Design and characterization of a precision fluid dispensing valve

Precision fluid dispensing is a complicated but yet relevant process where fluid is dispensed in a controlled manner. It is important and applicable in an array of applications ranging from dispensing of food products, biomedical applications to dispensing of adhesive and encapsulants in the semi-conductor industry. This paper discusses the design and characterization of a precision fluid dispensing hybrid valve based on the time-pressure, positive displacement pump, and adhesive jetting technologies. The main advantage of this dispensing method is that the amount of fluid dispensed is independent of the standoff height and does not rely on surface tension between the substrate and the fluid for clean dispensation. Specifically, the dispensed fluid is jetted from a fixed needle height, and hence, repeatability and accuracy is improved while eliminating vertical travel. A prototype valve was built and tested for precision and accuracy of milligrams over a range of pressures and time. The test results are promising, indicating high repeatability and accuracy for low to medium viscous materials and are comparable to existing commercially available precision dispensing systems.     

An empirical approach to modelling fluid dispensing for electronic packaging

Fluid dispensing is a popular process in semiconductor manufacturing industry which is commonly used in die-bonding as well as microchip encapsulation for electronic packaging. Modelling the fluid dispensing process is important to understand the process behaviour as well as determine optimum operating conditions of the process for a high-yield, low cost and robust operation. Previous studies of fluid dispensing mainly focus on the development of analytical models. However, an analytical model for fluid dispensing, which can provide accurate results, is very difficult to develop because of the complex behaviour of fluid dispensing and high degree of uncertainties of the process in a real world environment. In this project, an empirical approach to modelling fluid dispensing was attempted. Two common empirical modelling techniques, statistical regression and neural networks, were introduced to model fluid dispensing process for electronic packaging. Development of neural network based process models using genetic algorithm (GA) and Levenberg−Marquardt algorithm are presented. Validation tests were performed to evaluate the effectiveness of the developed process models from which a multiple regression model and a GA trained neural network with the architecture of 3-15-1 were identified to be the process models of the fluid dispensing respectively for the encapsulation weight and encapsulation thickness.     

机器人贴装涂胶过程建模与时序分析

空间太阳电池帆板的贴装生产过程目前在国内依旧采用单一手工操作,很难保证质量.该文对太阳电池帆板自动贴装机器人的涂胶过程进行了流动特性建模与时序状态分析,确定了机器人单片涂胶周期和串联涂胶周期,得到了机器人任一涂胶拐点处的时序值,及任意时刻机器人对应的涂胶位置坐标.通过对机器人的涂胶过程分析,得到了针管内胶体流动的速度场模型,并确定了胶体流量算式,给出了不同变量条件下涂胶过程的速度场模型及涂胶流量模型,为空间太阳帆板的自动贴装涂胶生产提供了可靠的数据模型.     

The process modelling of epoxy dispensing for microchip encapsulation using fuzzy linear regression with fuzzy intervals

Epoxy dispensing is a popular way to perform microchip encapsulation for chip-on-board (COB) packages. However, the determination of the proper process parameters setting for a satisfactory encapsulation quality is difficult due to the complex behaviour of the encapsulant during the dispensing process and the inherent fuzziness of epoxy dispensing systems. Sometimes, the observed values from the process may be irregular. In conventional regression models, deviations between the observed values and the estimated values are supposed to have a probability distribution. However, when data is scattered, the obtained regression model has too wide of a possibility range. These deviations in processes such as epoxy dispensing can be regarded as system fuzziness that can be dealt with satisfactorily using a fuzzy regression method. In this paper, the fuzzy linear regression concept with fuzzy intervals and its application to the process modelling of epoxy dispensing for microchip encapsulation are described. Two fuzzy regression models, expressing the correlation between various process parameters and the two quality characteristics, respectively, were developed. Validation experiments were performed to demonstrate the effectiveness of the method for process modelling.     

跨尺度微管微球三维半自动装配点胶系统

设计和搭建了一个3D半自动装配点胶系统,用于完成跨尺度零件微管与微球的三维装配点胶任务。系统主要由体视显微镜、变焦金相显微镜、发光二极管(LED)背光源、pL级点胶机、微操作手和零件夹持器组成。采用显微镜高低倍转换的方式实现了零件跨尺度特征的检测。基于提出的半自动装配点胶策略,并配合人工引导和显微视觉伺服技术,快速完成了跨尺度零件的半自动高精度对准和插入点胶。在搭建完成的系统上开展微管与微球的装配点胶实验,对提出的方法和装配精度进行了实验验证。结果表明,系统的位置对准误差优于1μm,角度对准误差优于0.5°,可以实现末端直径10μm的微管与孔径12μm的微球之间的装配和胶接,基本满足对该组件的装配精度和成功率要求。     

