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84 MMS April 2017 mmsonline.com FEATURE components. However, these minor adjustments proved a small price to pay for one particularly attractive feature: the ability to measure with three distinct beams that target the same location on the workpiece, but from different vectors. As the part passes through, these beams scan its entire diameter, each taking a different cross section from the same point. The control software derives the extent of any ovality from differences between the three cross-sectional measurements. The team spent even more time figuring out how to precisely space the incoming parts for inspection (and possible rejection) in the first place. The process begins with pneumatically forcing the single-file line of parts up a vertical shaft. A mechanical stop at the summit brings the topmost part to a halt, and the others pile up be ne ath. Pushing the topmost pa r t for wa rd releases the stop and allows the next part to rise in its place, "kind of like a Pez dispenser," Mr. Bannayan notes. Pushing parts out of the so-called Pez dispenser is a task performed by the "porcupine," the team's nickname for the inverted conveyor lining the roof of the track. Downward-protruding fingers sweep in and intercept each individual part from behind. These fingers maintain contact throughout the laser and camera scans until they swing up and out of the way at the end of the conveyor, pushing the parts into the grinder in the process. The upside-down configuration eliminates the risk of the conveyor's bulk inter fering with the non-contact inspection, Mr. Bannayan says. It also facilitates the use of a V-shaped track that keeps parts perfectly perpendicular to the inspec- tion systems. This would be difficult to accomplish with a flat conveyor, even absent concerns about getting in the way of the laser or cameras. Although decidedly cleaner, approaching from above came with its own set of challenges, he says. For example, the porcupine's fingers required multiple design iterations to work properly. The final version of the finger design features a sharp Here is a closer look at the pre-grind singulation system, conveyor fingers and laser ovality check. A second laser diameter check after the grind acts as a control on the process, continuously feeding data that's used for automatic size com- pensation.