Original Date: 08/30/2004
Revision Date: 01/18/2007
Best Practice : Hard Turning
TOMAK Precision is a principal supplier of hydraulic valve ball pistons to the aerospace industry. To improve the quality of the ball pistons, while concurrently increasing its profit margin, TOMAK Precision developed a Hard Turning process that replaced conventional grinding methods.
For more than 48 years, TOMAK Precision has manufactured parts using conventional grinding equipment. As a principle supplier of hydraulic valve ball pistons to the aerospace industry, it also developed a capability to perform precision machining and lapping. TOMAK Precision has always prided itself on maintaining strong relationships with its customers and has continuously sought to improve the quality of its products. To meet its customers’ needs, TOMAK Precision invested in machining and test equipment, and developed new manufacturing processes that consistently produced higher quality ball pistons. TOMAK Precision also recognized that it was important to remain competitive and expand in the marketplace. The company needed to find ways to reduce its operating costs and increase profit margin.
To meet its goals, TOMAK Precision re-examined its manufacturing process and identified areas that had potential for cost savings. Ball pistons require a material that can be heat treated to produce a hardened surface. Until a few years ago, TOMAK Precision used conventional grinders to produce hardened ball pistons that met acceptable standards and were cost effective. The manufacture of ball pistons using the old grinding method involved six handling operations, which included grinding a piston groove, neck, and ball, chamfering the top and bottom of the piston, and then tumbling it to break the edges. To reduce its operating costs, TOMAK Precision developed a process that allowed the ball pistons to be turned rather than ground. Although the company recognized the advantages of using Computer Numerically Controlled (CNC) equipment to reduce the number of handling operations and cycle time, the material could not be “hard turned” due to limitations in the tooling. TOMAK Precision partnered with one of its tooling vendors to develop inserts (tooling) that could be used on a CNC machine for hard turning the ball pistons. After experimenting for approximately one year, TOMAK Precision took advantage of improvements in carbide technology. The company devised a tooling set-up that allowed the CNC machine to use its vendor's inserts, even though these inserts were not advertised for use in applications involving the turning of hard materials (Rockwell hardness of 58C or greater). Convinced that it could make the process work, TOMAK Precision purchased two high precision lathes that were dedicated to hard turning the ball pistons.
By using a Hard Turning process, TOMAK Precision significantly reduced its cycle times and operating costs. For a lot of 1,000 ball pistons, TOMAK Precision realized a reduction of almost 35% in work hours and 25% in costs. Hard Turning yielded numerous benefits including fewer machines required, less time in inspection, less handling, lower operating costs, and reduced cost of rework. As a result of its efforts to partner with its vendors and improve its manufacturing processes, TOMAK Precision improved the quality of its product and built its profit margin. Additionally, the company changed some of its other grinding processes to Hard Turning, which led to more consistent part production and greater flexibility in adding CNC machinists to its workforce.
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