Integration Based on STEP Standards

Integration Based on STEP Standards

Xun Xu (University of Auckland, NZ)
DOI: 10.4018/978-1-59904-714-0.ch011
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Abstract

The integration model (Model B) as discussed in the previous chapter makes use of exchangeable neutral data formats such as IGES (1980). Neutral data formats provide a middle tier to connect CAD and CAM systems. Thus, Model B can create a collaborative manufacturing environment and make the design data exchange possible for large projects at the international level. Yet, some problems still remain. IGES was designed to exchange geometrical information only, so additional design or manufacturing information (such as feature information) within a proprietary model is ignored. During data exchange, some information may become astray during data transfer; geometry stitching or model repair is often needed. Plus, IGES is not an international standard. As previously discussed, there are also problems common to both Models A and B (Figure 10.1). Different data formats (e.g. IGES and ISO 6983-1, 1982) are used in the designto- manufacturing chain. Data loss occurs in the transaction from design to manufacturing because only low-level, step-by-step sequential machining commands are passed onto the CNC controllers, leaving the complete product model behind. Of particular significance has been the endeavour made by the International Organization for Standardization to introduce the STEP Standard (i.e. ISO 10303-1 [1994]). Major aerospace and automotive companies have proven the value of STEP through production implementations resulting in savings of US $150 million per year (Gallaher, O’Connor & Phelps, 2002, PDES, Inc. 2006). Moreover, STEP has recently been extended to cater to manufacturing data modelling and execution with an aim to fill the information gap between CAD/CAPP/CAM and CNC. The standard is informally known as STEP-compliant Numerical Control, or otherwise STEP-NC for short. It was given an ISO name of “ISO 14649: Data model for Computerized Numerical Controllers (ISO 14649-1, 2003)”, which defines the STEP-NC Application Reference Model. With STEP being extended to model manufacturing information, a new paradigm of integrated CAD/CAPP/CAM/CNC is emerging. This is illustrated in Figure 11.1. The key to this paradigm is that no data conversion is required and the data throughout the design and manufacturing chain are preserved. This chapter focuses on the use of STEP standards to support data exchange between CAD systems as well as facilitate data flow between CAD, CAPP, CAM, and CNC systems. Also discussed are the specific integration issues between CAD and CAPP, CAPP and CAM, and CAM and CNC using STEP standards. STEP-NC data model is a relatively new member in the STEP family, but it completes the entire suite of STEP standards from design to NC machining. Both Physical File Implementation Method (ISO 10303-21, 1994) and XML Implementation Method (ISO/TS 10303-18, 2004) are presented as the two popular ways of implementing STEP and STEP-NC.
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Data Exchange Using Step And Step-Nc

STEP has been briefly introduced in Chapter II. This section discusses the standard from the perspective of being a useful tool to support data exchange and integration. The keys to the STEP standard are, a. its generic nature, b. computer-interpretable format, and c. consistent data implementations across multiple applications and systems. They permit different implementation methods to be used for storing, accessing, transferring and archiving product data. The specification of a representation of product information is provided by a set of integrated resources. Each integrated resource comprises a set of product data descriptions, written in EXPRESS (ISO 10303-11, 1994) known as resource constructs. One set may be dependent on other sets for its definition. Similar information for different applications is represented by a single resource construct. The integrated resources are divided into two groups: generic resources and application resources. The generic resources are independent of applications and can reference each other. The application resources can reference the generic resources and can add other resource constructs for use by a group of similar applications. Application resources do not reference other application resources. (Figure 1)

Figure 1.

Integrating CAD/CAPP/CAM/CNC

The integrated resources define a generic information model for product information. They are not sufficient to support the information requirements of an application without the addition of application specific constraints, relationships and attributes. STEP defines Application Protocols in which the integrated resources are interpreted to meet the product information requirements of specific applications, in other words Application Reference Model. The interpretation is achieved by selecting appropriate resource constructs, refining their meaning, and specifying any appropriate constraints, relationships and attributes. This interpretation results in an Application Interpreted Model. It is these AIMs that STEP brings data of differing applications under the same roof.

