Showing papers in "Production Planning & Control in 2002"
TL;DR: In this article, the benefits of vendor managed inventory (VMI) are analyzed from the viewpoint of managing the replenishment process of the entire product range, not from a single stock keeping unit.
Abstract: Managing the order-delivery processes between organizations is a key issue in supply chain management. Despite the increasing application of just-in-time (JIT), lean and agile practices and new information systems that increase the visibility in supply chains, a lot of problems still remain. Surveys among European companies indicate that no signifi cant improvements have taken place in delivery performance during last decade. Vendor managed inventory (VMI) is a recent alternative for the order-delivery process. The fundamental change is that the ordering phase of the process is abolished, and the supplier is given both authority and responsibility to take care of the entire replenishment process. Despite of its advantages VMI has not yet become a standard mode of operation in companies. In this paper the benefits of VMI are analyzed from the viewpoint of managing the replenishment process of the entire product range, not the viewpoint of a single stock keeping unit. A time-based analysis method is develop...
149 citations
TL;DR: In this paper, the authors identified the characteristics of the process industries that influence the possibilities for rework in these industries, based on a framework provided by Flapper and Jensen ( International Journal of Production Research, 1999, to be published).
Abstract: For all kinds of reasons, rework, i.e. the transformation of products not fulfilling preset specifications into products that do, is an important issue in process industries. Despite a considerable amount of published research on planning and control of rework, and in addition many papers referring to the existence of rework in the process industries, hardly any attention has been paid to the consequences of many process industries specific characteristics for execution, planning and control of rework operations. Here are identified the characteristics of the process industries that influence the possibilities for rework in these industries, based on a framework provided by Flapper and Jensen ( International Journal of Production Research , 1999, to be published). How the available operations management literature assists in determining operational strategies for planning and control of rework in process industries is assessed. It is concluded that many relevant and interesting problems have not been addr...
128 citations
TL;DR: In this paper, the authors developed a model to determine an optimal integrated vendor-buyer inventory policy for flawed items in a just-in-time (JIT) manufacturing environment.
Abstract: This article develops a model to determine an optimal integrated vendor-buyer inventory policy for flawed items in a just-in-time (JIT) manufacturing environment. The aim is to minimize the total joint annual costs incurred by the vendor and the buyer. The proposed model extends the integrated vendor-buyer inventory model by accounting for imperfect quality items. The expected annual integrated total cost function is derived and an analytic solution procedure is proposed to determine the optimal policy. Finally, numerical examples are also given to illustrate the solution procedure presented in this article.
127 citations
TL;DR: An extension of the job shop models that are used in the theoretical studies is proposed that can explain the differences between the results of theoretical studies and empirical studies into the effects of workload control on performance and shows that, under certain conditions, without workload control the shop performance can become unstable.
Abstract: In this paper we propose an extension of the job shop models that are used in the theoretical studies, that can explain the differences between the results of theoretical studies and empirical studies into the effects of workload control on performance. The extension assumes that the workload level affects the effective processing times in a shop and is based on the results of empirical research on the relationship between workload and shop performance. Using computer simulation we investigate the effects of workload based work order release on the shop performance under the new job shop model. The simulation results confirm the effect of workload control on shop performance found in empirical studies, and show that, under certain conditions, without workload control the shop performance can become unstable
107 citations
TL;DR: In this paper, the authors provide a review of the results in this field (mainly of the last ten years) for the due date determination models where due dates are defined depending on the processing times (common slack due dates, total-work-content or processing-plus-wait due dates) or on the jobs' positions in the schedule.
Abstract: The Just-In-Time concept in industry according to which jobs are to be completed as close to their due dates as possible, has stimulated research on the scheduling problems with due date assignment and non-regular objective criteria dependent on earliness and tardiness costs. The paper provides a review of the results in this field (mainly of the last ten years) for the due date determination models where due dates are defined depending on the processing times (common slack due dates, total-work-content or processing-plus-wait due dates) or on the jobs' positions in the schedule. The main objective of the paper is to survey the most useful results in the static deterministic settings, outlining the properties of optimal solutions and the complexity of the proposed algorithms.
