Multiple criteria approach for solving feeder assignment and assembly sequence problem in PCB assembly

The feeder assignment and assembly sequence problem in printed circuit board (PCB) assembly with the twin objectives of minimizing magazine travel time and minimizing board travel time is presented in this study. The problem uses Dynamic Pick-and-Place (DPP) model where robot arm, board and magazine move together with different speeds based on relative coordinates between consecutive assembled points. The difficulty of the problem is that the feeder assignment depends on assembly sequence and vice versa. A new approach is proposed to improve the existing approaches. The trade-off between two strategies, assembly by area and assembly by component types, can give better results. The numerical experiments proved the efficiency of the new algorithm.     

Job sequencing and component set-up on a surface mount placement machine

In this paper, the problem of sequencing PCB assembly jobs on an automatic SMD placement machine is addressed. The objective is to minimize the makespan. Moreover, both the job arrival times and the precedence constraints for those jobs requiring component placement on the primary and secondary side of the same board must be taken into account. A considerable set-up time occurs when switching from one board type to another, which depends on the number of component feeders to be replaced in the magazine of the assembly machine. The exchange of component feeders is complicated by the fact that each feeder occupies a different number of magazine positions. Theoretically, the minimum makespan required for a given batch of jobs could be derived by solving the order sequencing and the component set-up problems simultaneously. However, optimal solutions are practically unattainable for problems of realistic size. Therefore, efficient heuristic solution procedures are developed which exploit component commonality between PCB types. The numerical results obtained indicate the practicality of the proposed heuristics in an industrial application.     

基于DNA遗传算法的表面贴装生产线负荷优化分配

印制电路板组装任务的负荷优化分配包含设备约束、工艺约束等大量约束,是电子行业表面贴装生产线中的一类重要优化问题。其优化目标是在生产节拍给定和一定约束条件下,使得不同贴装机负荷均衡,任务分配达到最优。首先,根据不同表面贴装机、不同吸嘴及多种类型元件匹配的的复杂性,提出贴装机任务分配组合优化的问题;然后分析设备和元件的参数、组装可行性、贴装时间,以及贴装优化关系等因素,并提出假设条件,建立了平衡率最大化条件下的负荷分配组合优化的数学模型;最后,针对贴装生产线负荷分配问题的复杂性与特殊性,通过改良编码方式后的DNA遗传算法来优化组合数学模型,计算适应度,并借助MATLAB进行仿真求解,进而找到最优解。结果表明：本文提出的贴装生产线负荷分配方法可以解决带复杂约束的印制电路板组装负荷优化分配问题,提高设备的平衡率和生产效率,促进生产线的优化运行。     

A heuristic approach for component scheduling on a high-speed PCB assembly machine

The collect-and-place machine is one of the most widely used placement machines for assembling electronic components on the printed circuit boards (PCBs). Nevertheless, the number of researches concerning the optimisation of the machine performance is very few. This motivates us to study the component scheduling problem for this type of machine with the objective of minimising the total assembly time. The component scheduling problem is an integration of the component sequencing problem, that is, the sequencing of component placements; and the feeder arrangement problem, that is, the assignment of component types to feeders. To solve the component scheduling problem efficiently, a hybrid genetic algorithm is developed in this paper. A numerical example is used to compare the performance of the algorithm with different component grouping approaches and different population sizes.     

Optimizing the number of stations in assembly lines under learning for limited production

This paper considers finding the optimal number of stations for an assembly line producing a limited quantity of a new product under learning conditions. This type of production characterizes heavy products (such as airplanes and communication systems) and science-based industries (e.g. laser cutting devices and special equipment for hospitals). These products are manufactured in assembly line fashion in small batches of a few hundred. Since the products are assumed to be totally new to the workers, the learning phenomenon is significant (i.e. task times decrease from cycle to cycle as experience is gained). Therefore, standard balancing methods are no longer applicable. Determining the number of stations has a large effect on the production rate while the actual assignment of tasks to stations helps to fine tune the cycle time. Thus, the number of stations can be regarded as a strategic decision variable . This paper discusses two ways for determining the optimal number of stations, namely as a cost minimization problem and as a profit maximization problem.     

