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Sheet metal forming processes Erdi Karaçal Mechanical Engineer University of Gaziantep

The document describes various sheet metal forming processes and provides characteristics of each. It discusses roll forming for parts with complex cross-sections and high production rates but high tooling costs. Stretch forming is described as suitable for low quantity production but with high labor costs and tooling/equipment costs depending on part size. Drawing is outlined as having high production rates but also high tooling and equipment costs.

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Sheet-Metal Forming Processes Process Characteristics Roll forming Long parts with constant complex cross-sections; good surface finish; high production rates; high tooling costs. Stretch form-ing Large parts with shallow contours; suitable for low-quantity production; high labor costs; tooling and equipment costs depend on part size. Drawing Shallow or deep parts with relatively simple shapes; high production rates; high tooling and equipment costs. Stamping Includes a variety of operations, such as punching, blanking, embossing, bending, flanging, and coining; simple or complex shapes formed at high production rates; tooling and equipment costs can be high, but labor costs are low. Rubber-pad forming Drawing and embossing of simple or complex shapes; sheet surface protected by rubber membranes; flexibility of operation; low tooling costs. Spinning Small or large axisymmetric parts; good surface finish; low tooling costs, but labor costs can be high unless operations are automated. Superplastic forming Complex shapes, fine detail, and close tolerances; forming times are long, and hence production rates are low; parts not suitable for high-temperature use. Peen forming Shallow contours on large sheets; flexibility of operation; equipment costs can be high; process is also used for straightening parts. Explosive forming Very large sheets with relatively complex shapes, although usually axisym-metric; low tooling costs, but high labor costs; suitable for low-quantity production; long cycle times. Magnetic-pulse forming Shallow forming, bulging, and embossing operations on relatively low-strength sheets; most suitable for tubular shapes; high production rates; requires special tooling. TABLE 7.1 General characteristics of sheet-metal forming processes. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7
Localized Necking F E1 E2 E2 = E3 G/2 (a) (b) (c) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 E1 2F~110° Diffuse neck Localized neck (d) FIGURE 7.1 (a) Localized necking in a sheet-metal specimen under tension. (b) Determination of the angle of neck from the Mohr's circle for strain. (c) Schematic illustrations for diffuse and localized necking, respectively. (d) Localized necking in an aluminum strip in tension; note the double neck. Source: S. Kalpakjian.
Lueders Bands Yupper Ylower Stress 0 Strain (a) Yield-point elongation Yielded metal Lueder!s band Unyielded metal Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 (b) (c) FIGURE 7.2 (a) Yield-point elongation and Lueders bands in tensile testing. (b) Lueder's bands in annealed low-carbon steel sheet. (c) Stretcher strains at the bottom of a steel can for common household products. Source: (b) Courtesy of Caterpillar Inc.
Stress-Corrosion Cracking FIGURE 7.3 Stress-corrosion cracking in a deep-drawn brass part for a light fixture. The cracks have developed over a period of time. Brass and 300-series austenitic stainless steels are particularly susceptible to stress-corrosion Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 cracking.
Shearing Process Punch Sheet Die A B D C c Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 T F Punch Slug Sheet Die Fracture surface Penetration Clearance FIGURE 7.4 Schematic illustration of the shearing process with a punch and die, indicating important process variables.
Hole & Slug Fracture angle Breakout dimension (a) Penetration depth Rollover depth Burnish depth Burr height Fracture depth Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Sheet thickness Burnish dimension Flattened portion under the punch Burr height Dishing Burr Rough surface Smooth surface (burnished) Ideal slug A C B D (b) FIGURE 7.5 Characteristic features of (a) a punched hole and (b) the punched slug. Note that the slug has a different scale than the hole.
Shearing Mechanics Die 1. 2. 3. 120 (a) (b) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Punch Clearance, c 120 140 (HV) 160 140 200 220 180 140 140 160 180 200 180 160 200 120 120 160 200 180 FIGURE 7.6 a) Effect of clearance, c, on the deformation zone in shearing. Note that, as clearance increases, the material tends to be pulled into the die, rather than being sheared. (b) Microhardness (HV) contours for a 6.4-mm (0.25-in.) thick AISI 1020 hot-rolled steel in the sheared region. Source: After H.P. Weaver and K.J. Weinmann. Force Penetration 0 FIGURE 7.7 Typical punch force vs. penetration curve in shearing. The area under the curve is the work done in shearing. The shape of the curve depends on processing parameters and material properties. Maximum punch force: Fmax = 0.7(UTS)tL
Shearing Operations Discarded Punching Blanking Perforating (a) (b) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Parting Lancing Notching Slitting FIGURE 7.8 (a) Punching and blanking. (b) Examples of shearing operations on sheet metal.
Fine Blanking Blanking punch Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 (a) (b) Upper pressure pad Stinger (impingement ring) Sheet metal Punch Slug Sheet Die Upper pressure pad Clearance Fracture surface Lower pressure cushion Blanking die Lower pressure cushion Support FIGURE 7.9 (a) Comparison of sheared edges by conventional (left) and fine-blanking (right) techniques. (b) Schematic illustration of a setup for fine blanking. Source: Feintool International Holding.
Rotary Shearing FIGURE 7.10 Slitting with rotary blades, a process similar to opening cans. Driven cutter Workpiece Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Clearance Ilding cutter
Shaving & Beveled Tooling FIGURE 7.11 Schematic illustration of shaving on a sheared edge. (a) Shaving a sheared edge. (b) Shearing and shaving combined in one punch stroke. Sheared edge (a) (b) Double-bevel shear Convex shear Blank thickness (a) (b) (c) (d) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Sheet Die Sheet Die Clearance FIGURE 7.12 Examples of the use of shear angles on punches and dies. Compare these designs with that for a common paper punch. Shear angle Punch Die Bevel shear Punch Die
Progressive Die Piercing punch Stripper (a) (b) Ram Blanking punch Pilot Scrap Die Stop Finished washer FIGURE 7.13 (a) Schematic illustration of producing a washer in a progressive die. (b) Forming of the top piece of a common aerosol spray can in a progressive die. Note that the part is attached to the strip until the last operation is completed. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Strip Scrap Strip First operation Slug Part
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Tailor-Welded Blanks FIGURE 7.14 Examples of laser-welded and stamped automotive body components. Source: After M. Geiger and T. Nakagawa. (a) (b) Blanking; laser cutting Laser welding Stamping Legend g 60/60 (45/45) m 20/20 Hot-galvanized alloy steel sheet. Zinc amount: 60/60 (45/45) g/m2. Double-layered iron-zinc alloy electroplated steel sheet. Zinc amount 20/20 g/m2. 1 mm 1 mm m 20/20 0.8 mm g 45/45 g 60/60 1 mm g 45/45 1 mm g 45/45 0.7 mm 1.5 mm 0.7 mm 0.8 mm 1.25 mm Floor plate 2.0 mm Motor-compartment side rail 0.7 mm 0.7 mm 1.5 mm Quarter inner with integrated shock-absorber support Fender with integrated reinforcement Girder 1.5 mm 2.0 mm Shock-absorber support 2.5 mm 1.5 mm 0.7 mm 1.5 mm 0.7 mm
Bending & Minim Bend Radius Length of bend, L Bend radius (R) Thickness (t ) (a) (b) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 7.5 (a) Bending terminology. Note that the bend radius is measured to the inner surface of the bend, and that the length of the bend is the width of the sheet. (b) Relationship between the ratio of bend-radius to sheet-thickness and tensile reduction of area for a variety of materials. Note that sheet metal with a reduction of area of about 50% can be bent and flattened over itself without cracking, similar to folding paper. Source: After J. Datsko and C.T. Yang. 20 15 10 5 R t = (60/ r ) - 1 0 0 10 20 30 40 50 60 70 Tensile reduction of area (%) T Bend allowance, Lb Bend angle, A A Bend radius, R Bevel angle Setback Material Condition Material Soft Hard Aluminum alloys 0 6t Beryllium copper 0 4t Brass, low leaded 0 2t Magnesium 5t 13t Steels austenitic stainless 0.5t 6t low carbon, low alloy, and HSLA 0.5t 4t Titanium 0.7t 3t Titanium alloys 2.6t 4t TABLE 7.2 Minimum bend radii for various materials at room temperature.