100 citations
TL;DR: In this article, a hybrid approach is proposed which is a specific problem solving procedure combin Experimental results of the hybrid approach for the developed system show that more realistic solutions with respect to the analytic model reflecting stochastic nature of real systems are quite different from the initial analytic solutions.
Abstract: Production-distribution planning is the most important part in supply chain management. To solve this integrated planning problem, either analytic or simulation approach have been developed. However, these two approaches have their own demerits in problem solving. In this paper, a hybrid approach is proposed which is a specific problem solving procedure combin Experimental results of the hybrid approach for the developed system show that more realistic solutions with respect to the analytic model reflecting stochastic nature of real systems are quite different from the initial analytic solutions.
100 citations
TL;DR: The state-of-the-art in published research on workload control as applied to the semiconductor industry is described in this article, where the focus is on examining the concepts behind workload control heuristics and evaluating their effectiveness, overhead requirements, and implementability.
Abstract: The state-of-the-art in published research on workload control as applied to the semiconductor industry is described. The focus is on examining the concepts behind workload control heuristics and evaluating their effectiveness, overhead requirements, and implementability. Individual sections provide an overview of the distinctive elements in a semiconductor manufacturing environment, general dispatching and order release methods, workload control strategies developed for semiconductor manufacturing, and future directions.
98 citations
TL;DR: The theoretical and practical knowledge regarding the WLC concept are brought together and a review and classification of strengths and weaknesses reported from analytical research and the extensions that have been developed based on practical experiences are discussed.
Abstract: Workload control (WLC) has been elaborated in the early 1980s to a hierarchical production control concept for job shop manufacturing. In the 1990s the analytical research at the University of Groningen focused on assessing the strengths and weaknesses of this concept and on developing alternatives. Research at the University of Hannover focused on improving the practical applicability of the WLC concept. While the practical experiences confirm the strengths of the WLC concept, some extensions of the basic concept have been developed which may overcome some weaknesses suggested in literature. This paper aims at bringing the theoretical and practical knowledge regarding the WLC concept together. It gives a review and classification of strengths and weaknesses reported from analytical research and it discusses the extensions that have been developed based on practical experiences.
96 citations
TL;DR: In this paper, the authors examine the recently published ISO 9001 : 2000 quality management system standard to see how it addresses these issues, under the headings of compatibility, scope and organizational culture.
Abstract: Analysis of the literature and examination of the various models of integration and testing in the field, have revealed five key issues relating to management system integration. This paper examines the recently published ISO 9001 : 2000 quality management system standard to see how it addresses these issues, under the headings of compatibility, scope and organizational culture. The examination reveals that while compatibility with the ISO 14001 and OHSAS 18001 standards has been improved in some areas, a different approach and model of a management system has been used. The paper suggests that differences in the scope of the standards are also likely to give rise to different sub-cultures which will hinder integration, and scope and culture are more important than compatibility. This leads the authors to conclude that new models of integration should be based on an approach and definitions which can be used in any management system, as well as an integrated one. Models of an integrated managemen...
95 citations
TL;DR: Workload control (WLC) systems can be seen as a natural extension of input-output control systems which allow both the control of jobs into the shop and control of capacity which affects the flow of finished goods out of the shop.
Abstract: Workload control (WLC) systems can be seen as a natural extension of input-output control systems which allow both the control of jobs into the shop and the control of capacity which affects the flow of finished goods out of the shop. In previous research, it has been shown that WLC can help to reduce manufacturing lead times, even if the total workload processed by the shop in a given time period is maintained at a constant rate. However, the relative contributions of the input control mechanisms versus the output control mechanisms have not been clearly determined. This paper seeks to explore this which affects the flow of finished goods out of the shop. In previous research, it has been shown that WLC can help to reduce manufacturing lead times, even if the total workload processed by the shop in a given time period is maintained at a constant rate. However, the relative contributions of the input control mechanisms versus the output control mechanisms have not been clearly determined. This paper seeks...
