Alloy maker's 'pallet-able' strategy reduces setup times.
Since tungsten has a high melting point, it is practically impossible to cast. To circumvent this problem, M&I has developed a sintered tungsten alloy called Wolfmet, which has a mass 60 percent greater than lead while combining desirable engineering properties such as high-tensile strength, good machineability, and superior heat resistance.
Consequently, the company's development of Wolfmet has generated a demand for a variety of parts. In turn, M&I has had to fashion a workholding strategy to keep its CNC machining centers operating efficiently.
Exactly what is Wolfmet?
M&I Wolfmet tungsten components are manufactured by mixing tungsten powder with other metallic powders such as nickel, copper, or molybdenum. The mixture is then pressed into a die, at which point it is still relatively soft but can undergo complex machining operations. After sintering, tungsten alloys are as easy to machine as cast iron.
Designers in the aerospace and defense industries use tungsten alloy parts to solve weight and balance problems in parts such as flight surfaces, helicopter blades, trim weights, and inertia systems. The material's high density al lows designers to add weight in constricted areas where precision is important. Think, for example, balancing the control surfaces of aircraft, or fixing the precise positioning of weight, center of gravity, and balance on Formula One racing cars.
The material is also used for applications as diverse as high-voltage electrical contacts, aluminium die-casting tooling, and radiation shields. In fact, one of M&I's most important customers, Elekta Oncology, is a manufacturer of gamma knife scanners and precision radiation therapy machines used to treat cancerous tumors. Tungsten blades located in the columnator are used to fine-tune the shape of the radioactive close to match the shape of a tumor, leaving adjacent tissue unaffected.
Liam Hand is a production engineer at M&I Materials, with responsibility for, among other things, designing models and fixtures for machining the rough-sintered tungsten billets into finished, precision components. The operation has a selection of CNC machining centers, most of which incorporate Midaco Micro Pallet Changer systems from Elk Grove Village, IL-based Midaco Corp. From a production point-of-view, one of the biggest challenges on the production floor is the variety of parts produced for different customers.
"With around 200 different components to manufacture on our current order book, flexibility is the key to make maximum use of the machining centers," says Hand. "Before we used the MIDACO Micro Pallets, we had a lot of machine down-time. Setups between different parts were taking up to 90 minutes each--clearly not ideal in a volume-production environment. During an information gathering session, it was calculated that on our three machining centers, over a 12 month period, 625 hours had been spent setting up jobs."
M&I stumbled across the Midaco Micro Pallet Changers. Group product director Cameron Haworth found them on the Internet. As an endorsement of the product, Haworth and production manager Mark Cleverly visited Hamble Aerostructures in Southampton, England, which deployed a MIDACO system to combat its own lengthy setup times. Suitably impressed, M&I discounted competitor systems and bought its first MIDACO receiver in January 2005. To date, the company has purchased four receivers and 12 pallets.
"Now we can load and unload parts when another pallet is being worked," says Hand. "We've been measuring the setup times for the past 10 months, to see how they compare. We don't have the compiled data just yet, but we're anticipating reductions of up to 85 percent. Most of the fixtures for the pallets we have machined easily in-house--in many cases the fixtures and pallets have been made fully interchangeable. The Midaco Micro Pallets have proven to be a reliable and very cost-effective answer to our particular challenges." Midaco Corp., www.rsleads.com/610tp-152
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|Publication:||Tooling & Production|
|Date:||Oct 1, 2006|
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