Strategic advantages of interoperability for global manufacturing using CNC technology

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Abstract

In the domain of manufacturing, computer numerically controllers (CNC) technology is a major contributor to the production capacity of the enterprises. The advances in CNC technology coupled with enhancements in computing systems have provided the basis to re-examine the way in which computer-aided systems (CAx) can be used to enable global manufacturing. Interoperability of the various components of the CAx chain is therefore a major prerequisite for manufacturing enterprises for becoming strategically agile and consequently globally competitive. Being interoperable, resources can be utilized interchangeably in a plug-and-produce manner. Over the last 8 years the eminence of a STEP standard for machining entitled STEP-NC (numerical control) has become a well-known vehicle for research to improve the level of information availability at the CNC machine tool. In this paper, the authors introduce the background to the evolution of CNC manufacturing over the last 50 years and the current standards available for programming. A review of the literature in interoperable CNC manufacturing is then provided relating to milling, turn–mill and other NC processes. The major part of the paper provides a strategic view of how interoperability can be implemented across the CAx chain with a range of standards used to regulate the flow of information. Finally, the paper outlines the advantages and major issues for future developments in interoperability, identifying future key requirements and limiting factors.

Introduction

Since the first NC (numerical control) machine was developed in the 1950s, computer numerically controllers (CNC) technology has had a radical effect on the growth of manufacturing across the globe. From this humble beginning, today's CNC multi-process workstation configurations have evolved to support production from high-volume car engine manufacture to low-volume volatile component production. These configurations provide enormous manufacturing flexibility with modular options to produce an enormous range of geometrically complex components, from micro- to multi-metre sized parts, from materials such as aluminium to titanium alloys. Modern multi-process machines not only provide milling or turning capabilities but also allow drilling, milling, turning, laser hardening and grinding to be used on a single machine in one part setup.

In parallel with these machine tool and process developments, CNC vendors have built their proprietary versions and brands of controllers based on programmable logic controllers (PLCs) and PC hardware and software designs. From the early 1980s, CNC vendors started to develop extended programming extensions together with 2D manual data interface (MDI) programming capabilities. These systems were the forerunner of today's 3D feature based machine tool programming systems which incorporate the machine tool vendor's specific programming capabilities. These machine-programming systems provided valuable assistance in enabling SMEs to program simple parts at the machine, but the programming was specific to a machine controller type. In contrast, more complex parts were programmed using computer aided design (CAD)/computer aided manufacturing (CAM) or CAM systems using post-processors which translated the high-level CAPP/CAM commands of such systems to G and M codes for a particular machine. Parts programmed using these systems enabled manufacturers to store geometry and tool paths in a vendor-specific format, and using purchased post-processors gave users quality-assured consistent NC output for their machines.

Though machine programming systems and CAD/CAM systems provide good solutions to program modern CNC machines, they can still be considered as bespoke approaches and islands of information with little or no ability to transfer information between the systems. Thus, users become bound and tied into a system for programming specific part types (i.e. simple contours and holes, feature based, sculptured surface), and then limited to particular machines by controllers or system post-processors. This lack of interoperability provides the driver for research reported in this paper, and the outlined standardized solutions for this paradigm shift in the CNC domain.

The paper provides a strategic view on how interoperability can be implemented for the programming of CNC machine tools. In the initial part of the paper the background and arguments for interoperability in CNC manufacture are outlined, together with a review of NC information standards and their impact. The major part identifies the possible solutions and scenarios for interoperability together with the shortcomings of the approaches. The latter parts provide a view of the advantages of interoperability in a global manufacturing together with the future challenges for its implementation in CNC environments.

Section snippets

A historical background of interoperability in CNC manufacturing

The standard of programming NC machine tools has remained fundamentally unchanged since the early 1950s when the first NC machine was developed at M.I.T. (Massachusetts Institute of Technology), USA. The early NC machines and today's CNCs utilize the same standard for programming, namely G&M codes formalized as the ISO 6893 standard [1]. Starting in the 1970s, significant development has been made towards automatic and reliable CNC machines with new processes such as punching & nibbling, laser

Review of STEP-NC-based interoperable CNC manufacturing research

This section outlines specific areas of STEP-NC-based interoperable research and developments for the various CNC manufacturing processes. The authors recognize that this list is not comprehensive, but can be used as a representative example of STEP-NC-based interoperable manufacturing research:

Enabling interoperability in the CAx manufacturing chain

Interoperability is defined as the ability of computer-based systems to exchange information seamlessly [60]. Martin [61] further defines three levels of connectivity between various systems: unified systems where essentially all information is transferred with no requirement for alterations, integrated systems where information is exchanged in accordance to pre-defined standards and interoperable systems where dynamic information exchange rules are created as required. A CNC manufacturing

Strategic advantages of interoperability for global businesses

The implementation of interoperability has an enormous impact on all manufacturing sectors from large global businesses to the small or even micro manufacturing enterprise as described below.

  • (i)

    At the global level, aerospace and automotive worldwide companies will not only have the added ability to transfer component manufacture not only to identical duplicate plants with identical equipment, but also will be able to use equivalent equipment/machine tools and controllers with the confidence and

Challenges in implementation of interoperability in CNC manufacturing environments

Though these advantages are tremendously encouraging, a number of issues relating to CNC manufacturing interoperability have been formulated based on the requirements identified by Newman [63] and Xu et al. [64]. These issues relate to the directions of current and future research and are outlined below:

  • (i)

    Business factors: The sole beneficiary of enabling interoperability across the CAx chain is the manufacturing user. The advent of manufacturing interoperability for the first time gives these

Conclusions and future work

The changing economic climate has made global manufacturing a growing reality over the last decade, forcing companies to design, manufacture and assemble products across the world. The standards ISO10303 and ISO14649 (STEP and STEP-NC) have been developed to introduce interoperability into manufacturing enterprises. Current implementations of these standards, together with the inherent complexity of STEP compliant CNC controllers, have demonstrated that a global interoperable STEP-NC system is

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