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October 30, 2003-- Reduces aerospace machining cost by 80%

Switching to a new carbide drill with a special geometry designed to reduce cutting thrust has helped an aerospace components manufacturer reduce the cost of drilling a high-temperature alloy part by better than 80 percent. Three operations-center drilling, drilling, and reaming-were originally required to make a 0.1875'' hole in an Inconel 718 component. Surface speed on the drilling operation was limited to 28 surface feet per minute (sfm) and an average of 18 pieces were produced per regrind. Tooling and machining costs for the j company's 2,000-piece annual volume ran slightly over $2000.

J.F Fredericks specializes in producing aerospace components such as elbows, fittings, rings, and fuel nozzles from high-temperature alloys such as Inconel, titanium, Hastelloy, and similar materials on a contract basis. Customers include Howmet Corporation, Chromalloy, U.S. Navy, IMO, Kamatics Corp., Samsung America, Volvo Flygmotor AB, Fiat Avio S.p.A, Watervliet Arsenal, Textron Lycoming, United Technologies, General Electric, and many others. The company has 75 employees, a 25,000-foot climate controlled building, and a wide range of CNC equipment such as 11 four-, sixand eight-axis mill- turn lathes, four CNC grinding machines, two horizontal machining centers, two CNC drilling machines, and three turning centers. J.F. Frederick's total quality management program has been developed to meet Department of Defense guidelines and Mil Specs 45208A and 9858A. The company also provides process engineering, tool design, CNC programming, and document control services to its customers.

Toutant and Klopp inspect a Kennametal SE284 Dynapoint drill that eliminated JF Frederick's need for a center drilling and reaming operations and reduced machining time by 90 percent. Tool life increased to 150 pieces per regrind.

In an effort to reduce costs, J. F. Fredericks Tool Co., Farmington, CT, decided to try Kennametal's new Sculptured Edge (SE)284 Dynapoint drills which have a special positive-rake chisel point with an extremely large active cutting area that substantially reduces stress and provides freer chip flow on high-temperature alloys. The new drills eliminated the need for the center drilling and reaming operation, made it possible to increase cutting speed to 75 sfm, and increased tool life to 150 pieces per regrind. Drill cost per hole fell from about 15 cents to about 11 cents per part. More important from a cost standpoint, machining time was reduced by more than 90 percent, from 54.0 seconds to 5.1 seconds per part. "The bottom line was that these new drills reduced our annual machining costs from $2,096 to $396," says Frank Klopp, manufacturing foreman.

Frank Klopp, JF Frederick' Manufacturing Supervisor, loads a Kennametal SE284 drill into a high-precision collet chuck. In all, Kennametal's new Dynapoint drills reduced this client's annual cost to make 2,000 holes from $2,096 to $396.

Tough material to drill

The hole mentioned above is used to fixture the part for a later operation. The hole is produced in a Tsugami FMA5-II horizontal machining center. This five-axis machining cell features a space- saving vertical pallet magazine that enables unmanned machining and also enables chips to drop directly onto the chip pan. The part material, Inconel 718, is based on the AMS 5596 specification and has a hardness of 38 Rockwell C. "This is a very difficult material to drill," Klopp explains. "Its high nickel content makes it very gummy, so it tends to chip or break inserts. In an effort to avoid that, we ran the cobalt steel drills at a relatively slow speed and feed rate, which increased machining time. Yet the cobalt drills used to chip or break very quickly around their flutes, cutting lip, or at the outside corners. These drills also had a tendency to walk or wander at the beginning of the cut so we were forced to use a center drilling operation which ate up additional cycle time."

