chute assemblies are parts of a three-phase high-voltage inter- rupter switch used in the electrical power distribution industry. Refer to the tool-steel selection section of this chapter (Sec. 8.2) to determine the types of tool steels generally used to produce such molds. 8.12 The Five Major Rules of Die Making Tooling practices and die making are exacting arts and sciences. The tool design engineer and tool and die maker require great skill, knowledge, and experience. Several designs may be possible for any particular tooling and die-making problem, but there is usually only one solution that is best for the given conditions and tooling objectives. With this in mind, the following five major tooling and die-making rules will help the new tool designer and die maker to achieve his or her goals: 1 Define the stamping or die-making problem correctly. 2. Select the design that is best for all conditions. Tooling, Die Making, Molds, Jigs, and Fixtures 629 Figure 8.56 A complex, compound mold for the parts shown in Fig. 8.57. Walsh CH08 8/30/05 10:05 PM Page 629 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Tooling, Die Making, Molds, Jigs, and Fixtures 630 Chapter Eight Figure 8.57 Plastic parts (cycloaliphatic epoxy) made from the mold shown in Fig. 8.56. Figure 8.58 A complex, compound mold for the acrylic plastic parts shown in Fig. 8.59. Walsh CH08 8/30/05 10:05 PM Page 630 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Tooling, Die Making, Molds, Jigs, and Fixtures 3. Permit the fabrication of the die parts without difficulty. 4. The finished parts of the die must be assembled easily by the die maker. 5. The tool or die must function well and solve the stamping, tool, or die problem exactly as intended. Clean and precise working drawings of the die and all its parts must be produced by the tool engineering department, and the die maker must transform these drawings into an accurate working die using the information provided by the tooling engineer and the die maker’s own experience and skill. The production of functional and accurate parts, through tooling, is the beginning of and the most important part of a sometimes long and complex process that determines the success of the fin- ished product. Tooling, Die Making, Molds, Jigs, and Fixtures 631 Figure 8.59 Acrylic plastic parts made from the mold shown in Figure 8.58. Walsh CH08 8/30/05 10:05 PM Page 631 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Tooling, Die Making, Molds, Jigs, and Fixtures Walsh CH08 8/30/05 10:05 PM Page 632 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Tooling, Die Making, Molds, Jigs, and Fixtures Chapter 9 Sheet Metal Practices and Layout The branch of metalworking known as sheet metal comprises a large and important element. Sheet metal parts are used in count- less commercial and military products. Sheet metal parts are found on almost every product produced by the metalworking industries throughout the world. Sheet metal gauges run from under 0.001 to 0.500 in. Hot-rolled steel products can run from 1 ⁄2 in thick to no. 18 gauge (0.0478 in) and still be considered as “sheet.” Cold-rolled steel sheets generally are available from stock in sizes from no. 10 gauge (0.1345 in) down to no. 28 gauge (0.0148 in). Other sheet thicknesses are available as special-order “mill run” products when the order is large enough. Large manufacturers who use vast tonnages of steel products such as the automobile makers, switch-gear producers, and other sheet metal fabricators may order their steel to their own specifications (composition, gauges, and physical properties). The steel sheets are supplied in flat form or rolled into coils. Flat- form sheets are made to specific standard sizes unless ordered to special nonstandard dimensions. 9.1 Carbon and Low-Alloy Steel Sheets Carbon steel sheets and coils are produced in the following grades or classes: 633 Walsh CH09 8/30/05 10:08 PM Page 633 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Source: McGraw-Hill Machining and Metalworking Handbook Hot rolled ■ Low carbon (commercial quality) ■ Pickled and oiled ■ 0.40/0.50 carbon ■ Abrasion resistant ■ Hi-Form (A715), high strength/low alloy (grades 50 and 80) ■ A607 specification, high strength/low alloy (INX 45, INX 50, ExTen 50) ■ A606 specification, high strength/low alloy (Cor-Ten) Note: The code numbers indicate the yield strength of the high strength/low-alloy steels; i.e., INX 45 ϭ 45,000 psi yield; grade 80 ϭ 80,000 psi yield. Cold rolled ■ Low carbon (commercial quality) ■ Special killed (drawing quality) ■ Auto prototype (special killed drawing quality) ■ Vitreous enameling ■ Plating quality ■ Stretcher leveled The applications for the previously listed sheet steels are as follows: Hot-rolled applications Low carbon (commercial quality). Conforms to American Society for Testing and Materials (ASTM) A569 and is used for tanks, barrels, farm implements, and other applications where surface quality is not critical or important. Pickled and oiled. Conforms to ASTM A569 and is used for auto- motive parts, switch gear, appliances, toys, and other applications where a better surface quality is required and paint and enamel adhere well. Carbon content is 10 percent maximum, and this material may be formed easily and welded the same as low-carbon sheet (commercial quality). 634 Chapter Nine Walsh CH09 8/30/05 10:08 PM Page 634 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Sheet Metal Practices and Layout 0.40/0.50 carbon. Has 50 percent more yield strength and abra- sion resistance than low-carbon sheets. May be heat-treated for more strength and hardness. Used for scrapers, blades, tools, and other applications requiring a strong, moderate-cost steel sheet. Abrasion resistant. Medium carbon content and higher manganese greatly improve resistance to abrasion. Brinell hardness ϭ 210 minimum. Uses include scrapers, liners, chutes, conveyors, and other applications requiring a strong, abrasion-resistant steel sheet. Formability is moderate. A607 specification. Lowest-cost low-alloy steel sheet. Low carbon content ensures good formability. Excellent weldability. Typical uses include utility poles, transmission towers, automotive parts, truck trailers, and other applications requiring a low-cost, high strength alloy steel sheet. A606 specification. Five times more resistant to atmospheric corro- sion than low-carbon steel. Excellent weldability and formability. A715 specification. Fine-grained columbium-bearing series of high- strength steel. Enhanced bending and forming properties. Tough and fatigue resistant, with excellent weldability using all welding processes. Yield-point levels range from 40,000 to 80,000 psi. Cold-rolled applications Low carbon (commercial quality). Produced with a high degree of gauge accuracy and uniform physical characteristics. Excellent surface for painting (enamel or lacquer). Good for stamping and moderate drawing applications. Improved welding and forming characteristics, with uses such as household appliances, truck bodies, signs, panels, and many other applications. Special killed (drawing quality). Used for severe forming and drawing applications. Freedom from age hardening and fluting. Conforms to ASTM A365 specification. Auto prototype (special killed drawing quality). Used for prototype work and other deep drawing applications. Closely controlled gauge thickness with better tolerances compared with commercial- quality grades. Vitreous enameling. Cold rolled from commercially pure iron ingots for porcelain-enameled products. Textured surface and suitable for Sheet Metal Practices and Layout 635 Walsh CH09 8/30/05 10:08 PM Page 635 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Sheet Metal Practices and Layout forming and moderate drawing applications and flatwork. Con- forms to ASTM A424, grade A. Plating quality. Two finishes are provided that are suitable for most plating applications: commercial bright and extralight matte. Stretcher leveled. Uniform, high-quality matte sheets, further processed by stretching to provide superior flatness. Furnished resquared or not resquared. Resquared sheets have the stretching gripper marks removed. Used in the manufacture of table tops, cabinets, truck body panels, partitions, templates, and many other applications. Conforms to ASTM A336 specification. Galvanized sheet and coil. The galvanic coating is zinc, and it is applied to standard steel sheets or coils in two basic methods: hot- dipped galvanized and electrogalvanized. The hot-dipped galvanized processes are known as Ti-Co galvanized, galvanized bonderized, galvannealed, galvannealed A, and hot-dipped galvanized. Galva- nizing specifications are found in ASTM A526 and A527. Some of the hot-dipped sheets may have 1.25 oz zinc per square foot of surface area and others a lighter deposit. Electrogalvanized sheets are cold-rolled steel sheets coated with zinc by electrolytic deposition and conform to ASTM A591. These sheets should be painted if they are to be exposed to outdoor condi- tions. These sheets can be formed, rolled, or stamped without