Structured approach to the design of a production data analysis facility. Part 1: Conceptual design and information requirements

The paper reports research into a workshop-oriented machine and inspection framework for a contemporary metalworking small manufacturing enterprise (SME) that cannot be satisfactorily achieved by the rigid scaled-down versions of software applications employed within larger companies. It identifies a structured approach to the design and conceptualization of a production data analysis framework that is supported by the use of order and manufacturing data. A major feature of the framework is its generic applicability and totally integrated approach to provide rapid manufacturing control from intelligent feedback data from the inspection and manufacturing data analysis activities of manufactured components. This production data analysis approach is formally expressed through the combined application of both the activity analysis formalism of IDEF0 and object-oriented information analysis methodology of Booch. The systematic approach employed by the integrated production data analysis framework provides both product and manufacturing process control in order to close the manufacturing feedback loop. These integrated phases are described and involve the concurrent machine operation and inspection planning, simultaneous production code generation, comparative tolerance analysis, and manufacturing data analysis of manufactured components. The final part of the paper provides a critical discussion on a number of major issues of the approach and identifies the advantages and limitations of the research.     

A freeform surface manufacturing approach by integration of inspection and tool path generation

Freeform surfaces have been widely used in various engineering applications. Increasing requirements for the accuracy of freeform surfaces have led to significant challenges for the manufacturing of these surfaces. A method for manufacturing of freeform surfaces is introduced in this paper by integrating inspection and tool path generation to improve manufacturing quality while reducing manufacturing efforts. Inspection is conducted by comparing the digitised manufactured surface with the design surface to identify the error regions. In this new inspection technique, the areas on the manufactured surface that are beyond the design tolerance boundaries are used as the objective function during the localisation process, in order to minimise post-inspection machining efforts. The tool path generation methods are then selected based on the geometric characteristics of the identified error regions, for creating tool paths to remove the errors. Computational efficiency, machining efficiency, and quality are considered in this integrated method.     

A multi-level modelling system for the design of flexible machining installations

Modern flexible manufacturing facilities can be highly complex, consisting of the latest developments in machine tool technology, automated material handling systems and sophisticated cell controllers. The design and management of such systems requires a large number of decisions and choices with regard to production mix, assignment of fixtures and cutting tools. A large number of commercial computer modelling packages are now available in the market place. Although these allow valuable assistance in the analysis of a manufacturing facility, they usually take significant amounts of time to build models and require a large amount of training, and can be constraining in their application. This paper establishes a research prototype for a multi-level approach for the realization of a three-phase design and modelling system for flexible machining facilities. It portrays the view of an integrated fully data-driven solution underpinned by a machining cell database, and outlines three major areas of work within the structure, i.e. the 'Cell Configurator', 'Evaluator' and 'Emulator'. The approach is demonstrated and supported throughout the paper by an industrial case study of a modern three-machine flexible machining cell, illustrating the use of the underlying methodology behind the approach and typical inputs/outputs at each phase. The final part of the paper provides a discussion of the approach adopted based on user comments and in relation to commercial simulation tools available.     

A framework for characterising energy consumption of machining manufacturing systems

Energy consumption in machining manufacturing systems is increasingly of interest due to concern for global climate change and manufacturing sustainability. To utilise energy more effectively, it is paramount to understand and characterise the energy consumption of machining manufacturing systems. To this end, a framework to analyse energy consumption characteristics in machining manufacturing systems from a holistic point of view is proposed in this paper. Taking into account the complexity of energy consumption in machining manufacturing systems, energy flow is described in terms of three layers of machining manufacturing systems including machine tool layer, task layer and auxiliary production layer. Furthermore, the energy consumption of machining manufacturing systems is modelled in the spatial and temporal dimensions, respectively, in order to quantitatively characterise the energy flow. The application of the proposed modelling framework is demonstrated by employing a comprehensive analysis of energy consumption for a real-world machining workshop. The characteristics of energy consumption for machine tool layer, task layer and auxiliary production layer are, respectively, obtained using quantitative models in the spatial and temporal dimensions, which provides a valuable insight into energy consumption to support the exploration of energy-saving potentials for the machining manufacturing systems.     

Developing a virtual machining model to generate MTConnect machine-monitoring data from STEP-NC

The ability to predict performance of manufacturing equipment during early stages of process planning is vital for improving efficiency of manufacturing processes. In the metal cutting industry, measurement of machining performance is usually carried out by collecting machine-monitoring data that record the machine tool’s actions (e.g. coordinates of axis location and power consumption). Understanding the impacts of process planning decisions is central to the enhancement of the machining performance. However, current methodologies lack the necessary models and tools to predict impacts of process planning decisions on the machining performance. This paper presents the development of a virtual machining model (called STEP2M model) that generates machine-monitoring data from process planning data. The STEP2M model builds upon a physical model-based analysis for the sources of energy on a machine tool, and adopts STEP-NC and MTConnect standardised interfaces to represent process planning and machine-monitoring data. We have developed a prototype system for 2-axis turning operation and validated the system by conducting an experiment using a Computer Numerical Control lathe. The virtual machining model presented in this paper enables process planners to analyse machining performance through virtual measurement and to perform interoperable data communication through standardised interfaces.     

