Reviewing Iso 14649 Through Iso10303

VOL. 11, NO. 10, MAY 2016 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences

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REVIEWING ISO 14649 THROUGH ISO10303

Noordiana Kassim1, Yusri Yusof2 and Mohd Zakiyamani Awang2 1Center for Diploma Studies, University Tun Hussein Onn, Malaysia 2Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia 3Faculty of Electrical and Electronic Engineering, Universiti Tun Hussein Onn Malaysia E-mail: [email protected]

ABSTRACT STEP-NC was designed to replace ISO 6983 G-codes with a modern, associative communications protocol that connects computer numerical controlled (CNC) process data to a product description of the part being machined. STEP-NC is a machine tool control language that extends the ISO 10303 STEP standards with the machining model in ISO 14649 or also known as STEP-NC. The combinations of implementation methods and application protocols defined in STEP and STEP-NC standards provide standardized physical file formats and data access interfaces for those physical file formats that can cover all the aspects of design and manufacturing activities. The data exchanges between different systems will no longer have barriers through the implementation of STEP-NC in the computerized manufacturing environment. It will provide the missing link between CAD to CAM applications. This paper will review ISO 14649 which is STEP-NC through an understanding of STEP which is ISO 10303 standard for the computer-interpretable representation and exchange of product manufacturing information.

Keywords: STEP, STEP-NC, ISO14649, ISO10303, CNC.

INTRODUCTION the use of such national standards represented best current The set of documents that forms the ISO 10303- practice, all required considerable effort to achieve series standard is commonly called STEP is an acronym effective results. for the Standard for the Exchange of Product data model. By the middle 1980s, it had become apparent that STEP is the result of the experience gained by the industry’s needs would only be properly addressed by a community of users and developers of standards through more comprehensive international effort that would not the initial efforts for standardizing data exchange. The only improve on the existing specifications, but also fulfill purpose of STEP, as stated in the document giving the requirements for life-cycle product data support [4]. fundamental principles of STEP [1] is “to specify a form for the representation and unambiguous exchange of The following factors contribute to the perceived computer-interpretable product information throughout the deficiencies of standards such as IGES [4]: life of a product”. . The specification is open to ambiguous interpretation, The actual designation of the STEP standard is and there are therefore variations in the quality of ISO 10303 Industrial Automation System – Product Data translator software. Representation and Exchange. STEP provides a computer . Every CAD system vendor supports a subset of the interpretable representation and exchange of product data. standard applicable to their own product. Product data represents information about the product in . The standards are limited to the exchange of formal manner suitable for communication, interpretation, geometric information (the two- or three-dimensional or processing by human beings or by computers. shapes of objects), engineering drawings, and some The objective of STEP is to provide a neutral non-graphical data such as connectivity. mechanism capable of describing product data throughout the product life cycle independent of any particular The STEP project was initiated in 1984 with the system. STEP is a proactive effort, the focus being placed intention to create a single international standard, covering on developing a standard that caters for various user all aspects of CAD/CAM exchange. The standard should groups. Recently, STEP has been extended to cater for be able to describe product data from its implementation manufacturing data modeling and execution with an aim to such that it would be suitable for neutral file exchange but filling the information gap between CAD/CAM/CAPP also provide the basis for shared product databases, for chain and CNCs [2]. long-term archiving [3]. Major aerospace and automotive The need for data exchange standards was companies have proven the value of STEP through originally recognized in the late 1970s and led to the production implementations, resulting in saving of 150 development of specifications such as the Initial Graphics million per year in the U.S [5]. Exchange Specification (IGES) in the USA, Standard STEP development is a multinational effort. At D’Exchange et de Transfert (SET) in France, and Verband present, nineteen countries participate in the development der Automobilindustrie-Flachen-Schnittstelle (VDA-FS) of ISO10303 (STEP). The coordination of these efforts is in Germany. These standards all prescribe the use of accomplished through the International Standards standard file formats for the exchange of data [3]. While Organization (ISO) [6]. Within ISO, there is a Technical

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Committee known as TC 184, which deals with Industrial and Conformance Tools. Figure-1 illustrates the structure Automation Systems and Integration. Further, within this of the STEP standard. technical committee there exists a sub-committee known as Subcommittee 4 (SC4) which coordinates and controls the development of the STEP standard throughout the world. The Sub Committee's title is Industrial Data [3].