flaking, peeling, or cracking of the zinc coating. These galvanized sheets have the same gauge thickness as cold-rolled sheets. Applications include cabinets, signs, light fixtures, and others where an excel- lent finish is required. Coating weight is typically 0.1 oz/ft 2 , or each side is 0.00008 in thick. Trade names include Paint-Lok, Bethzin, Gripcoat, Lifecote 1, Weirzin Bonderized, and others. Aluminized and long-terne sheets. Sheet steel is also aluminized and produced in long-terne sheets. Aluminized steel sheet is hot-dip coated on both sides with aluminum-silicon alloy by the continuous method. Strong and corrosion resistant, aluminized sheet is also inexpensive. The aluminum coating is typically 0.001 in thick on both sides, or 0.40 oz/ft 2 . Aluminized sheet conforms to the ASTM A463 specification. Applications include dry kiln fan walls, dryers, incinerators, mufflers, and oven and space-heater components. Long-terne sheet is a soft steel coated with an 85 percent lead and 15 percent tin alloy for maximum ease in soldering. These long- terne sheets conform to ASTM A308 and are used for soldered 636 Chapter Nine Walsh CH09 8/30/05 10:08 PM Page 636 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Sheet Metal Practices and Layout tanks, automotive accessories, hood and radiator work, and many other stamped and formed products. As can be seen from the preceding descriptions of sheet steels that are available commercially, the selection of a particular steel for a particular sheet metal application is relatively easy. Not only are there a great number of different sheet metal stocks available, but special sheet steels may be ordered to your specifications when quantities are large enough to justify their production by American steel makers. 9.2 Nonferrous Sheet Metal The nonferrous sheet metals include aluminum and aluminum alloys, copper and copper alloys, magnesium alloys, titanium alloys, and other special alloys. See Chap. 4, “Materials and Their Uses,” for data and specifications on the nonferrous as well as the ferrous materials that are specified by the American Society for Testing and Materials (ASTM) and the Society of Automotive Engineers (SAE). Supplier catalogs are also available from companies such as Ryerson, Vincent, Atlantic, Alcoa, Reynolds, Anaconda, Chase, and others, and they may be selected from an industrial supplier master index such as the Thomas Register of American Manufacturers. 9.3 Machinery for Sheet Metal Fabrication Some of the typical machinery found in a large manufacturing plant for processing and producing sheet metal parts includes ■ Shears, hydraulic and squaring ■ Press brakes ■ Leaf brakes ■ Roll-forming machines ■ Automatic [computer numerical controlled (CNC)] multistation punch presses ■ Single-die punch presses, strippit and unipunch setups ■ Slitting machines ■ Stretcher-bending machines ■ Hydropresses (Marforming presses, Martin-Marietta Corp.) Sheet Metal Practices and Layout 637 Walsh CH09 8/30/05 10:08 PM Page 637 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Sheet Metal Practices and Layout ■ Pin routers ■ Yoder hammers ■ Spin forming machines ■ Tumbling and deburring machines ■ Sand-blasting equipment ■ Explosive forming facilities ■ Ironworkers (for structural shapes) The designer and tool engineer should be familiar with all machin- ery used to manufacture parts in a factory. These specialists must know the limitations of the machinery that will produce the parts as designed and tooled. Coordination of design with the tooling and manufacturing departments within a company is essential to the quality and economics of the products that are manufactured. Our modern machinery has been designed and is being improved con- stantly to allow us to manufacture quality products at affordable prices to consumers. Medium- to large-sized companies can no longer afford to manufacture products whose quality standards do not meet the demands and requirements of the end user. 9.3.1 Modern sheet metal manufacturing machinery The processing of sheet metal begins with the hydraulic shear, where the material is squared and cut to size for the next opera- tion. Figure 9.1 shows a typical hydraulic shear with the capacity to do a 120-in cut in up to no. 7 gauge steel sheet. These types of machines are the “workhorses” of the typical sheet metal depart- ment because all operations on sheet metal parts start at the shear. Figure 9.2 shows a Wiedemann Optishear, which shears and squares sheet metal to a high degree of accuracy. Blanks used in blanking, punching, and forming dies are produced on this machine, as are other flat and accurate pieces that proceed to the next stage of manufacture. The flat, sheared sheet metal parts then may be routed to punch presses, where holes of various sizes and patterns are produced. Figure 9.3 shows a medium-sized CNC multistation turret punch press, which is both highly accurate and very fast. (See Chap. 1, “Modern Metalworking Machinery and Measuring Devices,” for other types of machinery used by the metalworking industry.) 