Chi Fai Cheung

A theoretical and experimental investigation of surface roughness formation in ultra-precision diamond turning

In this paper, a model-based simulation system is presented for the analysis of surface roughness generation in ultra-precision diamond turning. The system is based on a surface roughness model which takes into account the effect of tool geometry, process parameters and relative tool-work vibration. It is evaluated through a series of cutting experiments. The results indicate that the system can predict well the surface roughness profile and the roughness parameters of a diamond turned surface under various cutting conditions. With the use of the spectrum analysis techniques, the system can also help to analyze the effect of vibration on the surface quality of workpiece and to diagnose the machine faults. The potential application of the system in process optimization is also discussed in the text.

Characterisation of nanosurface generation in single-point diamond turning

This paper describes a parametric analysis of nanosurface generation in single-point diamond turning (SPDT). The properties of the surface roughness profiles were extracted and analysed using the power spectrum analysis method. A series of face cutting experiments was undertaken on an aluminium alloy under various cutting conditions. The results indicate that the power spectrum of a surface roughness profile is basically composed of several periodical components that can be correlated to different process parameters and mechanisms of surface generation. Moreover, it is found that the tool feed, tool geometry, spindle error motions and relative vibration between the tool and the workpiece are not the only dominant components contributing to the surface generation in SPDT. Materials swelling and tool interference are other important factors. Based on these findings, relationships are proposed to explain the influence of tool interference on the variation of the spectral components and process parameters. The implications of these findings on the optimisation of the surface quality in SPDT are also discussed.

A dynamic surface topography model for the prediction of nano-surface generation in ultra-precision machining

Abstract Materials induced vibration has its origin in the variation of micro-cutting forces caused by the changing crystallographic orientation of the material being cut. It is a kind of self-excited vibration which is inherent in a cutting system for crystalline materials. The captioned vibration results in a local variation of surface roughness of a diamond turned surface. In this paper, a dynamic surface topography model is proposed to predict the materials induced vibration and its effect on the surface generation in ultra-precision machining. The model takes into account the effect of machining parameters, the tool geometry, the relative tool–work motion as well as the crystallographic orientation of the materials being cut. A series of cutting experiments was performed to verify the performance of the model and good correlation has been found between the experimental and simulation results.

A web-based collaborative product design platform for dispersed network manufacturing

Abstract Many multi-national companies have operations in geographically different locations. They need to communicate and work concurrently on large amount of complex product data with their factories, sub-contractors as well as suppliers across the border. The use of e-mail and fax are far from satisfactory as they are time consuming and ineffective. In this paper, a web-based collaborative product design platform is proposed which enables authorized users in geographically different locations to have access to the company’s product data such as product drawing files stored at designated servers and carry out product design work simultaneously and collaboratively on any operating systems. There is no need for the users to install any utility software at their ends since the access is based on a remote screen sharing technique built upon a Browser/Server and thin client technology. This results in substantial saving in the cost and the product development time in a network environment.

A multi-perspective knowledge-based system for customer service management

Abstract The e-business arena is a dynamic, complex and demanding environment. It is essential to make optimal reuse of knowledge of customer services across various functional units of the enterprise. On the other hand, it is also important to ensure that the customer service staff can access and be trained up with dynamically updated knowledge that meets the changing business environment of an enterprise in customer services. However, conventional way of customer service management (CSM) is inadequate to achieve the multi-perspective of an enterprise for achieving knowledge acquisition, knowledge diffusion, business automation and business performance measurement so as to drive the continuous improvement of the customer service quality. In this paper, a multi-perspective knowledge-based system (MPKBS) is proposed for CSM. The MPKBS incorporates various artificial intelligence technologies such as case-based reasoning (CBR) and adaptive time-series model which are used for decision analysis, performance measurement and monitoring. A prototype customer service portal has been built based on the MPKBS and implemented successfully in a consultancy business.

A multi-spectrum analysis of surface roughness formation in ultra-precision machining

The formation of surface roughness in ultra-precision diamond turning is investigated using a multi-spectrum analysis method. The features on a diamond turned surface are extracted and analyzed by the spectrum analysis of its surface roughness profiles measured at a finite number of radial sections of the turned surface. It is found that the tool feed rate, the spindle rotational speed, the tool geometry, the material properties, as well as the relative tool-work vibration are not the only dominant components contributing to the generation of surface roughness. The material induced vibration caused by the variation of material crystallography is another major factor. The vibration causes a significant variation of the frequency of the surface modulation of the machined surface. With the use of the multi-spectrum analysis method, it is possible to conjecture the patterns of this vibration as well as to evaluate the properties of the workpiece materials.

Applications of virtual manufacturing in materials processing

Abstract Virtual manufacturing (VM) is an emerging technology that mimics real manufacturing operations with models, simulations and artificial intelligence. VM is a knowledge and information-based technique developed in recent years. With the use of the VM technologies, many aspects of the activities can be integrated and realised into one system. The manufacturing cost and time-to-market can be reduced. The associated technologies of VM and their key techniques related to materials processing and current research work are highlighted. Emphases are placed on the social and technological aspects in the development of VM systems. Some practical application examples of VM in materials processing are presented.

A systematic approach for knowledge auditing: a case study in transportation sector

Purpose – This paper aims to present a systematic approach for knowledge auditing which is composed of a number of stages with the focus on the establishment of an overall framework and customized tools for knowledge auditing.Design/methodology/approach – The systematic approach for knowledge auditing is composed of eight phases: orientation and background study, cultural assessment, in‐depth investigation, building knowledge inventory and knowledge mapping, knowledge network analysis and social network analysis, recommendation of knowledge management strategy, deploying KM tools and building collaborative culture, and continuous knowledge re‐auditing, respectively.Findings – A systematic approach for knowledge auditing is proposed and trial successfully implemented in a railway company. The results show that the systematic knowledge auditing approach yields a number of benefits that include the identification of the critical knowledge and the subsequent recommendations can be derived for better managing ...

Modelling and simulation of surface topography in ultra-precision diamond turning

Abstract This paper describes a model for the simulation of surface topography in ultra-precision diamond turning. In the model, the kinematics of the diamond turning process is characterized by machining parameters, the tool geometry as well as the relative motion between the tool and the workpiece. The topography of the machined surface is generated by a linear mapping of the predicted surface roughness profiles on the surface elements of a cross lattice. A series of cutting experiments was carried out. Good correlation is found between the simulated topography and the three-dimensional topography obtained from the optical interferometer. The model can be used for the optimization of the diamond turning process without the need for costly trial-and-error cutting tests. With the use of equi-contour mapping techniques, the model can also help to identify surface features like traces of tool motion and surface waviness. Potential applications of the modelling technique to other processes and tool and workpiece combinations are also discussed.

Study of factors affecting the surface quality in ultra-precision diamond turning

Abstract This paper deals with an investigation of the process factors and the material factors affecting the surface roughness in ultra-precision diamond turning. The process factors involve cutting conditions, tool geometry, and relative tool-work vibration which are related to the cutting geometry and the dynamic characteristics of the cutting process. The material factors considered are material anisotropy, swelling, and crystallographic orientation of the work materials. Experimental results indicate that the influence due to the process factors can be minimized through a proper selection of operational settings and better control of dynamic characteristics of the machine. The material factors, on the other hand, exert consistent influence on the surface roughness which can not be minimized solely by an optimization of process parameters and machine design. Based on these findings, some suggestions are proposed for the optimization of the surface quality in ultra-precision diamond turning.