284 Modern Metalworking Copyright Goodheart-Willcox Co., Inc. 17.2.9 High Energy Rate Forming The introduction of super-tough alloys and the need to shape large aerospace and marine components brought about the development of nontraditional forming processes. When conventional means, such as presses and drop hammers, were used on super- tough alloys, the metals tended to regain their origi- nal shape, Figure 17-21. To avoid this tendency, known as springback, other techniques have been developed. One of these techniques is high energy rate forming or g HERF.F F Allegheny Ludlum Steel Corp. Figure 17-18. A diagram of the rotating die tube bending technique. A—Preparing the tube for bending. The filler material prevents the tube from collapsing during the bending operation. B—Steps in bending a tube. C—It is not necessary to fill the tube before bending if a reinforcing mandrel is used. Filling or packing before bending Filling with sand and tamping Wood plug at both ends Pressure Clampp Stock Plug Filling with wood's metal after applying a light oil film on interior surface, and solidifying same by applying cold water. A 1st position 2nd position Pressure 45° This block travels with the stock, thus eliminating damage to its surface. Stock B 3rd position Pressure C lam p Tube 90° Stock C Rotating die Held in fixed position Sliding block moves with work Mandrel bar Clamp Clamp C lam p Goodheart-Willcox Publisher Figure 17-19. Sequence followed for roll forming channel. Initial stock before rolling 1st pass 2nd pass 5th pass 6th pass Final pass Enlarged g view of formed stock 3rd pass 4th pass 12 6 Salvagnini America Inc. Figure 17-20. A bending machine with a brush worktable. Sheet metal blank Brushes support the sheet metal blank