Aydin Nassehi

A review of hybrid manufacturing processes – state of the art and future perspectives

Today, hybrid manufacturing technology has drawn significant interests from both academia and industry due to the capability to make products in a more efficient and productive way. Although there is no specific consensus on the definition of the term ‘hybrid processes’, researchers have explored a number of approaches to combine different manufacturing processes with the similar objectives of improving surface integrity, increasing material removal rate, reducing tool wear, reducing production time and extending application areas. Thus, hybrid processes open up new opportunities and applications for manufacturing various components which are not able to be produced economically by processes on their own. This review paper starts with the classification of current manufacturing processes based on processes being defined as additive, subtractive, transformative, joining and dividing. Definitions of hybrid processes from other researchers in the literature are then introduced. The major part of this paper reviews existing hybrid processes reported over the past two decades. Finally, this paper attempts to propose possible definitions of hybrid processes along with the authors’ classification, followed by discussion of their developments, limitations and future research needs.

A new software platform to support feature-based process planning for interoperable STEP-NC manufacture

Computer numerical control (CNC) manufacturing has evolved with the use of faster, more precise and more capable CNC controllers and machine tools. The enhancements in machine tools however have not been integrated under a common platform to support computer aided design (CAD)/computer aided manufacturing (CAM)/CNC software interoperability and as a result a plethora of standards are being used for these systems. ISO 10303 (STEP) and ISO 14649 (STEP-NC) seek to eliminate the barriers in the exchange of information in the CNC manufacturing chain and enable interoperability throughout the manufacturing software domain. With the progress on standardization and implementation, computer systems in the manufacturing process chain require evolution to support the STEP-compliant planning and manufacture. The current paper introduces a novel software platform entitled the Integrated Platform for Process Planning and Control (IP3AC) to support STEP-NC compliant process planning (computer aided process planning (CAPP)/CAM). A prototype process planning system (PPS) based on the platform is then presented as a sample application in the light of future interoperable planning and manufacture. The PPS has been developed with the application of a two-stage strategy for STEP-NC part program generation, namely general workplan generation and specific workplan generation. The work is verified through the use of case study components.

Process comprehension for shopfloor manufacturing knowledge reuse

Computer numerical controlled (CNC) machines play an important role in the production capacity of manufacturing enterprises. With the advance of computing technology, computer-aided systems (CAx) have been intensively used together with the CNC machines. The information flow from CAx to CNC machines is unidirectional, due to the widespread use of G&M codes to programme the CNC machines and the mechanism of the generation of part programmes. The CNC machines at the shopfloor have been isolated from the CAx chain. There is no automatic way to capture and feedback the shopfloor knowledge. Reusing shopfloor process knowledge offers the enterprises opportunities to improve manufacturing quality and control while enabling savings in cost and time. Rapid product development relies heavily on quick and reliable process planning and knowledge reuse to facilitate the process plan efficiently and effectively. In this research, the process comprehension approach has been utilised to capture the process knowledge at the shopfloor. A novel method has been proposed to reuse the process knowledge with different manufacturing resources. In this paper, a short review on manufacturing knowledge management is provided. The process comprehension approach is then presented. An example part is used as the case study to illustrate the knowledge capture using process comprehension and how the process knowledge can be utilised to manufacture the product with new manufacturing resources.

Virtual visual sensors and their application in structural health monitoring

Wireless sensor networks are being increasingly accepted as an effective tool for structural health monitoring. The ability to deploy a wireless array of sensors efficiently and effectively is a key factor in structural health monitoring. Sensor installation and management can be difficult in practice for a variety of reasons: a hostile environment, high labour costs and bandwidth limitations. We present and evaluate a proof-of-concept application of virtual visual sensors to the well-known engineering problem of the cantilever beam, as a convenient physical sensor substitute for certain problems and environments. We demonstrate the effectiveness of virtual visual sensors as a means to achieve non-destructive evaluation. Major benefits of virtual visual sensors are its non-invasive nature, ease of installation and cost-effectiveness. The novelty of virtual visual sensors lies in the combination of marker extraction with visual tracking realised by modern computer vision algorithms. We demonstrate that by deploying a collection of virtual visual sensors on an oscillating structure, its modal shapes and frequencies can be readily extracted from a sequence of video images. Subsequently, we perform damage detection and localisation by means of a wavelet-based analysis. The contributions of this article are as follows: (1) use of a sub-pixel accuracy marker extraction algorithm to construct virtual sensors in the spatial domain, (2) embedding dynamic marker linking within a tracking-by-correspondence paradigm that offers benefits in computational efficiency and registration accuracy over traditional tracking-by-searching systems and (3) validation of virtual visual sensors in the context of a structural health monitoring application.

Toward interoperable CNC manufacturing

Most manufacturing enterprises now employ compute numerical control (CNC) technology in their production chain. Improving the performance and flexibility of the computer aided design (CAD)/computer aided manufacturing (CAM)/CNC chain can therefore, have a significant effect on the competitiveness of such enterprises. Whereas hardware capabilities of these systems have increased proactively over the last few decades, the software components have been updated reactively to support the enhancements found on the newer generation of CNC machines. This passive approach has led to severe incompatibilities between the various CAD/CAM/CNC solutions. This paper presents the impediments and issues arising from such incompatibilities and proposes a new framework to overcome these barriers in achieving interoperability in the CAD/CAM/CNC chain. In the suggested framework different components of the CAD/CAM/CNC chain can exchange information with one another regardless of their native standards. The different elements comprising the framework are demonstrated by utilizing a test component in a dynamic manufacturing scenario.