STEP - ISO 10303 Objectives of STEP The purpose of STEP is to specify a form for the representation and unambiguous exchange of computer- interpretable product information throughout the life of a product[7]. STEP permits different implementation methods to be used for storing, accessing, transferring, and archiving product data [7]. The STEP project was initiated with the following objectives [3]: . The creation of a single international standard, covering all aspects of CAD/CAM data exchange. . The implementation and acceptance of this standard in industry, superseding various national standards and specifications. . The standardization of a mechanism for describing product data, throughout the life-cycle of a product,

and independent of any particular system. . The separation of the description of product data from Figure-1. Structure of the STEP standard [7]. its implementation, such that the standard would not only be suitable for neutral file exchange, but also The Parts of STEP may be grouped by type as provide the basis for shared product databases, and for follows. The Parts are numbered so that all Parts of the long-term archiving. same type fall in the same number range. The range is given below after the type. Not all numbers are used. Additional objectives of the original developers There are several hundred application modules. of STEP included the creation of a single international An application protocol can be built by including standard covering all aspects of CAD/CAM data exchange a (usually large) number of application modules. Using and the implementation and acceptance of this standard by application modules is a more recent architectural industry in lieu of other methods [8]. Automatically approach than using application interpreted constructs and generated process plans, often require further input from may replace application interpreted constructs. the engineers on the shop floor to ensure their appropriateness to the actual status of the resources and STEP description method production policies as dictated by the manufacturing The description methods are defined via the data enterprise. In order to enable the process planning system modeling language, EXPRESS. EXPRESS is a completely to determine the most effective plan with respect to the generic modeling language and can therefore be used to actual available resources, it is necessary to provide model data objects of any type. It is a formal language for resource information that reflects the status of the physical the definition of entity-attribute data models. Its original devices at the time that they will be utilized for use was for the definition of standard data models manufacturing the part. STEP-compliant methodology will describing 3D graphical representations of physical represents resources that is extended to allow the objects, i.e., CAD drawings. representation of machine tool capability profiles in a The EXPRESS language is completely time-based manner while enabling users to define custom declarative and implementation independent, making it rules and policies [9]. well suited for the standardized data models. On the other hand, EXPRESS is a data modeling language, which Structure of STEP means it only defines entities and their properties, and The STEP standard is separated into many parts. does not define methods that might be applied to those These parts cover from presenting the standard, entities in an application context[10]. implementation architectures, conformance testing, The EXPRESS language does not define any resource information models and application protocols. implementation methods. Therefore, additional The parts are called Description Methods, Information implementation methods are defined to describe STEP Models, Application Protocols, Implementation Methods instances for building product exchange models. There are several implementation technologies available [11]:

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. A product model specific file format called Part 21 the complexity, different groups of developers and physical file; different speed in the development processes, the splitting . A variety of programming language bindings that into several APs was needed. But this splitting made it allow an application programmer to open a data set difficult to ensure that APs are interoperable in and access values in its entity instances. Bindings overlapping areas. Main areas of harmonization are: AP have been developed for C, C++ and Java 214 and AP 203 in the area of 3D mechanical design. AP . The three methods for mapping the EXPRESS 214 took over all of the functionality of the earlier AP 203 defined data into XML described by Part 28 Edition 1 edition and then extending the capabilities significantly. and The second edition of AP 203 (published in 2011) took . The XML Schema-governed representation of over bigger parts of AP 214 by adding again new EXPRESS described by Part 28 Edition 2. functionality. The upcoming AP 242 will formally replace AP 203, AP 214 and other mechanical design APs. In STEP Application protocols (AP) middle 2010 the development of the new major AP 242 Application protocols (APs) are the managed model based 3D engineering was initiated. The implementable data specifications of STEP. APs include first edition of AP 242 is expected to be dedicated to an EXPRESS information model that satisfies the specific replace the most successful STEP APs 203, 214 and other product data needs of a given application context. APs APs in the mechanical design area in an upward may be implemented using one or more of the compatible way. implementation methods. They are the central component of the STEP architecture, and the STEP architecture is STEP implementation designed primarily to support and facilitate developing STEP implementations fall into several APs. Many of the components of an application protocol categories. Translators take data from preexisting systems are intended to document the application domain in and convert it into STEP AP defined data. The tool application-specific terminology. converts non STEP data into STEP data. Other This facilitates the review of the application protocol by applications might take STEP data as input, and then domain experts. Below are some of the 200 series perform some function on it, generating more STEP Application Protocols (APs) that are currently available output. An example of such a thing would be an for mechanical. application that takes partial AP information from several sources, like geometry from a CAD system and . AP 201: Explicit Draughting. Simple 2D drawing configuration information from a CM system, and then geometry related to a product. No association, no merges them into a complete AP exchange file. Another assembly hierarchy. category might be an application that takes specific AP . AP 203: Configuration controlled 3D designs of data and performs some analysis on it, such as a finite mechanical parts and assemblies. element package or a geometry visualizer. These . AP 204: Mechanical design using boundary applications should all work from STEP exchange files representation. and possibly a shared database as well, so it is important to . AP 209: Composite and metallic structural analysis consider how the application will be tied to the EXPRESS and related design. information models of the various APs that they will work . AP 214: Core data for automotive mechanical design with [4]. processes. . AP 235: Materials information for the design and ISO 14649 verification of products. STEP-NC . AP 236: Furniture product data and project data. The emergence of STEP-NC is essential when . AP 242: Managed model based 3D engineering talking about an information model for better CAD/CAM (under development). information sharing. STEP-NC, the manufacturing

