A simultaneous-mounting process for automated printed circuit board assembly

Current robotized printed circuit board assembly systems allow one component to be inserted onto the board at a time and the corresponding design usually causes complicated operation planning problems for plant engineers. This paper addresses an opportunity for productivity improvement in automated printed circuit board assembly through the design of a new assembly mechanism from plant engineer's viewpoint. The mechanism not only will allow simultaneous insertions of multiple components but also will simplify the component placement planning task.     

A LISP-based heuristic scheduler for automatic insertion in electronics assembly

Computer solutions have not made a very significant impact on scheduling problems. This reflects the fact that algorithmic solutions are often not appropriate for scheduling problems. Scheduling problems are more amenable to heuristic solution techniques. This paper describes a heuristic system for job scheduling in printed circuit board assembly. The main part of the system is written in Common LISP.     

A Petri Net based approach to determine the disassembly strategy of a product

In order to protect the environment and regain value added to products, a process known as disassembly has come into the limelight. This process is to be applied to reuse abandoned goods and materials. Manufacturers are being forced to establish disassembly plants and to develop their products' designs so as to maintain the government's dictate to dispose off their products in an environmentally responsible manner. This research presents a cost-based heuristic analysis for a circuit board assembly. Various components of the product and their assembly relationships are represented by a Petri Net diagram. Firing the transitions of the disassembly Petri Net is integrated with cost-based indices to develop an effective disassembly strategy. The methodology discussed here simplifies the decisionmaking process involved in disassembly planning. A comprehensive disassembly process planning system is proposed here and is exemplified by a case study of circuit board assembly.     

Optimization of the assignment of circuit cards to assembly lines in electronics assembly

Process planning is an important and integral function for ensuring efficient operations in printed circuit card assembly systems. This paper presents a new approach for solving the circuit card to assembly line assignment problem to minimize assembly time. This problem occurs frequently in process planning for electronic assembly systems and involves considering other interelated process planning problems. The line assignment problem is formulated as a large-scale mixed-integer programming problem and then solved using problem decomposition along with the branch-and-bound algorithm. Techniques for improving the solution time are discussed, and the solution approach is demonstrated using industry representative data sets from Lucent Technologies. For the data sets considered, the solution approach provides solutions within 3% of optimal in approximately 6 min of computation time on a Sun UltraSparc 2 Workstation. The solution approach developed for addressing the line assignment problem can serve as a useful decision-support tool by offering significant opportunities to improve the productivity and throughput of the assembly lines with improved process plans. The approach also allows planning engineers to respond faster to changes in production requirements. This research will be of interest to researchers in printed circuit card assembly systems and to practitioners in both original equipment manufacturing and contract assembly firms.     

Simulation-based performance analysis and optimization of electronics assembly equipment

Due to the high degree of automation in modern printed circuit board (PCB) assembly, production planning and scheduling in this industry relies heavily on the accuracy of the underlying models of the automated machinery. In this paper, the derivation of such mathematical models is exemplified for one of the most wide-spread machine types (the so-called chip shooter). Moreover, a simulation system for practical use in the electronics assembly is presented which incorporates various types of assembly machines. It serves as a tactical production planning aid as well as a test field for the analysis of the kinematic processes of PCB assembly machines. Such simulation, tailored to the specifics of a production environment, gives reliable estimates of the achievable production volume. Considerable deviations between the performance figures provided by the machine supplier and the actual result can thus be explained, and potential assembly system configurations be compared by drawing on reliable measures. Since the equipment is modelled at a level which takes precise account of its specific kinematics, a detailed analysis of the operations of the individual machine can also be performed revealing potential bottlenecks in its design. These insights are used to optimize machine design and control. Methods based on graph theory as well as on modern numerical search algorithms have been developed for the latter purpose. They lead to considerable performance improvements.     

Towards automatic generation of plans for automated assembly

The present CAD/CAM systems still lack the appropriate CAE component that would allow more efficient assembly planning in the effort to integrate the product design, assembly system design, assembly device programming and assembly execution. The problem is related to both the complexity and incompleteness of the planning methodology, and the lack of the algorithmized planning elements. The previous explorations often concentrated on particular planning elements such as assembly sequence, neglecting the urge of integral and a more general approach. Furthermore, they sometimes pose tedious requirements on the user, causing him/her to focus more on the planning method than on the planning goal. The paper presents a CAD-based prototyping system for the generation of plans for automated assembly. It uses many relevant well-established concepts in the assembly planning field and proposes a few new ones (especially regarding assembly process space structuring), trying to achieve the highest possible level of automation, and to highlight the problems of computer implementation of the planning knowledge. A mechanical product to be assembled is, at first, a CAD modelled assembled product. After that, the planning elements such as assembly sequence, assembly paths and parts positions of disassembled product are defined, providing the basis for assembly device design and assembly execution.     