80 citations
TL;DR: The resident scheduling problem at hospitals concerned with prescribing work-nights for residents is addressed while considering departmental staffing and skill requirements as well as residents' preferences and heuristic solution procedures are developed for the different identified scheduling scenarios.
Abstract: This paper addresses the resident scheduling problem (RSP) at hospitals concerned with prescribing work-nights for residents while considering departmental staffing and skill requirements as well as residents' preferences. Three scenarios that represent most situations and account for various departmental requirements and needs are described. Although similar scheduling problems are considered in the literature, no analysis exists that adequately deals with the speciffic nature of this problem. The problem is modeled as a mixed-integer program and heuristic solution procedures are developed for the different identified scheduling scenarios. These procedures exploit the inherent network structure of the problem which is an important feature that enhances problem solvability. For the sake of comparison, the problem is also solved exactly via the CPLEX-MIP (version 6.0) package. The contribution of this work is important since many hospitals are still utilizing manual techniques in preparing their own schedu...
TL;DR: In this article, the problem of managing the flow of material into a manufacturing cell in order to maximize the output rate for a given level of work-inprocess inventory is considered.
Abstract: Many firms seeking production economies and quicker throughput times have adopted cellular manufacturing techniques. New product introductions, increased product variety and process changes all add elements of uncertainty to the cell, and dynamic management techniques are required to achieve the benefits expected. This paper considers the problem of managing the flow of material into a manufacturing cell in order to maximize the output rate for a given level of work-inprocess inventory. The manufacturing cell is patterned after an Intel facility that assembles and tests microprocessors for the computer industry. The cell is studied under conditions in which a single bottleneck arises and those under which there are multiple bottlenecks. Alternative procedures for releasing material into the cell are evaluated in order to determine which offer the greatest advantage to managers.
TL;DR: In this paper, the performances of three workload limiting policies are analysed, and the following are the three objectives: assessing whether the method of workload limiting affects the performance of Order Review and Release strategies; investigating the performances when the mix imbalance changes; evaluating the robustness of the workload limiting methods considered.
Abstract: The performances of three workload limiting policies are analysed, and the following are the three objectives: (i) assessing whether the method of workload limiting affects the performances of Order Review and Release strategies; (ii) investigating the performances of the workload limiting methods when the mix imbalance changes; (iii) evaluating the robustness of the workload limiting methods considered. The methodological pattern followed required a simulation model of a dynamic job shop system and all the workload limiting methods are tested by resorting to a fractional factorial experimental design with repetitions. Results coming from simulation campaign show that the 'upper bound only' method is the best performer. Furthermore three different mix imbalance levels have been tested, showing that 'workload balancing' method allows closer performances to those of the 'upper bound only'. Finally 'workload balancing' is proven to be the most robust, but not all the results are statistically significant for...
TL;DR: This paper compares the performance of two meta-heuristic methods proposed to solve the identical parallel machine scheduling problem with sequence dependent setup times by combining a population-based method with local search procedures.
Abstract: The aim of this paper is to compare the performance of two meta-heuristic methods proposed to solve the identical parallel machine scheduling problem with sequence dependent setup times. The goal is to minimize the makespan. The first algorithm is a tabu search based heuristic and the second a memetic approach, which combines a population-based method with local search procedures. As benchmarks for small-sized instances, optimal and lower bound values are used provided by a dichotomous search. For larger instances, the comparisons rely on the best known solutions provided by an exhaustive search variant of the tabu procedure.
TL;DR: In this article, the authors describe the implementation of information systems to support the production planning and scheduling functions in two steel processing business units of a steel plant, and discuss typical issues that have to be solved when ERP and APS systems are integrated.
