Comparing JIT,MRP and TOC,and embedding TOC into MRP

The traditional material requirements planning (MRP) system for planning and controlling production systems is being replaced more and more by just-in-time (JIT) and the theory of constraints (TOC). Because JIT and TOC share many elements with MRP and because MRP is very flexible, it is not difficult to make MRP behave like JIT or TOC. Consequently manufacturers with MRP systems need not dismantle them to implement JIT or TOC. A five-step technical procedure for embedding TOC into MRP is presented in this paper along with an illustrative example from a microelectronics plant. Next a simple production line is analysed using a Markov chain model to examine the types of improvements each approach makes and the effect of these improvements on the performance of the line. Performance measures are the mean and variance of the output, shortage, inventory level, and cycle time of the production line. Insights are developed into the reasons for the superior performance of JIT and TOC.     

MRPⅡ、JIT和TOC集成的实证研究

ＭＲＰⅡ、ＪＩＴ和ＴＯＣ是目前被广泛应用的生产和运作管理系统,在许多企业中被证明为提高生产经营水平的有效工具,但如果能把它们集成为一个有机的整体,充分发挥三者的优势,将能更大地提高企业效益。为此提出了将ＭＲＰⅡ、ＪＩＴ和ＴＯＣ三者进行集成的思路;以计划为主线;运用ＴＯＣ理论来发现制约因素,提出改进方向;以ＭＲＰⅡ为主进行生产计划的制定,重点是对制约环节进行计划和控制;以ＪＩＴ为主进行现场管理和改善     

A CBFSA approach to resolve the distributed manufacturing process planning problem in a supply chain environment

In this competitive world cost and lead time reduction are of prime concern for manufacturing firms. To achieve this objective manufacturing entities are adopting several management philosophies such as Total Quality Management (TQM), just-in-time (JIT), and theory of constraints (TOC). The present paper addresses the advanced computer-aided process planning (ACAPP) problem in a distributed manufacturing supply chain environment and aims at cost and lead times reduction under several technological constraints. To deal with the complexity of the problem the constraint based fast simulated annealing (CBFSA) algorithm has been explored in this article. Extensive computations have been performed over the well-known benchmarks of advanced planning problems and the results obtained prove the superiority of the proposed algorithm over the prior approaches.     

推拉结合的生产计划与控制方法的应用研究

为解决制造企业生产系统面临的多品种、小批量的计划与控制问题，参考当前流行的生产管理理论，提出了一种推拉结合的生产计划与控制方法．该方法将MRP、JIT和TOC理论在不同计划和控制层面上进行综合应用，辅助车间快速有效地实现生产作业控制．该方法在制造执行系统（MES）平台的具体实现及在某制造型企业的应用验证了其可行性和有效性．     

The role of MRP in repetitive manufacturing

This paper discusses the findings of a study of production planning and control systems in nine repetitive manufacturers in the southeast United States. The purpose of the study was to identify the methods used by repetitive manufacturers to plan and control production. The companies in the study were selected so that three companies were noted for their use of MRP, three others were noted for their use of JIT, and three others were noted for their use of theory of constraints (TOC) (formerly OPT). The principle finding from the study was that all nine companies used a blend of production planning techniques using MRP as a framework to accomplish production planning. This finding was especially surprising when the companies had been specifically selected upon the recommendation of a panel of experts because some companies were known to be superior in the application of JIT and TOC methods     

A review and comparison of hybrid and pull-type production control strategies

In order to overcome the disadvantages of Kanban Control Strategy (KCS) in non-repetitive manufacturing environments, two research approaches have been followed in the literature in past two decades. The first approach has been concerned with developing new, or combining existing, pull-type production control strategies in order to maximise the benefits of pull control while increasing the ability of a production system to satisfy demand. The second approach has focused on how best to combine Just-In-Time (JIT) and Material-Requirements-Planning (MRP) philosophies in order to maximise the benefits of pull control in non-repetitive manufacturing environments. This paper provides a review of the research activities in these two approaches, presents a comparison between a Production Control Strategy (PCS) from each approach, and presents a comparison of the performance of several pull-type production control strategies in addressing the Service Level vs. WIP trade-off in an environment with low variability and a light-to-medium demand load. Correspondence to: John Geraghty     

MRP,JIT和MRP／JIT混合式生产管理方法及其适用性研究

从ＭＲＰ,ＪＩＴ和ＭＲＰ／ＪＩＴ混合式生产管理方法的特点分析入手,在实际生产和需求环境中抽取７种主要因素,讨论它们对实施各种生产管理方法的影响,为制造企业正确选择生产管理模式提供一种实用的方法。     

A contingency perspective of just-in-time purchasing: globalization,implementation, and performance

This paper uses a survey-based methodology to examine the performance impact of Just-In-Time (JIT) purchasing strategies. Over the past decade much has been written concerning JIT philosophies; however, relatively little empirical research has been conducted that evaluates the impact of JTT on performance. Similarly, little work has been performed to evaluate the role of JIT in global competitive strategies. This paper uses contingency theory's environment-strategy-performance relationship to consider vital issues—planning, organizational support, and implementation status—affecting the success of JIT purchasing strategies. The findings suggest that JIT purchasing strategies represent an appropriate response to global competition and that JIT purchasing can have a significant positive impact on performance improvement when adequate planning and support are in place.     

