The sensitivity of job mix and load capacity bottlenecks on inventory and due date performance in a manufacturing system

Based on a benchmark job-lot manufacturing system a simulation study was carried out to compare the performance of just-in-time (JIT) shop control system Kanban with conventional job-shop control procedures. The shop control policies were tested under a good manufacturing environment and the effects of job mix and load capacity bottlenecks on various shop control policies were tested. From the simulation results, it is inferred that there are shop control procedures that perform better than the Kanban in a job shop. It has been observed that even with adequate capacity, bottleneck areas surface due to fluctuations in the shop load. Kanban is not appropriate in such a situation because capacity bottlenecks can significantly reduce the ell'ectiveness of a pull system. The disparateness in the processing requirements for jobs can seriously undermine the performance of the shop. This is the type of shop environment where the shop control procedures will be most effective. Although Kanban came out best when the load capacity bottlenecks and the disparateness of the job mix were removed, the selected shop control variable combinations closely approximated the Kanban result. Although many features of JIT can be implemented in any system, companies trying to adopt JIT should remember that Kanban requires a rigid system intolerant of any deviation.     

The permutation flow shop problem with just in time production considerations

This research presents a variation to the permutation flow shop problem where Just In Time (JIT) production requirements are taken into account. The model developed in this research employs dual objectives. In addition to the traditional objective of minimizing the production makespan, minimization of Miltenburg's material usage rate is also incorporated. In this model, multiple units of any product are permitted in the production sequence. However, the minimization of material usage rates attempts to prevent batch scheduling of products and allows unit flow of products as required in demand flow manufacturing. A solution method is proposed for determining an optimal production sequence via an efficient frontier approach and Simulated Annealing (SA). Test problems and specific performance criteria are used to assess the solutions generated by the proposed method. Experimental results presented in this paper show that the use of the efficient frontier and SA provide solutions that approach the optimal solution for the performance measures used in this research.     

Relationships among JIT practices: an interpretive modeling approach

Abstract

This research develops a model of relationships among components of Total-JIT, including JIT-information, JIT-manufacturing, JIT-purchasing, and JIT-selling, to establish an implementation hierarchy based on relative importance. The data collected relates to the relationships among JIT components and two performance measures, supply chain competency and organizational performance. Two groups are used in the research, one group of five operations management academics and another group of 30 practicing operations managers working in U.S. manufacturing firms. An interpretive structural modelling methodology is used to develop alternative structural models. The academics’ data show JIT-information emerging as lynchpin of relationships, directly impacting all other JIT practices and both performance measures. The practitioners’ data indicates that all JIT practices and performance measures are interactive as components and outcomes. This study is the first to apply interpretive structural modelling to investigate the interplay among total-JIT components and the performance measures of supply chain competency and organizational performance.     

A FRAMEWORK AND MEASUREMENT INSTRUMENT FOR JUST-IN-TIME MANUFACTURING

While Just-in-Time (JIT) manufacturing has emerged as one of the major tools to enhance manufacturing competitiveness, no attempt has been made to develop a reliable and valid measurement instrument for empirical research in JIT. Without such an instrument, generalization beyond the immediate sample is difficult or misleading. We have proposed a JIT framework and developed a valid and reliable instrument with 16 summated scales for dimensions that capture essential aspects of JIT useful in assessing its impact in manufacturing environments. In addition, we discuss in detail the interactive nature of JIT practice. And, we propose a step-by-step approach to reliability and validity testing. Four JIT practices (equipment layout, pull system support, supplier quality level, and Kanban) are identified as major contributing factors to JIT performance.     

Analysis and Approximation of a JIT Production Line: A Comment

A recent Decision Sciences article by Jordan [9] presented a Markov-chain model of a just-in-time (JIT) production line. This model was used to estimate average inventories and production rates to find the optimal number of kanbans. Results for expected production rate were found to be consistently lower than those obtained by Huang, Rees, and Taylor [8] in a previous Decision Sciences article. Jordan attributed this unexpected outcome to some procedural problems in Huang et al.'s simulation methodology. In this paper, Markov-numerical analysis is used to compare the performance of Jordan's and Huang et al.'s methods of production control. Simulation analysis is then used to determine the effects of finite withdrawal cycle times. Results show that, for equal numbers of kanbans, Huang et al.'s two-card method of production control provides substantially greater expected production rates than Jordan's method. These results suggest that the Jordan model should not be applied to the problem of setting kanban numbers on manual JIT lines. Finally, we comment on the efficiency of Jordan's iterative method to obtain performance measures of tandem queues.     