Abstract: This article describes the implementation of information systems to support the production planning and scheduling functions in two steel processing business units of a steel plant. In particular, the integration of the implementation of two systems is described: Enterprise Resource Planning (ERP) and Advanced Planning and Scheduling (APS). The article presents a functional architecture that integrates the two systems, and discusses typical issues that have to be solved when ERP and APS systems have to be integrated. Lessons learnt included the importance of an architecture to facilitate discussions, issue management, the importance of the primary process, differences between an ERP and APS implementation and differences in process descriptions.
TL;DR: In this paper, a new way of researching into supply chain management is introduced by adopting a supplier perspective by adopting mixed integer linear planning and simulation models, which takes into account firm and forecast orders (customer's forecast purchasing orders) and the behaviour of the supplier's suppliers and suppliers' subcontractors.
Abstract: A new way of researching into supply chain management is introduced by adopting a supplier perspective. Details are given of mixed integer linear planning and simulation models. The planning model takes into consideration firm and forecast orders (customer's forecast purchasing orders) and the behaviour of the supplier's suppliers and suppliers' subcontractors. The simulation model takes into account the dynamic behaviour of the supply chain and includes the planning production behaviour of a supplying company based on the planning model. The supplier manager can use the simulation model to determine what kind of parameters most affect company performances and then propose new management rules. Quantitative results that prove the benefits of integrating forecast orders for an aeronautic supplier have been provided.
TL;DR: In this paper, the authors investigated the linking mechanisms between successive companies and the collective efficiency of the supply chain from a just-in-time (JIT) perspective, focusing on the link mechanisms between different companies and their collective efficiency.
Abstract: Just-in-time (JIT) has been a widely recognized production philosophy alternative since the early 1980s. JIT principles and techniques have been widely adopted in many manufacturing firms. More recently, supply chain management has evolved as a discipline focusing on the design, planning and control of processes linking the initial raw materials to the ultimate consumption of the finished product. Supply chain efficiency is dependent on the efficiencies of the individual manufacturing organizations and the ability to connect along the supply chain. In this paper supply chain management from a JIT perspective is investigated, focusing on the linking mechanisms between successive companies and the collective efficiency of the supply chain.
TL;DR: In this paper, the authors compare input control based on aggregate shop loads with that based on bottleneck resource loads and compare two appropriate release mechanisms and compared in flow and job shops in two different environments.
Abstract: This study compares input control based on aggregate shop loads with that based on bottleneck resource loads. Two appropriate release mechanisms are developed and compared in flow and job shops tha...
TL;DR: In this article, the problem of the optimal design of multistage systems with Kanban control mechanism is investigated and the optimization problem generalizes those from literature by considering a general criterion function and including the lot sizes as decision variables.
Abstract: The problem of the optimal design of multistage systems with Kanban control mechanism is investigated. The optimization problem generalizes those from literature by considering a general criterion function and including the lot sizes as decision variables. Since no analytical solutions can be expected simulation combined with a genetic algorithm is used. The simulator KaSimIR as well as the optimization tool LEO are briefly described. Some examples demonstrate the usability of the approach.
TL;DR: In this paper, the possibility of using virtual (logical) cells as a reconfiguration strategy in order to achieve performance targets of manufacturing cells facing changing production requirements is investigated, and the creation of virtual cells is decided based on the overall performance of the system that is determined by the proposed integrated framework.
Abstract: Reconfiguration of manufacturing systems is discussed and all integrated framework which is mainly based on multiple objective simulation optimization is proposed for reconfiguration of manufacturing cells. The possibility of using virtual (logical) cells as a reconfiguration strategy in order to achieve performance targets of manufacturing cells facing changing production requirements is investigated. Creation of virtual cells is decided based on the overall performance of the system that is determined by the proposed integrated framework. In the framework generic capability units which are known as Resource Elements (RE) are used to define processing capabilities of virtual cells and processing requirements
TL;DR: In this paper, the authors proposed a genetic algorithm simultaneously to solve the issues pertaining to (i) what type of and how many testers should be invested for forthcoming orders for wafer and chip of a semiconductor testing facility under budget constraint and (ii) how to allocate tester capacity for the orders so that the profit of a company can be maximized.