AI-Based Process Planning for Electronic Assembly

Diversity of electronic products, lack of human expertise, and inconsistency among manually generated process plans increase the necessity of developing Computer Aided Process Planning (CAPP) systems for electronic assembly. Artificial Intelligence (AI) offers a few techniques to develop CAPP systems which would behave in a 'knowledgeable' manner. Two rule-based CAPP systems, a backward-chaining system developed in M. 1 shell and a forward-chaining system developed in OPS 5, and an object-oriented system developed in Objective-C are discussed. The CAPP systems generate processes and select a set of machines to perform the generated processes for a given product. In the rule-based CAPP systems, product characteristics and bill of components are stored in working memory and capabilities of the available machines are stored as rules. In the object-oriented CAPP system, product as well as the available machines are represented as objects. A central decision module which does pattern matching and sends messages to appropriate machines (objects) is developed     

Detection of capacitor electrolyte residues with FTIR in failure analysis

Detecting leakage from liquid aluminum electrolytic capacitors is not easy. Typically there is very little evidence of leakage because the electrolyte is volatile and leaves behind only trace residues. Liquid aluminum electrolytic capacitors are known to cause catastrophic failures where there is complete loss of functionality due to a short or open circuit. In the study presented in this paper, printed circuit board assemblies from a test and measurement system used in a clean room environment failed. Two units failed, causing burning in a particular area on the printed circuit board assembly. The failure area included several surface mount liquid aluminum electrolytic capacitors, and several others were mounted very close to the burnt region. A study was initiated to evaluate the cause of failure. Careful optical inspection revealed some residues on the outer side of the rubber seals of two of the electrolytic capacitors. Through using Fourier transform infrared analysis and a process of experimentation and analysis, it was determined that the residues were produced by liquid electrolyte that leaked out of the capacitor at some point in the field. The leaked electrolyte that came out of the capacitor was believed to be the cause of failure that led to the burning of the printed circuit board assembly.     

Aggregate line capacity design for PWB assembly systems

In a multi-product, flexible manufacturing environment, line capacity of printed wiring board (PWB) assembly systems may need to be adjusted at the beginning of each aggregate planning period because of demand fluctuation over multiple periods. A model of production planning and equipment changeover scheduling at the aggregate level is developed. In the described model, three kinds of equipment changeover methods, i.e. adding machine, removing machine and transferring machine, are involved. Because the model is a large-scale integer programming problem, it cannot be solved directly. A solution approach is developed, which first solves a recursive linear programming problem to obtain a rough set of machines to be added and a rough set of machines to be removed for each machine line in each period, then applies a branch and bound heuristic to the rough sets to obtain near-optimal solutions to the equipment changeover scheduling problem. Computational studies show the financial benefit both on capital cost and equipment changeover costs.     

Estimating printed circuit board assembly times using neural networks

Several production planning tasks in the printed circuit board (PCB) assembly industry involve the estimation of the component placement times for different PCB types and placement machines. This kind of task may be, for example, the scheduling of jobs or line balancing for single or multiple jobs. The simplest approach to time estimation is to let the production time be a linear function of the number of components to be placed. To achieve more accurate results, the model should include more parameters (e.g. the number of different component types, the number of different component shapes, the dimensions of the PCBs, etc.). In this study we train multilayer neural networks to approximate the assembly times of two different types of assembly machines based on several parameter combinations. It turns out that conventional learning methods are prone to overfitting when the number of hidden units of the network is large in relation to the number of training cases. To avoid this and complicated training and testing, we use Bayesian regularisation to achieve efficient learning and good accuracy automatically.     

AUTOMATED PROCESS PLANNING FOR PRINTED CIRCUIT CARD ASSEMBLY

Printed circuit card assemblies form the core of a vast array of contemporary manufactured products. The technologies for assembling printed circuit cards require a hierarchy of complex decisions for grouping card types and processes, staging components at assembly machines, arranging feeders, and sequencing placement operations. This paper is motivated by the largely unmet needs of industrial process planners for computer aids. Our objective is to develop a framework for the printed circuit card assembly process planning problem and to assess the current state of the research on appropriate models and solution methods. We first provide an overview of the essential elements of printed circuit card terminology, assembly technologies, and assembly system operations. Then we propose a decision hierarchy, survey the published literature, and identify needs for future research.     

Integrated methodology for board assignment and component allocation in printed circuit board assembly

An approach to minimize makespan for assigning boards to production lines is described. Because of sequence-dependent set-up times, board assignment and component allocation have to be performed concurrently. An integrated methodology is developed to obtain a solution to these two problems. The methodology consists of seven phases: printed circuit board grouping, family decomposition, subfamily sequencing, Keep Tool Needed Soonest (KTNS) procedure, component set-up determination, component allocation and board assignment. Application of the methodology to industrial problems demonstrates that it can solve large-scale problems efficiently. In addition, the effect of two key parameters, feeder capacity and threshold value, on the performance of the solution procedure was examined. The results indicate that feeder capacity has an impact on total workload imbalance but not on the global makespan. Threshold value, a measure of effectiveness of joining a component type to a component group for a printed circuit board family, has a significant effect on the global makespan. The interactions of threshold value, and variations in printed circuit board requirement and component usage also affect global makespan.     