Bending Mechanics FIGURE 7.16 The effect of length of bend and edge condition on the ratio of bend radius to thickness for 7075-T aluminum sheet. Source: After G. Sachs and G. Espey. Cracks No cracks Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 4 3 2 1 0 Bend radius Thickness 1 2 4 8 16 Length of bend Thickness Plane stress Plane strain Rough edge Smooth edge Rolling direction Elongated inclusions (stringers) Rolling direction (a) (b) (c) FIGURE 7.17 (a) and (b) The effect of elongated inclusions (stringers) on cracking in sheets as a function of the direction of bending with respect to the original rolling direction. This example shows the importance of orienting parts cut from sheet to maximize bendability. (c) Cracks on the outer radius of an aluminum strip bent to an angle of 90°; compare this part with that shown in (a).
Springback T FIGURE 7.19 Springback factor, Ks, for various materials: (a) 2024-0 and 7075-0 aluminum; (b) austenitic stainless steels; (c) 2024-T aluminum; (d) 1/4-hard austenitic stainless steels; and (e) 1/2- hard to full-hard austenitic stainless steels. A factor of Ks =1 indicates that there is no springback. Source: After G. Sachs. After Ri Rf Before A Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Af Ai Af FIGURE 7.18 Terminology for springback in bending. Note that the bend angle has become smaller. There are situations whereby the angle becomes larger, called negative springback (see Fig. 7.20). 1.0 0.9 0.8 0.7 0.6 0.5 s) Springback factor (K a b c d e 1 5 10 20 R/T No springback Increasing springback Springback factor: Ks = αf αi = (2Ri/t)+1 (2Rf/t)+1 Springback estimation: Ri Rf = 4 ! RiY Et "3 −3 ! RiY Et " +1
Negative Springback Punch Wire specimen Die (a) (b) (c) (d) FIGURE 7.20 Schematic illustration of the stages in bending round wire in a V-die. This type of bending can lead to negative springback, which does not occur in air bending (shown in Fig. 7.24a). Source: After K.S. Turke and S. Kalpakjian. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7
Springback Compensation , 90° , 90° 90° 90° Wb (a) (b) (c) (d) Rocker Sheet Die 1. 3. FIGURE 7.21 Methods of reducing or eliminating springback in bending operations. Source: After V. Cupka, T. Nakagawa, and H. Tyamoto. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 2. (e) P counter
Die-Bending Operations (a) V die (b) Wiping die W Punch Die FIGURE 7.22 Common die-bending operations, showing the die-opening dimension W, used in calculating bending forces, as shown in Eq. (7.11). Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 W Bending force: Fmax = k(UTS)Lt2 W
Press Brake Operations Main Flywheel gear Main gear Ram FIGURE 7.23 (a) through (e) Schematic illustrations of various bending operations in a press brake. (f) Schematic illustration of a press brake. Source: Courtesy of Verson Allsteel Company. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Die holder (f) Connections Motor Clutch and brake unit Side housing Floor line Crown Bed Channel forming (a) Joggle (b) Hemming (flattening) (c) Two-stage lock seam (d) Offset forming (e)
Bending Operations (a) (b) Adjustable roll 1. 2. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 7.25 (a) Bead forming with a single die. (b)-(d) Bead forming with two dies in a press brake. (c) Bending in a 4-slide machine Roll bending Driven rolls (d) Sheet Polyurethane roll Punch Die Air bending FIGURE 7.24 Examples of various bending operations. Formed bead Die (a) (b) (c) (d)
Flanging Operations Straight flange Joggled flange Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Piercing punch Spring-loaded stripper Sheet Die block or die button Spring-loaded pressure bushing FIGURE 7.26 Illustrations of various flanging operations. (a) Flanges formed on flat sheet. (b) Dimpling. (c) Piercing sheet metal with a punch to form a circular flange. In this operation, a hole does not have to be prepunched; note, however, the rough edges along the circumference of the flange. (d) Flanging of a tube; note the thinning of the periphery of the flange, due to its diametral expansion. (a) (c) (b) (d) Stretch flange Shrink flange Reverse flange Slug Piercing punch (retracted) Stripper plate Sheet Die Before After Flange Tube
Roll-Forming (a) (b) FIGURE 7.27 (a) The roll-forming operation, showing the stages in roll forming of a structural shape. (b) Examples of roll-formed cross-sections. Source: Courtesy of Sharon Custom Metal Forming, Inc. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7
Bending and Forming Tubes Form block (fixed) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 7.28 Methods of bending tubes. Using internal mandrels, or filling tubes with particulate materials such as sand, prevents the tubes from collapsing during bending. Solid rods and structural shapes are also bent by these techniques. Mandrels for tube bending (d) Stretch bending (a) Draw bending (b) Compression bending (c) Plug Balls Laminated Cable Clamp Form block (rotating) Pressure bar Chuck Workpiece Chuck Form block (fixed) Wiper shoe Clamp FIGURE 7.29 A method of forming a tube with sharp angles, using an axial compressive force. Compressive stresses are beneficial in forming operations because they delay fracture. Note that the tube is supported internally with rubber or fluid to avoid collapsing during forming. Source: After J.L. Remmerswaal and A. Verkaik. Die Punch Tube Rubber or fluid Stops Die Punch 1. 2.
Stretch-Forming Workpiece Tool Stretch gripper Hydraulic stretching unit Turntable FIGURE 7.30 (a) Schematic illustration of a stretch-forming operation. Aluminum skins for aircraft can be made by this process. Source: Cyril Bath Co. (b) Stretch forming in a hydraulic press. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Crosshead Ram Upper tool Clamping fixture Workpiece Lower tool Bed 1. 2. 3. (b) Stretching (a) Table-mounted gripper Adjustable slide
Bulging Die FIGURE 7.32 (a) Bulging of a tubular part with a flexible plug. Water pitchers can be made by this method. (b) Production of fittings for plumbing by expanding tubular blanks with internal pressure; the bottom of the piece is then punched out to produce a “T” section. Source: After J.A. Schey. (c) Sequence involved in manufacturing of a metal bellows. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 (b) (a) (c) Before After Ring Punch Knockout rod Rubber plug Die insert Two-piece die (hinged) Fluid Fluid Workpiece Bulged tube Compressed tube
Forming with a Rubber Pad (a) (b) (c) Metal punch Blank Polyurethane pad FIGURE 7.33 Examples of bending and embossing sheet metal with a metal punch and a flexible pad serving as the female die. Source: Polyurethane Products Corporation. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7
Sheet Hydroforming Pressure-control valve Rubber diaphragam FIGURE 7.34 The principle of the hydroform process, also called fluid forming. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Draw ring Punch Blank Forming cavity (oil filled) 1. 2. 3. 4. Part
Tube Hydroforming Die holder plate (a) (b) FIGURE 7.35 (a) Schematic illustration of the tube hydroforming process. (b) Example of tube hydroformed parts. Automotive exhaust and structural components, bicycle frames, and hydraulic and pneumatic fittings can be produced through tube hydroforming. Source: Schuler GmBH. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Horizontal cylinder Cylinder holder bracket Die holder plate Slide plate Centering Bed plate Hydroformed part Top die Seal punch Bottom die
Spinning (a) Mandrel FIGURE 7.36 Schematic illustration of spinning processes: (a) conventional spinning, and (b) shear spinning. Note that in shear spinning, the diameter of the spun part, unlike in conventional spinning, is the same as that of the blank. The quantity f is the feed (in mm/rev or in./rev). Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Blank Roller Cone to t f A (b) Tool Mandrel Blank FIGURE 7.37 Typical shapes produced by the conventional spinning process. Circular marks on the external surfaces of components usually indicate that the parts have been made by spinning, such as aluminum kitchen utensils and light reflectors.