Abstract: Semiconductor manufacturing and testing requires intensive capital investment Practical experiences in this industry indicate that a few savings on capacity may result in millions of benefit per year This paper focuses on the issues pertaining to (i) what type of and how many testers should be invested for forthcoming orders for wafer and chip of a semiconductor testing facility under budget constraint? and (ii) how to allocate tester capacity for the orders so that the profit of a company can be maximized? This research develops a genetic algorithm simultaneously to resolve the two issues A mathematical model is constructed and its answer serves as a benchmark The experimental results show that the proposed algorithm is robust to the change of budgets and algorithm parameters, and the performances are close to the ones provided by the mathematical model
TL;DR: In this paper, the inventory replenishment problem for deteriorating items with normally distributed shelf life, continuous time-varying demand, and shortages under the inflationary and time discounting environment is formulated as a dynamic programming model and solved by numerical search techniques.
Abstract: This paper deals with the inventory replenishment problem for deteriorating items with normally distributed shelf life, continuous time-varying demand, and shortages under the inflationary and time discounting environment. The reasons of choosing normal are twofold: it is one of the most important probability phenomena in the real world due to the classical central limit theorem, and it is also one of the most commonly used lifetime distributions in reliability contexts. The problem is formulated as a dynamic programming model and solved by numerical search techniques. The solutions of the model determine the optimal replenishment schedule over a finite planning horizon so that the present worth of the future costs associated with the system is minimized. In the extensive experiments, we validate the model, demonstrate the optimal replenishment schedule and lot-size, and carry out a comparative study to ascertain its contribution. In addition, sensitivity analysis was provided to help identify the most cr...
TL;DR: In this paper, the authors introduce several concepts and definitions related to Theory of Constraints design and management of unbalanced lines and illustrate the concep- tation of the theory.
Abstract: The purposes of this paper are, first, to introduce several concepts and definitions related to Theory of Constraints design and management of unbalanced lines and, second, to illustrate the concep...
TL;DR: The purpose of this paper is to examine how far simulation studies of maintenance systems are neglecting simulation-related statistical issues, which may leave simulation results suspicious and hard to explain.
Abstract: The purpose of this paper is to examine how far simulation studies of maintenance systems are neglecting simulation-related statistical issues This negligence may leave simulation results suspicious and hard to explain Several simulation factors are used to identify the strength of executed simulation experiments and to evaluate the level of clarity and reliability of the simulation models The factors includes purpose of simulation, simulation model, model assumptions, distribution and random variables, simulation languages and computers, program verification and model validation, design of experiment, and analysis of the output For this purpose, the literature is reviewed and subjected to the evaluation It is observed that most papers define clearly their objectives, simulation languages, and model performance measures However, verification, validation, experimental design, and output analysis are the most unclear factors
TL;DR: In this article, a state-dependent dispatch rule is developed to improve overall system performance, which consists of cycle time, work in process, throughput and due date performance, and the simulation results show that the TOC-based state dependent dispatch rule improves four performance measures simultaneously.
Abstract: Wafer fabrication industries encounter challenging tasks to justify their performance among conflicting measures when making dispatch policy decisions. A state-dependent dispatch rule is developed to improve overall system performance, which consists of cycle time, work in process, throughput and due date performance. The theory of constraints is adopted as guiding principle to derive the state-dependent dispatch rule. Three state variables (machine utilization, machine queue length, and contention factor) and three dispatch rules (two boundary, shortest time to next visit, and fastest time for next visit) are considered to construct the dispatch rule. Response surface methodology is also applied to this study. A near-realworld fab model is developed to test the performance of the new rule. The simulation results show that the TOC-based state dependent dispatch rule improves four performance measures simultaneously.
TL;DR: In this paper, it is argued that the derivation of simple rules for lot sizing is an important research topic, and a model for deriving such rules is presented, assuming that the batches are processed by an M/G/1 server.