An Entropy Measure of Flow Dominance for Predicting Operations Performance

The flow of jobs within a system is an important operating characteristic that influences system performance. While the majority of previous studies on manufacturing performance consider product flows only as an implicit parameter of the design, we introduce an explicit measure of flow dominance based on entropy and test its efficacy in predicting the performance of manufacturing systems. In computing entropy flow dominance (EFD), we aggregate information embedded in the routings of all products within a system into a single measure. EFD is designed to indicate on a 0–1 scale the level of flow dominance, where 1 represents a pure flow shop and 0 represents a pure job shop. The result is a simple measure that provides managers a way to explain and predict complex phenomena. Our experimental results indicate that EFD is a statistically significant determinant of manufacturing system performance. Furthermore, the model including EFD as an independent variable accurately predicts manufacturing system performance as measured by job flow time, flow time standard deviation, and work in process. We note that the same results can also apply to service systems, such as the “back‐room” low‐contact type systems, that have similar characteristics as manufacturing systems.     

Organizational modifications to support JIT implementation in manufacturing and service operations

This study investigates JIT implementation practices and performance in manufacturing and service organizations in the US. Literature related to JIT usage and performance in both sectors is reviewed. A field study is then conducted to investigate the actual implementation experiences of a selected group of service and manufacturing users of JIT. Our findings from the literature and the field study are used to develop four research hypotheses that are tested using survey data from 130 manufacturing and 61 service firms. Manufacturing and service firms that had engaged in modifications such as operator and management training and improving linkages with suppliers prior to implementing their JIT systems experienced less implementation problems and achieved higher levels of success than firms that placed less emphasis on these modifications. This paper details and discusses these and other results from our study. In addition, managerial implications of our findings are presented.     

An Experimental Comparison of Time-Based and Economic-Based Scheduling Methods to Maximize Net Present Value*

In the past, performance in dynamic-scheduling environments was primarily measured in terms of time or physical shop characteristics. Objectives such as mean tardiness, flow time, and work-in-process inventory were commonly used. Today, there is increasing interest in the use of more advanced economic performance measures. These measures have the more comprehensive objective of maximizing ownership wealth by economically scheduling jobs and tasks. This study presents a large-scale experiment testing time-based and economic-based scheduling methods in a dynamic job shop. These methods are evaluated on their ability to maximize net present value (NPV). The study considers the just-in-time (JIT) delivery environment. The job shop is hypothetical, but is based on models of real production situations. Results show that the use of very detailed economic information in a sophisticated manner generally improves economic performance. Where due dates are easy to achieve, however, time-based scheduling methods are at least as good as those based on economics. Also, where utilization is high and due dates tight, early cost information in release and dispatch is detrimental to schedule value.     

Production planning in a MRP/JIT repetitive manufacturing environment

Some literature suggests that the best approach to production planning is a complete implementation of just-in-time. It has also been suggested that JIT replaces material requirements planning, and computerized procedures are an unnecessary complex burden on management especially in a highly repetitive environment. This article examines the JIT programme at the John Deere Engine factory. In 1985 the factory began a JIT programme with the belief that it would replace their MRP system. The results of the JIT programme are examined and management's conclusion that the best approach is a blend of JIT and MRP is explored.     

Experimental earliness/tardiness production planning with the due window system

In order to use the philosophy of JIT to improve the production planning method of MRP-II, we propose the experimental software system of the earliness/tardiness produc tion planning problem with due window. By means of the approaches and model reported in this paper, the optimal production planning can be achieved. The recommended model extends the problem of due window from the shop scheduling level into the aggregated planning level of mass manufacturing systems. Simulation results have demonstrated that the experimental software is a useful tool for the production management of repetitive manufacturing enterprises.     