638 Chapter Nine Walsh CH09 8/30/05 10:08 PM Page 638 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Sheet Metal Practices and Layout [...]... being fed past each stage of rolls until the final roll-formed section is completed The number of different cross sections of roll-formed sheet metal parts is limitless The roll-formed part is usually made to a specific length or stock length or may be produced to any special length required Figure 9.15 is a sample page of roll-formed sections taken from the Dahlstrom catalog of molded and rolled sections... On certain parts where great stiffness and rigidity are required, a method called beading is employed The beading is carried out at the same time as the part is being hydropressed, Marformed, or hard-die formed See Fig 9.23b and Chap 8, “Tooling, Die Making, Molds, Jigs, and Fixtures,” for more data on beading sheet metal parts Another method for stiffening the edge of a long sheet metal part is to... Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Walsh CH09 8/30/05 10: 08 PM Page 661 Sheet Metal Practices and Layout Sheet Metal Practices and Layout 661 On double-curved surfaces such as are found on automobile and truck bodies and. .. required rigidity or strength ■ Do not design a part that is impractical to bend on the type of machinery with which your operation is equipped ■ Keep brake-formed parts in a size range where the parts can be handled manually by the brake operators, unless your operation is equipped with automatic machinery or other special-handling equipment ■ When using hot-rolled steel sheets, use tolerances on your parts... laser-cutting operation Figure 9.12 A laser-cut part based on the drawing in Fig 9.11, showing the smooth, accurate cut Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Walsh CH09 8/30/05 10: 08 PM Page 649 Sheet Metal Practices and. .. press-brake bent is held in a set of grippers at each end of the part The part is stretched and pulled against the radiused die block simultaneously by the gripper arms, thus forming the part to the specified radius Allowance is made for “springback” of the formed part by overbending and then allowing the metal to spring back or return to the correct form Downloaded from Digital Engineering Library @ McGraw-Hill. .. 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Walsh CH09 8/30/05 10: 08 PM Page 641 Sheet Metal Practices and Layout Sheet Metal Practices and Layout 641 Figure 9.4 A small press brake with digital back gauge Figure 9.5 American standard wire-gauge-measuring tool Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)... cross-sectional shape to the finished part Samples of rollformed parts can be seen in Fig 9.15 Welding-process cutting and water-jet cutting The sheet metal stock sheet may be oxyacetylene torch cut with an automatic torch cutting machine, or it may be plasma cut, arc cut, or waterjet cut Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill. .. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Walsh CH09 8/30/05 10: 08 PM Page 647 Sheet Metal Practices and Layout Sheet Metal Practices and Layout 647 Figure 9.9 A modern laser-cutting machine with CNC controller Figure 9 .10 Close-up... of laser-cutting machine cutting the part shown in Figs 9.11 and 9.12 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website Walsh CH09 8/30/05 10: 08 PM Page 648 Sheet Metal Practices and Layout 648 Chapter Nine Figure 9.11 A scaled AutoCad . commercial bright and extralight matte. Stretcher leveled. Uniform, high-quality matte sheets, further processed by stretching to provide superior flatness. Furnished resquared or not resquared. Resquared. strength and abra- sion resistance than low-carbon sheets. May be heat-treated for more strength and hardness. Used for scrapers, blades, tools, and other applications requiring a strong, moderate-cost. coils. Flat- form sheets are made to specific standard sizes unless ordered to special nonstandard dimensions. 9.1 Carbon and Low-Alloy Steel Sheets Carbon steel sheets and coils are produced in the