可重构制造系统集成设计框架研究

提出了基于可重构制造单元的可重构制造系统集成设计框架.在该框架中,从规划和运行方面阐述了可重构制造系统的设计目标、设计流程及采用的关键技术,建立了支持可重构制造系统实施的计算机辅助设计系统的功能模型和体系结构,并讨论了系统的内部集成和外部集成问题.根据该设计框架,开发了集重构、布局规划、生产调度和仿真优化为一体的软件系统,该系统现已应用于航天、船舶和兵器部门.     

Integrated control chart system for time-between-events monitoring in a multistage manufacturing system

This article develops a control chart system consisting of several individual time-between-events (TBE) charts, each of which is used to monitor the time between successive events at different process stages in the manufacturing of a product in a multistage manufacturing system. The design algorithm considers all the TBE charts within a system in an integrative and optimal manner. Numerical studies show that the proposed design algorithm improves the performance characteristics of the chart system significantly and thus the product quality is further guaranteed. The proposed control chart system is easy to understand and operate; thus, the floor operators can utilize and understand it as easily as for the traditional system.     

Effect of non-Newtonian lubrication on the separation of a sphere from a flat

A numerical analysis is presented to study the effect of lubrication with non-Newtonian fluid on the separation flow of a fully flooded sphere from a flat under the condition of constant applied load. Different non-Newtonian fluid models were utilized to account for the microstructure and rheology of additives suspended in the film lubricant, namely those models for couple stress, micropolar, and power-law fluids. The equation of motion of the sphere was used to examine the effect of the sphere inertia on accelerating the separation process as the film viscous force decreases. This required solving the film pressure field, which is derived from a modified Reynolds equation and later computed numerically by a forth-order Runge-Kutta integration scheme. Several parameters were examined such as the time to complete separation, the length scale of the additives, the variation in lubricant's viscosity due to the presence of the additives, the sphere mass and radius, and the applied force on the sphere. Compared to the Newtonian fluid case, the results of the numerical solution indicated that there is a delay on the separation time for large non-Newtonian parameters, i.e., parameters representing additives characteristic length, additives concentration, and power-law indices.     

Development of a knowledge-based manufacturing modelling system based on IDEF0 for the metal-cutting industry

This paper looks into a new area for knowledge-based system application, that of manufacturing modelling. The objective is to develop a knowledge-based manufacturing modelling system that can be used to build company-specific as-is and to-be IDEF0 models, and can therefore greatly reduce the turnaround time and effort involved in IDEF0 modelling of manufacturing systems, which can be time-consuming if done manually or even with the aid of a commercially available software package like DESIGN/IDEF. This is especially so when the systems being modelled are large and complex. Besides, there is also the inconsistency problem associated with conventional IDEF0 modelling systems owing to the terms and terminologies in IDEF0 not being precisely defined, and hence being subject to individual interpretations. In this paper, a knowledge-based IDEF0 modelling system that can not only automate the tiresome and time-consuming process of manufacturing modelling but can also eliminate the inconsistency problem is proposed. The paper explains the knowledge-based approach to automated generation of IDEF0 models, and also identifies the kinds of domain knowledge that are required for the construction of the knowledge-based manufacturing modelling system.     

分散网络化制造模式下集成质量系统的研究

论文在简要分析了分散网络化生产系统之后,提出了分散网络化集成质量系统的概念,首次将集成质量系统的功能,由传统的单一企业扩展到通过分散网络化制造网络联系在一起的不同地域的多个合作企业,并着重分析了分散网络化集成质量系统的体系结构和功能模型。     

Integrated precision inspection system for manufacturing of moulds having CAD defined features

An integrated precision inspection system has been developed for manufacturing moulds having CAD defined features. The techniques of precision measurement are implemented for CAD/CAI integration for moulds having sculptured surfaces with some basic features, such as, holes, slots and bosses. Features to be inspected are chosen in the CAD environment, and inspection planning is performed for each feature. The sampling-point strategies are: uniform distribution, curvature dependent distribution, or hybrid distribution of the two depending on the complexity of the sculptured surface. Line and plane features are divided into subintervals, and the measurement points are distributed at random positions in the subinterval. Prime number subintervals are considered for a circle feature, in order to avoid possible periodic distortion of the measurement features. The measurement path planning is performed considering collision avoidance and coordinate matching between the coordinates. The output of the planning is the machine code for a specific CMM having CNC capability. The machine code is downloaded to a specific CMM, and the measurement results are fed back to the computer. A new algorithm, called MINIMAXSURF, is developed to evaluate the form error precisely for sculptured surfaces. The algorithm considers the radius of the touch probe and evaluates the profile tolerance successfully by removing the unavoidable setup errors. The developed measurement system has been applied to real moulds, demonstrating high performance and accuracy.     

