March 2011 / Volume 63 / Issue 3|
Dedicated fixtures simplify pump housing machining
By CTE Staff
Weir Minerals North America, Madison, Wis., manufactures pumps, hydrocyclones, valves, screen machines and media, and rubber and wear-resistant linings for mining, oil field and industrial applications.
When the company needed machining of 108 "×108 " Class 40 cast iron slurry pump housings, it contacted Advanced Machine & Engineering Co., Rockford, Ill., to perform part of the required contract manufacturing.
Courtesy of AME
With each weighing more than 5,000 lbs. and consisting of a frame and cover section, the housing sets presented a workholding challenge for AME. They required milling, drilling and boring. In addition, they required an A and B load, which meant four setups were needed to produce a complete housing assembly. Rigidity was also key to avoid vibration and distortion from the enormous load and tooling masses involved. AME was machining two to three housing sets per week.
Although AME was delivering pump housing sets to specification and on time using nondedicated fixturing, part setup took too long, according to Steve Schubert, AME’s vice president of operations. Changeovers took up to 8 hours. Locating and clamping the housings was quite tedious, and the methods used raised several safety concerns in materials handling, strapping and clamp positioning.
In addition, clamping forces were less than optimal, which increased machining cycle time and reduced tool life.
“The challenge was to design a fixture that was within the weight limitations of our machine table without compromising the structural integrity and rigidity of the fixture itself,” Schubert said. “We also needed a design that would allow for quick change of the workpiece, as we did not have a two-pallet machine. Finally, but most important of all, we were extremely concerned about safety. We needed a fixture that would allow safe usage for the machine tool operator and be secure enough to not allow one of these massive parts to fall off of the table.”
AME’s solution came from its product line. The company developed a single, dedicated AMROK fixture measuring 120 " wide × 110 " high, with adjustable jacks to support the pump sections during machining on a horizontal mill.
The switch to a dedicated fixture resulted in multiple benefits. Because the fixture held both A and B loads for each workpiece, setup times were reduced to less than 50 percent of the previous method. The dedicated fixture also improved locating and clamping, resulting in a 45 percent reduction in machining cycle time per pump set, improved part quality and surface finish, and enhanced operator safety by using standardized lifting, locating and clamping methods.
AME shared the savings with its customer, and Weir Mineral was so pleased that it transferred work from other contract manufacturers and awarded the entire project to AME.
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