In the past, the center drilling operation was run at 397 rpm, 39 sfm, 0.0018 inches per revolution (ipr) feed rate, and 0.7 inch per minute (ipm) feed rate. Tool life with a 3/8'' by 90-degree cobalt spotting drill was 200 holes per tool and the tools could not be reground. The tools cost $20.67 each, so tool cost per hole was about $0.103. The cycle time was about 12.4 seconds which, based on a machine cost of $60 per hour, yielded a machining cost of $0.207 per part. The total cost for this operation was $0.310 per part. The drilling operation was run at 594 rpm, 28 sfm, 0.0013 ipr, and 0.8 ipm. A cobalt steel #15 drill provided 18 holes per regrind and an average of 50 regrinds. The tool cost $2.82 and reconditioning cost was $0.45, yielding a drill cost per hole of $0.028. Machining time was 25.2 seconds so machining cost per part was $0.421, resulting in a total cost for this operation of $0.448. The reaming operation was run at 795 rpm, 39 sfm, 0.0015 ipr, and 1.2 ipm. The 3/16'' 4FL carbide end mill provided 300 pieces per tool and could not be reground. The tool cost $5.07 so tool cost per part was $0.017. This operation took 16.4 seconds, yielding a machine cost of $0.273 per part and a total cost of $0.290 for the operation. Total cost of making the hole was $1.048 and annual production costs for 2,000 pieces were $2,096.40.

Klopp felt there was considerable room for improvement on this operation so he spoke to Rene Toutant, senior metalworking sales engineer for Kennametal based in Windsor, CT. Toutant informed him that Kennametal had recently introduced a new line of carbide drills especially designed for cutting high-temperature alloys. The new drills have a higher positive rake angle than existing products, so they are ideal for cutting Inconel, Rene 41, titanium alloys, and other similar materials used in the aerospace and medical industries. Unlike carbide drills that basically duplicate the design of previous high-speed steel drills, SE 284 drills take full advantage of the physical properties of carbide. The unique SE point creates a smooth transition from the major cutting edge to the drill point, allowing the drill to actively cut metal over the full distance from the center to the outer diameter. The self-centering capability and superior rigidity of the new drills prevent the drill from wandering or walking at the beginning of the cut. As a result, these drills produce very consistent, concentric holes. Rather than ramming chips into the face of the drill, the flute's design tightly curls them and moves them up and out of the hole, providing further reductions in cutting force. The 284/285 drills are offered in an uncoated 9.5 percent cobalt submicron grade called K715 that provides high strength and resistance to built-up edge, two properties that are critical in machining high-temperature alloys.

Kennametal SE 284 Dynapoint drills have an exceptionally high positive rake angle, making them ideal for aerospace and medical manufacturing applications in Inconel, Rene 41, titanium alloys, and other such materials.

Reductions in machining cost

"Rene set up a test to see how the new tools would perform on this drilling operation," Klopp says. "He said that the positive- rake chisel point would eliminate the need for a centering operation. He also recommended substantial increases in cutting speed and feed rate in order to take full advantage of the improved performance of the new geometry and cutting material." Trials were run using a B284A04500 drill, a metric size that produces a 0.177'' hole. The tool was run at 1,617 rpm, 75 sfm, 0.0025 ipr, and 4 ipm. At these elevated conditions, the new tool still produced 150 holes. The new tool costs $67.50 and can be reground 8 times, for a tool cost per hole of $0.109. The big advantage came in the reduction of machine time to only 4.8 seconds, which reduced the machine cost per part to $0.080. Since this drill is smaller than the actual hole size, the reaming operation was still required, yielding a total tool cost per hole of $0.126, a total machine cost per hole of $0.353, and a total cost per hole of $0.480. "Based on these tests, which showed that the tools could reduce the annual cost of producing the part from $2,096.40 to $958.50, we made the decision to switch to the new drills," Klopp says.

Klopp says that he took advantage of Kennametal's regrinding service to ensure that the drills were reground to the original factory specifications. Kennametal knows the exact geometry to which the drills were originally ground while independent regrinders often have to guess. For example, in order to optimize performance of a drill over its intended application range, Kennametal often hones a controlled portion of the cutting edge by a precise amount or in other cases, uses a sharp edge. Independent regrinders usually just apply a standard hone which means performance won't be as high.

"The new drill has performed exactly as the test predicted over the past six months," says Klopp. "But a month or so ago, Rene came to me with an even better alternative. Kennametal had just expanded its SE284 line to cover inch size drills including a 0.1875 inch diameter drill that can be used to produce our hole to specifications without the need for a reaming operation. We have tested the new drills and will shortly be putting them into pr\oduction. Once we do, we will have reduced the total machining costs on this operation from over $2,000 to under $400 on an annual basis," he concludes. Kennametal Inc.,

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