Shear Spinning to tf Mandrel t FIGURE 7.38 Schematic illustration of a shear spinnability test. Note that as the roller advances, the spun part thickness is reduced. The reduction in thickness at fracture is called the maximum spinning reduction per pass. Source: After R.L. Kegg. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 to Blank ! Spun piece Flange Roller Tensile reduction of area (%) 0 10 20 30 40 50 60 70 80 100 80 60 40 20 0 Tube spinning Shear spinning FIGURE 7.39 Experimental data showing the relationship between maximum spinning reduction per pass and the tensile reduction of area of the original material. See also Fig. 7.15. Source: S. Kalpakjian. Maximum spinning reduction per pass (%) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 True strain at fracture in tension (Pf)
Tube Spinning FIGURE 7.40 Examples of (a) external and (b) internal tube spinning, and the process variables involved. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 (a) (b) External Mandrel Roller Forward Workpiece f to t Backward f f Die f Internal Ft
Incremental Sheet-Metal Forming Clamp Blank Rotating tool (a) (b) FIGURE 7.41 (a) Illustration of an incremental forming operation. Note that no mandrel is used, and that the final part shape depends on the path of the rotating tool. (b) An automotive headlight reflector produced through CNC incremental forming. Note that the part does not have to be axisymmetric. Source: After J. Jesweit. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7
Explosive Water level Ground level Workpiece Hold-down ring Die Vacuum line Tank Water Air Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Explosive Forming FIGURE 7.43 Effect of the standoff distance and type of energy-transmitting medium on the peak pressure obtained using 1.8 kg (4 lb) of TNT. The pressure-transmitting medium should have a high density and low compressibility. In practice, water is a commonly used medium. Standoff FIGURE 7.42 Schematic illustration of the explosive forming process. Although explosives are typically used for destructive purposes, their energy can be controlled and employed in forming large parts that would otherwise be difficult or expensive to produce by other methods. 60 50 40 30 20 10 0 Peak pressure (psi s 103) m 0 0.5 1 1.5 400 300 200 100 0 MPa 0 1 2 3 4 5 Standoff (ft) Pressure generated: p = K ! !3 W R a
Electrohydraulic and Magnetic-Pulse Forming Switch Switch Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 7.44 Schematic illustration of the electrohydraulic forming process. Electrodes Water Clamp Sheet Die Capacitor bank Charger FIGURE 7.45 (a) Schematic illustration of the magnetic-pulse forming process. The part is formed without physical contact with any object, and (b) aluminum tube collapsed over a hexagonal plug by the magnetic-pulse forming process. Coil (a) (b) CL Coil current Eddy current Tube After forming Mandrel Before
Superplastic Forming Mold Stop-off Clamp FIGURE 7.46 Two types of structures made by combining diffusion bonding and superplastic forming of sheet metal. Such structures have a high stiffness-to-weight ratio. Source: Rockwell Automation, Inc. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Mold Before After Product (a) (b)
Peen-Forming FIGURE 7.47 Schematic illustration of a peen forming machine to shape a large sheet-metal part, such as an aircraft-skin panel. Note that the sheet is stationary and the peening head travels along its length. Source: Metal Improvement Company. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Traversing gantry machine Stationary workpiece Track Track
Honeycomb Structures Adhesive FIGURE 7.48 Methods of making honeycomb structures: (a) expansion process, and (b) corrugation process; (c) assembling a honeycomb structure into a laminate. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 (b) Roll Corrugated block Corrugated panel Corrugated Corrugating sheet rolls (a) Roll Sheet Block Expanded panel Slice (c) Adhesive impregnated scrim cloth (optional) Face sheet Expanded honeycomb core Face sheet
Deep-Drawing Punch Blankholder force Blankholder Blank Die (draw ring) Do Pressure plate FIGURE 7.49 (a) Schematic illustration of the deep drawing process on a circular sheet-metal blank. The stripper ring facilitates the removal of the formed cup from the punch. (b) Variables in deep drawing of a cylindrical cup. Note that only the punch force in this illustration is a dependent variable; all others are independent variables, including the blankholder force. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Rd (a) (b) Dp T F c Rp Before After Punch Blank holder Blank Blank Drawn cup Die Spring stripper ring
Deformation in Flange and Wall (a) (b) FIGURE 7.50 Deformation of elements in (a) the flange and (b) the cup wall in deep drawing of a cylindrical cup. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 B A
Pure Drawing vs. Pure Stretching A (a) (b) (c) FIGURE 7.51 Examples of (a) pure drawing and (b) pure stretching; the bead prevents the sheet metal from flowing freely into the die cavity. (c) Unsupported wall and possibility of wrinkling of a sheet in drawing. Source: After W.F. Hosford and R.M. Caddell. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Unsupported wall Punch Blankholder force Die Die A! Blankholder Punch Die Deforming area Failure Bead Deforming area Failure
Draw Beads Metal Flow Draw bead Die Bead Original blank edge FIGURE 7.52 (a) Schematic illustration of a draw bead. (b) Metal flow during drawing of a box-shaped part, using beads to control the movement of the material. (c) Deformation of circular grids in drawing. (See Section 7.7.) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Bead Bend-and-straighten Deep draw Blank edge after drawing Bead CL CL Zero minor strain (a) (b) (c) Punch Blankholder
Ironing FIGURE 7.53 Schematic illustration of the ironing process. Note that the cup wall is thinner than its bottom. All beverage cans without seams (known as two-piece cans) are ironed, generally in three steps, after being deep drawn into a cup. Cans with separate tops and bottoms are known as three-piece cans. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Punch Die Cup
Anisotropy FIGURE 7.54 Definition of the normal anisotropy, R, in terms of width and thickness strains in a tensile-test specimen cut from a rolled sheet. Note that the specimen can be cut in different directions with respect to the length, or rolling direction, of the sheet. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 R = Ew Et Ew Et El Material ¯R Zinc alloys 0.4-0.6 Hot-rolled steel 0.8-1.0 Cold-rolled rimmed steel 1.0-1.4 Cold-rolled aluminum-killed steel 1.4-1.8 Aluminum alloys 0.6-0.8 Copper and brass 0.6-0.9 Titanium alloys (!) 3.0-5.0 Stainless steels 0.9-1.2 High-strength low-alloy steels 0.9-1.2 TABLE 7.3 Typical range of the average normal anisotropy ratio, R, for various sheet metals. Normal anisotropy: R = εw εt = ln ! wo wf ln ! to tf Average anisotropy: ¯R = R0+2R45+R90 4 Planar anisotropy: ΔR = R0−2R45+R90 2
Anisotropy and Effects Interstitial-free Aluminum-killed Rimmed 4 6 8 10 12 3.0 2.2 FIGURE 7.55 Effect of grain size on the average normal anisotropy for various low-carbon steels. Source: After D.J. Blickwede. 4.0 3.0 2.0 1.0 Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 2.6 1.8 1.4 1.0 ASTM grain number Average normal anisotropy (R) FIGURE 7.56 Effect of average normal anisotropy, R on limiting drawing ratio (LDR) for a variety of sheet metals. Source: After M. Atkinson. Limited drawing ratio (LDR) 0.2 0.4 0.6 1.0 2.0 4.0 6.0 Average strain ratio (R avg) Copper, brass, aluminum Steel Titanium Zinc FIGURE 7.57 Typical earing in a drawn steel cup, caused by the planar anisotropy of the sheet metal.
