Originally Published EMDM November 2005
EQUIPMENT NEWS
Diamond suspension finishes small bores and wires to single-micron tolerance
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Single tubular parts and wires or batch quantities can be finished with high precision by means of equipment that employs a rotating spindle and a suspension containing diamond particles. The machinery employs a process developed by Schläfli Engineering Ltd. (Büren an der Aare, Switzerland) called wire-DSM manufacturing after its basis in diamond-suspension machining. Parts processed may have outside diameters of 0.5 to 8 mm and lengths to 890 mm or bores of 0.05 to 5 mm and lengths to 300 mm. The equipment can be used for diameter definition, bore sizing, imparting cylindrical concentricity to the bore, and surface finishing; it does not drill holes, but rather polishes them to the exacting tolerances and finishes desired.
Depending on material hardness, material makeup, and throughput aims, achievable tolerances are as high as ±1 µm in diameter, ±0.5 µm in roundness, ±0.5 µm in concentricity, and 0.025 Ra for surface finish. Soft to very hard and brittle materials may be machined, including such challenges as tungsten carbide, ceramic, ruby, and polycrystalline diamond. The process accurately and efficiently removes stock amounts ranging from 5 to 150 µm over the entire length to be machined. Special fixtures allow tubular parts with nonstandard outside diameters up to 20 mm and overall length of 300 mm to be clamped.
Bore sizing involves the use of a high-precision wire 10 to 20 m long around which the part is rotated. The machines employed can maintain process stability and control throughout part production. Parts can be cast in the DSM machine’s arbor before placement in the machine for sizing in order to prevent tube walls from expanding while machining takes place.
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