Mechanical Engineering Series

Editor-in-ChiefFrederick F. Ling

For further volumes: http://www.springer.com/series/1161

Mechanical Engineering Series

Frederick F. LingEditor-in-Chief

The Mechanical Engineering Series features graduate texts and research monographs toaddress the need for information in contemporary mechanical engineering, including areasof concentration of applied mechanics, biomechanics, computational mechanics, dynamicalsystems and control, energetics, mechanics of materials, processing, production systems,thermal science, and tribology.

Advisory Board/Series Editors

Applied Mechanics F.A. LeckieUniversity of California,Santa Barbara

D. GrossTechnical University of Darmstadt

Biomechanics V.C. MowColumbia University

Computational Mechanics H.T. YangUniversity of California,Santa Barbara

Dynamic Systems and Control/ D. BryantMechatronics University of Texas at Austin

Energetics J.R. WeltyUniversity of Oregon, Eugene

Mechanics of Materials I. FinnieUniversity of California, Berkeley

Processing K.K. WangCornell University

Production Systems G.-A. KlutkeTexas A&M University

Thermal Science A.E. BerglesRensselaer Polytechnic Institute

Tribology W.O. WinerGeorgia Institute of Technology

ABC

James G. Conley

Rapid Tooling Guidelines

Wanlong Wang • Henry W. Stoll

For Sand Casting

permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY

or dissimilar methodology now known or hereafter developed is forbidden.

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to proprietary rights.

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© Springer Science+Business Media, LLC 2010

Wang Consulting International

USAwangwl@hotmail.com

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Henry W. Stoll

2145 Sheridan Road

James G. Conley

Northwestern UniversityMcCormick School of Engineering

USA

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Springer New York Dordrecht Heidelberg London

Library of Congress Control Number: 2010920244

ISSN 0941-5122ISBN 978-1-4419-5730-6 e-ISBN 978-1-4419-5731-3DOI 10.1007/978-1-4419-5731-3

Wanlong Wang

1415 Bellevue Avenue

Burlingame, CA 94010Unit 6

Department of Mechanical EngineeringNorthwestern University

2001 Sheridan Road

Kellogg School of Management and

Evanston, IL 60208

Evanston, IL 60208-3111

Series Preface

Mechanical engineering, an engineering discipline forged and shaped by the needs of the industrial revolution, is once again asked to do its substantial share in the call for industrial renewal. The general call is urgent as we face profound issues of productivity and competitiveness that require engineering solutions among others. The Mechanical Engineering Series features graduate texts and research monographs intended to address the need for information in contemporary areas of mechanical engineering.

The series is conceived as a comprehensive one that covers a broad range of concentrations important to mechanical engineering graduate education and research. We are fortunate to have a distinguished roster of consulting editors on the advisory board, each an expert in one of the areas of concentration. The names of the consulting editors are listed on the facing page of this volume. The areas of concentration are applied mechanics, biomechanics, computational mechanics, dynamic systems and control, energetics, mechanics of materials, processing, production systems, thermal science, and tribology. Austin, Texas Frederick F. Ling

v

Preface

Sand casting is a versatile manufacturing process with a history that dates back thousands of years. As automation and production technologies have evolved with time, sand casting methods have advanced to realize improved adaptability and efficiency. The process is now used for both large and small dimensioned products in both high volume and small batch production lot sizes. Many metals and alloys that can be poured in a foundry can use the sand casting process.

A chronic challenge in managing sand casting production is the efficient (cost,

time) fabrication and maintenance of the elements that form the sand molds, specifically patterns and core tooling. Traditionally, sand casting patterns and tooling are produced manually from wood or dimensionally stable synthetic materials. The advance of numerical controls and computer numerically controlled (CNC) machining dramatically improves the efficiency and reliability of this form of tooling production.

With the invention and commercialization of the stereo lithography process in

1986, a variety of new and improved layered manufacturing processes were introduced to the marketplace. The working materials of these processes evolved from laser cured epoxy to wood like layered paper, engineering plastics and other forms. With the appropriate part data, rapid prototyping processes could produce patterns and core box tooling directly, hence the dawn of rapid tooling. While CNC fabrication processes are accurate, they consume a considerable amount of working material to get to the net tooling shape. They are also time consuming, often a critical variable in a world of short supply chains.

In this environment of dynamic technological change, the use of either CNC or

emergent rapid tooling techniques to produce parts that have uncertain demand curves, like military hardware, becomes an important question for procurement professionals.

