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    Early Cost Estimation of Injection Molds 315: Glossary Index 365 369

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    omardzst
    mold jnection

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    Early Cost Estimation of Injection Molds 315: Glossary Index 365 369

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    omardzst
    14 views6 pages
    mold jnection

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    mold jnection

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    Download as pdf or txt
    14 views6 pages

    Early Cost Estimation of Injection Molds 315: Glossary Index 365 369

    Uploaded by

    omardzst
    mold jnection

    Copyright:

    © All Rights Reserved
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    of 6

    Contents xv

    References 312

    8. Early Cost Estimation of Injection Molds 315


    8.1 Introduction 315
    8.2 Cost Function Approximation Using Neural Networks 317
    8.3 Cost-Related Factors for Injection Molds 320
    8.4 The Neural Network Training 325
    8.4.1 The Neural Network Architecture 325
    8.4.2 The Training Process 327
    8.4.3 Training and Validation Results 328
    8.4.4 Neural Networks for Different Cost Ranges 329
    8.5 Summary 331
    References 332

    9. Case Studies: IMOLD® and IMOLD-Works for Mold Design 335


    9.1 Intelligent Mold Design and Assembly Systems 335
    9.1.1 Knowledge-Based Mold Design Systems 335
    9.1.2 IMOLD® Overview 338
    9.1.3 Development Platforms 339
    9.1.4 Functional Modules 340
    9.2 A Windows-Based Mold Design and Assembly System 344
    9.2.1 3D Windows-Native CAD Systems 345
    9.2.2 System Implementations 351
    9.2.3 Graphical User Interfaces (GUIs) 352
    9.2.4 Windows-Based Die Casting Die Design Systems 357
    9.2.5 Illustrative Examples 358
    9.3 Summary 362
    References 362

    Glossary 365
    Index 369
    1
    Introduction

    1.1 CAD/CAM TECHNOLOGY IN TOOLING APPLICATIONS


    Tool engineering constitutes an important branch of manufacturing engi-
    neering as any direct improvement of existing tooling processes or an introduc-
    tion of novel processes could significantly improve the production efficiency,
    product quality and reduce design and processing time. This would enhance the
    competitiveness of a manufacturing company and maintain its leading edge over
    its competitors. Tooling design is as an important topic as the manufacturing
    process itself. Without suitable tooling, manufacturing processes are often crip-
    pled or rendered totally inefficient. The trade of a tooling designer, however, has
    been traditionally linked to long years of apprenticeship and skilled craftsman-
    ship. There appears to be more heuristic know-how and knowledge acquired
    through trial-and-error than deep scientific analysis and understanding. With the
    increasing use of computer tools and technology, this scenario has changed rap-
    idly since the introduction of CAD/CAM/CAE tools in the early 1980s. It is to
    the authors' beliefs that CAD/CAM technologies will play more and more im-
    portant roles in the tooling industry to shorten the design and manufacturing
    time.
    This chapter introduces the background of CAD/CAM technology for tool-
    ing design and highlights some of the R&D efforts in this area. One area is in the
    design of tooling for molds and die casting dies which will be discussed in detail
    in the rest of the chapters of this book. Another area is tooling for supporting ma-
    chining operations, i.e., jigs and fixtures for orienting, locating, and supporting
    1
    2 Chapter 1

    parts in a machining center. All these areas used to rely heavily on skilled tool
    designers, and unfortunately, there is a worldwide shortage of such people due to
    long years of acquiring the necessary skill and the reluctance of the younger gen-
    eration to enter into this trade.

    1.1.1 Fixture Design

    1.1.1.1 Introduction
    Fixtures are generally mechanical devices used in assisting machining, as-
    sembly, inspection, and other manufacturing operations. The function of such
    devices is to establish and secure the desired position(s) and orientation(s) of
    workpieces in relation to one another and according to the design specifications
    in a predictable and repeatable manner. With the advent of CNC technology and
    the capability of multi-axis machines to perform several operations and reduce
    the number of set-ups, the fixture design task has been somewhat simplified in
    terms of the number of fixtures which would need to be designed. However,
    there is a need to address the faster response and shorter lead-time required in
    designing and constructing new fixtures. The rapid development and application
    of Flexible Manufacturing System (FMS) has added to the requirement for more
    flexible and cost-effective fixtures. Traditional fixtures (e.g., dedicated fixtures)
    which have been used for many years are not able to meet the requirements of
    modern manufacturing due to the lack of flexibility and low reusability. The
    replacement of dedicated fixtures by modular and flexible fixtures is eminent in
    automated manufacturing systems, due to much smaller batch sizes and short-
    ened time-to-market.
    Modular fixtures are constructed from standard fixturing elements such as
    base-plates, locators, supports and clamps. These elements can be assembled to-
    gether without the need of additional machining operations and are designed for
    reuse after disassembly [1]. The main advantages of using modular fixtures are
    their flexibility and the reduction of time and cost required for the intended manu-
    facturing operations. Automation in fixture design [2,3,4] is largely based on the
    concept of modular fixtures, especially the hole-based systems, due to the follow-
    ing characteristics: (a) predictable and finite number of locating and supporting
    positions which allow heuristic or mathematical search for the optimum positions,
    (b) ease in assembly and disassembly and the potential of automated assembly
    using robotic devices, (c) relative ease of applying design rules due to the finite
    number of element combinations.