Abstract: An important basis for workload control (WLC) is the existence of functional relationships between the mean level of work-in-process (WIP) and the values of important goal variables, like average flow time, capacity utilization, etc. These functional relationships are largely influenced by the lot sizes. This means that the usual objective of lot sizing must be supplemented by considering the impact of lot sizes on the relationships between WIP and the other goal variables. Here it is shown that this insight leads to flow time oriented lot sizing models. This type of lot sizing models is analysed. It is argued that the derivation of simple rules for lot sizing is an important research topic, and a model for deriving such rules is presented. Some rules are derived from the model, assuming that the batches are processed by an M/G/1 server, and it is shown that these rules support insights based on simulation in the 1980s. Topics for future research are outlined as well.
TL;DR: In this paper, the effects of a number of essentially different work order release and flow time allowance policies on the assembly order flow times and assembly order due date performance are investigated, and the results show that the best performance is obtained with simultaneous work-order release, an average operation flow-time allowance equal to the average operation waiting time and equalized flow time allowances per work order in an assembly order.
Abstract: The effects of a number of essentially different work order release and flow time allowance policies on the assembly order flow times and assembly order due date performance are investigated. Work orders within an assembly order have different routing length. The assembly order flow time is the time that elapses between the release of the first work order and the completion of the last work order of the assembly order. The timing of the release of work orders, and the distribution of the flow time allowance over the work orders in an assembly order were varied, and used systematic computer simulation to investigate the effects on performance. The results show that the best performance is obtained with simultaneous work order release, an average operation flow time allowance equal to the average operation waiting time and equalized flow time allowances per work order in an assembly order.
TL;DR: An iterative scheduling process is suggested as an extension of existing paradigms to solve practical production scheduling problems and to bridge the gap between theory and practice in production scheduling and control.
Abstract: This paper provides an excursion into various scheduling problems arising in the manufacturing environment and possible approaches that can be taken to solve them. It reviews the research in production scheduling from the perspective of designing and operating a production system and examines the research strategies adopted to find the solution of the practical problems. This review is in the form of the paradigms that evolved during the twentieth century and shows the transition in theory and practice of each paradigm. It covers the fundamental frameworks of scheduling theory, outlining various approaches that can be taken to solve (optimally or approximately) such problems, and the difficulties arising in their practical use. Subsequently, an iterative scheduling process is suggested as an extension of existing paradigms to solve practical production scheduling problems and to bridge the gap between theory and practice in production scheduling and control.
TL;DR: In this paper, the authors claim that problem identification and problem-solving processes can be integrated into work processes by embedding tests in work that evaluate performance with every exchange of products, services, and information.
Abstract: This paper asserts that problem identification and problem-solving processes can be integrated into work processes by embedding tests in work that evaluate performance with every exchange of products, services, and information. These tests make it unambiguous when, where, and by whom problem solving is necessary. This hastens improvement and deepens process knowledge frequently and at low-cost. These assertions are based on an ethnographic study of how some firms sustain outstanding performance through iterative problem solving, a concern of organizational and operations management theory. This field research revealed attributes of just-in-time (JIT) as it is practiced by Toyota and its affiliates - companies that have been associated with JIT and that have been recognized for outstanding performance - that have not been fully explored previously. Whereas JIT&'s role in controlling material flows through sequential processes has been much discussed, Toyota and its affiliates also use JIT to evaluate work-...
TL;DR: In this article, the implications for operations management resulting from increased environmental interest and change are addressed in the areas of operations strategy, production and inventory management, and OR/MS techniques.
Abstract: While many businesses have traditionally resisted changes brought about by government legislation and pressure from the public, many firms, through reluctant adoption or willing change, have found that a pro-environment stance can enhance a number of goals. Changes brought about by environmental considerations have been deeply felt in the area of operations management. This paper looks at implications for operations management resulting from increased environmental interest and change. Specifically, the areas of operations strategy, production and inventory management, and OR/MS techniques are addressed. A number of propositions and research questions are presented in order to encourage and provide direction for research into the areas of operations management that are impacted by environmental management.