A CNC RETROFIT ON A JOHNSFORD VMC IS INCREASING tire-mold manufacturing efficiency at King Machine 30% to 50%. The Akron, Ohio, company installed a Sinumerik 840Di control package consisting of drives, motors, and an AD14 board to interface with its external spindle system.
"We use the CNC for axismotion control, as well as spindle and auxiliary systems such as the toolchanger, lube system, and two rotary tables on the Johnsford," says Rob Snodgrass, programming manager at King. The machine does light milling and simultaneous 4/5-axis engraving on sidewall sections of tire molds, which measure between 25 and 60 in. in diameter and are made from 1020 steel or 6061 aluminum.
King internally stores both the mold part program and machine data on its own network. With a standard ethernet connection, the CNC accepts millions of lines of code in a few seconds. Operators at King then run an entire part program or block search to a specific area in the program instantly.
According to Snodgrass, the Sinumerik CNC is the fourth different control package the company has used on machines performing the same or similar work. He says, "Operators spent minimal time relearning the Johnsford VMC because the new control is familiar in feel and operation to our older controls."
Siemens Energy & Automation Inc.
ELK GROVE VILLAGE, ILL.
Shop secures crankshaft job
BEFORE IT COULD MACHINE 160,000 CRANKSHAFTS FOR A MAJOR ENGINE MANUFACTURER, Trace-A-Matic Corp. had to figure out how to hold the odd-shaped parts. So the Brookfield, Wis., shop contacted its distributor Engman-Taylor Co. of Minomonee Falls, Wis., for assistance. Engman-Taylor turned to Enerpac Workholding in Milwaukee for parts and technical expertise to build two workholding fixtures for the big job.
The fixtures consist of Enerpac's swing cylinders, block cylinders, and hydraulic work supports. In addition, the company supplied the necessary power unit for the fixtures to clamp parts consistently.
"The design of these fixtures was a cooperative effort between ourselves, our distributor, and Enerpac," says Karl Krueger, team leader at Trace-A-Matic. "We are especially grateful for the knowledge available from the manufacturer; it allowed us to purchase the right parts to properly build the fixtures."
Tooling shop delivers in days with new VMCs
ELITE MOLD & ENGINEERING BECAME the benchmark for other shops by building aluminum prototype tooling on a three-week basis. But that wasn't good enough. Its competitors caught up, so the Sterling Heights, Mich., shop has revamped its manufacturing philosophies and now measures deliveries in days.
To meet such short delivery times, Elite bids on jobs with high machining-to-labor ratios, incorporates the latest in software and computers, keeps a well-stocked toolroom, and makes efficient purchases with vendors. But probably the most significant change is a 60% reduction in machining time because of three Fadal Performance Series VMC 3020s with Siemens 840D controls.
"Typically, we run machines at 50 to 60 ipm, and a 60% increase seems like a drastic change," says Paul Patrash, general manager at Elite. "But with the 3020s and their controls, we now run 200 to 250 ipm at 10,000 rpm to produce good surface finishes and hold tolerances of 0.0002 in."
High-performance AC axis-drive motors and large-diameter, 40-mm ballscrews produce 3,800 lb of thrust, making the 3020 well suited for Elite's fast machining operations. Heavy cast iron boxways with nonmetallic liners provide maximum surface-area contact for vibration damping and rigidity. The boxways are hardened and ground, and the friction-free liners are on all gibs and way surfaces to ensure consistently tight machining tolerances. Positive-displacement lubrication over the full length of the way surfaces virtually eliminates machine stickslip.
The machine's Siemens 840D control executes programs fast for smooth surface finishes when contouring at high spindle speeds. It also has lookahead, dynamic feed forward, and programmable acceleration. Smoothed acceleration reduces wear on mechanical parts and optimizes travel response.
Using the 3020's contouring mode with programmed corner rounding, Elite quickly machines corners to reduce cycle time. A dynamic preprocessing buffer — first in, first out — increases program-execution speed. Programs are smaller, and spline interpolation using A, B, and C splines to generate smooth transitions makes for faster machining.
"To obtain long stretches of unattended machining and reduce the number of setups, mold halves are completed with a single setup," explains Ed Howell, shop supervisor at Elite. "Raw blocks are squared up, ejector systems completed, and part shapes are machined complete. On larger jobs, pairing up the VMCs lets us cut a cavity on one machine and a core on the other. These are some of the procedures that reduce our overall completion time."
While most machines require a cool-down period after running at maximum speed, the 3020 maintains a constant temperature with Cool Power, a special refrigerated cooling system that controls thermal growth and repeatability problems. A heat-transfer agent circulates through the machine spindle nose, around the spindle cartridge and headstock, and through the center of the gundrilled ballscrews.
