Original Date: 08/30/2004
Revision Date: 01/18/2007
Best Practice : Equipment Investment Strategy
Due to increasing customer demands for parts with smaller dimensional tolerances, TOMAK Precision decided to partner with its customers by making a capital investment in test equipment that improved its capability to accurately measure parts. This led directly to the development of a precision machining and lapping process that consistently produces ball pistons with roundness of 0.00005 inch or less.
TOMAK Precision has a long history of manufacturing hydraulic valve parts for the aerospace industry that require precision machining and grinding. Ball pistons are one of TOMAK Precision’s core products. Ball pistons have a spherical geometry that must be produced to roundness tolerances that meet customers’ requirements. Historically, customers required ball pistons that had 50 to 100 millionths sphericity. To test for roundness, TOMAK Precision tested samples with an Orthotest "ball" gage, which utilizes a "two point" check, accurate to 25 millionths sphericity. Until a few years ago, this test was sufficient for the manufacture of ball pistons.
TOMAK Precision wanted to grow its business and expand its customer base, and recognized that producing ball pistons using existing roundness tolerance criteria would not be acceptable to all of its customers. One company began to reject ball pistons that had 60 to 70 millionths sphericity. While working with the customer to resolve the discrepancies, TOMAK Precision learned that the customer was using a Mahr Federal Form Scan Machine, model MMQ6100, to measure the roundness of the ball pistons produced by TOMAK Precision (Figure 2-2). The set-up of the equipment allowed for single point contact of the test sample with accuracy to 0.000001 inch.
Committed to improving its partnerships, TOMAK Precision decided to "get on the same page" with its customers and made a capital investment in more accurate test equipment. This approach was consistent with the company’s long-term strategy to invest in new equipment each year. Ultimately, this strategy led to the purchase of the same type of equipment used by its customer at a cost of approximately $15,000. This decision not only provided TOMAK Precision with an increased test capability to measure precision machined parts, but it helped refine the current ball grinding and lapping process. This process now allows the company to consistently produce spheres with roundness tolerances of 50 millionths of sphericity or less. TOMAK Precision continues to research methods to further refine its precision machining and lapping process. This has resulted in the production of parts with as little as 20 to 30 millionths of sphericity and solidified its position in the marketplace as a sole source supplier of ball pistons for many aerospace companies.
Figure 2-2. Mahr Federal Form Scan Machine
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