Reverse engineering of machining operation planning

Computer-aided process planning (CAPP) is becoming increasingly crucial to today's computer-integrated manufacturing (CIM) and rapid production. To automate the process planning, feature-based operation planning systems have been suggested and studied extensively. In such a system, given a machining feature, the operator requires practical machining operation data for the feature. In this research, a system of reverse engineering is proposed to extract machining features and their associated machining operation data. Furthermore, a machining know-how database containing the extracted data is created for future operation planning. Since successful NC programs contain the machining know-how of skilled workers, the system is aimed at extracting the machining know-how data from the NC programs through reverse engineering. The extraction of the machining features and feature topologies has been addressed previously. The present paper deals with the extraction of machining operation data, including operation sequence, cutting conditions, machining type and cutting mode. A prototype of the system is developed and a machining know-how database is generated. The extraction of machining features and their associated machining operations has been verified through a variety of NC programs.     

Globally optimal tool paths for sculptured surfaces with emphasis to machining error and cutting posture smoothness

Global optimisation for manufacturing problems is mandatory for obtaining versatile benefits to facilitate modern industry. This paper deals with an original approach of globally optimising tool paths to CNC-machine sculptured surfaces. The approach entails the development of a fully automated manufacturing software interface integrated by a non-conventional genetic/evolutionary algorithm to enable intelligent machining. These attributes have been built using already existing practical machining modelling tools such as CAM systems so as to deliver a truly viable computer-aided manufacturing solution. Since global optimisation is heavily based on the formulation of the problem, emphasis has been given to the definition of optimisation criteria as crucial elements for representing performance. The criteria involve the machining error as a combined effect of chord error and scallop height, the tool path smoothness and productivity. Experiments have been designed considering several benchmark sculptured surfaces as well as tool path parameters to validate the aforementioned criteria. The new approach was implemented to another sculptured surface which has been extensively tested by previous research works. Results were compared to those available in the literature and it was found that the proposed approach can indeed constitute a promising and trustworthy technique for the global optimisation of sculptured surface CNC tool paths.     

Computer-aided design,manufacturing and inspection system integration for optical lens production

The main objectives of this research are the development of an integrated manufacturing strategy and the construction of a database management system for the design, machining and inspection of sculptured surfaces. Specifically, the optical lens for colour display tube/colour picture tube is selected as an application example to show the effectiveness and efficiency of the developed manufacturing strategy and database construction methods. In the machining strategy, the total machining time reduction method is proposed for the rough cutting operation based on the optimum tool path planning. In the finish cutting operation, a modified cutter contact variable step method is employed, and optimal tool paths are generated by selecting the proper tool radius within the given tolerance of a designed model. In the inspection strategy, the shortest measuring path is calculated to reduce the inspection time in CMM. In addition, an efficient database management system, which conducts the process from the surface design stage to the inspection result analysis stage, is constructed for the optimization of the sculptured surface manufacturing process. Finally, the required simulation and experimental works are carried out to verify the proposed strategy.     

Computer-aided fixture design system for comprehensive modular fixtures

Fixture design plays an important role at the planning stage before shop-floor production. A desired fixture design can be employed to hold the workpart securely so that slippage and excessive deformation can be prevented during machining. Therefore, appropriate fixturing contributes highly to machining quality. To reduce lead time and the human effort devoted to fixture planning, computer-aided fixture design (CAFD) is required. In this paper, a CAFD system consisting of three modules, i.e. Fixture Data Management, Fixture Element Selection and Fixture Layout Design, is developed. According to fixture feature recognition and classification, a comprehensive fixture database in the Fixture Data Management module is constructed to maintain efficiently the fixture-related data. The domain of the fixture database consists of modular mechanical fixtures, modular hydraulic fixtures and modular V-blocks. After expertise extraction, suitable fixture elements can be automatically selected according to the machining conditions in the Fixture Element Selection module. Finally, by integrating previous reasoning algorithms, fixturing locations and orientations are determined. Feasible fixture layouts that meet manufacturing and inspection specifications can be generated in the Fixture Layout Design module. The prototype system is implemented under commercial CAD and database management system (DBMS) software. Comprehensive fixture databases and a rule-based knowledge base are built to provide effective data management. The paper aims to propose a systematic CAFD framework and application system to provide efficient decision support for different types of fixture planning.     