A Component Analysis of the Impact of Evaluative and Objective Feedback on Performance

Despite the frequency with which performance feedback interventions are used in organizational behavior management, component analyses of such feedback are rare. It has been suggested that evaluation of performance and objective details about performance are two necessary components for performance feedback. The present study was designed to help clarify which components are required for maximal effectiveness by comparing four conditions: (a) combined evaluative and objective feedback, (b) evaluative feedback alone, (c) objective feedback alone, and (d) no feedback. A total of 105 undergraduate students were recruited to work on a simulated bank check processing task while being exposed to one of the four feedback conditions. The number of checks correctly processed served as the dependent variable. Results suggest that a combination of objective and evaluative feedback is necessary for maximal performance.     

The Impact of Modular Assembly on Supply Chain Efficiency

This article studies the impact of modular assembly on supply chain efficiency. In the modular assembly approach, a manufacturer acquires pre‐assembled modules from its suppliers, rather than the individual components, as in the traditional assembly approach. We analyze the competitive behavior of a two‐stage modular assembly system consisting of a manufacturer, and a supplier who pre‐assembles two components into a module. The firms can choose their own inventory policies and we show the existence of Nash equilibrium in the inventory game. Moving from the traditional to the modular approach has a twofold effect on the supply chain. First, we investigate the effect of centralizing the component suppliers. It can be shown that when there is no production time shift, the module supplier always holds more component inventories than suppliers do in the traditional approach, which yields a lower cost for the manufacturer. However, the suppliers, and therefore the supply chain may incur a higher cost in the modular approach. Second, we study the effect of a shift in production time from the manufacturing stage to the supplier stage. From numerical studies, it has been found that such a lead time shift always benefits a centralized supply chain, but not necessarily so for a decentralized system. Combining the two effects, we find that the modular approach generally reduces the cost to the manufacturer and the supply chain, which explains the prevalence of modular assembly from the perspective of inventory management. These results also provide some insight into how firms can improve supply chain efficiency by choosing the right decision structure and lead time configuration.     

Making Boards Effective: An Empirical Examination of Board Task Performance

Despite the increasing attention of management scholars to boards of directors, there is still scant evidence on the antecedents of board task performance. The lack of significant results seems to be due to some theoretical and methodological choices followed by scholars, i.e. the almost exclusive reliance on agency theory and the use of demographic data. Following the call for dismantling the fortresses dominating past studies, this paper contributes to opening the 'black box' of boards of directors, developing a conceptual model that considers the impact of board members' diversity, commitment and critical debate on board task effectiveness in performing its service and control tasks. We collected primary data through a questionnaire survey, and we tested the model controlling for board, firm and industry characteristics. Our findings suggest that (i) the predictors we identified, and particularly the board members' commitment, are far more important than board demographics to predict board task performance; (ii) firm and industry contexts exert a significant influence on board task performance; (iii) predictors have a different impact on specific sets of tasks. Thus, our findings support the idea that several board characteristics and contingencies at both industry and firm level must be acknowledged in board design.     

An Evolutionary Algorithm for Sequencing Production on a Paced Assembly Line

A new sequencing method for mixed‐model assembly lines is developed and tested. This method, called the Evolutionary Production Sequencer (EPS) is designed to maximize production on an assembly line. The performance of EPS is evaluated using three measures: minimum cycle time necessary to achieve 100% completion without rework, percent of items completed without rework for a given cycle time, and sequence “smoothness.” The first two of these measures are based on a simulated production system. Characteristics of the system, such as assembly line station length, assembly time and cycle time, are varied to better gauge the performance of EPS. More fundamental variation is studied by modeling two production systems. In one set of tests, the system consists of an assembly line in isolation (i.e., a single‐level system). In another set of tests, the production system consists of the assembly line and the fabrication system supplying components to the line (i.e., a two‐level system). Sequence smoothness is measured by the mean absolute deviation (MAD) between actual component usage and the ideal usage at each point in the production sequence. The performance of EPS is compared to those of well‐known assembly line sequencing techniques developed by Miltenburg (1989), Okamura and Yamashina (1979), and Yano and Rachamadugu (1991). EPS performed very well under all test conditions when the criterion of success was either minimum cycle time necessary to achieve 100% production without rework or percent of items completed without rework for a given cycle time. When MAD was the criterion of success, EPS was found inferior to the Miltenburg heuristic but better than the other two production‐oriented techniques.     

