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Technology update
Composite dies for titanium part manufacture
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Nor-Ral machined blocks made from Ciba's Ren Shape 5166 material are machined to make the die for a metal aircraft part.
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A material developed by Ciba Specialty Chemicals has enabled aircraft part manufacturers to quickly and economically machine metal-forming dies used in part production. Nor-Ral Plastics, Inc. used Ciba's Ren Shape 5166 material for constructing composite dies. Nor-Ral was able to cut the die, punch, and ring for both left- and right-hand parts using its five-axis CNC mill in about 30 h. The die set was then installed in a 200-t, single-action press, which was used to form highly contoured titanium aircraft components.
To begin part manufacture, Nor-Ral took customer-supplied parts, mounted them on boards, and probed them to measure surface dimensions. This information was imported into CAD software and used to develop the part designs required for CNC machining.
To build the die sets for the titanium parts, workers bonded pieces of Ren Shape 5166 board using Ciba's Ren-Weld 100 epoxy adhesive, building up machinable blocks of the desired sizes. The Ren Shape 5166 metal-forming stock comes in boards measuring 31.5 x 15.8 x 4 in or 61 x 20 x 2 in. After the adhesive cured for 24 h, the blocks were mounted on 1-in aluminum base plates, which were first abraded with a grinder. A layer of 10-oz fiberglass cloth was laid down and wetted with Ren-Weld 100 adhesive.
While the epoxy was still tacky, dies and punches were bonded to the plates and placed in a high-speed mill and cut to size. Nor-Ral technicians rough cut the composite board stock using a two-flute, flat-end hardened steel router at 13,000 rpm and 150 in/min with a 0.100-in depth cut. The board was finished at 10,000 rpm and 100 in/min with a 0.020-in step-over.
Nor-Ral machined blocks made from Ciba's Ren Shape 5166 material are machined to make the die for a metal aircraft part.
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To prepare the press for operation, the punch, die, and clamp ring were installed along with 16 die-compression springs that were sandwiched between the 1-in base plates around the perimeter of the die. A 0.040-in-thick titanium blank was then loaded into the press, which brought down the die to form the part.
"It was difficult to draw the 90° contour on this particular part," explained Brent Martin, Nor-Ral General Manager. "To solve the problem, we used die springs with varying compression factors. The springs allowed us to control the amount of pressure exerted on different areas of the titanium blank, ensuring metal flow in the desired directions and avoiding formation of wrinkles, dimples, and bows."
Frank Bokulich
Aerospace Engineering May 2000
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