Special Processing of Large and Small Aerospace Parts

Article From: Products Finishing,

Posted on: 9/1/1996

Large and small chromium-plated parts need special processing and inspection...

Diamond Chrome Plating, Inc. in Howell, Michigan, does not use automated plating lines. The sizes and intricate shapes of the parts plated callfor special handling, processing and inspection.

More than half of the work done is aerospace related, includingaircraft landing gear components, hydraulic servo components, engine management parts, actuators, pins and frame parts. The other half is divided among commercial hydraulics, piston rods, cylinders, artillery, crankshaft bearings, dies and molds.

According to Jack Beatty, general manager, the work done at Diamond Chrome Plating is labor intensive. Usually,selective plating is done on low-volume parts. All plating is manual, using no barrels. The company will not automate because parts require precision processing. Many of the parts have three different coatings on different areas,and somerequire asmany as 30 separateplating operations.

Diamond Chrome Plating maintains more than 20 hard chromium plating tanks capable of handling parts in excess of 30 ft and depths to 10 ft. An array of rectifiers, some capable of delivering more than 10,000 amps, are available for larger parts. Items weighing up to four tons can be processed.

Diamond Chrome is one of the two test sites in Michigan involved in a U.S. EPA Common Sense Initiative program run through the Industrial Technology Institute in Ann Arbor. The program is evaluating methods that existing platers can use to meet the new MACT standards without completely replacing ventilation systems. It appears that Diamond Chrome can meet the new standards by using fume suppressants in conjunction with its existing equipment and some work practice modifications. Work is continuing.

The plating company is proficient in three general processes: hard chrome, electroless nickel and vacuum cadmium. It generally plates electroless nickel on parts less than three feet long or one and a half feet in diameter.

The vacuum cadmium plating chamber handles pieces to approximately five ft long and two ft wide. Limits vary with part geometry. Vacuum cadmium is an engineering coating applied at thicknesses similar to electroplated cadmium (0.0002 to 0.0005 inch nominal). It is done in a vacuum chamber similar to those in traditional vacuum plating. Diamond Chrome also does low embrittlement electrolytic cadmium plating: LHE-cadmium and cadmium-titanium.

Other plating capabilities include precision dense chromium, sulfamate nickel and zinc nickel. Abrasive and glass bead blasting, polishing, welding, baking, passivating, cleaning and degreasing as required to prepare parts for plating are some of the company's support operations.

"There are two types of plating performed: precision plating to size for immediate use, and overplating (heavy plating) to beground to finish. In both cases, it is necessary to know the plating thickness. Precision plated parts must meet tolerances called out by the customer. Overplated parts must have sufficient chromium to clean-up in grinding without causing lost grinding time due to excessive plating build-up," said Mr. Beatty. Hand-held CGX coating thickness measurement gages solved the company's problem.

Eleven gages are assigned to working leaders in the chromium and cadmium plating departments, as well as the Final Inspection department. Gages also haveright angle probesfor measuring in holes. This has saved labor costs, since poor quality products are not shipped to customers who end up returning them for rework.

Diamond ChromePlating startedoperation in January 1954 in a small 7,500-sq-ft building in the center of Howell, Michigan, east of Lansing and west of Detroit. The company started with three employees, one plating tank and a station wagon.

Five expansions over the years have resulted in its present 35,000-sq-ft operation that fills a city block and houses offices, laboratory, tool room, storage and processing areas. Approximately 80 employees staff a 24-hr a day operation. Its trucks provide pickup and delivery along the I-94 expressway corridor.

The company's plating processes are approved by mostaircraft manufacturers. Many of the company's customers supply components to Allied Signal, Boeing, General Dynamics, General Electric, BF Goodrich Landing Gear Division, Hamilton Standard, Menasco, McDonnell Douglas, Messier-Dowty, Pratt and Whitney, and Sikorsky. With end users like these, precision plating is paramount

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