Evaluation of routing flexibility of a flexible manufacturing system using simulation modelling and analysis

Routing flexibility is a major contributor of the flexibility of a flexible manufacturing system (FMS). The present paper focuses on the evaluation of the routing flexibility of an FMS with the dynamic arrival of part types for processing in the system. A typical FMS configuration is chosen for detailed study and analysis. The system is set at five different levels of routing flexibility. Operations of part types can be processed on alternative machines depending upon the level of routing flexibility present in the system. Two cases have been considered with respect to the processing times of operations on alternative machines. A discrete-event simulation model has been developed to describe the operation of the chosen FMS. The performance of the system under various levels of routing flexibility is analyzed using measures such as mean flow time, mean tardiness, percentage of tardy parts, mean utilisation of machines, mean utilisation of automatic-guided vehicles, and mean queue length at machines. The routing flexibility for producing individual part types has been evaluated in terms of measures such as routing efficiency, routing versatility, routing variety and routing flexibility. The routing flexibility of the system has been evaluated using these measures. The flexibility levels are ranked based on the routing flexibility measure for the system. The ranking thus obtained has been validated with that derived using fuzzy logic approach.     

基于I-deas的锅炉三维造型系统

锅炉三维造型系统是《锅炉ＣＡＤ应用系统》的子系统,三维实体建模是进行有限元分析和空间管路干涉检查的基础。本文对系统软硬件平台、锅炉部分典型部件造型、空间管路中心线快速构造及参数化设计的实现方法作了介绍。     

传感器黑箱数学建模理论研究现状及应用

针对传感器的数学建模问题,本文介绍了作为目前研究前沿之一的基于黑箱建模的各种建模方法的建模理论、实现过程及应用的研究状况。并就应用中的优点及存在的可改进问题进行了分析比较．指出传感建模研究中需要关注的几个方向。     

制造系统多Agent智能控制平台研究

将多Agent智能控制技术应用到现代生产制造中,可以使制造系统具有较高的柔性、开放性和可重配置性。对制造系统多Agent控制系统体系结构、合同网和语言规划、通信方式和协商机制以及建模过程和方法进行了比较详细的分析和讨论,并最终给出原型控制系统和优化结果,为多Agent系统的开发指出了一条可行的道路。     

Object-oriented approach of MCTPN for modelling Flexible manufacturing systems

Manufacturing industry is facing a stricter challenge than ever before owing to the rapid change in market requirements. Flexible manufacturing systems (FMSs) have a much greater capability than traditional fixed-type production systems for coping with the rapid change. In this paper, a modified coloured-timed Petri net (MCTPN) is developed to model the dynamic activities in an FMS. The MCTPN provides an object-oriented and modular method of modelling manufacturing activities. It includes colour, time, modular and communication attributes. The features of object-oriented modelling allow the FMS to be modelled with the properties of classes, objects, and container trees. Since the system activities can be encapsulated and modularised by the proposed MCTPN, the manufacturing systems can be easily constructed and investigated by the system developers. It makes the concept of software IC possible for modelling complex FMSs. Once all of the MCTPN objects are well defined, the developers need to consider only the interfaces and operations relating to the MCTPN objects. In order to demonstrate the capability of the proposed MCTPN, the FMS in the Manufacturing Automation Technology Research Center (MATRC) of the National Taiwan University will be stimulated and justified by using the proposed MCTPN along with the G2 expert system.     

Scheduling algorithms for a two-machine flexible manufacturing system

The flexible manufacturing system (FMS) considered in this paper is composed of two CNC machines working in series—a punching machine and a bending machine connected through rollers acting as a buffer system of finite capacity. The main difference between the present problem and the standard two-machine flow shop problem with finite intermediate capacity is precisely the buffer system, which in our problem consists of two stacks of parts supported by rollers: the first stack contains the output of the punching machine, while the second stack contains the input for the bending machine. When the second stack is empty, the first stack may be moved over. Furthermore, the capacity of each stack depends on the particular part type being processed.The FMS can manufacture a wide range of parts of different types. Processing times on the two machines are usually different so that an unbalance results in their total workload. Furthermore, whenever there is a change of the part type in production, the machines must be properly reset—that is, some tools need to be changed or repositioned.A second important difference between the present problem and the usual two-machine flow shop problem is the objective. Given a list ofp part types to be produced in known quantities, the problem considered here is how to sequence or alternate the production of the required part types so as to achieve various hierarchical targets: minimize the makespan (the total time needed to complete production) and, for instance, compress the idle periods of the machine with less workload into a few long enough intervals that could be utilized for maintenance or other reasons.Although Johnson's rule is optimal in some particular cases, the problem addressed in the paper isNP-hard in general: heuristic procedures are therefore provided.     

