Dealing with feature interactions for prismatic parts in STEP-NC

Determining the precedence of machining features is a critical issue in feature-based process planning. It becomes more complex when geometric interaction occurs between machining features. STEP-NC, the extension of STEP (ISO 10303) standard developed for CNC controllers, is a feature-based data model. It represents all the geometric and topological product data minus feature interactions. In this paper, machining precedence of interactive and non-interactive STEP-NC features is discussed. Local and global precedence of machining features are defined on the basis of geometric constraints, such as geometric interaction of features and feature approach face and technological constraint such as access direction of the cutting tool. A software tool has been developed to visualize the STEP-NC part model and to generate the graphs of feature interaction and feature precedence. The output can be then used to augment the STEP-NC data in order to generate the optimal sequence of operations.     

Design of a STEP compliant system for turning operations

The changing economic climate has made global manufacturing a growing necessity over the last decade, forcing companies from East and West to collaborate beyond geographic boundaries in the design, manufacture and assembly of products. The ISO 10303 and ISO 14649 Standards (STEP and STEP-NC) have been developed to introduce interoperability into manufacturing enterprises so as to meet the challenges of responding to production on demand. This paper describes and illustrates a STEP compliant CAD/CAPP/CAM System for the manufacture of rotational parts on CNC turning centers. The information models to support the proposed system together with the data models defined in the ISO 14649 standard used to create the NC programs are also described. A structured view of a STEP compliant CAD/CAPP/CAM system framework supporting the next generation of intelligent CNC controllers for turn/mill component manufacture is provided. Finally a proposed computational environment for a STEP-NC compliant system for turning operations (SCSTO) is described. SCSTO is the experimental aspect of the research and is supported by information models that and have been constructed using a structured methodology and object-oriented methods. SCSTO was developed to generate a Part 21 file based on machining features to support the interactive generation of process plans utilizing feature extraction. A case study component has been developed to prove the concept of using the milling and turning parts of ISO 14649 to provide a turn-mill CAD/CAPP/CAM environment.     

Advanced CNC system with in-process feed-rate optimisation

Tight quality requirements and stringent customer demands are the main thrust behind the development of new generation machine tool controllers that are more universal, adaptable and interoperable. The development of some international standards such as STEP and STEP-NC presents a vision for intelligent CNC machining. Implementation of STEP-NC enabled Machine Condition Monitoring (MCM) is presented in this paper. The system allows optimisation during machining in order to shorten machining time and increase product quality. In the system, an optiSTEP-NC, an AECopt controller and a Knowledge-Based Evaluation (KBE) module have been developed. The aim of the optiSTEP-NC system is to perform initial feed-rate optimisation based on STEP-NC data to assist process planners in assigning appropriate machining parameters. AECopt acts as a connector between the process planner and machining environment with the intention to provide adaptive and automatic in-process machining optimisation. KBE based-MTConnect is responsible for obtaining machining know-how. Optimisation is performed before, during or after machining operations, based on the data collected and monitored such as machining vibration, acceleration and jerk, cutting power and feed-rate.     

A novel methodology for cross-technology interoperability in CNC machining

In CNC part programmes, the lack of standardisation for representing part geometry and semantics of manufacturing operations leads to the necessity for existence of a unique part programme for each machine. Generating multiple programmes for producing the same part is not a value adding activity and is very time consuming. This wasteful activity can be eliminated if users are given the ability to write an NC program for a specific machine and robustly convert the program to syntax suitable for another CNC machine with a different structure. This, cross-technology interoperability, would enable for parts manufactured on old CNC machines using legacy code to be manufactured on new CNC machines by automatically converting the programmes. Every NC programme is written based on various categories of information such as: cutting tool specifications, process planning knowledge and machine tool information. This paper presents an approach for cross-technology interoperability by refining high-level process information (i.e., geometric features on the part and embedded manufacturing resource data) from NC programmes. These refined items of information stored in compliance with the ISO14649 (STEP-NC) standard may then be combined with new manufacturing resource information to generate NC code in a format that is compatible with machines based on different technologies. The authors provide a framework for this process of identification, semantic interpretation and re-integration of information. The focus of this paper is on asymmetric rotational components as the initial application area. To demonstrate the proposed cross-technology interoperability approach, a C-axis CNC turn–mill machine and a 4 axis CNC machining centre have been used with a simple test component.     