Development of a dual-robot system for prototype production

A dual-robot machining system has been developed for manufacturing complex objects. The system consists of two six-axis industrial robots with flexible tool changers, a CAD/CAM package for geometric design and toolpath generation, a robot simulation package for collision avoidance, and a vision system for robot calibration. It offers the flexibility to reconfigure the robots of the system to accommodate workpieces of different shapes and sizes. A prototype of the system has been successfully developed and tested, and shows satisfactory performance in machining quality and control over the configurations of the robots. Examples are given of the application of the system to machining objects with spherical and sculptured surfaces. The system has been shown to be flexible, reconfigurable, automatic, and capable of manufacturing complex prototypes in the current industry environment.     

Non-productive tool path optimisation for four-axis milling using the simulated annealing algorithm

The paper concerns the development of generic computer aided optimisation techniques for the minimisation of residence time of a multi-component pallet in a horizontal machining centre. A general methodology has been established to take a part program for a multi-faced pallet, that involves many components, typically 20–30, and tool changes, segment it to extract the position and machining conditions embedded in it, automatically re-sequence the machining operations to find the optimum total tool path, and regenerate a new part program with the optimised machining sequence. A range of case studies has been used to: validate the software, and to demonstrate its ability to minimise the total pallet residence time. The techniques developed can be used for semi-automatic part programming of the entire pallet with multi-components, and with an auto-selection multi-tool facility. The software is capable of achieving a large reduction in part programming time, as well as reducing the non-machining time. It is shown that the use of the optimisation package with a range of part programs reduces the total pallet residence time by a factor between 9.5 and 36%, and consequently has the potential to achieve considerable economic gains.     

Manufacturing data analytics using a virtual factory representation

Large manufacturers have been using simulation to support decision-making for design and production. However, with the advancement of technologies and the emergence of big data, simulation can be utilised to perform and support data analytics for associated performance gains. This requires not only significant model development expertise, but also huge data collection and analysis efforts. This paper presents an approach within the frameworks of Design Science Research Methodology and prototyping to address the challenge of increasing the use of modelling, simulation and data analytics in manufacturing via reduction of the development effort. The use of manufacturing simulation models is presented as data analytics applications themselves and for supporting other data analytics applications by serving as data generators and as a tool for validation. The virtual factory concept is presented as the vehicle for manufacturing modelling and simulation. Virtual factory goes beyond traditional simulation models of factories to include multi-resolution modelling capabilities and thus allowing analysis at varying levels of detail. A path is proposed for implementation of the virtual factory concept that builds on developments in technologies and standards. A virtual machine prototype is provided as a demonstration of the use of a virtual representation for manufacturing data analytics.     

Improving productivity of a multi-product machining line at a motorcycle manufacturing plant

This paper introduces a case study to improve productivity of a multi-product transmission case machining line at a motorcycle manufacturing plant. First, the manufacturing process is introduced to characterise the production flow. Through structural modelling, such a process is simplified through aggregations and transformed into a two-stage Bernoulli line model with split dedicated machines and finite buffers. Using Markov chain analysis, the system throughput can be estimated. The results are validated by plant data. To improve system productivity, through numerical experiments, we investigate the impacts of increasing machine efficiency, varying demands and implementing different loading policies. Such a study provides a quantitative tool for plant engineers and managers to improve production operations.     

Automatic virtual metrology for wheel machining automation

Total inspection after wheel machining becomes essential for safety consideration and continuous improvement. However, conducting wheel-by-wheel actual metrology is very expensive and time-consuming. A novel idea is to use virtual metrology (VM) that predicts wheel quality based on process data collected from machine tool with a slight supplement of actual metrology data. The technology of automatic virtual metrology (AVM) has been proposed by the authors and successfully deployed in hi-tech industries, such as semiconductor, display and solar cell. The purpose of this study was to propose an approach to apply the AVM system factory-wide to wheel machining automation (WMA) for achieving total inspection of all the precision items of WMA under mass production environment.     

Unified representation of fixtures: clamping,locating and supporting elements in CNC manufacture

A CNC machining operation is the outcome of the application of the integrated capabilities of various resources within the CNC machining centre. Part fixtures, clamping and other location mechanisms are essential subsets of CNC machining resources. Today, various fixturing techniques and attachments available in the market allow manufacturers to enhance their production capability without buying expensive machine tools. This technology-rich fixturing domain is detached while representing and exchanging machine tool resource information for making manufacturing decisions. The research work in this article utilises the STEP-NC compliant unified manufacturing resource model (UMRM) for representing fixtures in conjunction with the parent CNC machining centre. Thus, UMRM is enhanced in this context to represent various fixtures such as universal vises, chucks, pallets and auxiliary rotary tables among others. The major contribution of this article is the application of the extension of the UMRM approach for representing fixturing domain, which allows generic modelling of fixtures and loading devices in addition to machine workpiece and process modelling. This would enable the stage of automated process planning and manufacturing. The universal approach in representing resource information allows the data to be utilised for making a wide variety of manufacturing decisions.     

