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http://72.3.142.35/mghdxreader/jsp/FinalDisplay.jsp;jsessionid=aag1B0 Cataloging-in-Publication Data is on file with the Library of Congress 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 DOC/DOC ISBN 0-07-146271-6 The sponsoring editor for this book was Larry S Hager and the production supervisor was Richard C Ruzycka It was set in Times Roman by International Typesetting and Composition The art director for the cover was Handel Low Printed and bound by RR Donnelley This book is printed on recycled, acid-free paper containing a minimum of 50% recycled, de-inked fiber McGraw-Hill books are available at special quantity discounts to use as premiums and sales promotions, or for use in corporate training programs For more information, please write to the Director of Special Sales, McGraw-Hill Professional, Two Penn Plaza, New York, NY 10121-2298 Or contact your local bookstore Information contained in this work has been obtained by The McGraw-Hill Companies, Inc (“McGraw-Hill”) from sources believed to be reliable However, neither McGraw-Hill nor its authors guarantee the accuracy or completeness of any information published herein and neither McGraw-Hill nor its authors shall be responsible for any errors, omissions, or damages arising out of use of this information 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 of an appropriate professional should be sought Copyright © 2006, 1998 by Ivana Suchy., McGraw-Hill of 11/1/2007 8:46 AM Suchy_CH01.qxd 11/08/05 10:28 AM Page Source: HANDBOOK OF DIE DESIGN CHAPTER 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 bathtubs? 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 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 Suchy_CH01.qxd 11/08/05 10:28 AM Page BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS FIGURE 1-1 CHAPTER ONE Threaded part, replaced by other, less expensive means 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 FIGURE 1-2 Metal stamping dies 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 Suchy_CH01.qxd 11/08/05 10:28 AM Page BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS FIGURE 1-3 Various sheet-metal products Metal stamping die production output can be enormous, with huge quantities of highquality 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 1-4 Metal-stamped replacements 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 Suchy_CH01.qxd 11/08/05 10:28 AM Page BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS CHAPTER ONE FIGURE 1-5 Additional sheet-metal replacements 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 FIGURE 1-6 Grain of materal in sheet-metal strip 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 Suchy_CH01.qxd 11/08/05 10:28 AM Page BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS 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 powder 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 manufacturing 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 influences 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 opening 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 graindependent 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 material, such bends are rarely seen cracking or becoming distorted, and the whole structural FIGURE 1-7 Forces applied to a casting 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 Suchy_CH01.qxd 11/08/05 10:28 AM Page BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS FIGURE 1-8 CHAPTER ONE Grain variation in sheet-metal strip 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 directions (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 produced by many other manufacturing methods For example, die cast parts can be impressive 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) FIGURE 1-9 Grain of material in bending 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 Suchy_CH01.qxd 11/08/05 10:28 AM Page BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS FIGURE 1-9 (Continued) Sintered metals have no grain-generated backbone at all and may fail if used in highstress applications Forged materials 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 FIGURE 1-10 Sample of a cast part 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 Suchy_CH01.qxd 11/08/05 10:28 AM Page BASIC DIE DESIGN AND DIE-WORK INFLUENCING FACTORS CHAPTER ONE FIGURE 1-11 Forged and extruded parts quite low strength when compared to metal parts of the same shape, they suffer from cracking 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 dependence 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 prompting such distortion to emerge at all, along with the factors contributing to its width and volumnar growth, are explained in greater detail in Chap 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 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 ... 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 height of the die) is another production-influencing factor The width of the opening in the press plus the width of the proposed die must definitely be in congruence The possibility of reorders... second nut or a drop of Loctite In die work, the manufacturability of parts is dependent on much narrower range of influences The main areas of concern are Grain direction of the material Openings,