| 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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