In an effort to inform such decision, the authors undertook an analysis of how

tools and sand castings may be produced for a variety of part geometries. With the support of the Defense Logistics Agency, Clinkenbeard, and Lufkin, the authors developed best practice guidelines for rapid tooling of sand castings. The methodology used included:

• Identification and selection of components (w/ solid model) suitable for

sand casting; • Evaluate tooling error sources for sand casting;

vii

• Produce the rapid tooling (by either CNC, RT or a combination) and create castings;

• Express tool path selection framework for sand casting; • Dimensional metrology investigation of rapid tooling patterns, molds and

resultant castings using best practices; • Analysis of tooling related costs and lead times.

The results of these investigations provide the research foundation for this

book.

Rapid Tooling Guidelines For Sand Castingviii

Acknowledgement

The authors are grateful to Dan Gearing of the Defense Logistics Agency, Joseph Santner of the American Foundry Society and Ron Gustafson of Clinkenbeard for their support of the research that provides the foundation for this book.

James Conley would also like to acknowledge the early career support of Prof.

Morris E. Fine of Northwestern University and Dr. Akio Urakami of the Ryobi Group of Companies. Both positively influenced the author’s logic for addressing the practical challenges described in this manuscript.

The authors also want to express their appreciations to Alex Greene, Editorial

Director, and Ciara.Vincent from Springer US for their support in realizing the publication of this work.

ix

Chapter 1 Sand Casting Processes...................................................................... 1 1.1 Basic Steps in Making Sand Castings.......................................................... 1

1.1.1 Patternmaking ...................................................................................... 2 1.1.2 Coremaking .......................................................................................... 3 1.1.3 Molding................................................................................................ 3 1.1.4 Melting and Pouring............................................................................. 3 1.1.5 Cleaning ............................................................................................... 4

1.2 Mold Making Processes............................................................................... 4 1.2.1 Green-sand molding ............................................................................. 4 1.2.2 Dry-sand molding................................................................................. 7 1.2.3 Core-sand molding ............................................................................... 8 1.2.4 Shell molding ....................................................................................... 8

Chapter 2 Tool Design and Construction for Sand Casting ........................... 11 2.1 Sand-Casting Tool Design and Construction............................................. 11 2.2 Pattern Type............................................................................................... 15

2.2.1 Loose Patterns .................................................................................... 16 2.2.2 Gated Patterns .................................................................................... 17 2.2.3 Match-Plate Patterns .......................................................................... 17 2.2.4 Cope & Drag Patterns ........................................................................ 19

2.3 Pattern Design............................................................................................ 20 2.3.1 Pattern and Core Box Materials ......................................................... 20 2.3.2 Pattern Allowances............................................................................. 23 2.3.3 Draft ................................................................................................... 27 2.3.4 Parting Line........................................................................................ 28

Table of Contents

Preface................................................................................................................. vii

Acknowledgement ................................................................................................ ix

xi

Series Preface........................................................................................................ v

2.4 Master Pattern Fabrication.........................................................................30 2.4.1 Manual Fabrication.............................................................................31 2.4.2 Computer Numerical Control Machining...........................................32 2.4.3 Fast Freeform Fabrication ..................................................................33

2.5 Core and Core Box Fabrication .................................................................34 2.5.1 Core Fabrication Process....................................................................34 2.5.2 Core Boxes .........................................................................................35

Chapter 3 Fast Freeform Fabrication Methods and Processes ......................37 3.1 Fast Freeform Fabrication (FFF) Processes ...............................................38

3.1.1 Stereolithography Apparatus (SLA)...................................................38

3.1.3 Fused Deposition Modeling (FDM) ...................................................41 3.1.4 Selective Laser Sintering (SLS) .........................................................42 3.1.5 Solid Ground Curing (SGC)...............................................................44 3.1.6 Three Dimensional Printing (3DP).....................................................45 3.1.7 Sanders Prototype (SP).......................................................................46

3.2 FFF Model Building Procedure .................................................................48 3.2.1 CAD Modeling and Data Preparation ................................................48 3.2.2 Machine Setup....................................................................................49 3.2.3 Building..............................................................................................50 3.2.4 Post Processing...................................................................................50

Chapter 4 Rapid Tooling Processes ..................................................................53 4.1 CNC Based Tooling Process......................................................................54 4.2 Rapid Tooling Processes Based on Fast Freeform Fabrication..................55

