Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com http://72.3.142.35/mghdxreader/jsp/FinalDisplay.jsp;jsessionid=aag1B0 1 of 1 11/1/2007 8:46 AM Catalo g in g -in-Publication Data is on file with the Librar y of Con g ress Copyright © 2006, 1998 by Ivana Suchy. All rights reserved. Printed in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a data base or retrieval system, without the prior written permission of the publisher. 1 2 3 4 5 6 7 8 9 0 DOC/DOC 0 1 0 9 8 7 6 5 ISBN 0-07-146271-6 The sponsoring editor for this book was Larry S. Hager and the production supervisor was Richard C. R uzycka. It was set in Times Roman by International Typesetting and Composition. The art director for the cover was Handel Low. P rinted and bound by RR Donnelley. 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This work is published with the understanding that McGraw-Hill and its authors are supplying information but are not attempting to render engineering or other professional services. If such services are required, the assistance o f an appropriate professional should be sought. Copyright © 2006, 1998 by Ivana Suchy., McGraw-Hill Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS 1-1 SHEET-METAL STAMPING IN COMPARISON WITH OTHER METAL FABRICATING PROCESSES In today’s practical and cost-conscious world, sheet-metal parts have already replaced many expensive cast, forged, and machined products. The reason is obviously the relative cheapness of stamped, or otherwise mass-produced parts, as well as greater control of their technical and aesthetic parameters. That the world slowly turned away from heavy, ornate, and complicated shapes, and replaced them with functional, simple, and logical forms only enhanced this tendency. Remember old bath- tubs? They used to be cast and had ornamental legs. Today they are mostly made of coated sheet metal, if not plastics. Manufacturing methods for picture frames, chandeliers, door and wall hardware, kitchen sinks, pots and pans, window frames, and doors were gradually replaced by more practical and less costly techniques. But, sheet-metal stampings can also be used to imitate handmade ornamental designs of previous centuries. Such three-dimensional decorations can be stamped in a fraction of time the repoussé artist of yesterday needed. Metal extrusions, stampings, and forgings, frequently quite complex and elaborate, are used to replace handmade architectural elements. Metal tubing, metal spun products, formings, and drawn parts are often but cheaper substitutes of other, more expensive merchandise. Metal stampings, probably the most versatile products of modern technology, are used to replace parts previously welded together from several components. A well-designed sheet-metal stamping can sometimes eliminate the need for riveting or other fastening processes (Fig. 1-1). Stampings can be used to improve existing designs that often are costly and labor-intensive. Even products already improved upon, with their production expenses cut to the bone, can often be further improved, further innovated, further decreased in cost. The metal stamping die (Fig. 1-2) is an ideal tool that can produce large quantities of parts that are consistent in appearance, quality, and dimensional accuracy. It is a press tool capable of cutting the metal, bending it, drawing its shape into considerable depths, embossing, coining, finishing the edges, curling, and otherwise altering the shape and the outline of the metal part to suit the wildest imaginable design concepts. Figure 1-3 shows samples of these products. CHAPTER 1 1 Suchy_CH01.qxd 11/08/05 10:28 AM Page 1 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: HANDBOOK OF DIE DESIGN Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com The word “die” in itself means the complete press tool in its entirety, with all the punches, die buttons, ejectors, strippers, pads, and blocks, simply with all its components assembled together. When commenting on these little technical ingenuities, it is important to stress the role of designers of such products, both artistic and technical. Their thorough knowledge of the manufacturing field will definitely enhance not only the appearance, but the functionality, overall manufacturability, and cost of these parts. 2 CHAPTER ONE FIGURE 1-1 Threaded part, replaced by other, less expensive means. FIGURE 1-2 Metal stamping dies. Suchy_CH01.qxd 11/08/05 10:28 AM Page 2 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. BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS 3 Metal stamping die production output can be enormous, with huge quantities of high- quality merchandise, as shown in Figs. 1-3 and 1-4; pouring forth from the press. For that reason technical ignorance is not readily excusable, as the equal quantities of rejects can be generated just the same way. 1-1-1 Grain of Material Often, parts produced by various manufacturing methods can be redesigned to suit the sheet-metal mass production (Fig. 1-5). FIGURE 1-3 Various sheet-metal products. FIGURE 1-4 Metal-stamped replacements. Suchy_CH01.qxd 11/08/05 10:28 AM Page 3 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. BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com When designing such replacements, there are several aspects to be evaluated. The first and probably the most important is the grain of material (Fig. 1-6). Sheet metal of every form, be it a strip or a sheet, displays a definite grain line. It is the direction along which the material was produced in the mill-rolling process. In coils, the grain direction always runs lengthwise, parallel