可变产能的按订单装配系统库存和生产决策研究

本文基于一个ATO 生产商的实践,考虑一个需求不确定并具有子装配件的单周期ATO 系统,为了应对较长的采购提前期和有限产能的挑战,生产商可以在得到确定的需求之前提前采购零件,装配子装配件以至于最终产品。由于产品物料清单结构中存在子装配件作为可选的中间件,因此完全使用零件和使用子装配件装配最终产品的不同,造成装配能力在时间上具有可变性。我们对此问题建立了利润最大化模型,分析在上述ATO 环境中的最优库存和生产决策。通过一系列最优解的性质,我们得到了该问题的有效解决方法。     

印刷电路板组装生产线调度优化问题建模

印刷电路板(printed circuit board,PCB)组装是电子制造的基础,其核心生产过程包括电子元器件的表面贴装。分别基于典型的表面贴装机(CM402)、以及由高速贴片机(CM402)与多功能贴片机(DT401)组成的流水线的机械特征与生产特性,对上述组装机及组装流水线的调度问题建立优化模型,为进一步的算法开发以及电子制造生产调度的智能化提供理论支持。     

Assembly block storage location assignment at a shipyard: a case of Hyundai Heavy Industries

It is not a trivial issue how to manage assembly blocks at a shipyard. Based on the project experience in Hyundai Heavy Industries, currently the largest shipbuilding company in the world and the leader in the Korean merchant shipbuilding industry, this study points out the difficulties on the block stockyard operations, formalises the assembly block storage location assignment problem, and develops the assembly block storage location assignment algorithm, the purpose of which is to reduce the number of unproductive block moves. Through simulation experiments for various situations, this study demonstrates the usefulness of the assembly block storage location assignment algorithm. In addition, this study examines the impacts of block move sequence rules and of block stockyard layouts on the block stockyard operations.     

Why and when female directors are less engaged in their board duties: An interface perspective

Female representation on boards is perhaps one of the most studied topics in board-governance research. At the same time, much is unknown about female directors' task engagement within boards. Drawing from psychological theory on societal gender beliefs, our study tests whether the impact of director gender on supervisory task engagement hinges on status dynamics in two relational interfaces: the director–board interface and the director–CEO interface. According to this perspective, female directors show less task engagement because gender is a diffuse status cue that creates status differentiation within the director–board interface. Multi-source board survey data (n = 61 boards, n = 315 directors) confirms that, within the confines of the boardroom, female directors do, indeed, receive lower-status ratings than male directors. This effect is weaker when boards have a female chair. Furthermore, lower status explains perceived lower task engagement of female directors, but this link critically hinges on the CEO–director interface. The impact of status differences is more pronounced when directors intersect with a relatively dominant CEO. All in all, the results demonstrate that relational interfaces play a key role for female directors’ task engagement in their board duties.     

Conflict in the boardroom: a participant observation study of supervisory board dynamics

We develop a conflict-oriented model of board task performance and argue that a common framework, that is, a shared understanding of its role, helps boards to perform well. Conflict is the mediating effect through which this plays out. We posit that a common framework increases board task performance because it reduces intragroup relationship conflicts, increases task conflicts within the board, and reduces conflicts in the relationship between board and CEO. We explore the model through a comparative participant observation study of 11 supervisory boards in action. The results show that while low levels of relationship conflict are typically considered a sign of a well-functioning board, the avoidance of relationship conflict negatively impacts board task performance and may lead to ‘cognitive blindness’. Boards of directors should manage—rather than avoid—relationship conflict. Based on our findings, we suggest an extended model of conflict in boards that takes into account the negative effect of conflict avoidance.     

Power and trust in board–CEO relationships

In this paper we develop and test a theoretical model that reduces relational risks to solve the puzzle of conflicting task requirements imposed on boards of directors in listed companies. Doing so unites two seemingly conflicting tasks—board control and service tasks—through examining relational risks between the board and the CEO. We also present two mechanisms that could reduce relational risks. One is board power over the CEO, and the other board trust in the CEO. Practitioners could apply these two mechanisms to achieve better performance of board control and service tasks simultaneously. We test hypotheses using 441 survey responses collected in 2005. The result shows a good fit between the model and survey data, indicating examining relational risks is a rewarding approach to understanding conflicting board task performance, and board control over the CEO and board trust in the CEO are two effective mechanisms to reduce relational risks.     