Hybrid make-to-stock and make-to-order systems: a taxonomic review

Production planning and control (PPC) systems that employ aspects from both make-to-order (MTO) and make-to-stock (MTS) production control are known as hybrid MTS/MTO systems. While both MTO and MTS separately have been studied extensively, their combined use has received less attention. However, the literature on this topic is growing and this paper shows that the review performed in this paper is an important addition to the field. We categorise relevant literature according to a novel taxonomy and show that hybrid MTS/MTO production control can be used in different contexts. In addition, an overview of the modelling techniques and methods used in these papers is provided. Based on the reviewed literature, relevant research questions and directions for future research are identified. Finally, it is shown that hybrid MTS/MTO production control is prevalent in practice by discussing research with industrial applications. The paper contains an overview of research on hybrid MTS/MTO production control to be used as reference for researchers active in the field, and provides managerial insights and directions for future research on this topic.     

Managing system constraints: a cost/utilization approach

Modern management philosophies, such as just in time (JIT), the theory of constraints (TOC) and total quality management (TQM), place a strong emphasis on operations management. These approaches create techniques and procedures for effective flow of materials, but do not provide sufficient tools to consider the economic outcomes of the various alternatives. This paper applies the cost/utilization model to the analysis of production lines and materials flow. The model combines the Pareto approach with the TOC approach. The Pareto approach concentrates on the important and costly elements of the organization. TOC focuses on the organization's constraints. It is presented in a simple graphic display aimed to allow managers to locate better constraint resources, detect faults in the planning of the production line, examine improper fluctuations in the process and pinpoint their sources. The model is a top-management decision-support tool that may be applied in areas such as buffer policy, assessment of protective capacity, investment in production resources and identification and priorization of areas for improvement.     

Optimal design of a hybrid push/pull serial manufacturing system with multiple part types

The objective of this research is to investigate the possibility of integrating Manufacturing Resource Planning (MRP)/push and Just in Time (JIT)/pull strategies in a multiproduct multistage serial manufacturing system. Each workstation is able to undertake different operations and so to produce more than one type of in-process item. A modified version of a horizontally integrated hybrid push/pull production system is developed. The system can be optimized by locating points of integration, and determining the optimal values of safety stocks for the push part and numbers of Kanbans for the pull part. A modification of genetic algorithm (GA) chromosomes and crossover procedures is developed for the optimization. The optimization involves evaluations of stochastic performance measures by a discrete event simulation model. The motivating case study of a tube shop in an aerospace manufacturer is presented. This research extensively explores the question of whether each part type should have its own junction point (less constrained) or whether there should be one common junction point for the overall system (easier to implement).     

Integration of production planning,project management and logistics systems for supply chain management

The objective of this research was to develop an integrated framework to handle application modules in enterprise resource planning (ERP) and supply chain management (SCM) systems that traditionally needs to be interfaced on a case-by-case basis. This paper presents a framework integrating various modules in both systems, for planning, control and execution of materials, resources and operations. The framework enables planning and execution over a range of areas, from flow to project-based manufacturing and distribution from suppliers to customers. This document presents the conceptual framework development along with algorithms for scheduling paths, and illustrated numerical examples in the supply chain environment. The numerical evaluation of scheduling paths and planning of components, in the integrated networks, shows that the developed framework could cater for ERP/SCM application modules. The framework also facilitates simultaneous planning of many components, and eliminates the need for separate modules in ERPSCM systems. It enhances planning, control and execution, and simplifies the vendor follow-up system by integrating supplier components into the integrated network. The framework therefore becomes a new production planning (PP) module in integrated ERP/SCM systems and can provide links to other manufacturing philosophies, such as just-in-time (JIT).     

多产品串并联连续生产系统主生产计划方法

某些生产过程包含了若干连续生产的流水线,其中一些是并行的,而有一些于另外一些是串行的.因此,构成了一个串并联生产系统.在多产品生产的情况下,其主生产计划问题变得非常复杂.针对这种情况,提出了将MRP与JIT相结合的解决方案.根据该方案思想建立了主生产计划模型,并采用遗传算法求解.仿真结果表明,该方案效果良好.     