with the longer edge. The grain direction 4 CHAPTER ONE FIGURE 1-5 Additional sheet-metal replacements. FIGURE 1-6 Grain of materal in sheet-metal strip. Suchy_CH01.qxd 11/08/05 10:28 AM Page 4 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. BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com in sheets may vary, and designers must always make themselves familiar with it prior to planning a production run of any kind. In contrast, cast or forged parts display a different grain direction, and in sintered pow- der metal parts the grain is completely gone. For this reason, each of these manufacturing methods can be used to produce items for different applications. For example, a part, shown in Fig. 1-7, will display a different reaction to various forces and stresses when made by the forging method than when obtained through other manu- facturing processes. Where the forging would possess a great resistance to tensile and compressive forces along the A-A line, the same part, when made from sintered powder metal, may break or collapse under the same force. With this shape being cast, the location of the gate is of extreme importance, as it influ- ences the part’s sturdiness in various directions. In the casting gated at the longer end (as pictured in Fig. 1-7b), the opposite end will be more susceptible to breakage, as the molten metal will reach that portion later, when already cooling down. The existence of an open- ing in that area will divide the flow of material and thus create a so-called knit line, along which a separation, resulting in defects and possible breakage, may occur. The same casting, when gated in the middle (Fig. 1-7c), will have an equal breakage proneness at both ends. However, these ends will be somewhat sturdier, as the molten metal will reach them sooner than in the case of Fig. 1-7b. Of course, the existence of openings may have the same detrimental effect described earlier. A similar product, made of sheet metal, as pictured in Fig. 1-8, will also display a grain- dependent behavior; the part with the lengthwise grain will be considerably sturdier along the A-A line of force than the same shape positioned across the grain line. Where used sensibly, the grain in sheet-metal material can serve as a backbone of future products. In formed parts where bends are oriented perpendicularly to the grain of mater- ial, such bends are rarely seen cracking or becoming distorted, and the whole structural BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS 5 FIGURE 1-7 Forces applied to a casting. Suchy_CH01.qxd 11/08/05 10:28 AM Page 5 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. BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com consistency of the part is greater. Where such bends “across the grain” cannot be achieved, bends under an angle should be attempted (see Fig. 1-9). In parts with bends in both direc- tions (Fig. 1-9b), a 45° deviation from the grain line can be extremely helpful. Aside from other advantages, sheet-metal parts are stronger and sturdier than parts pro- duced by many other manufacturing methods. For example, die cast parts can be impres- sive with their intricate shapes, nonconcentric rounds, and full-bodied mass. But they have no distinct grain direction, and where strength is required their increased thickness often serves as a substitute for sturdiness (see Fig. 1-10). 6 CHAPTER ONE FIGURE 1-8 Grain variation in sheet-metal strip. FIGURE 1-9 Grain of material in bending. Suchy_CH01.qxd 11/08/05 10:28 AM Page 6 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. BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Sintered metals have no grain-generated backbone at all and may fail if used in high- stress applications. Forged materials do have their strength and sturdiness, but this is, again, outweighed by their bulkiness, as shown in Fig. 1-11a. Same with extruded materials (Fig. 1-11b): the grain is there, the strength is there, the columnar strength is impressive, but the increased bulkiness cannot be overlooked. Additionally, the span of applications for these products is limited and highly specific. Plastic parts, similarly to cast products, have but the material flow to depend on and that provides them with more defects than support. And since plastic materials are generally of BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS 7 FIGURE 1-9 (Continued) FIGURE 1-10 Sample of a cast part. Suchy_CH01.qxd 11/08/05 10:28 AM Page 7 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. BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com quite low strength when compared to metal parts of the same shape, they suffer from crack- ing when stressed or flexed, often brittle, pestered with serious aging problems, and greatly affected by weathering effect. They are almost useless in many applications where sheet metal can substitute for them with ease. Yet, for some reason, today’s manufacturers often go into extremes of supporting a fragile plastic insert with a sturdy wire mesh or producing a complicated sheet-metal structure covered by a plastic wrapper, just to be able to use plastics. Where fillers are used in plastics moldings, the proneness of such parts to cracking can be greatly enhanced, with dependence on the percentage of filler material utilized. And considering the pressure today’s plastic parts’ production places on the petroleum industry, we actually may have no plastic parts to speak of 50 years down the road, especially when taking into account the enormity of our mass production and mass consumption. 