automation software that builds an automatic measuring routine directly from the CAD fle. Te eChek software, which operates motorized comparators made by Quality Vision International, allows a measurement sequence to be created simply by clicking on features of the CAD model. Feature details are automatically extracted from the CAD fle. eChek provides complete feature measurement and construction capabilities including GD&T.; Tis capability transforms a simple comparator into a sophisticated 2D coordinate measuring machine, while eliminating the tedious task of "programming" the measurement routine. Digital Cameras Add Productivity Digital camera technology has also helped to modernize optical comparators. Te ability to take a digital snapshot or video of the screen image at any point in the inspection is invaluable for documenting defects or for creating detailed work instructions for part inspections. Digital cameras can play an even more important role when used to make measurements. Te fundamental comparator technique is to mark the position of the stage when a part's edge crosses the centerline of the comparator screen. For decades, automatic edge detectors synchronized with the stage position readout have automated this process, eliminating the operator's judgment from the measurement uncertainty. In the 1980s, early solid state video cameras began to be integrated into comparator optics to image a portion :: This side-by-side comparison shows an optical comparator from the 1960s and one made today. Outwardly, they are similar, but they are built on very different technology. productionmachining.com :: 33

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