Superabrasives speed machining of sintered sprockets

Superabrasives speed machining of sintered sprockets

Holroyd Edgetek machines sintered sprockets.


Chain drives and sprockets that provide longer intervals between servicing have replaced rubber belts and pulleys on most modern automobile engines. The sprockets, as well as automotive gears, are manufactured by a sintering process that gives the parts a homogeneous and stress-free composition; however, sintered materials are difficult to machine and cannot be conventionally turned. CNC controlled Holroyd Edgetek machines (www.holroyd.com) use a superabrasive turning system (SAT) employing cubic boron nitride wheels at surface speeds of up to 656.2 ft./sec., in what the company refers to as a high-efficiency deep grinding (HEDG) technique. According to Holroyd sales director Paul Hannah, "The use of an Edgetek SAT machine enabled one automotive manufacturer to machine powdered metal timing sprockets and reduce tooling costs by 75% as a result of the machine's ability to perform interrupted cuts successfully." In another automotive application, a sintered triple drive sprocket was extremely difficult to turn conventionally because of the requirement for interrupted cuts. Previously, the customer was using tooling with CBN inserts that cost $50 to $75 each. These were turning each sprocket groove in 1 minute 10 seconds, but were lasting only a maximum of 50 components, resulting in a consumable cost per part of about $1. Machining the same component on an Edgetek SAT machine reduced the cycle time to 22 seconds. Moreover, set-up time was reduced and throughput was increased to 15,000 components per CBN wheel, each of which costs $500. At that price, the consumable cost per part was cut to 3.3 cents per component. The company says its Edgetek machines can machine rotors and impellers, medical instruments, hand tools, air foils, nozzle guides, airframe actuation components, ducting supports, mechanical seals, and other components made from ceramics, nickel, tool steel, Waspalloy, Inconel, Hastelloy and Stellite.

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