Modern Machine Shop

JAN 2018

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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BETTER PRODUCTION Shops Using Technology trials that were conducted at the University of Sheffield's Advanced Manufacturing Research Centre (AMRC) in the United Kingdom. To pursue better results within the test parameters, Kenna- metal modified an existing tool design: its "Harvi" end mill featuring unequally spaced flutes to break up chatter, eccentric relief to extend tool life and a tapered core for stability during heavy cutting. That modified tool is now available to the aircraft manufacturer and to others in the toolmaker's new "Harvi III Aerospace" line. The AMRC testing focused on forged titanium 6Al4V. Three sets of cutting parameters addressed both traditional-milling and high- velocity approaches for the aircraft maker. In each case, the three sets of parameters were designated as "current," "meets" and "exceeds" expectations. In the traditional rounds, a 0.1-inch radial depth of cut was specified, with cutting speeds ranging from 150 to 200 to 250 sfm for current, meets and exceeds categories, respectively. In the high-velocity testing, depth of cut dropped to 0.02 inch, while speeds increased to 400, 450 and 500 sfm, respectively. Strict guidelines governed what kinds of tooling could be used. Initially, the solid carbide end mills in all these cases had to be 1.25 inches in diameter, with a f lute length of 4 inches, corner radii of 0.09 inch, and a f lute count of either five or six. Further test- ing then evaluated different combinations of tool diameter, length and corner radius (up to the full radius of a ballnose tool), Mr. Muel- ler says. Tools were required to achieve axial depth of cut of 2 inches while extending from the holder exactly 4.5 inches. And in all of this (sorr y, metric system), only imperial units were allowed. Within these constraints, the tooling supplier was free to put for ward its best choice of tool coating, carbide substrate and cutting geometr y. Kennametal put considerable work into find- ing the tooling that would excel in these tests, Mr. Mueller says. The company performed its own testing at its facilities in Germany, Ten- nessee and North Carolina using five different machining centers. Chip f low and formation were analyzed using high-speed cameras, and he says a refined tool-grinding process was developed as a result of this analysis. Ultimately, nearly 300 different tools were produced for use in the project, and 15,000 cubic inches of Precision Workholding Technology New Rapid Change Power Chucks feature a patented jaw design where only the top jaw is changed, elimi- nating the investment in multiple sets of base jaws or expensive mono block jaws. Rapid Change™Jaw Chucks Fast Changeover, High Accuracy, MicroCentric Quick

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