Punch Force Ironing Increasing clearance FIGURE 7.58 Schematic illustration of the variation of punch force with stroke in deep drawing. Arrows indicate the initiation of ironing. Note that ironing does not begin until after the punch has traveled a certain distance and the cup is partially formed. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Punch force (F ) Stroke Maximum punch force: Fmax = πDpto(UTS) ! Do Dp −0.7 Punch corner radius (a) (b) Die corner radius FIGURE 7.59 Effect of die and punch corner radii on fracture in deep drawing of a cylindrical cup. (a) Die corner radius too small; typically, it should be 5 to 10 times the sheet thickness. (b) Punch corner radius too small. Because friction between the cup and the punch aids in the drawing operation, excessive lubrication of the punch is detrimental to drawability.
Redrawing Tractrix Die Punch Blankholder Drawn cup Die Cup partially redrawn (a) Conventional redrawing (b) Reverse redrawing Punch Blankholder Drawn cup Die Cup partially redrawn FIGURE 7.60 Reducing the diameter of drawn cups by redrawing operations: (a) conventional redrawing, and (b) reverse redrawing. Small-diameter deep containers may undergo several redrawing operations. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Punch Sheet 1. 2. FIGURE 7.61 Stages in deep drawing without a blankholder, using a tractrix die profile. The tractrix is a special curve, the construction for which can be found in texts on analytical geometry or in handbooks. Die 3. Cup
Punch-Stretch Test Bead Sheet Punch FIGURE 7.62 Schematic illustration of the punch-stretch test on sheet specimens with different widths, clamped along the narrower edges. Note that the narrower the specimen, the more uniaxial is the stretching. (See also Fig. 7.65.) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Sheet width Bead (a) Side view (b) Top view
Forming Limit Diagram Plane strain Equal (balanced) biaxial Low-carbon steel Brass High-strength steel Aluminum alloy (a) (b) Pure shear 140 120 100 80 60 40 20 0 FIGURE 7.63 (a) Forming-limit diagram (FLD) for various sheet metals. Note that the major strain is always positive. The region above the curves is the failure zone; hence, the state of strain in forming must be such that it falls below the curve for a particular material; R is the normal anisotropy. (b) Illustrations of the definition of positive and negative minor strains. If the area of the deformed circle is larger than the area of the original circle, the sheet is thinner than the original thickness because the volume remains constant during plastic deformation. Source: After S.S. Hecker and A.K. Ghosh. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Major strain, After positive stretching Minor strain, positive Major strain Minor strain Minor strain, negative Before stretching Minor strain (%) Major strain (%) Simple tension (for R = 1) Failure zone Safe zone 260 240 220 0 20 40 60 80
Formability Testing FIGURE 7.64 An example of the use of grid marks (circular and square) to determine the magnitude and direction of surface strains in sheet-metal forming. Note that the crack (tear) is generally perpendicular to the major (positive) strain. Source: After S.P. Keeler. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 7.65 Bulge test results on steel sheets of various widths. The first specimen (farthest left) stretched farther before cracking than the last specimen. From left to right, the state of stress changes from almost uniaxial to biaxial stretching. Source: Courtesy of Ispat Inland, Inc.
Strains in an Automobile Major strain (%) 10 8 6 4 2 Trunk lid Roof Front door Minor strain (%) Major strain (%) 0 24 22 0 2 4 10 8 6 4 2 0 24 22 0 2 4 Front fender 1 3 FIGURE 7.66 Major and minor strains in various regions of an automobile body. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Minor strain (%) Major strain (%) 10 8 6 4 2 0 24 22 0 2 4 Minor strain (%) 1 3 5 7 1 5 9 1 3 75 Major strain (%) 10 8 6 4 2 0 24 22 0 2 4 Minor strain (%)
Design Considerations Poor Better 43.2 mm 39.6 mm 13.2 mm 11.4 mm FIGURE 7.67 Efficient nesting of parts for optimum material utilization in blanking. Source: Society of Manufacturing Engineers. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Poor Better Best 3 x sheet thickness (a) Closed corner 3 x sheet thickness (b) Relief notch Closed corner Relief notch FIGURE 7.68 Control of tearing and buckling of a flange in a right-angle bend. Source: Society of Manufacturing Engineers.
Design Considerations (cont.) Poor Good Tearing Notch (a) Poor Good Poor Good (b) (c) Notch FIGURE 7.69 Application of notches to avoid tearing and wrinkling in right-angle bending operations. Source: Society of Manufacturing Engineers. Sharp radius Sharp radius Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Poor Better x Poor Good Bend line R (a) (b) x R Bend line FIGURE 7.70 Stress concentrations near bends. (a) Use of a crescent or ear for a hole near a bend. (b) Reduction of the severity of a tab in a flange. Source: Society of Manufacturing Engineers. FIGURE 7.71 Application of (a) scoring, or (b) embossing to obtain a sharp inner radius in bending. However, unless properly designed, these features can lead to fracture. Source: Society of Manufacturing Engineers. Before After (a) (b)
Economics of Sheet-Metal Forming Spinning 8 7 6 5 4 3 2 FIGURE 7.72 Cost comparison for manufacturing a cylindrical sheet-metal container by conventional spinning and deep drawing. Note that for small quantities, spinning is more economical. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 0.3 m diameter Drawing 0 1 2 3 4 5 Number of parts (x 103) 1 0 Cost per part (relative) 0.19 m
Cast Study: Drum Cymbals Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 7.73 (a) A selection of common cymbals; (b) detailed view of different surface texture and finish of cymbals. Source: Courtesy W. Blanchard, Sabian Ltd. (a) (b) FIGURE 7.74 (a) Manufacturing sequence for production of cymbals. Source: Courtesy W. Blanchard, Sabian Ltd. 1. As-cast 2. After rolling; multiple rolling/annealing cycles necessary 3. Stretch formed and trimmed 4. Hang hole punched 5. Stretch formed 6. Hammered 7. Lathe-turned and polished
Cymbal Hammering (a) (b) FIGURE 7.75 Hammering of cymbals. (a) Automated hammering on a peening machine; (b) hand hammering of cymbals. Source: Courtesy W. Blanchard, Sabian Ltd. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7

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Sheet metal forming processes Erdi Karaçal Mechanical Engineer University of Gaziantep

  • 1.
