<Emphasis Type="Bold">An Integrated Machining Approach for a Centrifugal Impeller</Emphasis>

When a 3-axis CNC machining centre is used for producing an impeller, great difficulties, i.e. collisions between the cutting tool and the impeller, can occur. The blade of an impeller is usually designed with a ruled surface. As the surface is normally twisted in design to achieve the required performance, it can cause overcut and collision problems during machining. The hub of the impeller is usually designed with an irregular surface, and is machined within a narrow and deep groove. The issues – how to satisfy the quality requirements of the part, reduce the machining time, and avoid the occurrence of collision – become an integral problem. This work develops an integrated 5-axis machining module for a centrifugal impeller by combining related machining technologies. As a result, cutter location (CL) data based on the geometric model of blade and hub are generated. Finally, the CL data are confirmed through software simulation. The results of verification show that the machining methodology and procedure adopted are successful.     

<Emphasis Type="Bold">Prediction of Surface Topomorphy and Roughness in Ball-End Milling</Emphasis>

Milling is today the most effective, productive and flexible-manufacturing method for machining complicated or sculptured surfaces. Ball-end tools are used for machining 3D freeform surfaces for dies, moulds, and various parts, such as aerospace components, etc. Milling data, such as surface topomorphy, surface roughness, non-deformed chip dimensions, cutting force components and dynamic cutting behaviour, are very helpful, especially if they can be accurately produced by means of a simulation program. This paper presents a novel simulation model, the so-called MSN-Milling Software Needle program, which is able to determine the surface produced and the resulting surface roughness, for ball-end milling. The model simulates precisely the tool kinematics and considers the effect of the cutting geometry on the resulting roughness. The accuracy of the simulation model has been thoroughly verified, with the aid of a wide variety of cutting experiments. Many roughness measurements were carried out on workpieces, which were cut using a 5-axis machining centre. The calculated roughness levels were found to be in agreement with the experimental ones. The proposed model has proved to be suitable for determining optimal cutting conditions, when finishing complex surfaces. The software can be easily integrated into various CAD-CAM systems.     

轧辊成形刀片刀刃的最少轴数控磨削

对轧辊成形刀片刀刃的数控磨削方法进行了探讨。分析了采用二轴联动和2.5DCNC加工得到的不同后角,得出了采用2轴联动加工得到的后角过小和至少必须采用2.5DCNC加工方法进行加工的结论。     

<Emphasis Type="Bold">Reconfigurable Computing for Tool-Path Computation</Emphasis>

Tool-path generation is one of the most complex problems in computer-aided manufacturing. Although some efficient strategies have been developed to solve it, most of them are only useful for 3- and 5-axis standard machining. The algorithm called virtual digitising computes the tool path by means of a virtually digitised model of the surface and a geometry specification of the tool and its motion, so it can be used even in non-standard machining (retrofitting). This algorithm is simple, robust, and avoids the problem of tool-surface collision. However, its computing cost is high. Presented in the paper there is a virtual digitising optimisation that takes advantage of reconfigurable computing (using field programmable gates arrays) in order to improve the algorithm speed. A comparative study will show the gain and precision achieved.     

<Emphasis Type="Bold">Thermal Modelling of Surface Grinding Using Implicit Finite Element Techniques</Emphasis>

A finite element model is proposed to simulate the precision and ultraprecision grinding of steel and to describe the temperature fields developed during the process. The grinding is modelled using the commercial implicit finite element code MARC. In order to obtain the input data required for the model and to examine the heat damage induced to the workpiece, a series of experiments was performed with the same grinding conditions, but using different aluminium oxide grinding wheels of different bonding on the same work material. Comparison between numerical results obtained from the proposed model and experimental predictions, as well as numerical and analytical calculations reported in the literature, revealed a good agreement between theory and practice, indicating therefore that the model may be suitable for industrial applications.     

<Emphasis Type="Bold">Monitoring of Ultraprecision Machining Processes</Emphasis>

New demands are being placed on monitoring systems in the manufacturing environment because of recent developments in machining technology and machine tool design. In-process sensors are used to generate control signals to improve both the control and productivity of manufacturing systems. Numerous different sensors are available for monitoring and controlling the machining environment including force, power, and acoustic emission (AE) sensors. This paper first discusses the requirements for sensor technology for precision manufacturing process monitoring in general. Details are also given about AE and its application for process characterisation and monitoring in ultraprecision machining.     

<Emphasis Type="Bold">Ultraprecision Diamond Turning of Glass with Ultrasonic Vibration</Emphasis>

By applying ultrasonic vibration to a single-crystal diamond tool-tip, ductile machining of fused silica can be achieved even for 2 m depth of cut. The increase in the critical depth of cut is significant and is a function of the ratio of vibration speed to cutting speed. Surface roughness Ra of 100 nm was obtained for up to 2 m depth of cut.     