A structured methodology to implement judiciously the right JIT tactics

In order to enhance the competitiveness and efficiency of manufacturing operations, many companies arc looking at implementing key strategic technologies. Two of the most predominant programs are ‘just-in-time’ and ‘synchronous organizations’. However, their impacts on improving quality and reducing time-to-market have been mixed. It is not very clear why, in some cases, results are poor, when in a similar situation, programmes have proved to work well. There are conflicting reasons reported for such a discrepancy. Some have argued that during J IT implementation either a right mix of tactics was not selected at the outset or the process was not carefully monitored to see whether a mid-course correction or change in tactics was necessary. In order to (a) protect the manufacturing and strategic teams from making the same/similar mistakes and (b) sustain a series of successful activity throughout during the strategic implementation cycle, this paper outlines a structured methodology. The method utilizes a matrix-based procedure to dynamically (over time) measure the effectiveness of a line of JIT tactics against the organization's principles and objectives. The operating procedure suggests first (a) using a method for monitoring the changing conditions of market and business and then (b) using the metrics to guide the management with a new line of tactics that might have better impact on the newly aligned company goals. In an effort to help managers and engineers decide on a proper line of tactics to implement JIT, a line of JIT quality matrices (JQM) is developed. JQM provides a framework to guide group managers to ‘plan, pick and choose’ a set of effective JIT techniques. An approach similar to quality function deployment (QFD) is used to generate the JIT house and their corresponding JQM matrices. With the JQM-based structured methodology, managers can design the best line of JIT strategy blended with JIT theory and adapted to the manufacturing environments in which it is expected to operate.     

The Bullwhip Effect—Impact of Stochastic Lead Time,Information Quality,and Information Sharing: A Simulation Study

We use a simulation model called ‘SISCO’ to examine the effects in supply chains of stochastic lead times and of information sharing and quality of that information in a periodic order‐up‐to level inventory system. We test the accuracy of the simulation by verifying the results in Chen et al. (2000a) and Dejonckheere et al. (2004). We find that lead‐time variability exacerbates variance amplification in a supply chain, and that information sharing and information quality are highly significant. For example, using the assumptions in Chen et al. (2000a) and Dejonckheere et al. (2004), we find in a numerical experiment of a customer‐retailer‐wholesaler‐distributor‐factory supply chain that variance amplification is attenuated by nearly 50 percent at the factory due to information sharing. Other assumptions we make are based on interviews or conversations with managers at large supply chains.     

精益生产组成要素之间的关系研究

基于资源基础理论探讨精益生产组成要素之间的关系,并以华南地区118家制造企业为研究样本进行实证研究。研究结果表明:员工参与正向影响TQM/TPM,但对JIT的实施并没有直接的影响,需要通过TQM/TPM间接影响;TQM正向影响TPM的实施;TQM、TPM正向影响JIT,且TQM通过TPM间接影响JIT。研究结论对精益生产的相关理论和实践都有重要的价值和意义。     

Alternate Routing Strategies in Batch Manufacturing: An Evaluation

Batch manufacturing firms are experiencing significant changes because of technological developments in work center design, such as flexible manufacturing systems (FMS) and planning/control tools like computer-aided process planning (CAPP). These new developments provide production managers with some solutions to a number of complex problems. For example, numerical-controlled (NC) machine center installations are effective in providing quality parts because of tight tolerance specifications built into the equipment. However, these highly efficient centers create bottlenecks that constrain shop throughput, since production planners tend to rely too much on them. To help improve manufacturing planning, we introduce an important element to the batch production scheduling component of CAPP's mission—evaluating possible alternate routes. Production scheduling encompasses job route selection as well as machine center assignment (loading), job releasing, and setting due dates. In this paper, three routing strategies requiring different levels of shop floor information are tested and evaluated using computer simulation. Shop performance is measured by total cost and traditional measures of job flow time, lateness, and tardiness.     

The effect of the drum-buffer-rope (DBR) approach on the performance of a synchronous manufacturing system (SMS)

The main objective of any manufacturing system is to organize the resources in a shop floor for effective transformation of raw materials into finished products. Synchronous manufacturing (SM) is a manufacturing management philosophy that has a set of principles, procedures and techniques where every action is evaluated in terms of a common global goal of the organization (Seetharama et al., 1997, Production Planning and Inventory Control). A manufacturing system that adopts the above principle is called as synchronous manufacturing system (SMS). In order for a manufacturing plant to achieve the benefits of a synchronous operation, a logistical manufacturing (SM) is a manufacturing management philosophy that has a set of principles, procedures and techniques where every action is evaluated in terms of a common global control system that is manageable and results in predictable performance is required. The drum-buffer-rope (DBR) approach, which is a generalized system, satisfies the above requirements through computer simulation. This paper focuses on the effect of DBR principles on the performance of a synchronous manufacturing system. A case study has been taken up in a small-scale industry and analysis has been carried out on the effect of the DBR approach on the performance of the system. This work has been performed on an IBM/PC compatible system using the promodel software and C language.     

