<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">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">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">Roundness Error Prediction with a Volumetric Error Model Including Spindle Error Motions of a Machine Tool</Emphasis>

This paper proposes a modified volumetric error model that includes spindle error motions as well as geometric errors. The model is constructed using rigid-body kinematics and homogeneous transformation matrices and an additional error matrix describing spindle error motions is included. The suggested model predicts the positioning errors at a given axis position as a function of both the axis position and the engaged spindle rotation angle. Two circular interpolation tests (inner and outer circle of the same radius) are simulated and the machined part profiles are predicted. To verify the simulation results, machining tests are performed according to the ISO 10791-7 standard. The error model with spindle errors shows a better agreement, between the simulated and measured roundness errors, than the simple geometric model. It can be seen that the geometric errors determine the basic part profiles and the spindle errors change the basic profiles according to the magnitude of the errors and the spindle rotation angle.     

<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.     

<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">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">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">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">Determination of the Optimal Parameters for Freeform Surface Measurement and Data Processing in Reverse Engineering</Emphasis>

One objective of this work is to determine the optimal combination of the probe diameter and grid distance for freeform surface measurement, and another is to determine the optimal parameters for the local Shepard interpolation. The optimal combination of the probe diameter and grid distance for freeform surface measurement was determined through a Taguchi matrix experiment. The smaller the probe diameter and grid distance, the better the accuracy of the surface normal based on the configured matrix experimental result. The optimal parameters, namely the exponent and the radius R, for the local Shepard interpolation were determined by using the minimisation method of the root-mean-square normalised error (RMSNE) between the measured data points and the theoretical data points on a standard steel ball surface. The optimal parameters determined were actually applied to the measurement of a freeform surface (mouse surface) on a coordinate measuring machine (CMM). The local Shepard interpolation method was used to interpolate 16 control points from 1054 measured data points. Bi-cubic Bezier- and B-spline surface CAD models were constructed through these interpolated control points.     

<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">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">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">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">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">CNC Rake Grinding for a Taper Ball-End Mill with a Torus-Shaped Grinding Wheel</Emphasis>

A new grinding method using a torus-shaped grinding wheel and a machining path generation method with a novel moving coordinate system are proposed. With this new grinding method, the smooth spiral rake surface of a taper ball-end mill with constant helical angle and constant normal rake angle can be formed during one grinding process and the normal rake angle can be obtained accurately. The novel moving coordinate system is established based on taking account of both the cutting edge curve and the cutter body surface. By means of the novel moving coordinate system, the machining path generation becomes very simple. The proposed grinding method and the machining path generation method are verified by 3D simulation results.     

Two-Body Abrasive Wear of the Outside Shell Surfaces of Mollusc <Emphasis Type="Italic">Lamprotula fibrosa</Emphasis> Heude, <Emphasis Type="Italic">Rapana venosa</Emphasis> Valenciennes and <Emphasis Type="Italic">Dosinia anus</Emphasis> Philippi

Natural biological surfaces and biomaterials have some distinguishing properties for adapting themselves to natural surroundings. The outside shell surfaces of mollusc species often undergo the abrasive wear action from the sand particles in water sand slurry in natural conditions. The two-body abrasive wear behavior of the outside shell surfaces of three mollusc species Lamprotula fibrosa Heude, Rapana venosa Valenciennes and Dosinia anus Philippi was examined. Abrasive material used for tests were quartz sand (96.5 wt.%) with three different size ranges and powdered bentonite (3.5 wt.%). The two-body abrasive wear tests were run on a rotary disc type abrasive wear testing machine. The results showed that the abrasion resistance of the outside shell surfaces of the three mollusc species was higher when the corrugations on the shell surfaces were perpendicular to the sliding direction of the abrasive material than that when the corrugations on the shell surfaces were parallel to the sliding direction of the abrasive material. Basically, the shell of Lamprotula fibrosa Heude possessed the highest abrasion resistance among the three species of shell; the abrasion resistance of the shell of Rapana venosa Valenciennes was the lowest; and the abraded depth of the three species of shell increased with an increased abrasive particle size and relative sliding velocity. The abraded surfaces were observed with scanning electron microscope.