Complex forms possible: several processes may be combined to produce one component, or a series of operations used to progressively form the part. • Working envelope of machine and uniform thickness of sheet can restrict design options.
124 Chapter 4
• No inserts or re-entrant angles. • Draft angles of 0.25° may be required. • Minimum bend radii are a function of material and sheet thickness, but typically four times the sheet thickness. • Keep radii as large as possible, particularly if parallel with grain of material. • Square or rectangular boxes limited by sharpness of corner detail required. • Minimum sheet thickness = 0.1 mm. • Maximum sheet thickness: deep drawing = 12 mm, bending = 25 mm, roll/stretch forming = 6 mm. • Sizes range from 2 to 600 mm diameter for deep drawing; 10 mm to 1.5 m width for roll forming; 2 mm to 3.6 m width for bending.