An information system for Just-In-Time

In recent years, U.S.'s worldwide industrial and economic leadership has been seriously challenged by many foreign countries. In order to counter the problem, many U.S. manufacturing companies have sought effective materials management systems such as MRP and the ‘Just-In-Time’ (JIT) system as used by many Japanese companies. Even through many practitioners and academicians have been studying the JIT concept and have recommended ways of adapting the concept to the U.S. manufacturing environment, not very many organizations are enjoying benefits of JIT system in full scale because of misunderstanding of information needs in JIT system. The objectives of this paper are (1) to identify information requirements of the materials management systems under JIT concept, (2) to compare them against the requirements under MRP system, and (3) to propose an integrated management information system to support materials management system in JIT environment. The goal of this paper is to facilitate more effective implementation of the JIT system, and stimulate further research on the subject matter.     

Implementation of just-in-time in a small company: A case study

This paper deals with the implementation of JIT in a small company in Taiwan that produces different kinds of automobile lamps such as rear combination lamps and front turn signal lamps. JIT systems have tremendous effects on all operations of a firm, including design, accounting, finance, marketing, distribution, etc., and thus are of interest to all levels of a firm's management. Realizing the success of JIT, large-scale manufacturing companies all over the world have implemented JIT in their production systems with the objective of improving their competitiveness. Nevertheless, small and medium enterprises SMEs play a major role in the national economy. However, JIT has not received serious attention from SMEs. Realising the importance of improving the performance of SMEs, a case study is presented to motivate practitioners to implement JIT in their SMEs. In addition, future research directions in the areas of implementing JIT in SMEs are presented.     

Impact of Information Technology Integration and Lean/Just‐In‐Time Practices on Lead‐Time Performance*

Managers seeking to improve lead‐time performance are challenged by how to balance resources and investments between process improvement achieved through lean/just‐in‐time (JIT) practices and information technology (IT) deployment. However, extant literature provides little guidance on this question. Motivated by both practical importance and lack of academic research, this article examines empirically the relationships among interfirm IT integration, intrafirm IT integration, lean/JIT practices, and lead‐time performance using data from IndustryWeek's Census of Manufacturers ( IndustryWeek, 2006 ). The results provide several new insights on the relationship between IT integration and lean/JIT practices. First, the study confirms that implementing lean/JIT practices significantly reduces lead time. Second, lean/JIT practices mediate the influence of IT integration on lead‐time performance. This suggests that process improvements that result from lean/JIT practices are important contributors to the success of IT integration. Even companies that have experienced success in reducing lead time through lean/JIT practices may benefit from IT integration practices such as those embodied in enterprise resource planning systems. The findings provide managers with empirical evidence and a theoretical framework on the balance between lean/JIT and IT for effecting improvement in lead‐time performance, thus offering practical guidance on this important question. Future research is needed to extend the lean/JIT practices in this study to supply chain practices and explore the relationship between supply chain practices and IT integration.     

Implementation of just-in-time methodology in a small company

This paper describes the implementation of JIT in a small manufacturing company and the benefits that resulted for the company's operations. Preliminary analysis identified various problems in the existing manufacturing operations. The pre-implementation and post-implementation conditions of the company arc detailed. The achievements of the JIT implementation included a reduction in material traversing, reduced lead limes and inventories leading to an overall reduction in the cost of manufacturing. A smooth flow of material from the raw material stage to the finished product stage was established. Three separate product lines were combined into a flexible manufacturing assembly line. With the adoption of a holistic approach to JIT implementation, it was found that even a small company can make significant strides towards world class manufacturing status. The experience gained by the company can encourage and benefit other small companies to embrace the JIT approach.     

A hybrid knowledge discovery model using decision tree and neural network for selecting dispatching rules of a semiconductor final testing factory

One of the most challenging production decisions in the semiconductor testing industry is to select the most appropriate dispatching rule which can be employed on the shop floor to achieve high manufacturing performance against a changing environment. Job dispatching in the semiconductor final testing industry is severely constrained by many resources conflicts and has to fulfil a changing performance required by customers and plant managers. In this study we have developed a hybrid knowledge discovery model, using a combination of a decision tree and a back-propagation neural network, to determine an appropriate dispatching rule using production data with noise information, and to predict its performance. We built an object-oriented simulation model to mimic shop floor activities of a semiconductor testing plant and collected system status and resultant performances of several typical dispatching rules, earliest-due-date (EDD) rule, first-come-first-served rule, and a practical dispatching heuristic taking set-up reduction into consideration. Performances such as work-in-process, set-up overhead, completion time, and tardiness are examined. Experiments have shown that the proposed decision tree found the most suitable dispatching rule given a specific performance measure and system status, and the back propagation neural network then predicted precisely the performance of the selected rule.