Optimal tolerance re-allocation for the generative process sequence

In generative process planning, the sequence of machining processes is decided according to the specifications of parts, such as tolerance values. However, in order to obtain the minimal manufacturing cost, the machining process sequence needs to be considered before tolerances are assigned. It is therefore difficult to assign optimal tolerances so that a minimum manufacturing cost is achieved. This paper presents an iterative approach for reallocation of tolerance within the given functional constraints to minimize the manufacturing cost. With the given values of tolerance and corresponding process sequences, which are derived from a handbook or a designer's experience as initial inputs, each iteration of tolerance re-allocation tries to improve the total cost by shifting tolerances along the different processes in the current sequence. The re-allocation problem is formulated as a mixed integer nonlinear programming problem. The Lagrange Multiplier method has been used to solve nonlinear programming, and an exhaustive search method has been adopted to guarantee the global optimum in solving the zero-one algorithm. A prototype system has been implemented in an object-oriented programming environment and a case study is presented to demonstrate the capability of the system.     

An integrated sustainability assessment framework: a case of turning process

Sustainable manufacturing is a valuable tool for measuring and enhancing the machining performance. The implementation of sustainability frameworks in concerned industries poses enormous challenges despite various frameworks available in the literature. Thus, the objective of this paper is to present an integrated sustainability assessment framework wherein two machining scenarios (dry and wet turning) have been analysed by conducting experiments based on the process for a manufactured component in an industry from economic and environmental perspectives. The study further evaluates the economic and environmental indicators such as cost per component and energy consumption for Taguchi array design using empirical relations to evaluate sustainability by grey relational analysis and further optimise the machining performance by particle swarm optimisation. The results, however, indicate the possibility of transitioning the machining process from wet to dry at specific operating conditions with improved performance. In addition to this, the study also presents an illustration of social sustainability assessment framework which has been proposed after consultation with various manufacturing industries in order to make it convenient for them to implement and enhance the sustainability aspects of the machining process.     

A Personal Desktop Liquid-Metal Printer as a Pervasive Electronics Manufacturing Tool for Society in the Near Future

It has long been a dream in the electronics industry to be able to write out electronics directly, as simply as printing a picture onto paper with an offi ce printer. The fi rstever prototype of a liquid-metal printer has been invented and demonstrated by our lab, bringing this goal a key step closer. As part of a continuous endeavor, this work is dedicated to significantly extending such technology to the consumer level by making a very practical desktop liquid-metal printer for society in the near future. Through the industrial design and technical optimization of a series of key technical issues such as working reliability, printing resolution, automatic control, human-machine interface design, software, hardware, and integration between software and hardware, a high-quality personal desktop liquid-metal printer that is ready for mass production in industry was fabricated. Its basic features and important technical mechanisms are explained in this paper, along with demonstrations of several possible consumer end-uses for making functional devices such as li ght-emitting diode(LED) displays. This liquid-metal printer is an automatic, easyto-use, and low-cost personal electronics manufacturing tool with many possible applications. This paper discusses important roles that the new machine may play for a group of emerging needs. The prospective future of this cuttingedge technology is outlined, along with a comparative interpretation of several historical printing methods. This desktop liquid-metal printer is expected to become a basic electronics manufacturing tool for a wide variety of emerging practices in the academic realm, in industry, and in education as well as for individual end-users in the near future.     

Integrated simulation application design for short-term production scheduling

This paper focuses on the development of an integrated short-term production scheduling simulation model for a complex manufacturing operation. The decision making tool has a front-end user data interface built with Microsoft Access and Visual Basic for Applications software. The model assists production planners to make informed decisions on how best to schedule simultaneously two lanes of daily or weekly production on a unique plastic parts manufacturing line. The advantages and disadvantages (model weaknesses) of using the simulation model, especially as a scheduling tool, are discussed. In this particular application, we find that the advantages far outweigh the disadvantages.     

Distributed product and facility prototyping in extended manufacturing enterprises

In order to reduce the cost at the early product development stages, the planners need methodologies and tools that would allow them to judge upon the implications of the product design on the required manufacturing processes and facilities for their production. This paper reports on a new theoretical platform and a pilot implementation of a decision-making environment for distributed product and facility prototyping in an extended enterprise. The approach is based on an exchange of requests and information between collaborative autonomous agents that support the design, manufacturing planning and facility formation activities. The decision-making is formalized as iterative matching of design, process and facility attributes using multilevel resource capability representation within the extended enterprise. The system is implemented as an XML/CORBA-based environment for conveying design and manufacture messages across traditional technology boundaries. The reported research aims to provide the designers with a rapid manufacturing feasibility assessment tool to be used at different design and planning stages in extended manufacturing enterprises.