January 2011 / Volume 63 / Issue 1|
HMC puts rail component producer on the fast track
By CTE Staff
Founded as Westinghouse Air Brake, Wabtec Corp. provided the first straight air brake systems to the railroad industry nearly 140 years ago. With 50 manufacturing plants and approximately 7,000 employees worldwide, the Wilmerding, Pa.-based company continues to manufacture railway components as well as power generation and off-highway equipment.
Wabtec’s Passenger Transit Div. plant in Spartanburg, S.C., recently put machining of two-piece drawbar assemblies on the fast track with installation of a new horizontal machining center. Increased demand drove the need for greater productivity on the drawbar machining operation, according to Dale Simms, manufacturing engineer. “We identified setup reduction and machine speed as two areas of opportunity for improvement,” he said.
Courtesy of MAG
Wabtec was machining the 400-lb. mild steel parts on a single-pallet HMC with limited reach, resulting in the need for another machine to mill hard-to-reach pads on the parts. “We were looking for a machine with a long spindle extension that would allow us to eliminate a second machine—and 2 hours of cycle time,” Simms said.
The search for an extended-spindle machine led Wabtec to MAG. Featuring a 31.5 " live-spindle reach, the Erlanger, Ky.-based company’s HMC 1600 eliminated the need for a second machine and setup for pad milling. The machine’s added capacity also allowed engineers to add the third major component of the drawbar assembly, the yoke, on the pallet as well, freeing up another machine in the process.
“Before we purchased a new machine, we ran tests at MAG’s Fond du Lac (Wis.) plant with the spindle extended 10 ", 15 " and 20 ",” Simms said. “The machine performed very well, and its twin-pallet design is inherently more productive than a single-pallet machine.”
Those dual, 63 "×49 " pallets and 360,000-position contouring table allow Wabtec to machine the drawbars as a set. The machine’s Z-axis reach of up to 31.5 " allows deep-cavity milling with shorter, more rigid cutting tools. Thermal compensation software on the live spindle dynamically offsets spindle growth to maintain the ±0.001 " tolerance required on the drawbars.
In addition to the machine’s rapid traverse rate of 1,378 ipm, 75-second pallet-changes and 15-second tool changes reduce cycle time, according to Simms. “It is remarkably fast for a large machine,” he said.
Wabtec uses multiple cutting tools to produce the drawbars and other railway components, including thread mills, boring bars and some specials. “We have two 50-tool pallets set up in a 100-tool magazine for the drawbar work, and we bought an extra 50-tool cart for some of the smaller jobs we run on the machine,” Simms explained.
The machine is also equipped with Renishaw probes and software to align castings on the fixtures and conduct preliminary checks on part features. All parts receive a final inspection on a coordinate measuring machine.
With the HMC 1600, drawbar machining productivity increased 66 percent. “Once we put the job on the MAG machining center, production jumped from 4.5 to 7.5 parts per day,” Simms said. “We realized a nice bonus, too, when we were able to add the third component of the assembly onto the pallet.” CTE
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