Production Machining

DEC 2014

Production Machining - Your access to the precision machining industrial buyer.

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difcult. "We were using a three-fute, 0.125-inch-wide groove milling insert that was 0.697-inch in diameter," Mr. Christilaw says. Running at 750 rpm and 9-ipm feed rate with 0.004-inch per tooth engagement, each groove took about 30 seconds—consuming 19 hours of the part's 80-hour machining time. "Tis didn't include the operator's time for in-process measure- ments, cutter compensation and insert changes," he says. Te company is a go-to supplier for nine GM plants, ofering a climate- controlled, 33,000-square- foot shop and 47-person staf capable of design and manufacture of gages, dies, tooling, fxtures and special machinery, as well as CNC machining of large fabrications. A part this size and confguration naturally attracts atten- tion when fxtured up, so Horn Application Engineer Brett Kischnick—visiting the shop to handle questions about lathe grooving—asked the operator about it and learned about the tool life and cycle time issues. He later proposed a solution with a Horn 713 12-fute groove milling insert, 0.854-inch in diameter and 0.118-inch wide. Te small diferences prove what a "game of inches" machining can be, because the new insert reduced cycle time for each groove is from 30 seconds to 5 seconds. Te larger tool diameter—only 0.157-inch larger—reduces the length per cut from 1.830 inches to 1.337 inches, which is about 27 percent. Increasing the number of cutter teeth from three to 12 allows a 400-percent increase in feed rate from 9 ipm to 36 ipm, while maintaining the same 0.004 inch per tooth engagement. In addition, the smaller width of the 12-tooth tool (0.118 inch versus 0.125 inch) leaves 0.008-inch material for the second pass on each groove. Tis produces a larger chip to minimize heat buildup in the tool, which is amplifed when trying to "rub of " 0.001 inch. "It is important to have enough stock to produce a good chip to carry the heat away," Mr. Kischnick explains. "Otherwise, the tool will absorb more cutting heat. Te cooler the tool, the longer it stays sharp." In fact, the 12-tooth tool lasts almost three times as long as the three- tooth tool: 45 minutes versus 18 minutes. Te 713 12-tooth milling cutters produce a smooth cut. Tey are designed for grooves as much as 0.185-inch deep and 0.039-inch to 0.118-inch wide in holes as small as 0.886-inch diameter. Tey are screwed to the front face of a standard carbide shank and utilize straight or staggered cutting edges, depending on the width. "Tese tiny grooves had always taken a big chunk of the total cycle time, but this new tool cuts that down to a proportion that's more in line with their size," Mr. Christilaw says. "Anytime you can cut 25 percent of the cycle time for a part by simply going to a diferent style tool, it's a real game changer." :: 41 Groove Milling Cuts Down Cycle Time for Inconel Part :: Milling the two tiny grooves inside each bore consumed 25 percent of the part's total cycle time when using a three-fute cutter, Cambron's original approach. For more Information: Horn USA :: 615-771-4100 :: Cambron Engineering :: For more articles related to this topic, visit PM's Milling Tools Zone. LINK :: :: Horn USA's 12-fute 713 milling cutter reduced the cycle time for each groove from 30 sec. to 5 sec.

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