ME2030: Manufacturing Processes – 1Metal Forming: Sheet Metal Operations S. Suryakumar, ME, IITH ME2230: Manufacturing Processes – 1 1 Sheet Metal Operations • Shearing • Punching • Bending • Deep drawing • Hydroforming S. Suryakumar, ME, IITH ME2230: Manufacturing Processes – 1 2 Shearing S. Suryakumar. ME. IITH ME2230: Manufacturing Processes – 1 3 . 125 mm to ±1. Suryakumar. The burr is a function of clearance between the punch and the die (which is nominally designed to be the material thickness).005 to ±0.125 mm to 6. • Material thickness ranges from 0.060 in).250 in).35 mm (0. IITH ME2230: Manufacturing Processes – 1 4 . ME.Shearing • Shearing is a process for cutting sheet metal to size out of a larger stock such as roll stock. which can be minimized to less than 10% of the material thickness. • The shearing process produces a shear edge burr.5 mm (±0. S. and the sharpness of the punch and the die.005 to 0. The dimensional tolerance ranges from ±0. Shears are used as the preliminary step in preparing stock for stamping processes. Suryakumar. ME.Dynamics S. IITH ME2230: Manufacturing Processes – 1 5 . ME. Suryakumar.Blanking / Punching S. IITH ME2230: Manufacturing Processes – 1 6 . Engineering Analysis: Clearance S. ME. Suryakumar. IITH ME2230: Manufacturing Processes – 1 7 . = Db. IITH ME2230: Manufacturing Processes – 1 8 .2c Hole punch dia. ME. = Db Hole die dia. = Db Blanking die dia. = Db+ 2c S.Clearance c = at c = clearance a = allowance t = thickness Blanking: Punch Blanking punch dia. Suryakumar. S. Suryakumar. IITH ME2230: Manufacturing Processes – 1 9 . ME. Suryakumar. ME. IITH ME2230: Manufacturing Processes – 1 10 .Clearance S. Force Required The force required for shearing is: F = S*t*L. ME. where S: shear strength of the sheet metal t: sheet thickness L: length of the cut edge The shear strength S can be estimated by: S = 0.7 * UTS. IITH ME2230: Manufacturing Processes – 1 11 . where UTS: the Ultimate Tensile Strength The above formula does not consider other factors such as friction S. Suryakumar. S.Example • A round disk of 150-mm diameter is to be blanked from a strip of 3.2-mm. and (b) blanking force. Determine (a) the appropriate punch and die diameters. half-hard cold rolled steel whose shear strength = 310 MPa. IITH ME2230: Manufacturing Processes – 1 12 . Suryakumar. ME. Sheet-metal Cutting Operations S. IITH ME2230: Manufacturing Processes – 1 13 . ME. Suryakumar. ME. (b) perforating. Suryakumar. (c) notching & seminotching S. IITH ME2230: Manufacturing Processes – 1 14 .(a) Slotting. ME. Suryakumar.Shaving and Fine Blanking S. IITH ME2230: Manufacturing Processes – 1 15 . During this process. Suryakumar. α = bend angle w = width of sheet R = bend radius S.Bending • Bending is defined as the straining of metal around a straight axis. “included” angle ME2230: Manufacturing Processes – 1 16 . IITH t = sheet thickness α′ = 180° .α. the metal on the inside of the neutral axis is compressed. while the metal on the outside of the neutral axis is stretched. ME. In V-bending the sheet metal blank is bent between a V-shaped punch and die. ME. Suryakumar.Types of Bending Two common bending methods are: – V-bending – Edge or wipe bending. IITH ME2230: Manufacturing Processes – 1 17 . The figure below shows a front view and isometric view of a V-bending setup with the arrows indicating the direction of the applied force: S. A pressure pad is used to apply a Force to hold the blank against the die.Types of Bending • Edge or wipe bending (conducted in lab) involves cantilever loading of the material. while the punch forces the workpiece to yield and bend over the edge of the die. The figure below clearly illustrates the edge (wipe)-bending setup with the arrows indicating the direction of the applied force (on the punch): S. Suryakumar. IITH ME2230: Manufacturing Processes – 1 18 . ME. ME. IITH ME2230: Manufacturing Processes – 1 19 . Suryakumar.Bending Analysis S. IITH ME2230: Manufacturing Processes – 1 20 .Bending Analysis S. ME. Suryakumar. Suryakumar.Bending Analysis Springback is defined as the increase in included angle of the bent part relative to the included angle of the forming tool after the tool is removed. ME. IITH ME2230: Manufacturing Processes – 1 21 . After springback: • The bend angle will decrease (the included angle will increase) • The bend radius will increase S. Suryakumar. Hemming. IITH ME2230: Manufacturing Processes – 1 22 . ME. Seaming.Flanging. and Curling S. Suryakumar.Deep Drawing S. ME. IITH ME2230: Manufacturing Processes – 1 23 . Suryakumar.S. IITH ME2230: Manufacturing Processes – 1 24 . ME. IITH ME2230: Manufacturing Processes – 1 25 .Hydroforming S. Suryakumar. ME. Suryakumar. IITH ME2230: Manufacturing Processes – 1 26 .Have a nice day! S. ME.