The Effects of Self-Monitoring on Safe Posture Performance

The purpose of the present study was to examine the effects of self-monitoring on safe positioning of individuals performing a typing task and an assembly task using a multiple baseline design across behaviors and tasks. The study took place in an analogue office setting with seven college student participants. The dependent variable was the percentage of observations scored as safe, and each session was recorded via a hidden camera. Each block of sessions included completing a typing task for two 9-minute sessions and an assembly task for two 9-minute sessions. During baseline, participants received information regarding safe positions and demonstrated the positions. In the self-monitoring phase, participants recorded whether a targeted posture was safe or at-risk. If constraints of the study permitted it, a third phase was implemented. In the third phase, if the targeted postures improved at least 20 percentage points over baseline during self-monitoring, additional behaviors were monitored. Otherwise, an overt camera condition was implemented during the third phase in addition to self-monitoring. Five of the 17 dependent variables exposed to the self-monitoring intervention resulted in substantial changes in safety performance, and an additional six behaviors resulted in a mean improvement of more than 10% from baseline to intervention. The camera present condition produced differential improvement for two of the 12 exposed postures. This information could lead to a viable alternative for improving occupational safety.     

A Production–Inventory Model for a Push–Pull Manufacturing System with Capacity and Service Level Constraints

We study a hybrid push–pull production system with a two‐stage manufacturing process, which builds and stocks tested components for just‐in‐time configuration of the final product when a specific customer order is received. The first production stage (fabrication) is a push process where parts are replenished, tested, and assembled into components according to product‐level build plans. The component inventory is kept in stock ready for the final assembly of the end products. The second production stage (fulfillment) is a pull‐based assemble‐to‐order process where the final assembly process is initiated when a customer order is received and no finished goods inventory is kept for end products. One important planning issue is to find the right trade‐off between capacity utilization and inventory cost reduction that strives to meet the quarter‐end peak demand. We present a nonlinear optimization model to minimize the total inventory cost subject to the service level constraints and the production capacity constraints. This results in a convex program with linear constraints. An efficient algorithm using decomposition is developed for solving the nonlinear optimization problem. Numerical results are presented to show the performance improvements achieved by the optimized solutions along with managerial insights provided.     

突发事件应急救援人员的派遣模型研究

本文针对突发事件应急救援人员派遣问题,考虑位于不同出救点的救援人员到达救援需求点执行救援任务的应急救援时间满意度,以及救援人员对不同应急救援任务的胜任程度,以应急救援时间满意度最大以及救援人员完成救援任务的"效果"最佳为目标,建立了突发事件应急救援人员派遣的优化模型。针对优化模型的特点,给出了有效的求解方法。最后,通过一个算例分析说明了构建的模型及所给出的求解方法的可行性和有效性。     

A Comparison of Due Date Setting,Resource Assignment,and Job Preemption Heuristics for the Multiproject Scheduling Problem*

This research examines a heuristic, rule-based approach for setting due dates in a multiproject, multijob, or assembly shop. Due date estimation is a challenging problem because the operating environment is capacitated, involves the allocation of multiple resources, and allows for the preemption of resources from one project or job to another. The dynamic, continuous arrival of new jobs or orders frequently results in the preemption of resources through the application of managerially determined priority policies. These preemption policies have a significant impact on the ultimate completion time of a job or a project. A three-factor, full-factorial computer simulation experiment is used to assess the relative effectiveness of combinations of four due date setting heuristics, five resource assignment heuristics, and three resource preemption heuristics. Recommendations are made for the selection of due date and resource assignment heuristic combinations under the three preemption policies examined.     

SOLVING A COMBINED PART-SELECTION,MACHINE-LOADING,AND TOOL-CONFIGURATION PROBLEM IN FLEXIBLE MANUFACTURING SYSTEMS*

Loading too many or too few copies of tools may result in waste of tool magazine slots and unnecessary machine shutdowns. This is a consequence of not integrating the tool-configuration problem with other flexible manufacturing system (FMS) planning problems. Solving part-selection, machine-loading and tool-configuration problems independently may cause entire solutions to be infeasible. We propose both an approach to the explicit formulation of tool configuration problems and the simultaneous solution of part-selection, machine-loading and tool-configuration problems. We developed and solved sequentially some associated bicriteria models sequentially. We also discussed the effects of considering some secondary objectives on system performance and described the concepts of critical magazine size and critical machining time using an example problem. Unnecessary allocation and under-use of tool magazine capacity and machining time could be reduced by considering the critical magazine size and machining time. Finally, we suggest using a method based on Lagrangian relaxation for solving large size problems.