Data Exchange between CAD Systems

The STEP standard was initially designed to offer a neutral data exchange method in replacement of IGES. The two APs that have been established to mainly support design data exchanging and sharing are the AP for configuration controlled 3D designs of mechanical parts and assemblies (AP 203) (ISO 10303-203, 1994), and the AP for the core data for automotive mechanical design processes (AP 214) (ISO 10303-214, 1994). Currently, most of the commercial CAD systems can output STEP AP-203 and/or STEP AP-214 files via STEP translators. According to the report from Research Triangle Institute (1999), when STEP is used as a neutral format to exchange wireframe and surface data between commonly used commercial CAD systems, it fares better than IGES. This indicates that STEP is ready to replace IGES. However, the STEP standard is much more than a neutral data format that translates geometrical data between CAD systems. The ultimate goal of STEP is to provide a complete computer-interpretable product data format, so that users can integrate business and technical data to support the whole product life cycle: design, analysis, manufacturing, sales and customer services.

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Dedication
Table of Contents
Foreword
A.Y.C. Nee
Acknowledgment
Xun Xu
Chapter 1
Xun Xu
One of the key activities in any product design process is to develop a geometric model of the product from the conceptual ideas, which can then be... Sample PDF
Geometric Modelling and Computer-Aided Design
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Chapter 2
Xun Xu
Today, more companies than ever before are involved in manufacturing various parts of their end products using different subcontractors, many of... Sample PDF
CAD Data Exhange and CAD Standards
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Chapter 3
Xun Xu
Products and their components are designed to perform certain functions. Design specifi- cations ensure the functionality aspects. The task in... Sample PDF
Computer-Aided Process Planning and Manufacturing
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Chapter 4
Feature Technology  (pages 75-89)
Xun Xu
Throughout the course of the development of CAD, CAPP, and CAM systems, unambiguous representation of a design’s geometry and topology remain an... Sample PDF
Feature Technology
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Chapter 5
Feature Recognition  (pages 90-108)
Xun Xu
Conventional CAD models only provide pure geometry and topology for mechanical designs such as vertices, edges, faces, simple primitives, and the... Sample PDF
Feature Recognition
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Chapter 6
Feature Interactions  (pages 109-125)
Xun Xu
Feature interaction tends to have a wide range of consequences and effects on a feature model and its applications. While these may often be... Sample PDF
Feature Interactions
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Chapter 7
Xun Xu
Integrated feature technology promotes a closer connection between design and manufacturing through features. When machining features are... Sample PDF
Integrated Feature Technolog
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Chapter 8
CNC Machine Tools  (pages 165-187)
Xun Xu
The introduction of CNC machines has radically changed the manufacturing industry. Curves are as easy to cut as straight lines, complex 3-D... Sample PDF
CNC Machine Tools
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Chapter 9
Program CNCs  (pages 188-229)
Xun Xu
A CNC machine can be programmed in different ways to machine a workpiece. In addition to creating the cutting program, many other factors also need... Sample PDF
Program CNCs
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Chapter 10
Xun Xu
Technologies concerning computer-aided design, process planning, manufacturing and numerical control, have matured to a point that commercialized... Sample PDF
Integration of CAD/CAPP/CAM/CNC
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Chapter 11
Xun Xu
The integration model (Model B) as discussed in the previous chapter makes use of exchangeable neutral data formats such as IGES (1980). Neutral... Sample PDF
Integration Based on STEP Standards
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Chapter 12
Xun Xu
Function blocks are an IEC (International Electro-technical Commission) standard for distributed industrial processes and control systems (IEC... Sample PDF
Function Block-Enabled Integration
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Chapter 13
Xun Xu
In order to prepare manufacturing companies to face increasingly frequent and unpredictable market changes with confidence, there is a recognized... Sample PDF
Development of an Integrated, Adaptable CNC System
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Chapter 14
Xun Xu
A logical step after CNC machining is inspection. With inspections, Closed-Loop Machining (CLM) can be realized to maximize the efficiency of a... Sample PDF
Integrating CAD/CAPP/CAM/CNC with Inspections
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Chapter 15
Xun Xu
Today, companies often have operations distributed around the world, and production facilities and designers are often in different locations.... Sample PDF
Internet-Based Integration
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Chapter 16
Xun Xu
Companies that have been practicing CAD, CAPP, CAM, and CNC integration have now realized that there is a need to operate in a much broader scope... Sample PDF
From CAD/CAPP/CAM/CNC to PDM, PLM and Beyond
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Chapter 17
Key Enabling Technologies  (pages 354-393)
Xun Xu
While computers have proven to be instrumental in the advancement of product design and manufacturing processes, the role that various technologies... Sample PDF
Key Enabling Technologies
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