    Sheet-Metal Forming Processes Process Characteristics Roll forming Long parts with constant complex cross-sections; good surface finish; high production rates; high tooling costs. Stretch form-ing Large parts with shallow contours; suitable for low-quantity production; high labor costs; tooling and equipment costs depend on part size. Drawing Shallow or deep parts with relatively simple shapes; high production rates; high tooling and equipment costs. Stamping Includes a variety of operations, such as punching, blanking, embossing, bending, flanging, and coining; simple or complex shapes formed at high production rates; tooling and equipment costs can be high, but labor costs are low. Rubber-pad forming Drawing and embossing of simple or complex shapes; sheet surface protected by rubber membranes; flexibility of operation; low tooling costs. Spinning Small or large axisymmetric parts; good surface finish; low tooling costs, but labor costs can be high unless operations are automated. Superplastic forming Complex shapes, fine detail, and close tolerances; forming times are long, and hence production rates are low; parts not suitable for high-temperature use. Peen forming Shallow contours on large sheets; flexibility of operation; equipment costs can be high; process is also used for straightening parts. Explosive forming Very large sheets with relatively complex shapes, although usually axisym-metric; low tooling costs, but high labor costs; suitable for low-quantity production; long cycle times. Magnetic-pulse forming Shallow forming, bulging, and embossing operations on relatively low-strength sheets; most suitable for tubular shapes; high production rates; requires special tooling. TABLE 7.1 General characteristics of sheet-metal forming processes. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7
  • 2.
    Localized Necking F E1 E2 E2 = E3 G/2 (a) (b) (c) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 E1 2F~110° Diffuse neck Localized neck (d) FIGURE 7.1 (a) Localized necking in a sheet-metal specimen under tension. (b) Determination of the angle of neck from the Mohr's circle for strain. (c) Schematic illustrations for diffuse and localized necking, respectively. (d) Localized necking in an aluminum strip in tension; note the double neck. Source: S. Kalpakjian.
  • 3.
    Lueders Bands Yupper Ylower Stress 0 Strain (a) Yield-point elongation Yielded metal Lueder!s band Unyielded metal Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 (b) (c) FIGURE 7.2 (a) Yield-point elongation and Lueders bands in tensile testing. (b) Lueder's bands in annealed low-carbon steel sheet. (c) Stretcher strains at the bottom of a steel can for common household products. Source: (b) Courtesy of Caterpillar Inc.
  • 4.
    Stress-Corrosion Cracking FIGURE7.3 Stress-corrosion cracking in a deep-drawn brass part for a light fixture. The cracks have developed over a period of time. Brass and 300-series austenitic stainless steels are particularly susceptible to stress-corrosion Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 cracking.
  • 5.
    Shearing Process Punch Sheet Die A B D C c Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 T F Punch Slug Sheet Die Fracture surface Penetration Clearance FIGURE 7.4 Schematic illustration of the shearing process with a punch and die, indicating important process variables.
  • 6.
    Hole & Slug Fracture angle Breakout dimension (a) Penetration depth Rollover depth Burnish depth Burr height Fracture depth Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Sheet thickness Burnish dimension Flattened portion under the punch Burr height Dishing Burr Rough surface Smooth surface (burnished) Ideal slug A C B D (b) FIGURE 7.5 Characteristic features of (a) a punched hole and (b) the punched slug. Note that the slug has a different scale than the hole.
  • 7.
    Shearing Mechanics Die 1. 2. 3. 120 (a) (b) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Punch Clearance, c 120 140 (HV) 160 140 200 220 180 140 140 160 180 200 180 160 200 120 120 160 200 180 FIGURE 7.6 a) Effect of clearance, c, on the deformation zone in shearing. Note that, as clearance increases, the material tends to be pulled into the die, rather than being sheared. (b) Microhardness (HV) contours for a 6.4-mm (0.25-in.) thick AISI 1020 hot-rolled steel in the sheared region. Source: After H.P. Weaver and K.J. Weinmann. Force Penetration 0 FIGURE 7.7 Typical punch force vs. penetration curve in shearing. The area under the curve is the work done in shearing. The shape of the curve depends on processing parameters and material properties. Maximum punch force: Fmax = 0.7(UTS)tL
  • 8.
    Shearing Operations Discarded Punching Blanking Perforating (a) (b) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Parting Lancing Notching Slitting FIGURE 7.8 (a) Punching and blanking. (b) Examples of shearing operations on sheet metal.
  • 9.
    Fine Blanking Blankingpunch Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 (a) (b) Upper pressure pad Stinger (impingement ring) Sheet metal Punch Slug Sheet Die Upper pressure pad Clearance Fracture surface Lower pressure cushion Blanking die Lower pressure cushion Support FIGURE 7.9 (a) Comparison of sheared edges by conventional (left) and fine-blanking (right) techniques. (b) Schematic illustration of a setup for fine blanking. Source: Feintool International Holding.
  • 10.
    Rotary Shearing FIGURE7.10 Slitting with rotary blades, a process similar to opening cans. Driven cutter Workpiece Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Clearance Ilding cutter
  • 11.
    Shaving & BeveledTooling FIGURE 7.11 Schematic illustration of shaving on a sheared edge. (a) Shaving a sheared edge. (b) Shearing and shaving combined in one punch stroke. Sheared edge (a) (b) Double-bevel shear Convex shear Blank thickness (a) (b) (c) (d) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Sheet Die Sheet Die Clearance FIGURE 7.12 Examples of the use of shear angles on punches and dies. Compare these designs with that for a common paper punch. Shear angle Punch Die Bevel shear Punch Die
  • 12.
    Progressive Die Piercing punch Stripper (a) (b) Ram Blanking punch Pilot Scrap Die Stop Finished washer FIGURE 7.13 (a) Schematic illustration of producing a washer in a progressive die. (b) Forming of the top piece of a common aerosol spray can in a progressive die. Note that the part is attached to the strip until the last operation is completed. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Strip Scrap Strip First operation Slug Part
  • 13.
    Manufacturing Processes forEngineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Tailor-Welded Blanks FIGURE 7.14 Examples of laser-welded and stamped automotive body components. Source: After M. Geiger and T. Nakagawa. (a) (b) Blanking; laser cutting Laser welding Stamping Legend g 60/60 (45/45) m 20/20 Hot-galvanized alloy steel sheet. Zinc amount: 60/60 (45/45) g/m2. Double-layered iron-zinc alloy electroplated steel sheet. Zinc amount 20/20 g/m2. 1 mm 1 mm m 20/20 0.8 mm g 45/45 g 60/60 1 mm g 45/45 1 mm g 45/45 0.7 mm 1.5 mm 0.7 mm 0.8 mm 1.25 mm Floor plate 2.0 mm Motor-compartment side rail 0.7 mm 0.7 mm 1.5 mm Quarter inner with integrated shock-absorber support Fender with integrated reinforcement Girder 1.5 mm 2.0 mm Shock-absorber support 2.5 mm 1.5 mm 0.7 mm 1.5 mm 0.7 mm
  • 14.
    Bending & MinimBend Radius Length of bend, L Bend radius (R) Thickness (t ) (a) (b) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 7.5 (a) Bending terminology. Note that the bend radius is measured to the inner surface of the bend, and that the length of the bend is the width of the sheet. (b) Relationship between the ratio of bend-radius to sheet-thickness and tensile reduction of area for a variety of materials. Note that sheet metal with a reduction of area of about 50% can be bent and flattened over itself without cracking, similar to folding paper. Source: After J. Datsko and C.T. Yang. 20 15 10 5 R t = (60/ r ) - 1 0 0 10 20 30 40 50 60 70 Tensile reduction of area (%) T Bend allowance, Lb Bend angle, A A Bend radius, R Bevel angle Setback Material Condition Material Soft Hard Aluminum alloys 0 6t Beryllium copper 0 4t Brass, low leaded 0 2t Magnesium 5t 13t Steels austenitic stainless 0.5t 6t low carbon, low alloy, and HSLA 0.5t 4t Titanium 0.7t 3t Titanium alloys 2.6t 4t TABLE 7.2 Minimum bend radii for various materials at room temperature.
