Compression springs mounted in the press help control the amount of pressure on different areas of the titanium blank, helping produce wrinkle- and dimple-free parts.

Twenty highly contoured titanium aircraft parts needed for repair and overhaul were drawn into shape in dies machined from laminated composite boards. In only 30 hr, Nor-Ral Plastics Inc., Canton, Ga., machined the complete die sets -- die, punch, and ring -- for both left and right-hand parts. The composite, called Ren Shape 5166, is a machinable polyurethane available in 4 or 2-in.-thick boards measuring 31.5 x 15 in. and 61 x 20 in., respectively. The machined dies are said to be mar-free, resistant to abrasion, and capable of handling the 9,500-psi force needed to shape the titanium blanks.

To machine the composite, Nor-Ral first attached the composite boards to 1-in.-thick aluminum base plates. Then they rough cut the die sets using a two-flute, flat-end hardened-steel router at 13,000 rpm and 150 ipm with a 0.1-in. depth of cut. Finishing was at 10,000 rpm and 100 ipm.

Laminated blocks of Ren Shape 5166 composite manufactured by Ciba Specialty Chemicals, Performance Polymers, East Lansing, Mich., were machined on a five-axis high-speed mill to make metal forming dies for a low-volume production run.

The die sets went into a 200-ton, single-action press along with 16 die-compression springs. According to Nor-Ral spokesman Brent Martin, the springs each had different compression factors. This controlled the amount of force on different areas of the 0.04-in.-thick titanium blank. Use of the springs helped draw the difficult 90* contour by controlling how the metal flowed in certain areas of the blank. This eliminated wrinkles, dimples, and bowing of the formed parts.

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