Modern Machine Shop

APR 2017

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mmsonline.com April 2017 MMS 85 FEATURE angle on the back face of the tip. This eliminates the risk of the back corner unnecessarily knock- ing the part when the finger swoops up to begin its next revolution around the conveyor. Fingers are also constructed of heat-treated steel to ensure longevity. At first, properly timing the conveyor's rotation and the triggering of the inspections seemed relatively simple. That is, it could be based on known distances between the laser, the cameras, and the air blast that blows rejected parts into a side channel. This might have worked for a slower process. At two parts per second, however, even the slightest, most imperceptible elasticity within the conveyor track or the relatively lengthy fingers becomes a problem, Mr. Bannayan says. Given the fact that one mistimed fire of the laser, camera or air blast can be the difference between success and failure on a batch of thousands, the team opted to actuate these processes via laser sen- sors from Keyence instead. AUTOMATIC PROCESS CONTROL Inside the grinder, parts are presented to a wheel that measures 8 5 / 8 inches wide and 10 inches in diameter. The ability to use such a wide wheel in such a small platform (58 × 32 inches) is one advantage of the GT-610 centerless system, Mr. Bannayan says. Such dimensions make a wheel easy to manipulate during change-overs (which reportedly take only 15 minutes) without sacrific- ing the ability to remove material as progressively as possible by spreading the grind over more abrasive. He adds that manipulating the wheel is rare, let alone swapping for a new one. During initial testing, the wheel reportedly lasted through 20,000 parts before requiring redressing. Immediately downstre am is another laser diameter inspection. In this case, however, there's only one beam, and parts aren't separated out beforehand like at the pre-grind station. After the grind, they tend to nestle back against one another, filing past the laser in a continuous stream as it feeds diameter readings back to the control at a feverish pace of 500 per second. Singulation is unnecessary at this stage because the post-grind laser system is more about process control than quality control, Mr. Bannayan explains. The continuous stream of diameter data is col- lected, analyzed and fed back to the grinder's control for automatic size compensation as the wheel wears. "There's intelligence behind this data analysis," he says. "We're not trying to act on every reading; we're applying algorithms to filter out peaks, valleys and any anomalies to ensure we're measuring a certain average that we can control the system with." This isn't to suggest that red flags go ignored. Parts must be separated again and sent through final inspection on two eddy current sensors at a precisely controlled rate. This is accomplished by the cartridges shown here, each dedicated to a separate channel. Every index brings a new part into the cartridge and sends another up the tube toward the sensor. LEARN MORE mmsonline.com For video of the cell in action, visit short.mmsonline.com/hifeed.

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