<Emphasis Type="Bold">A Fuzzy Capacity-Allocation Model for Computerised Fabric-Cutting Systems</Emphasis>

In this paper, a fuzzy cpacity-allocation (FCA) model is proposed to solve the line-balancing problem in the computerised fabric-cutting process of garment manufacturing. A modular working concept was employed in which the operatives could be transferred between spreading and cutting operations at discrete points of time based on a periodic review of the work-in-progress (WIP) level and the deviation of the actual and the planned starting time of spreading. Experiments based on the actual production data representing different characteristics of the manufacturing environment were conducted to validate the performance of the FCA model. The experimental results indicated that the WIP level could be controlled, and the machine idle-time and makespan could be shortened.     

<Emphasis Type="Bold">Backlash Estimation of a Seeker Gimbal with Two-Stage Gear Reducers</Emphasis>

A novel technique for estimating the magnitude or contribution ratio of each stage backlash in a system with a two-stage gear reducer is proposed. The concept is based on the change of frequency response characteristic, in particular, the change of anti-resonant frequency and resonant frequency, due to the change of the magnitude of the backlash of each stage, even though the total magnitude of the backlash of a system with a two-stage gear reducer is constant. The validity of the technique is verified in a seeker gimbal and satisfactory results are obtained. It is thought that the diagnosis and maintenance of manufacturing machines and systems with two-stage gear reducers will become more efficient and economical by virtue of proposed technique.     

<Emphasis Type="Bold">A Multi-Agent-Based Agile Scheduling Model for a Virtual Manufacturing Environment</Emphasis>

In order to develop a multi-agent-based scheduling system for a virtual manufacturing environment, it is necessary to build various functional agents for all the resources and an agent manager to improve the scheduling agility. In this paper, a hybrid hierarchical model for agile job scheduling in a virtual workshop environment is proposed. The operations of the virtual manufacturing units, the negotiation processes and protocols among the agents are described in detail. Furthermore, forward and backward searching methods supported by the negotiation protocol are proposed for task assignment.     

<Emphasis Type="Bold">Optimisation of Plastic Injection Moulding Process with Soft Computing</Emphasis>

The paper presents a hybrid strategy in a soft computing paradigm for the optimisation of the plastic injection moulding process. Various plastic injection molding process parameters, such as mold temperature, melt temperature, injection time and injection pressure are considered. The hybrid strategy combines numerical simulation software, a genetic algorithm and a multilayer neural network to optimise the process parameters. An approximate analysis model is developed using a Back-propagation neural network in order to avoid the expensive computation resulting from the numerical simulation software. According to the characteristic of the optimisation problem, a nonbinary genetic algorithm is applied to solve the optimisation model. The effectiveness of the improved strategy is shown by an example.     

<Emphasis Type="Bold">Tracking Control and Reference Trajectory Generation in a LOM System</Emphasis>

An improvement in contour accuracy is acquired by the introduction of a tracking controller and a trajectory generation policy in a laminated object manufacture (LOM) system. A model of the positioning system is developed as the design basis of the tracking controller. A zero phase error tracking controller (ZPETC) is used to eliminate single axis following error, and thus reduce the contour error. Then the cross-coupled controller (CCC) is introduced to further minimise the contour error caused by the two-axis mismatch; the method of off-line generating of two-dimension reference trajectories followed by the positioning system is proposed. Simulation is developed using a Matlab model and satisfactory results are obtained.     

<Emphasis Type="Bold">Ductile or Partial Ductile Mode Machining of Brittle Materials</Emphasis>

This paper reports ductile or partial ductile mode machining of silicon, glass and some advanced ceramics. Results are presented using scanning electron micrographs of the machined surfaces. Grinding and lapping operations using inexpensive machine tools could produce ductile streaks on surfaces of these brittle materials under good conditions. Manufacture of spherical glass lenses by the fracture mode or partial ductile mode grinding followed by partial ductile mode lapping and ductile mode polishing is fast and economical. Using partial ductile mode grinding and ductile mode polishing has also been very successful for manufacturing aspherical glass lenses. Reduced polishing time and improved surface quality are due to the presence of ductile streaks. Ground silicon, ZrO2 and Al2O3 also showed ductile streaks. Toroidal SiC surfaces ground with flat-face cup wheels indicated 100% ductile machining, and did not require polishing.     

<Emphasis Type="Bold">Numerical Analysis of a Mask Type Stereolithography Process Using a Dynamic Finite-Element Method</Emphasis>

In many investigations, a liquid crystal display (LCD) has been used as the photo mask in a stereolithography system. The LCD mask has the potential to increase the speed of rapid prototyping (RP) fabrication as well as to reduce the system cost. Compared to the conventional laser-scanning technique used in 3D systems stereolithography apparatus (SLA), the reaction heat of layer curing is released as the area is exposed, and it is higher than that of the laser scanning in which the reaction heat only releases point-by-point. On the other hand, mask type stereolithography has a more serious shrinkage effect than the other methods and requires further analysis. This paper analyses the shrinkage deformation of the mask type stereolithography process. A simulation code based on the dynamic finite-element method has been developed to predict the 3D shrinkage and to monitor the RP fabrication, which consists of three stages of simulation which include the pre-processor, the analytic processor and the post-processor. In order to fabricate experimental parts, a mask type stereolithography system has been assembled. The principle of the experimental apparatus is also briefly described. For evaluation of the experimental and simulation results, a thin shell wall rectangular part was fabricated and measured. The simulation program developed has been proved to be in good agreement with the experimental results.     

