Using DIAbide on Hard-to-Machine Materials

Metal Matrix Composites (MMCs)


Diamond tools make it practical to machine Metal Matrix Composites The Advanced Materials and Manufacturing Technologies Group of MSE Technology Applications Inc. is involved in the production of MMC materials and the fabrication of parts from MMCs. A metal matrix composite typically uses aluminum as a binding material and it is strengthened with the addition of carbide powders of various combinations and concentrations. Machining a metal matrix material is similar to machining a grinding wheel. The MSE process can produce functionally gradient particulate loading in the metal matrix ranging from 20% to 55%. The particulate is very abrasive and cannot be machined with conventional carbide tools. MSE uses sp3 diamond-coated carbide inserts, end mills and drills to fabricate brake rotors and other MMC parts. An example is an MMC brake rotor (8-inch OD, 3-inch ID, 0.200 inch thickness) with 8 mounting holes and 20 cooling holes. According to Pat McCarthy, Project Manager for MMCs, “over 200 holes were drilled in these brake rotors with one sp3 diamond drill, whereas an uncoated carbide drill could not complete drilling a single hole.” MSE has achieved higher productivity and cost savings over carbide tooling. More important, sp3 diamond tools allow MSE to fabricate parts and incorporate features that are not possible using carbide tools.		MMC brake rotor Click on image for larger view.

Manufacturing motorcycle MMC brake rotors using diamond tools Swan Metal Composites in Woodinville WA manufactures front brake rotor assemblies for sport/racing motorcycles. The outer friction ring of the rotor is manufactured from a functionally gradient Al/SiC Metal Matrix Composite material. Use of the MMC material for the friction ring reduces the weight of the finished assembly by approximately 50% relative to OE and ferrous-based assemblies. For sport/racing motorcycles this translates to a tremendous improvement in handling through reduction of both unsprung and rotational mass. Swan Composites currently manufactures rotors for late model Ducati, Suzuki and Buell motorcycles. Tom Chamlee, President of Swan, chose sp3 SPG-422T-20 DIAbide inserts for rough and finish turning. The face and ID turning operations are interrupted cuts, adding to the demand on tool performance. Roughing: in facing and OD operations, a single corner of the SPG-422T-20 insert yields approximately 2.5 parts, or 10 parts per insert. The ID operation is conducted on the full edge of the insert, between two previously failed corners, and yields approximately 18 parts per edge, or approximately 60 parts per insert. This ability to extend the useful life of the tool illustrates the advantage of sp3 CVD tools in providing a diamond surface over the entire insert edge. Finishing: in facing, OD and chamfering operations a single corner of an SPG- 422T-20 insert lasts for approximately 20 parts. Milling: all milling is done in periphery-type operations. sp3 DIAbide endmills are yielding approximately 7-10 parts per flute length depth. These operations currently represent the largest portion of consumable tool usage. sp3 is working closely with Swan to develop tools that will allow increased feed rates coupled with improved durability. The goal is to improve Swan Metal Composites’ bottom line.		MMC raw casting
		Finished brake rotor Click on image for larger view.

Tool performance, machining MMCs and high-silicon aluminum.

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