1-1-2 Edge Formation Another important aspect to be considered when designing sheet-metal replacements for parts manufactured by other methods is the formation of the edge. A cast part (Fig. 1-12a) will always exhibit a parting line to some degree. The visibility of this line is dependent on tool quality; with well-manufactured and well-maintained tooling, the line can be almost invisible, but with worn-out dies, rough machining, and crude assembly and fit, that area may bulge out and perhaps even show a burr at some places. The existence of draft angle in cast parts is another necessity the designer has to take into account. If the same part were forged, it will have the edge characteristics similar to those of its cast counterpart. Sheet-metal products’ edges will be completely different. With depen- dence on the thickness of material and clearance between the punch and die, the sheet-metal parts’ cut or pierced edges will show a reasonably straight portion, with a slight distortion toward the surface opposite from the punch, as shown in Fig. 1-13. The mechanism prompt- ing such distortion to emerge at all, along with the factors contributing to its width and volumnar growth, are explained in greater detail in Chap. 2. Considering the terminology, here the word “die” describes the insert, which during the operation of the press receives the punch and retains the pierced slug or blanked part. Sometimes the term “die button” may be used interchangeably. The burr on metal-stamped products is a great aid in evaluating the sequence of the manufacturing process, as it clearly indicates the direction of punching (or blanking) of each opening and of each cut. 8 CHAPTER ONE FIGURE 1-11 Forged and extruded parts. Suchy_CH01.qxd 11/08/05 10:28 AM Page 8 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. BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com [...]... BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS FIGURE 1-1 7 15 Grain direction in formed sheet-metal parts FIGURE 1-1 8 Stresses and their relationship to the direction of grain (From Frank W Wilson, Die Design Handbook,” New York, 1965 Reprinted with permission from The McGraw-Hill Companies.) Downloaded from Digital Engineering Library @ McGraw-Hill... Version - http://www.simpopdf.com BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS FIGURE 1-1 2 9 Side view of the cast product Drawn parts’ edges are similar in that they display the characteristics of the cut metal, where produced from previously blanked material (see Fig 1-1 4a) This is due to the action of blankholder, which retains the outer rim of the... Unregistered Version - http://www.simpopdf.com BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS 25 However, in sheet-metal stamping, many scrap areas may be decreased, if not minimized, just by rearranging parts on the strip (Fig 1-3 1) Naturally, the size of the resulting strip, and consequently the size of the die must be kept in mind in the course of such evaluation... Die Design Handbook,” New York, 1965 Reprinted with permission from The McGraw-Hill Companies.) 1-3 - 2-2 Bosses or Buttons These are flat-bottomed circular depressions or elevations in sheet (see Fig 1-3 8) They are most often used for offsetting purposes, be it for hardware or for other applications Their sizes and heights with respect to the given material thickness are listed in Table 1-3 1-3 - 2-3 ... 10 Cost of the removal of a die from the press Cost of the installation of a die in the press (for the subsequent run) Cost of the machine’s downtime during the die removal and installation Cost of the press operator’s standby, if applicable Cost of the press adjustments and trial runs Cost of the first piece inspection and the cost of further adjustments and approvals, if applicable Cost of the extra... 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 Suchy_CH01.qxd 11/08/05 10:28 AM Page 33 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS 33 FIGURE 1-3 6... Split Unregistered Version - http://www.simpopdf.com BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS 21 On occasions where all sides of a box are to be butted against each other, a circular bend relief can sometimes be utilized A sample of such bend relief is shown in Fig 1-2 5 Here the round cutout removes that portion of material that would have... (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 Suchy_CH01.qxd 11/08/05 10:28 AM Page 17 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS FIGURE 1-2 0 17 Openings other than round Where the... 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 Suchy_CH01.qxd 11/08/05 10:28 AM Page 13 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS... Split Unregistered Version - http://www.simpopdf.com BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS 14 CHAPTER ONE 1-3 - 1-1 Grain Direction of the Material The ever-present grain of material must be taken into consideration first Unless absolutely necessary, it should not appear alongside a bend, a joggle, or any other deflection and elevation in the part’s surface Every sheet-metal material behaves . Terms of Use as given at the website. BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com BASIC DIE DESIGN AND DIE- WORK. action of blankholder, which retains the outer rim of the blank, while the middle of it is being drawn into depth. BASIC DIE DESIGN AND DIE- WORK INFLUENCING FACTORS 9 FIGURE 1-1 2 Side view of the. same way. 1-1 -1 Grain of Material Often, parts produced by various manufacturing methods can be redesigned to suit the sheet-metal mass production (Fig. 1-5 ). FIGURE 1-3 Various sheet-metal products. FIGURE