  • 15.
    Bending Mechanics FIGURE7.16 The effect of length of bend and edge condition on the ratio of bend radius to thickness for 7075-T aluminum sheet. Source: After G. Sachs and G. Espey. Cracks No cracks Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 4 3 2 1 0 Bend radius Thickness 1 2 4 8 16 Length of bend Thickness Plane stress Plane strain Rough edge Smooth edge Rolling direction Elongated inclusions (stringers) Rolling direction (a) (b) (c) FIGURE 7.17 (a) and (b) The effect of elongated inclusions (stringers) on cracking in sheets as a function of the direction of bending with respect to the original rolling direction. This example shows the importance of orienting parts cut from sheet to maximize bendability. (c) Cracks on the outer radius of an aluminum strip bent to an angle of 90°; compare this part with that shown in (a).
  • 16.
    Springback T FIGURE7.19 Springback factor, Ks, for various materials: (a) 2024-0 and 7075-0 aluminum; (b) austenitic stainless steels; (c) 2024-T aluminum; (d) 1/4-hard austenitic stainless steels; and (e) 1/2- hard to full-hard austenitic stainless steels. A factor of Ks =1 indicates that there is no springback. Source: After G. Sachs. After Ri Rf Before A Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Af Ai Af FIGURE 7.18 Terminology for springback in bending. Note that the bend angle has become smaller. There are situations whereby the angle becomes larger, called negative springback (see Fig. 7.20). 1.0 0.9 0.8 0.7 0.6 0.5 s) Springback factor (K a b c d e 1 5 10 20 R/T No springback Increasing springback Springback factor: Ks = αf αi = (2Ri/t)+1 (2Rf/t)+1 Springback estimation: Ri Rf = 4 ! RiY Et "3 −3 ! RiY Et " +1
  • 17.
    Negative Springback Punch Wire specimen Die (a) (b) (c) (d) FIGURE 7.20 Schematic illustration of the stages in bending round wire in a V-die. This type of bending can lead to negative springback, which does not occur in air bending (shown in Fig. 7.24a). Source: After K.S. Turke and S. Kalpakjian. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7
  • 18.
    Springback Compensation ,90° , 90° 90° 90° Wb (a) (b) (c) (d) Rocker Sheet Die 1. 3. FIGURE 7.21 Methods of reducing or eliminating springback in bending operations. Source: After V. Cupka, T. Nakagawa, and H. Tyamoto. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 2. (e) P counter
  • 19.
    Die-Bending Operations (a)V die (b) Wiping die W Punch Die FIGURE 7.22 Common die-bending operations, showing the die-opening dimension W, used in calculating bending forces, as shown in Eq. (7.11). Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 W Bending force: Fmax = k(UTS)Lt2 W
  • 20.
    Press Brake Operations Main Flywheel gear Main gear Ram FIGURE 7.23 (a) through (e) Schematic illustrations of various bending operations in a press brake. (f) Schematic illustration of a press brake. Source: Courtesy of Verson Allsteel Company. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Die holder (f) Connections Motor Clutch and brake unit Side housing Floor line Crown Bed Channel forming (a) Joggle (b) Hemming (flattening) (c) Two-stage lock seam (d) Offset forming (e)
  • 21.
    Bending Operations (a)(b) Adjustable roll 1. 2. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 7.25 (a) Bead forming with a single die. (b)-(d) Bead forming with two dies in a press brake. (c) Bending in a 4-slide machine Roll bending Driven rolls (d) Sheet Polyurethane roll Punch Die Air bending FIGURE 7.24 Examples of various bending operations. Formed bead Die (a) (b) (c) (d)
  • 22.
    Flanging Operations Straightflange Joggled flange Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Piercing punch Spring-loaded stripper Sheet Die block or die button Spring-loaded pressure bushing FIGURE 7.26 Illustrations of various flanging operations. (a) Flanges formed on flat sheet. (b) Dimpling. (c) Piercing sheet metal with a punch to form a circular flange. In this operation, a hole does not have to be prepunched; note, however, the rough edges along the circumference of the flange. (d) Flanging of a tube; note the thinning of the periphery of the flange, due to its diametral expansion. (a) (c) (b) (d) Stretch flange Shrink flange Reverse flange Slug Piercing punch (retracted) Stripper plate Sheet Die Before After Flange Tube
  • 23.
    Roll-Forming (a) (b) FIGURE 7.27 (a) The roll-forming operation, showing the stages in roll forming of a structural shape. (b) Examples of roll-formed cross-sections. Source: Courtesy of Sharon Custom Metal Forming, Inc. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7
  • 24.
    Bending and FormingTubes Form block (fixed) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 7.28 Methods of bending tubes. Using internal mandrels, or filling tubes with particulate materials such as sand, prevents the tubes from collapsing during bending. Solid rods and structural shapes are also bent by these techniques. Mandrels for tube bending (d) Stretch bending (a) Draw bending (b) Compression bending (c) Plug Balls Laminated Cable Clamp Form block (rotating) Pressure bar Chuck Workpiece Chuck Form block (fixed) Wiper shoe Clamp FIGURE 7.29 A method of forming a tube with sharp angles, using an axial compressive force. Compressive stresses are beneficial in forming operations because they delay fracture. Note that the tube is supported internally with rubber or fluid to avoid collapsing during forming. Source: After J.L. Remmerswaal and A. Verkaik. Die Punch Tube Rubber or fluid Stops Die Punch 1. 2.
  • 25.
    Stretch-Forming Workpiece ToolStretch gripper Hydraulic stretching unit Turntable FIGURE 7.30 (a) Schematic illustration of a stretch-forming operation. Aluminum skins for aircraft can be made by this process. Source: Cyril Bath Co. (b) Stretch forming in a hydraulic press. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Crosshead Ram Upper tool Clamping fixture Workpiece Lower tool Bed 1. 2. 3. (b) Stretching (a) Table-mounted gripper Adjustable slide
  • 26.
    Bulging Die FIGURE7.32 (a) Bulging of a tubular part with a flexible plug. Water pitchers can be made by this method. (b) Production of fittings for plumbing by expanding tubular blanks with internal pressure; the bottom of the piece is then punched out to produce a “T” section. Source: After J.A. Schey. (c) Sequence involved in manufacturing of a metal bellows. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 (b) (a) (c) Before After Ring Punch Knockout rod Rubber plug Die insert Two-piece die (hinged) Fluid Fluid Workpiece Bulged tube Compressed tube
  • 27.
    Forming with aRubber Pad (a) (b) (c) Metal punch Blank Polyurethane pad FIGURE 7.33 Examples of bending and embossing sheet metal with a metal punch and a flexible pad serving as the female die. Source: Polyurethane Products Corporation. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7
  • 28.
    Sheet Hydroforming Pressure-controlvalve Rubber diaphragam FIGURE 7.34 The principle of the hydroform process, also called fluid forming. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Draw ring Punch Blank Forming cavity (oil filled) 1. 2. 3. 4. Part
  • 29.