4.2.1 Stereolithography Based RT Methods................................................56 4.2.2 LOM based RT methods ....................................................................59 4.2.3 Selective laser sintering (SLS) Based RT Methods............................63 4.2.4 Fused Deposition Modeling (FDM) Based RT Methods....................66 4.2.5 Solid Ground Curing (SGC) Based RT Methods ...............................66 4.2.6 Other Tooling Processes.....................................................................66

Chapter 5 Sand Casting Dimensional Control.................................................69 5.1 Error Sources .............................................................................................69

5.1.1 Sand Casting Process..........................................................................70

Rapid Tooling Guidelines For Sand Casting

3.1.2 Laminated Object Manufacturing (LOM) ..........................................39

xii

2.3.5 Geometry Considerations................................................................... 28

5.1.3 Shrinkage ........................................................................................... 77 5.2 Geometric Dimensions and Tolerances ..................................................... 81

5.2.1 Dimensions......................................................................................... 82 5.2.2 Tolerances .......................................................................................... 83 5.2.3 Allowances......................................................................................... 84 5.2.4 Feature Control................................................................................... 84 5.2.5 Standards on Casting Dimensional Tolerances .................................. 87

5.3 Dimensional Metrology ............................................................................. 88 5.3.1 Basic Definitions................................................................................ 88 5.3.2 Types of Dimensional Error ............................................................... 89 5.3.3 Process Capability .............................................................................. 92

5.4 Measurement System Analysis .................................................................. 95 5.4.1 Procedures for Gage R & R Test........................................................ 95 5.4.2 Performing Gage R & R on Different Pieces of Equipment .............. 96

Chapter 6 Evaluating Tooling Alternatives ..................................................... 99 6.1 Decision Variables..................................................................................... 99

6.1.1 Fabrication Method ............................................................................ 99 6.1.2 Tool Material.................................................................................... 101 6.1.3 Tooling Approach ............................................................................ 101

6.2 Decision Factors ...................................................................................... 101 6.2.1 Data Status ....................................................................................... 102 6.2.2 Production Volume .......................................................................... 104 6.2.3 Prototype or Production?.................................................................. 105 6.2.4 Who Will Use the Tooling? ............................................................. 105 6.2.5 Part Geometry .................................................................................. 105 6.2.6 What Geometrical Features are Important?...................................... 106 6.2.7 Pattern Shop Capability.................................................................... 106 6.2.8 Tool Cost.......................................................................................... 107 6.2.9 Lead-Time........................................................................................ 107 6.2.10 Required Accuracy......................................................................... 107 6.2.11 Tool Durability............................................................................... 107

6.3 Decision Structure ................................................................................... 107 6.3.1 Universe of Possible Tooling Alternatives....................................... 108 6.3.2 Decision Constraints ........................................................................ 110

Table of Contents xiii

5.1.2 Rapid Tooling Process........................................................................73

6.3.4 Geometry Considerations .................................................................111 6.4 Decision Process ......................................................................................113

6.4.1 What is the Data Status?...................................................................113 6.4.2 Geometry Independent Requirements ..............................................114 6.4.3 Geometry Analysis ...........................................................................114 6.4.4 Develop Alternative Tooling Proposals ...........................................114 6.4.5 Negotiate the Final Selection............................................................115

Chapter 7 Tooling Alternative Selection Case Studies..................................117 7.1 Tooling Path Reviewing Form.................................................................117 7.2 Case Studies.............................................................................................117

7.2.1 Sensor Box .......................................................................................117 7.2.2 Hitch Housing ..................................................................................121 7.2.3 Yoke .................................................................................................123 7.2.4 Carrier Housing 1 .............................................................................125 7.2.5 Inlet Boost Pump..............................................................................127 7.2.6 Manifold ...........................................................................................128 7.2.7 Turbine Blade Machining Fixture ....................................................129 7.2.8 Upper Arm........................................................................................131 7.2.9 Rigid Connecting Link .....................................................................132 7.2.10 25mm Projectile .............................................................................134 7.2.11 Carrier Houseing 2 .........................................................................135 7.2.12 Muzzle Brake .................................................................................137 7.2.13 Ice Cleat..........................................................................................138 7.2.14 Roller Bracket ................................................................................140

References ..........................................................................................................157

Index ...................................................................................................................161

Appendix Glossary of Terms ............................................................................143

Rapid Tooling Guidelines For Sand Castingxiv

6.3.3 Cost, Time, and Quality Tradeoffs ................................................... 110