extension of STEP, annotates the design information with STEP AP 203 and STEP AP 214 manufacturing data[12]. It is being developed through Most of the previous researchers used generic international effort, following the success of the STEP AP 203 as their input file. This research will used international standard STEP, to provide a data model for generic STEP AP 214 as its input file. Generally, AP 203 CNC machines. A data model for basic milling, drilling is a "general" STEP format. AP 203 defines the geometry, and turning operations has already been developed. topology, and configuration management data of solid ISO 14649 or STEP-NC is free of the STEP models for mechanical parts and assemblies. This file type design data, or strictly speaking it was developed with an does not manage Colors and Layers. AP 214 has intention not to include the complete design data. The everything an AP 203 file includes, but adds colors, layers, absence of design information makes the bi-directional and geometric dimensioning and tolerance, and design data flow between design and manufacturing impossible. intent. AP 214 is considered an extension of AP 203. As a part of the STEP standard, STEP AP 238 inherits all The original intent of STEP was to publish one the information from STEP AP 203 and AP 224 plus an integrated data-model for all life cycle aspects. But due to

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www.arpnjournals.com interpreted model mapped from ISO 14649. Hence, bi- between these two (2) models is the degree to which they directional data exchange can be supported. Figure-2 use the STEP representation methods and technical portrays the relationship between ISO 14649 and some architecture. Both versions can be viewed as different APs of STEP ISO 10303. Based on the Figure-2, the implementation methods of STEP-NC. Industry is still nominal and tolerance of geometrical information would debating on whether to use AIM or ARM. Furthermore, be the foundation of the AP 203 and the entities for many inconsistencies among standards remain to be machining feature and tolerances capabilities are being resolved to standardize the STEP-NC data model. included in STEP AP 224. AP 238 is an integrated Therefore, a large amount of systems-building work is still resource file that covers all the relevant information needed to make STEP-NC related technology regarding machining operations. commercially viable.

CONCLUSIONS The primary goal of STEP is to facilitate interoperability among implementations of different STEP application protocols. This is accomplished through consistent mapping of similar requirements to the generic building data structures in the integrated resources. With the use of full fidelity STEP-NC data as direct input to a CNC machine, many bottlenecks to manufacturing productivity will be eliminated, such as cumbersome post processors, antiquated G-Codes, data redundancies and more [18]. The nature of STEP and STEP-NC data format makes it suitable not only as neutral data, but also as a platform for sharing, distributing and Figure-2. Relationships between ISO14649 and STEP archiving data. By adopting a universal data standard, the APs [13]. issue of incompatibility among the system structure can be averted [19]. ISO 14649 and ISO 10303-238 can be viewed as By using Workingstep as the basic entity, STEP- two different implementation methods of the STEP-NC NC expands a set of related entity such as machining standard. The ISO 14649 standard is more likely to be features, cutting tools and tolerance according to STEP used in an environment in which CAM systems have exact definition. The high-level information provided by STEP- information from the shop floor; whereas STEP AP 238, NC makes CNC programs more readable and modifiable; as a part of the STEP standard, is more suitable for a it also enables bi-directional data flow between CNC complete design and manufacturing integration. machines and CAM systems (or even CAD systems). STEP-NC provides direct input for CNC machine Because of these technical advantages and benefits in tools, consisting of product information such as geometry, STEP and STEP-NC, the research work reported in this features, machining steps and tool path [14-15]. Currently, thesis utilizes both STEP and STEP-NC as the CNC machines have to be programmed using G-codes, underpinning product and manufacturing models. which only describe the exact tool movements, without any information of the part being processed. Unlike G- REFERENCES codes, STEP-NC tells machine what to do instead of how to do it. [1] ISO10303-1, "Industrial automation systems and integration – Product data representation and Challenges of STEP-NC exchange – Part 1: Industrial Automation System and Although STEP-NC is appealing and gathering Integration- Product Data Representation and more and more interest from researchers, there are some Exchange Part 1: Overview and Fundamental challenges to overcome before it can be realized [16]. Principles," ed, 1994. Certain capabilities of CAM systems are moved to NC controllers, such as tools rotation information and feedrate [2] C. Brecher, et al., "Closed-loop CAPP/CAM/CNC by adopting STEP-NC. It results in much more Process Chain Based on STEP ans STEP-NC complicated controllers and requires more knowledge Inspection Tasks," International Journal of Computer from the machine operators [17]. Before STEP-NC can be Integrated Manufacturing, vol. Vol. 19, pp. pp. 570- practically used in manufacturing, new STEP-NC 580, 2006. compliant controllers for NC machines have to be developed first. NC controller manufacturers then have to [3] S. M. Amaitik, "Development of a STEP Feature- redesign the structures and strategies of their controllers to Based Intelligent Process Planning System for make it happen. There are two (2) versions of STEP-NC Prismitic Parts," Doctor of Philosophy, The Graduate being developed concurrently by ISO, ARM (ISO 14649) School of Natural and Applied Science, Middle East and AIM (ISO 10303 – AP 238). The main difference Technical University, 2005.

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