    Tube Hydroforming Dieholder plate (a) (b) FIGURE 7.35 (a) Schematic illustration of the tube hydroforming process. (b) Example of tube hydroformed parts. Automotive exhaust and structural components, bicycle frames, and hydraulic and pneumatic fittings can be produced through tube hydroforming. Source: Schuler GmBH. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Horizontal cylinder Cylinder holder bracket Die holder plate Slide plate Centering Bed plate Hydroformed part Top die Seal punch Bottom die
  • 30.
    Spinning (a) Mandrel FIGURE 7.36 Schematic illustration of spinning processes: (a) conventional spinning, and (b) shear spinning. Note that in shear spinning, the diameter of the spun part, unlike in conventional spinning, is the same as that of the blank. The quantity f is the feed (in mm/rev or in./rev). Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Blank Roller Cone to t f A (b) Tool Mandrel Blank FIGURE 7.37 Typical shapes produced by the conventional spinning process. Circular marks on the external surfaces of components usually indicate that the parts have been made by spinning, such as aluminum kitchen utensils and light reflectors.
  • 31.
    Shear Spinning to tf Mandrel t FIGURE 7.38 Schematic illustration of a shear spinnability test. Note that as the roller advances, the spun part thickness is reduced. The reduction in thickness at fracture is called the maximum spinning reduction per pass. Source: After R.L. Kegg. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 to Blank ! Spun piece Flange Roller Tensile reduction of area (%) 0 10 20 30 40 50 60 70 80 100 80 60 40 20 0 Tube spinning Shear spinning FIGURE 7.39 Experimental data showing the relationship between maximum spinning reduction per pass and the tensile reduction of area of the original material. See also Fig. 7.15. Source: S. Kalpakjian. Maximum spinning reduction per pass (%) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 True strain at fracture in tension (Pf)
  • 32.
    Tube Spinning FIGURE7.40 Examples of (a) external and (b) internal tube spinning, and the process variables involved. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 (a) (b) External Mandrel Roller Forward Workpiece f to t Backward f f Die f Internal Ft
  • 33.
    Incremental Sheet-Metal Forming Clamp Blank Rotating tool (a) (b) FIGURE 7.41 (a) Illustration of an incremental forming operation. Note that no mandrel is used, and that the final part shape depends on the path of the rotating tool. (b) An automotive headlight reflector produced through CNC incremental forming. Note that the part does not have to be axisymmetric. Source: After J. Jesweit. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7
  • 34.
    Explosive Water level Ground level Workpiece Hold-down ring Die Vacuum line Tank Water Air Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Explosive Forming FIGURE 7.43 Effect of the standoff distance and type of energy-transmitting medium on the peak pressure obtained using 1.8 kg (4 lb) of TNT. The pressure-transmitting medium should have a high density and low compressibility. In practice, water is a commonly used medium. Standoff FIGURE 7.42 Schematic illustration of the explosive forming process. Although explosives are typically used for destructive purposes, their energy can be controlled and employed in forming large parts that would otherwise be difficult or expensive to produce by other methods. 60 50 40 30 20 10 0 Peak pressure (psi s 103) m 0 0.5 1 1.5 400 300 200 100 0 MPa 0 1 2 3 4 5 Standoff (ft) Pressure generated: p = K ! !3 W R a
  • 35.
    Electrohydraulic and Magnetic-Pulse Forming Switch Switch Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 7.44 Schematic illustration of the electrohydraulic forming process. Electrodes Water Clamp Sheet Die Capacitor bank Charger FIGURE 7.45 (a) Schematic illustration of the magnetic-pulse forming process. The part is formed without physical contact with any object, and (b) aluminum tube collapsed over a hexagonal plug by the magnetic-pulse forming process. Coil (a) (b) CL Coil current Eddy current Tube After forming Mandrel Before
  • 36.
    Superplastic Forming Mold Stop-off Clamp FIGURE 7.46 Two types of structures made by combining diffusion bonding and superplastic forming of sheet metal. Such structures have a high stiffness-to-weight ratio. Source: Rockwell Automation, Inc. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Mold Before After Product (a) (b)
  • 37.
    Peen-Forming FIGURE 7.47Schematic illustration of a peen forming machine to shape a large sheet-metal part, such as an aircraft-skin panel. Note that the sheet is stationary and the peening head travels along its length. Source: Metal Improvement Company. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Traversing gantry machine Stationary workpiece Track Track
  • 38.
    Honeycomb Structures Adhesive FIGURE 7.48 Methods of making honeycomb structures: (a) expansion process, and (b) corrugation process; (c) assembling a honeycomb structure into a laminate. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 (b) Roll Corrugated block Corrugated panel Corrugated Corrugating sheet rolls (a) Roll Sheet Block Expanded panel Slice (c) Adhesive impregnated scrim cloth (optional) Face sheet Expanded honeycomb core Face sheet
  • 39.
    Deep-Drawing Punch Blankholder force Blankholder Blank Die (draw ring) Do Pressure plate FIGURE 7.49 (a) Schematic illustration of the deep drawing process on a circular sheet-metal blank. The stripper ring facilitates the removal of the formed cup from the punch. (b) Variables in deep drawing of a cylindrical cup. Note that only the punch force in this illustration is a dependent variable; all others are independent variables, including the blankholder force. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Rd (a) (b) Dp T F c Rp Before After Punch Blank holder Blank Blank Drawn cup Die Spring stripper ring
  • 40.
    Deformation in Flangeand Wall (a) (b) FIGURE 7.50 Deformation of elements in (a) the flange and (b) the cup wall in deep drawing of a cylindrical cup. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 B A
  • 41.
    Pure Drawing vs.Pure Stretching A (a) (b) (c) FIGURE 7.51 Examples of (a) pure drawing and (b) pure stretching; the bead prevents the sheet metal from flowing freely into the die cavity. (c) Unsupported wall and possibility of wrinkling of a sheet in drawing. Source: After W.F. Hosford and R.M. Caddell. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Unsupported wall Punch Blankholder force Die Die A! Blankholder Punch Die Deforming area Failure Bead Deforming area Failure
  • 42.
    Draw Beads Metal Flow Draw bead Die Bead Original blank edge FIGURE 7.52 (a) Schematic illustration of a draw bead. (b) Metal flow during drawing of a box-shaped part, using beads to control the movement of the material. (c) Deformation of circular grids in drawing. (See Section 7.7.) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Bead Bend-and-straighten Deep draw Blank edge after drawing Bead CL CL Zero minor strain (a) (b) (c) Punch Blankholder
  • 43.
    Ironing FIGURE 7.53Schematic illustration of the ironing process. Note that the cup wall is thinner than its bottom. All beverage cans without seams (known as two-piece cans) are ironed, generally in three steps, after being deep drawn into a cup. Cans with separate tops and bottoms are known as three-piece cans. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Punch Die Cup
  • 44.
    Anisotropy FIGURE 7.54Definition of the normal anisotropy, R, in terms of width and thickness strains in a tensile-test specimen cut from a rolled sheet. Note that the specimen can be cut in different directions with respect to the length, or rolling direction, of the sheet. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 R = Ew Et Ew Et El Material ¯R Zinc alloys 0.4-0.6 Hot-rolled steel 0.8-1.0 Cold-rolled rimmed steel 1.0-1.4 Cold-rolled aluminum-killed steel 1.4-1.8 Aluminum alloys 0.6-0.8 Copper and brass 0.6-0.9 Titanium alloys (!) 3.0-5.0 Stainless steels 0.9-1.2 High-strength low-alloy steels 0.9-1.2 TABLE 7.3 Typical range of the average normal anisotropy ratio, R, for various sheet metals. Normal anisotropy: R = εw εt = ln ! wo wf ln ! to tf Average anisotropy: ¯R = R0+2R45+R90 4 Planar anisotropy: ΔR = R0−2R45+R90 2
  • 45.