    1.1.1.2 Computer-A ided Fixture Research


    Fixture research employing computer aids started in the late 1970s and early
    1980s. In the initial years, interactive or semi-automated fixture design techniques
    (see Fig. 1.1) were built on top of commercial CAD/CAM systems and expert
    system tools. These approaches were mainly concerned with fixture configuration,
    Introduction 3

    Fig. 1.1 A computer-aided modular fixture design [2].

    and there was little analysis of the other aspects such as workpiece-fixture-cutting
    tool interactions.
    A comprehensive fixture research plan should involve the analysis at differ-
    ent computational levels, viz., geometric, kinematic, force and deformation analy-
    ses. The following sections will present brief overviews of the research activities
    in each of the above-mentioned areas, followed by the need to design an intelligent
    fixture which can be integrated with the machine tool.

    ( 1 ) Geometric Analysis
    Geometric analysis is closely associated with fixture planning and spatial
    reasoning. It determines the selection of the type and number of fixturing ele-
    ments, support and locating elements, the order of datum planes, etc. The analy-
    sis also includes the checking of interference between workpiece and fixturing
    elements, as well as cutting tools.
    Most of the early fixture research involved geometric analysis and synthe-
    sis of fixture construction with relatively little attention to kinematic and defor-
    mation analysis.

    (2) Kinematic Analysis


    Kinematic analysis is used to determine whether a fixture configuration is
    able to correctly locate and provide complete constraint to a workpiece.
    Previous work on fixture design automation offers relatively little consid-
    eration in providing a comprehensive fixture-element database and effective
    assembly strategies for the generation and construction of modular fixtures. The
    assembly of modular fixtures is to configure the fixture elements such as loca-
    4 Chapter 1

    tors, clamps and supports (in most cases, accessory elements are needed to gen-
    erate fixture towers to fulfill the fixturing functions) on the base-plate according
    to a fixturing principle (e.g., 3-2-1 principle). The determination of the locating,
    supporting and clamping points for the assembly of modular fixtures is a key
    issue in fixture design automation.

    (3) Force Analysis


    In a machining fixture, different forces are experienced, viz., inertial,
    gravitational, machining and clamping forces. While the first three categories of
    forces are usually more predictable, clamping force can be rather subjective in
    terms of magnitude, and point of application, as well as sequence of application.
    It has been widely accepted that a thorough analysis of all the forces in-
    volved in a fixture is a formidable task since it is an indeterminate problem with
    a large number of fixturing elements. When friction is taken into account, the
    problem becomes even more complex because both the magnitude and the direc-
    tion of the static friction forces are unknown. Recent effort in clamping force
    analysis can be found in [5,6].

    (4) Deformation Analysis


    Due to the complexity of force interaction, workpiece deformation can be
    attributed to a combination of factors. First, a workpiece would deform under
    high cutting and clamping forces. Second, a workpiece could also deform if the
    support and locating elements are not rigid enough to resist the above-mentioned
    forces. In reported literature, it is assumed that workpiece deformation is largely
    due to the first cause mentioned above. The most commonly used method in
    analysing workpiece deformation and fixturing forces is the finite-element
    method.

    1.1.2 Die and Mold Design


    Die and mold making is an important supporting industry since their related
    products represent more than 70% of the non-standard components in engineering
    consumer products. Their production runs are typically of small lot-size and with
    great varieties. The high demand for shorter design and manufacturing lead times,
    good dimensional and overall quality, and rapid design changes have become the
    bottlenecks in die and mold industry. For die and mold-making companies wish-
    ing to maintain the leading edge in local and international markets, they would
    attempt to shorten the manufacturing lead time by using advanced manufacturing
    equipment, automated manufacturing processes and improving the skill level of
    their employees.
    In 1909, Baekeland and his associates developed a synthetic material, Baké-
    lite, from phenol and formaldehyde, and this marked the early beginning of plastic

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