<Emphasis Type="Bold">Application of Neural Networks in Injection Moulding Process Control</Emphasis>

In order to produce precise injection moulding products, a closed-loop controller is employed instead of the open-loop control of a traditional injection moulding machine for monitoring the filling and post-filling phases of the injection processes. Since the injection moulding system has complicated and variable dynamics, the classical control theory is difficult to implement for the precise injection moulding processes. Here, two intelligent neural network control strategies are employed to adjust the injection speed of the filling phase and control the nozzle pressure of the post-filling phase. Since the neural controller has learning ability to track the variation of the injection processes, this control strategy has the advantages of adaptivity and robustness for general purpose application to an injection moulding machine. The experimental results show that this controller has good performance in the actual injection moulding processes.     

<Emphasis Type="Bold">Six-Axis Controlled Ultrasonic Vibration Cutting in Fabrication of a Sharp Corner</Emphasis>

The completion of machining in one setting leads to high accuracy and quality. Since ordinary machining is not capable of fabricating sharp corners, electrical discharge machining (EDM) is used. However, this requires a highly skilled machinist to set up the workpiece to maintain the accuracy of the product since two or more set-ups are involved in this process. In this study, a new manufacturing method for the fabrication of sharp corners is examined experimentally. Six-axis controlled cutting using a bore byte tool with the application of ultrasonic vibration has been applied in this method. Experimental resultshave shown the applicability of this method in the fabrication of sharp corners.     

<Emphasis Type="Bold">Accurate Machining of Freeform Surfaces by Restraining Cutter Contouring Errors</Emphasis>

Machined parts having sculptured surfaces pose challenges in the field of CAD/CAM. Sculptured surfaces are essential in the manufacture of components with curved geometry, which are demanded mostly in the aerospace and die and mould industries. This paper presents an adaptive cutter path restraining method for freeform surface machining and its implementation in milling. The ultimate goal is to achieve high contouring accuracy for sculptured parts machining which is a principal index for the performance evaluation of CNC machines. The proposed method is robust in achieving the desired surface cutting with the capability of satisfying pre-specified tolerance requirements using certain adaptive laws. The given tolerance is measured as the angular deviation by which the generated cutter path differs from the desired path. Since the feedrate is considered to be the most significant cutting parameter, only feedrate variations from 5 mm s^-1 to 30 mm s ^-1 are applied in this system. The tool paths generated with and without the adaptive mechanism are compared. The proposed methodology has been tested on a CNC milling system with an open-architecture controller. The experimental results demonstrate that the proposed tolerance feedback mechanism is very effective for producing parts with sculptured surfaces.     

<Emphasis Type="Bold">Optimisation of Apparel Manufacturing Resource Allocation Using a Generic Optimised Table-Planning Model</Emphasis>

Many small and medium-sized apparel manufacturers are employing traditional manual methods and computerised fabric-cutting systems for the fabric-spreading and cutting operations. This paper introduces a generic optimised table-planning (GOTP) model to minimise the spreading and cutting resources of fabric-cutting departments for the apparel manufacturing process. The proposed GOTP model consists of an AutoModule, aManualModule and a BalanceModule to handle three types of manufacturing setup, namely manual, computerised and manual–computerised systems. Three sets of production data reflecting the different characteristics of the nature of production involving small, medium-sized and large production orders are captured to validate the performance of the proposed model. A comparison of the results in industrial practice, and the GOTP model before and after applying the BalanceModule is also presented.     

<Emphasis Type="Bold">A New Simulation Optimisation System for the Parameters of a Machine Cell Simulation Model</Emphasis>

Combinatorial scheduling rules optimisation has been a focus of most of the studies about flexible manufacturing systems (FMS), in the design and control of which, the performance optimisation of a machine cell is of great importance. To optimise the performance of a machine cell, the paper describes the design of a simulation optimisation system. It is constructed according to the principle of separating the models from the algorithms. The system consists of a simulation module and an optimisation module. The optimisation algorithms are the core of the paper, a new hybrid optimisation algorithm is proposed by combining the features of region-shrunk genetic algorithms with an enhanced continuous tabu search. The paper provides an example to demonstrate the validity of the system.     

<Emphasis Type="Bold">The Optimal Design of a Cooling System for a Die-Casting Die With a Free Form Surface</Emphasis>

This study is on the finite element and abductive network method application to die-casting dies with free-form surfaces. The study aims to find the optimal cooling system parameters and decrease in deformation of a die-casting die. In order to avoid the numerous influencing factors, the free-form surface of a die-casting die is created as a non-linear Eq. of a polynomial function. The parameters of the cooling system, including the channel space and channel diameter, are adjusted according to the non-linear Eq.. An abductive network has been built for modelling the die-casting cooling parameters. The abductive network is composed of a number of functional nodes. Once the cooling system parameters are given, this network can predict the deformation of the die-casting accurately. A simulated annealing optimisation algorithm with a performance index is then applied to the neural network for searching for the optimal cooling system parameters and to obtain a satisfactory result.