Original Date: 08/30/2004
Revision Date: 01/18/2007
Best Practice : Ball Grinding
In order to meet the demands of its customers in the aerospace industry, TOMAK Precision developed a precision machining and lapping process that consistently produces ball pistons with roundness of 0.00005 inch or less and achieves a surface finish of four micro inches or lower.
Since 1953, TOMAK Precision has had a long history of manufacturing aerospace parts requiring precision machining and grinding. Over the past few decades, there has been an increasing demand for higher precision parts, especially in the aerospace industry, where the production of hydraulic valves has necessitated the manufacture of parts with closer dimensional tolerances. TOMAK Precision’s largest niche in the marketplace is in the manufacture of parts containing spherical geometries. Precision machining and grinding operations produce an estimated 50,000 ball pistons or piston pumps annually as shown in Figure 2-1. The ball pistons typically range in size from .10 inch to 1.0 inch in diameter. Until a few years ago, ball-grinding operations using conventional radius grinder equipment could, at best, produce spheres with roundness tolerances of 0.0001 inch. To achieve a high quality surface finish, an extensive amount of hand polishing was required to remove finish chatters.
To remain competitive in the marketplace, TOMAK Precision needed to consistently produce high quality precision parts, and developed a manufacturing process that produced spheres with smaller roundness tolerances and an improved surface finish. TOMAK Precision achieved this by making modifications to standard grinding methods being used in industry. Although it is often required to perform precision machining and grinding using materials with high toughness to produce complex geometries, TOMAK Precision now manufactures spherical parts with surface finishes to two micro inches, and 50 millionths of sphericity. The company employs the MIL-STD quality system to all levels of production and uses state-of-the-art test units to ensure quality monitoring and inspection.
As a result of its efforts, TOMAK Precision now produces hydraulic valve parts that exceed customers’ requirements, and is one of only a few companies that have the capability to manufacture high precision and high quality ball pistons for a relatively low cost.
Figure 2-1. Ball Piston
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