Concurrent multifunction deployment (CMFD)

Quality Function Deployment (QFD) is a powerful tool for quality planning in product design. In the course of time, the QFD method has passed over several improvements and adaptations to meet specific requests of particular working environments. The current needs and challenges in developing radical innovative and life-cycle optimised products require a concurrent approach of product planning against a complex set of objective functions (e.g. quality, cost, assembly, manufacturing, environment, technology, service, disposal, etc.). An advanced form of QFD that integrates concepts of concurrent engineering for planning product development with respect to multi-objective functions is presented in this paper. This framework is called Concurrent Multifunction Deployment (CMFD). TRIZ method was initially exploited to determine the appropriate vectors of intervention in formulating the CMFD methodology. A systematic algorithm supports the CMFD deployment process. It takes into account results from the analysis, innovation and evaluation phases over the product design process, too, ensuring a superior integration of the planning activities within the product development process.     

线路板印刷用Cu纳米粒子的研究进展

综述了电路印刷油墨用Cu纳米粒子在合成表征及应用方面的研究现状和发展趋势,并从工艺角度对其工业化生产做出了简要分析;归纳了电路板印刷油墨用Cu纳米粒子抗氧化技术进展;展望了今后印刷电子电路中Cu纳米导电材料的研究方向。     

Computer-aided production management issues in the engineer-to-order production of complex capital goods explored using a simulation approach

This paper describes the exploration of manufacturing planning and control issues in the capital goods industry using a simulation approach. The companies produce products which have deep and complex product structures and are produced in low volume on an engineer- or make-to-order basis (ETO, MTO). The work reported here draws on the results of surveys of companies involved in the manufacture of capital goods which identified their characteristics of ETO and MTO capital goods companies and their strategic issues. The planning and control approaches adopted in the manufacturing facilities and the difficulties experienced in the application of computer-aided production management (CAPM) systems were also examined. The simulation model developed enables complex manufacturing systems to be modelled and was configured to represent a typical ETO/MTO facility using industrial data. A series of full factorial experiments were performed to explore a number of production management problems identified in surveys including capacity planning, assembly planning and scheduling strategies. Conclusions are drawn on the effects on performance and capacity of: applying minimum set-up and processing times for both major and minor activities; using different data update periods and assembly lead times; and adopting various scheduling and despatching approaches. These results are compared with those obtained by other workers who used survey techniques alone, and have implications for the manufacturers of capital goods.     

Combined effects of linear and angular errors in pc board assembly

Automated printed circuit board assembly is a complex process where accuracy is a critical issue. This paper discusses the quantitative effects of linear and angular errors present in such a system on the successful assembly of through-hole components that have been properly registered. Both additive and statistical error compounding methods are illustrated. Mathematical models developed in this study can be used to determine the relative effects of critical system parameters and tolerances on proper insertion of the component into the pc board. Optimal design and control specifications can therefore be obtained for an efficient and successful assembly system.     

Optimal versus heuristic scheduling of surface mount technology lines

This paper presents and compares an exact and a heuristic approach for scheduling of printed wiring board assembly in surface mount technology (SMT) lines. A typical SMT line consists of several assembly stations in series and/or in parallel, separated by finite intermediate buffers. The objective of the scheduling problem is to determine the detailed sequencing and timing of all assembly tasks for each individual board, so as to maximize the line's productivity, which is defined in terms of makespan for a mix of board types. The limited intermediate buffers between stations result in a scheduling problem with machine blocking, where a completed board may remain on a machine and block it until a downstream machine becomes available. In addition, limited machine availability due to scheduled downtimes is considered. The exact approach is based on a mixed integer programming formulation that can be used for optimization of assembly schedules by using commercially available software for integer programming, whereas the heuristic approach is designed as a combination of tabu search and a set of dispatching rules. Numerical examples modelled after real-world SMT lines and some computational results are provided to illustrate and compare the two approaches.     

面向订单的生产计划与调度的综合优化

研究了一个多订单环境下的生产计划与调度集成优化问题,以实现准时生产为目标,综合考虑产品装配结构约束的订单任务计划与订单产品零部件的加工调度,采用直接面向客户订单的工序调度模式建立了计划和调度的综合优化整数规划模型.设计了带精英策略的蚁群算法作为该数学模型的求解方法,并通过对比试验为该算法选取最佳的搜索参数.实例仿真结果表明,所建模型的正确性以及蚁群算法求解该问题的可行性和有效性.