A unified manufacturing resource model for representation of computerized numerically controlled machine tools

Abstract The capability of any manufacturing system primarily depends on its available machine tools. Thus machine tool representation is a vital part of modelling any manufacturing system. With the rapid advances in computerized numerically controlled (CNC) machines, machine tool representation has become a more challenging task than ever before. Todays CNC machine tools are more than just automated manufacturing machines, as they can be considered multi-purpose, multi-tasking, and hybrid machining centres. This paper presents a versatile methodology for representing such state-of-the-art CNC machining system resources. A machine tool model is a conceptual representation of the real machine tool and provides a logical framework for representing its functionality in the manufacturing system. There are several commercial modelling tools available in the market for modelling machine tools. However, there is no common methodology among them to represent the wide diversity of machine tool configurations. These modelling tools are either machine vendor specific or limited in their scope to represent machine tool capability. In addition, the current information models of STEP-NC, namely ISO 14649, can only describe machining operations, technologies, cutting tools, and product geometries. However, they do not support the representation of machine tools. The proposed unified manufacturing resource model (UMRM) has a data model which can fill this gap by providing machine specific data in the form of an EXPRESS schema and act as a complementary part to the STEP-NC standard to represent various machine tools in a standardized form. UMRM is flexible enough to represent any type of CNC machining centre. This machine tool representation can be utilized to represent machine tool functionality and consequential process capabilities for allocating resources for process planning and machining.

Application of mobile agents in interoperable STEP-NC compliant manufacturing

As the ratio of transport costs to total product cost increases, manufacturers try to fulfil the demands of each geographical region with products manufactured within the same region. Since the manufacturing resources available at each venue can be varied, it is necessary to adapt the manufacturing process plan for each production facility. Traditionally, this process is carried out manually by engineers utilizing computer-aided design (CAD) files. With the advances in artificial intelligence technology and emergence of integration standards such as STEP, it is now possible to automate the CAD/computer-aided manufacturing (CAM)/computer numerical control (CNC) interface. Distributed artificial intelligence techniques and mobile agents in particular can be used to transfer information throughout the manufacturing network and construct the distributed knowledge-base required for the intelligent interoperable integration of product data models and manufacturing resources. This paper explores the application of mobile agents as enablers of interoperability in a global manufacturing enterprise. A novel manufacturing chain based on the STEP-NC standard is proposed and the application of agents for transfer of manufacturing information is studied. The research is demonstrated through the use of a prototype manufacturing decision support system developed using agents.

A Methodology for the Estimation of Build Time for Operation Sequencing in Process Planning for a Hybrid Process

The on-going industrial trend toward production of highly complex and accurate part geometries with reduced costs has led to the emergence of hybrid manufacturing processes where varied manufacturing operations are carried out in either parallel or serial manner. One such hybrid process being currently developed is the iAtractive process, which combines additive, subtractive, and inspection processes. The enabler for realizing the hybrid process production is the process planning algorithm. The production time estimation for the additive process, namely build time, is one of the key drivers for the major elements in the algorithm. This paper describes a method for predicting build times for operation sequencing for process planning of the iAtractive process. An analytical model is first proposed, theoretically analyzing the factors that affect build times, which is used to help with the design of four test parts together with 64 sets of variations. The experimental results indicate that part volume, and interactions of volume and porosity, height and intermittent factor have significant effect on build times. Finally, the build time estimation model has been developed, which were subsequently evaluated and validated by applying a wide range of the identified influential factors.

Using formal methods to model hybrid manufacturing processes

The on-going industrial trend towards high value sustainable manufacturing has led to the emergence of hybrid manufacturing processes and resources. This new generation of processes and resources combine the capabilities of a number of older technologies on a single platform. This increase in capability, however, comes at the cost of increasing complexity. Manufacturing processes, in general, can be categorised into subtractive processes, additive processes and transformative processes. While traditional machines supported a single type of these processes (e.g. a turn-mill machine that supports multiple metal removal - subtractive - processes), the new hybrid machines combine multiple types in one device. As a result, the current process and resource models have many shortcomings in representation of hybrid processes and hybrid machines. In this research formal methods are used to construct a new type of model for hybrid manufacturing processes. Formal methods are mathematically based techniques that allow clear and nonambiguous specification, development and, most importantly, verification of software and hardware systems. This paper utilises the ISO-standardised Z notation (named after Zermelo-Fraenkel set theory) to construct a formal model for hybrid manufacturing processes. The capabilities of the model in specification and verification of a hybrid device is then discussed through the use of a case study based on a prototype parallel kinematics hybrid manufacturing platform.

A STEP-NC Compliant Methodology for Modelling Manufacturing Resources

Manufacturing enterprises of all sizes, from small subcontractors and job shops to transnational aerospace and automotive giants, rely on a vast array of resources to generate added value and accomplish their business goals. These resources are comprised of human resource, knowledge resources and technological resources. Achieving business goals requires relevant, timely and well-calculated decision-making. A decision making process requires a model of the decision domain to be constructed with the necessary fidelity to achieve acceptable results and to determine the best course of action in the problem context. A reliable representation of manufacturing resources is therefore necessary for making correct decisions along the manufacturing chain. In this chapter a STEP-NC compliant methodology for representing technological manufacturing resources is presented. This modelling approach is based on mechanical elements that constitute machine tools and other manufacturing hardware together with their kinematic links and is developed with a focus on supporting process planning decisions. Models for various types of machines are presented at the end of the chapter to highlight the flexibility of this approach in modelling manufacturing resources.