This closed-loop system isolates the heat-transfer agent from chips and other contaminants. The heattransfer agent, which is monitored and chilled as required, maintains the temperature of positioning components to within ± 1° F of the VMC's ambient temperature. This minimizes thermal expansion and ensures consistent positioning repeatability, especially when machining molds with long cycle times.
Fadal Machining Centers
CHATSWORTH, CALIF.
Face mills keep HMC running at full capacity
TO HIKE THROUGHPUT OF GRAY CAST IRON PARTS, John Deere Waterloo Works, Waterloo, Iowa, forged close working partnerships between manufacturing engineers, a machine tool builder, and a tool supplier. Team members were charged with making the best use of the shop's new Mori Seiki MH-633 HMC to reduce cycle times and improve productivity of transmission covers. And a large portion of those improvements resulted from Sandvik Coromant's new milling technology.
The tooling company supplied a 3-in.-diameter CoroMill 290 face mill with 10 screwdown, siliconnitride inserts for roughing and another 290 with 6 silicon-nitride inserts and a single CB50 cubic-boronnitride (CBN) insert for finishing. The two-step/cutter process enables John Deere Waterloo Works to cut cycle time on its transmission covers 34%, exceeding original expectations.
While the old roughing process used silicon-nitride inserts, the 6-in.-diameter ISO-style milling cutters were unable to exploit the full power of the new machining center. However, the CoroMill 290 concept cutter is precision machined from hardened steel to minimize runout and withstand heavy cutting loads. In addition, the screwdown inserts are more accurate and stable than traditional clamp-in designs. The self-locating, screw-mounted inserts with carbide shims locate edges precisely and protect the cutter body. "The combination provides better repeatability with no presetting and more flexibility in cutter choices," says Curt Brown, the Sandvik Coromant representative working with John Deere.
The 3-in.-diameter 290 fits the new machine work envelope and lets Deere machine at full capacity. Roughing cuts run at 1,280 sfm with about a 0.014-in. chip load, which is much heavier than with the previous process.
The other 290 cutter with silicon-nitride inserts and a single CBN insert delivers fine finishes at Deere's high milling speeds. Extending 0.0005 in. beyond the silicon-nitride inserts, the CBN edge presents a wiper geometry with an extended face continuing after the cutting-nose radius.
This leading edge removes metal and produces a surface roughened by peaks and grooves. The extended face remains in contact with the work to wipe down or burnish away the peaks for a finish twice as smooth at the same surface speed or equally smooth at twice the surface speed.
Finishing cuts run at 3,500 sfm, again, about twice as fast as the old process. Feed is 0.006 ipr, and Deere is maxing-out the machine rpm and feedrates on some of the cuts but still getting a mirror finish. "We achieve better flatness and better finishes," comments Kallin Kurtz, project manager for cast iron redevelopment at John Deere.
Sandvik Coromant Co.
FAIR LAWN, N.J.
Drill's special geometry cuts machining costs
SWITCHING TO A NEW CARBIDE DRILL reduced the cost of drilling a hightemperature-alloy part by better than 80% for aerospace components manufacturer J.F. Fredericks Tool Co. in Farmington, Conn. The drills, Sculptured Edge (SE) 284 Dynapoints from Kennametal, sport a special positive-rake chisel point with an extremely large active cutting area that substantially reduces stress and provides freer chip flow on such hightemperature alloys.
"The bottom line is that these drills reduced our annual machining costs from $2,096 to $396," says Frank Klopp, manufacturing foreman at J.F. Fredericks. They eliminated a center-drilling and reaming operation, increased cutting speed to 75 sfm, and prolonged tool life to 150 pieces/regrind. But most importantly, drilling time dropped from 54 sec/part to 5.1.
Originally, it took three operations — center drilling, drilling, and reaming — to produce a 0.1875-in.-diameter hole in the Inconel 718 parts. Surface speed of the drilling operation was limited to 28 sfm, and the shop got an average of 18 pieces/regrind.
J.F. Fredericks runs the 284 Dynapoints on a Tsugami FMA5-II HMC. The part material has a 38-Rc hardness and is difficult to drill. "Its high nickel content makes it gummy, so it tends to chip or break inserts," says Klopp. "To avoid this, we ran our original cobalt-steel drills at relatively slow speeds and feeds, yet they would still chip or break around their flutes, cutting lips, or at the outside corners. The drills also walked or wandered at the beginning of the cut, so we had to use a center-drilling operation."
The special SE point on the 284 Dynapoint creates a smooth transition from the major cutting edge to the drill point. This lets the drill actively cut metal over the full distance from the center to the outer diameter. The drills are self-centering and rigid, which prevents them from walking or wandering at the beginning of a cut.
http://www.americanmachinist.com/304/Issue/Article/False/8316/Issue
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