Modern Machine Shop

DEC 2016

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72 MMS December 2016 mmsonline.com FEATURE flat; and other complex features deep inside of tubes typically requires long stylus extensions. Too long, in fact, to measure reliably, or sometimes even at all, with a passive scanning head and its static system of springs and displacement sen- sors. Instead, the company chose the Vast XT Gold, an active scanning head that leverages force generators and other internal components to maintain an even, user-specified level of force on the part surface. In the process, it compensates for any extra force created by long or heavy styli, says Kevin Donovan, senior technical sales engi- neer at Zeiss. Given the added complexity, active scanning of in-process parts also plays a critical role in keeping production of these tubular components on track. Finally, it helps slake newer customers' thirst for comprehensive form data, including for OD geometry and even parts that aren't tubular at all. "The more complex the feature, the greater the benefits of active scanning," Mr. March says. METROLOGY CATCHES UP Along with earning the necessar y credentials (Tube Hollows received AS9100 certification this past February), Mr. Morse says he and the rest of the leadership have viewed the addition of a CMM as a key step toward reaching the nex t phase of the company's developme nt since its founding. Getting there didn't take long. The company was founded in 2011 by a small team from a larger manufacturer that had been acquired. Armed with a small stable of essential hole-making equipment that had been left out of the acquisi- tion, Tube Hollows International moved from a smaller leased space to its current, 50,000-square- foot facility within one year. Mr. Morse credits steady growth since then to the company's sin- gular focus on its core niche, par ticularly its reputation for medical industry parts like titanium intramedullary rods and nitinol tubing. Nonetheless, focusing only on concentric, uniform-walled tubular components would leave out the aforementioned aerospace and energy work, which Mr. Morse and the rest of the leader- ship consider essential for future growth. Although more challenging—typical lead times range from 8 to 12 weeks, as opposed to 2 to 4 weeks for legacy jobs—these parts have proven to be well within Tube Hollows' machining capabilities, Mr. March says. However, measuring ID and OD sizes, TIR and surface finish isn't enough for customers that require fully defining complex-geometry ID forms. Unlike a handheld measuring instrument that would require projecting profile geometry based on a few select measurements, CMM scanning paints 3D contours in thousands of data points that can be interpreted directly. Form callouts like cylindricity, a combination of round- ness, straightness and taper measurements, are also easier and more precise. Still, even those inspections that could be relegated to hand gages are often conducted on Tube Hollows' borecentric technique (top) enables machinists to locate the ID in relation to the OD for a uniform- walled tube, even in bowed bar. That's a contrast to the con- ventional approach of turning down the OD to match (bottom). Curved Tube Curved Tube Uniform Wall Thickness Curved Hole O.D. Center I.D. Center Straight Hole Non- uniform Wall Thickness O.D. Center a t ends I.D. Center

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