Loading strategies for a class of just-in-time manufacturing system

In this paper, based on the group technology and the just-in-time manufacturing concepts, two loading models for optimal utilisation of the processing capabilities of an integrated manufacturing system consisting of a set of heterogeneous workstations are developed. These loading models are developed to integrate and utilise the available information from both the bill of materials and the process plans. The objective functions for these models are: the maximum tardiness and the makespan. In these models, the production quantity of each customer order for any part or product always equals its corresponding demand quantity; each part requires a finite number of aggregated stages of operation; job splitting is allowed; and the processing priorities of all the jobs during the planning time horizon are specified based on a desirable dispatching rule. The proposed mathematical programming models are fixed charge problems which are solved by compatible mixed integer programming algorithms. Finally, to provide additional decision-making capabilities, based on these models and their corresponding solution algorithms, a compatible decision support system is suggested.Notation l(1 toL) the product index - t(1 toN) the component (e.g., job type) index - i(1 toN) the job type priority index - j(1 toM) the workstation index - r(1 toR) the processing stage priority index - k(1 toK) the due date priority index - J _i,j,r,k the job with the job type priority indexi of the customer with the processing stage priority indexr and the due date priority indexk which has to be processed at the workstationj - L _i,r,k the number of units of the job with the job type priority indexi of the customer with processing stage priority indexr and the due date priority indexk (e.g. demand quantities) - t _i,j,r the required time to perform the processing stage priority indexr of each unit of the job with the job type priority indexi at the workstationj - D _i,r,k the due date of the job with the job type priority indexi of the customer with the processing stage priority indexr and the due date priority indexk - s _i,j,r the required time for setting up the workstationj for processing the job with the processing stage priority indexr, and the job type priority indexi - X _i,j,r,k the number of units of the job with job type priority indexi of the customer with the processing stage priority indexr, and the due date priority indexk to be produced at the workstationj - l _i,j,r,k the idle time at the workstationj prior to processing the job with the job type priority indexi and the processing stage priority indexr with the due date priority indexk - V the maximum tardiness - W the makespan of the operation - Y _i,j,r,k=1 ifX _i,j,r,k>0 - Y _i,j,r,k=0 ifX _i,j,r,k=0 - _i,j,r,k a sufficiently large constant (e.g. _i,j,r,kL _i,r,k)     

Finite element modelling for a piezoelectric ultrasonic system

In this paper, a three-dimension (3-D) mechanical element with an extra electrical degree of freedom is employed to simulate the dynamic vibration modes of the linear piezoelectric, piezoelectro-mechanic and mechanical behaviors of a metal disc structure embedded with a piezoelectric actuator. In piezoelectric finite element formulation, a discretized equation of motion is developed and solved by using the integration scheme to explain why an adaptive boundary condition, a simple support condition with three non-equal-triangular (120°–90°–150°) fixed points near the edge, which is the asymmetric disc used as the stator of the studied ultrasonic motor, for the mechanical design of an asymmetric disc-type piezoelectric ultrasonic stator, is defined so that a lateral elliptical motion of the contact point between stator and rotor can be realized for driving the rotor. It starts from hybrid elements with displacement and electric potential as the nodal d.o.f.s model and uses Guyan reduction and Householder-Bisection inverse iteration to find the displacement profile and displacement vector flow of the stator under frequency driving. The standing wave existence is also proven by the displacement patterns of the finite element theoretical model.     

Transfer matrix modelling for the 3-dimensional vibration analysis of piping system containing fluid flow

For three dimensional vibration analysis of piping system containing fluid flow, a transfer matrix formulation is presented. The fluid velocity and pressure were considered, that coupled to longitudinal and flexural vibrations. Transfer matrices were derived from direct solutions of the differential equations of motion of pipe conveying fluids, and the variations of natural frequency with flow velocities for straight and curved pipes were investigated. The results were confirmed to the corrections of known data. The scheme of this study can be easily applied to the related fields, using small size personal computers with core memory about 200kbytes.