    Anisotropy and Effects Interstitial-free Aluminum-killed Rimmed 4 6 8 10 12 3.0 2.2 FIGURE 7.55 Effect of grain size on the average normal anisotropy for various low-carbon steels. Source: After D.J. Blickwede. 4.0 3.0 2.0 1.0 Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 2.6 1.8 1.4 1.0 ASTM grain number Average normal anisotropy (R) FIGURE 7.56 Effect of average normal anisotropy, R on limiting drawing ratio (LDR) for a variety of sheet metals. Source: After M. Atkinson. Limited drawing ratio (LDR) 0.2 0.4 0.6 1.0 2.0 4.0 6.0 Average strain ratio (R avg) Copper, brass, aluminum Steel Titanium Zinc FIGURE 7.57 Typical earing in a drawn steel cup, caused by the planar anisotropy of the sheet metal.
  • 46.
    Punch Force Ironing Increasing clearance FIGURE 7.58 Schematic illustration of the variation of punch force with stroke in deep drawing. Arrows indicate the initiation of ironing. Note that ironing does not begin until after the punch has traveled a certain distance and the cup is partially formed. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Punch force (F ) Stroke Maximum punch force: Fmax = πDpto(UTS) ! Do Dp −0.7 Punch corner radius (a) (b) Die corner radius FIGURE 7.59 Effect of die and punch corner radii on fracture in deep drawing of a cylindrical cup. (a) Die corner radius too small; typically, it should be 5 to 10 times the sheet thickness. (b) Punch corner radius too small. Because friction between the cup and the punch aids in the drawing operation, excessive lubrication of the punch is detrimental to drawability.
  • 47.
    Redrawing TractrixDie Punch Blankholder Drawn cup Die Cup partially redrawn (a) Conventional redrawing (b) Reverse redrawing Punch Blankholder Drawn cup Die Cup partially redrawn FIGURE 7.60 Reducing the diameter of drawn cups by redrawing operations: (a) conventional redrawing, and (b) reverse redrawing. Small-diameter deep containers may undergo several redrawing operations. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Punch Sheet 1. 2. FIGURE 7.61 Stages in deep drawing without a blankholder, using a tractrix die profile. The tractrix is a special curve, the construction for which can be found in texts on analytical geometry or in handbooks. Die 3. Cup
  • 48.
    Punch-Stretch Test Bead Sheet Punch FIGURE 7.62 Schematic illustration of the punch-stretch test on sheet specimens with different widths, clamped along the narrower edges. Note that the narrower the specimen, the more uniaxial is the stretching. (See also Fig. 7.65.) Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Sheet width Bead (a) Side view (b) Top view
  • 49.
    Forming Limit Diagram Plane strain Equal (balanced) biaxial Low-carbon steel Brass High-strength steel Aluminum alloy (a) (b) Pure shear 140 120 100 80 60 40 20 0 FIGURE 7.63 (a) Forming-limit diagram (FLD) for various sheet metals. Note that the major strain is always positive. The region above the curves is the failure zone; hence, the state of strain in forming must be such that it falls below the curve for a particular material; R is the normal anisotropy. (b) Illustrations of the definition of positive and negative minor strains. If the area of the deformed circle is larger than the area of the original circle, the sheet is thinner than the original thickness because the volume remains constant during plastic deformation. Source: After S.S. Hecker and A.K. Ghosh. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Major strain, After positive stretching Minor strain, positive Major strain Minor strain Minor strain, negative Before stretching Minor strain (%) Major strain (%) Simple tension (for R = 1) Failure zone Safe zone 260 240 220 0 20 40 60 80
  • 50.
    Formability Testing FIGURE7.64 An example of the use of grid marks (circular and square) to determine the magnitude and direction of surface strains in sheet-metal forming. Note that the crack (tear) is generally perpendicular to the major (positive) strain. Source: After S.P. Keeler. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 7.65 Bulge test results on steel sheets of various widths. The first specimen (farthest left) stretched farther before cracking than the last specimen. From left to right, the state of stress changes from almost uniaxial to biaxial stretching. Source: Courtesy of Ispat Inland, Inc.
  • 51.
    Strains in anAutomobile Major strain (%) 10 8 6 4 2 Trunk lid Roof Front door Minor strain (%) Major strain (%) 0 24 22 0 2 4 10 8 6 4 2 0 24 22 0 2 4 Front fender 1 3 FIGURE 7.66 Major and minor strains in various regions of an automobile body. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Minor strain (%) Major strain (%) 10 8 6 4 2 0 24 22 0 2 4 Minor strain (%) 1 3 5 7 1 5 9 1 3 75 Major strain (%) 10 8 6 4 2 0 24 22 0 2 4 Minor strain (%)
  • 52.
    Design Considerations PoorBetter 43.2 mm 39.6 mm 13.2 mm 11.4 mm FIGURE 7.67 Efficient nesting of parts for optimum material utilization in blanking. Source: Society of Manufacturing Engineers. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Poor Better Best 3 x sheet thickness (a) Closed corner 3 x sheet thickness (b) Relief notch Closed corner Relief notch FIGURE 7.68 Control of tearing and buckling of a flange in a right-angle bend. Source: Society of Manufacturing Engineers.
  • 53.
    Design Considerations (cont.) Poor Good Tearing Notch (a) Poor Good Poor Good (b) (c) Notch FIGURE 7.69 Application of notches to avoid tearing and wrinkling in right-angle bending operations. Source: Society of Manufacturing Engineers. Sharp radius Sharp radius Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 Poor Better x Poor Good Bend line R (a) (b) x R Bend line FIGURE 7.70 Stress concentrations near bends. (a) Use of a crescent or ear for a hole near a bend. (b) Reduction of the severity of a tab in a flange. Source: Society of Manufacturing Engineers. FIGURE 7.71 Application of (a) scoring, or (b) embossing to obtain a sharp inner radius in bending. However, unless properly designed, these features can lead to fracture. Source: Society of Manufacturing Engineers. Before After (a) (b)
  • 54.
    Economics of Sheet-MetalForming Spinning 8 7 6 5 4 3 2 FIGURE 7.72 Cost comparison for manufacturing a cylindrical sheet-metal container by conventional spinning and deep drawing. Note that for small quantities, spinning is more economical. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 0.3 m diameter Drawing 0 1 2 3 4 5 Number of parts (x 103) 1 0 Cost per part (relative) 0.19 m
  • 55.
    Cast Study: DrumCymbals Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7 FIGURE 7.73 (a) A selection of common cymbals; (b) detailed view of different surface texture and finish of cymbals. Source: Courtesy W. Blanchard, Sabian Ltd. (a) (b) FIGURE 7.74 (a) Manufacturing sequence for production of cymbals. Source: Courtesy W. Blanchard, Sabian Ltd. 1. As-cast 2. After rolling; multiple rolling/annealing cycles necessary 3. Stretch formed and trimmed 4. Hang hole punched 5. Stretch formed 6. Hammered 7. Lathe-turned and polished
  • 56.
    Cymbal Hammering (a)(b) FIGURE 7.75 Hammering of cymbals. (a) Automated hammering on a peening machine; (b) hand hammering of cymbals. Source: Courtesy W. Blanchard, Sabian Ltd. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education ISBN No. 0-13-227271-7