Modern Machine Shop

APR 2017

Modern Machine Shop is focused on all aspects of metalworking technology - Providing the new product technologies; process solutions; supplier listings; business management; networking; and event information that companies need to be competitive.

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62 MMS April 2017 mmsonline.com QUALITY GAGING TIPS Columnist Despite what some internet addicts might think, we humans are analog creatures. Think about tr ying to cross a busy intersection on foot, for example. If our senses were digital, we'd be lim- ited to working with simple "on/off" information that would indicate that a car is present/not pres- ent. If we took several such "readings" over time, we would be able to extrapolate, but not directly detect, a car's direction, speed and acceleration. By the time we had done all that, however, the car would be long gone and we'd have to start col- lecting data on the next one. We'd never get across the road. But because our senses are analog, a brief glance is all we need to detect the car's presence, distance, direction, speed and accel- eration. This enables us to react safely, either by staying put or crossing the road, or by varying our rate of acceleration somewhere along a con- tinuous but finite scale of values. Gaging devices that have an analog meter provide more intuitive information than digital ones. Just watching the needle sweep across the dial of an analog amplifier from "a little on the plus side" to "a little more on the plus side" may provide a machinist with all the information he needs to make the right decisions that enable him to main- tain control over his process—even if he doesn't actually read any numbers on the dial. So in spite of the benefits of digital instruments (more on this below), analog systems still have an important role to play in gaging. A nalog amplif iers also excel in "dynamic" applications where the gage head moves relative to the par t (or vice versa). For example, when exploring parts for flatness using surface plate methods, the user slides the gage stand around on the plate and quickly observes the amount of variation in the part. If the user had a digital ampli- fier, he would have to position the stand, wait for a moment to read the value on the display, repo- sition the stand, read the display a second time and so on, until a sufficient number of data points had been collected. Yet, while we like analog devices, manufactur- ing them is becoming more and more difficult and expensive. Volumes are low and the par ts are many—a classic case for skyrocketing costs. The digital world may have to save the analog one. One option has been simulating an analog meter through a digital display. A digitally created meter hand sweeps back and for th across a graduated meter background, giving the look of an analog display. The problem with this simula- tion had been that the analog hand on the digital meter did not have the smooth, eye-pleasing motion of a real analog display. This is fine for a meter on a car dashboard, on which the rate of change is relatively slow, but in a dynamic gaging operation, trying to find the high spot on a round part as it is being rotated is made more difficult by a jumping digital display. The latest devices have evolved to the point that the digital displays almost look like real analog ones. The "needles" are clear and crisp, their When Digital Becomes Analog Today's digital displays look almost like real analog meters and can provide the same dynamic sensing. GEORGE SCHUETZ DIRECTOR OF PRECISION GAGES MAHR FEDERAL INC.

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