MRP和JIT两种生产管理系统的比较研究

长期以来，人们对ＭＲＰ和ＪＩＴ两种生产管理系统孰优孰劣一直争论不休。一方面，源于日本丰田公司看板系统的ＪＩＴ生产管理系统，随着日本经济的成功，使得许多人相信它在减少库存和在制品、缩短生产准备时间和生产提前期方面从根本上优于ＭＲＰ管理系统；另一方面，许多应用ＪＩＴ生产管理系统的企业并没有取得预期的经济效益，甚至生产效益没有任何改善。本文的目的，是通过建立两种生产管理系统的模型，进行计算机仿真研究，定     

A comparison of JIT and TOC buffering philosophies on system performance with unplanned machine downtime

The impact of buffering under just in time (JIT) and theory of constraints (TOC) is studied to determine whether a difference in performance exists in systems faced with unplanned machine downtime. Comparisons are based on results obtained from simulation of a five-station cell utilised in computer substrate manufacturing. Analysis of the simulation output suggests that the TOC technique, drum–buffer–rope (DBR), achieves higher levels of performance as measured by total output and lead time while reducing inventory requirements relative to the tested JIT technique, Kanban. Improved system performance stems from the strategic placement of buffers in DBR, which maximises protection of the constraint from variation rather than attempting to protect each individual station. Further, analysis suggests that DBR systems are more robust than JIT systems in that they are able to maintain higher levels of system performance across a range of inventory levels.     

Comparing dynamic risk-based scheduling methods with MRP via simulation

It is well known that material requirements planning (MRP) is a deterministic planning tool which heavily relies on accurate demand forecast, and that its performance under perturbed, constantly changing environment becomes questionable. Although many companies still use basic MRP as a planning tool, there are other alternative tools available. For example, Factory Physics Inc. has developed a tool called dynamic risk-based scheduling (DRS), which creates a set of policy parameters (e.g. work in process (WIP) level, lot sizes, re-order point, and re-order quantity) that work for a range of situations. The main objective of this paper is to compare DRS and MRP scheduling systems for single-machine and multi-machine systems via simulation. Their performance measures are compared for various systems assuming three levels of demand uncertainty. The simulation results suggest that DRS outperforms MRP in terms of robustness, fill rate and inventory level.     

A socio-technical perspective on e-government issues in developing countries: a scientometrics approach

Many researchers have analyzed e-government literature as a whole or a specific area to focus on statistical methodologies, lessons learnt, or problem related to the area. However, no investigation from socio-technical perspective on e-government issues, in developing countries (DCs), has been carried out. Utilizing scientometrics approach, we analyzed and synthesized e-government (EG) literature that deals with the issues/topics in developing countries from the lens of socio-technical theory (STT). 145 articles from 7 core e-government journals published during the last decade were selected and reviewed for analyzing e-government literature related to developing countries. The growth pattern of e-government literature showed that e-government studies pertaining developing countries issues/topics have rapidly increased during the last decade; covering a range of topics/issues studied from socio-technical aspects. We found that e-government literature in developing countries has somewhat adopted a balanced approach and is moving away from a merely theoretical or conceptual bases toward an empirical foundation; however, the literature lacked depth and balance in terms of issues/topics discussed and methodologies applied. In the light of the findings, strengths, limitations, and future directions for e-government research in developing countries are discussed.     

Choices in manufacturing strategy decision areas in batch production system – six case studies

The configuration of a production system can be described by the choices a firm makes in its manufacturing decision areas. Manufacturing strategy literature lacks empirical research in manufacturing decision areas. The current paper is an exploratory study using six case companies on alternative configurations that can exist in a batch production system. Choices made in decisions such as layout, shop floor control, etc., were found to be similar for all six companies that use batch process. However, there were a number of decisions that were found to be non-process specific and are influenced by product complexity, important competitive priorities, strategic orientation of manufacturing, top management decisions and the size of the company. The paper concludes with managerial implications and future research directions.     

MRP lot sizing with variable production/purchasing costs: formulation and solution

The research on lot sizing is extensive; however, no author in the literature reviewed to date provides an optimal solution algorithm to a prevalent problem which is found in manufacturing. A multi-level, general product-structure, variable-cost model is presented which follows the procedure of a closed-loop material requirements planning (MRP) system, and incorporates many conditions that production and material managers find in practice. A branch and bound (B&B7) algorithm is developed. The efficiency of B&B is derived from effective lower bounds and solution procedures which are determined on the basis of the space-time structure of the MRP lot-sizing problem and its non-convex total-cost function. This path-dependent lower bound is computationally efficient and guarantees an optimal solution. The B&B algorithm is tested on problems and compared to heuristics in the literature.     

A REVIEW OF PRODUCTION PLANNING AND SCHEDULING MODELS IN THE SEMICONDUCTOR INDUSTRY PART II: SHOP-FLOOR CONTROL

In the first part of this review [62] we described the characteristics of semiconductor manufacturing environments and reviewed research on system performance evaluation and production planning. In this paper we focus on shop-floor control problems. We classify research to date by the solution techniques used, and discuss the relative advantages and disadvantages of the various approaches. We discuss the relationship between shop-floor control and production planning and suggest future research directions.