高性能数控系统解释技术的研究与实现

针对高性能数控系统中解释器面临的要求,通过深入分析现有数控系统中解释器及与之交互的任务控制器的主要功能及实现方法,指出其在高速高精加工时存在的不足,在此基础上设计并实现了一种高效的NC代码解释机制;然后,对现有数控系统进行了基于STEP-NC的改造,提出了面向网络化制造STEP-NC数控系统的基本框架,并重点介绍了基于XML的STEP-NC程序解释器的设计与实现.     

Striving for a total integration of CAD, CAPP, CAM and CNC

Over the last 50 years, conventional programming of the numerical controlled (NC) machine tools has been based on a data model stipulated by ISO 6983, or otherwise known as G-codes. It was designed to sequentially pass instructions to the controls of machine tools with little, if any, intelligence. It has been realized that this standard has led to serious impediments for the fulfilment of total CAD/CAM integration. The forthcoming ISO 14649 defines a new interface for exchange of information between CAD/CAM systems and NC machine tools. ISO 14649 is strictly harmonized with ISO 10303 (STEP), hence the name STEP-NC meaning an extended STEP for numerical control. There has been substantial amount of research being carried out concerning STEP-NC, in particular EU and USA; its benefits and potentials are revealing and appealing. The manufacturing industry may have to embrace itself with a revolutionary change even more dramatic than that of introduction of numerical control about half a century ago.     

STEP-NC--新一代机床控制器

STEP－NC是新近提出的采用STEP规范的数控机床数据接口标准，STEP－NC控制器将不再使用G、M代码来编程，而使用STEP标准的三维产品数据模型加上工艺和刀具信息直接产生加工程序。本文介绍了STEP－NC的基本概念、研究概况，展望了其发展前景以及对未来制造业的重大影响。     

基于STEP-NC的CAD/CAPP/CNC系统集成及应用研究

传统数控系统的编程都是基于ISO 6983,其本质是面向过程的,传递到CNC的数控程序丢失了高层信息,使得CNC系统与上游的CAD/CAPP/CAM系统之间不能实现完整的信息传递。STEPNC的出现使CNC系统与其它系统间的信息交流与共享成为了可能。提出了一种基于STEP-NC的CAD/CAPP/CNC系统集成模型,对其实现原理和应用过程进行了介绍,并将其应用在柔性制造系统中,设计了一个基于STEP-NC的柔性制造系统平台。     

Reincarnation of G-code based part programs into STEP-NC for turning applications

As STEP-NC emerges as the new CNC control method and a fundamental means for realizing e-manufacturing, old manufacturing information based on the conventional manufacturing standard will become obsolete. In practice, replacement of G-code based part programs into STEP-NC is a huge task. In this paper, methods to interpret G-code based part programs into STEP-NC code are investigated. G-code is a compact, coded set of numbers for axis movements, while STEP-NC is very comprehensive and includes information about features, operations, strategies, cutting tools, and so on. It is thus very challenging to derive such comprehensive information from the low level G-code information. In this paper, we first clarify what should be given and what may be given, and then present algorithms for deriving STEP-NC information, such as geometric features, operations, etc., from the tool movement (G-code) based on expert reasoning. The algorithms are developed for the turning application. The developed algorithms were implemented and tested on G-code part programs used in actual practice.     

基于内核平台的开放式数控系统

分析了开放式数控系统国内外的研究现状,论述了当前数控系统中存在的不足以及今后的发展趋势,并在此基础上提出"基于内核平台的模块化、开放式数控系统",详细地介绍了该体系下基于内核平台的数控系统架构、内核平台建立、CNC加工信息到CAD产品模型的反馈三大部分的功能与实现技术.