A model for labour pooling in batch manufacturing

Cross-training workers to perform multi-skilled jobs is one of the modern trends in job design. As companies engage in downsizing, the remaining workforce is expected to do more and different tasks. This paper presents a formal definition and a practical solution for optimizing the size and cost of the pool of multi-skilled workers for production units operated under batch manufacturing. The pool size is optimized through a search procedure applied separately to just-in-time (JIT) and level production plans, which are derived from the stones heuristic. The method allows direct calculation of the cost savings from labour pooling. This paper was inspired by consulting in the food industry, where implementation of these results has significantly reduced labour costs.     

A simple lot-scheduling model for just-in-time manufacturing

In this paper we consider a single capacitated facility dedicated to the manufacturing of a set of sub-assemblies in a just-in-time (JIT) environment. The items processed on this bottleneck facility flow to a downstream assembly facility, where they are assembled according to a specified mix. We develop a simple and efficient lot-scheduling heuristic that generates feasible and least-cost manufacturing schedules for the bottleneck facility. Our heuristic was shown, through an extensive empirical comparison, to have significant advantages over an earlier proposed heuristic in the JIT literature in terms of cost performance and computational efficiency. Moreover, the results of the comparison revealed that our heuristic is more consistent with JIT objectives since it tends to generate manufacturing schedules with shorter production cycle times and fewer assemblies.     

Stochastic analysis of TPS: expose and eliminate variability by highly specifying WCP

A production system is designed with three elements: works, connections and pathways (WCP), which cover how people work, how people connect and how the production line is constructed, from the point of view of a flow unit. The design principle of highly specifying WCP leads to two operations pillars that support the Toyota production system (TPS): just-in-time (JIT) and autonomation. Some stochastic models are proposed to verify the logic of highly specifying work for JIT. The stochastic models show that works are highly specified to reduce the variability whereas highly specifying connections and pathways without resource pooling expose variability in works as low inventory exposes the hidden problems in a factory. To achieve JIT, highly specifying works in each workstation is fundamental; the key solution is to reduce the variability of works. The information entropy theory is used to verify the logic of highly specifying WCP for autonomation. Highly specifying WCP can reduce the information needed by workers to identify and solve problems in the flow unit.     

汽车行业本地化分阶段准时供货的实例

日本丰田汽车公司首创了准时生产方式，要求供应商准时供货。1990以来，上海汽车制造行业的一批合资企业开始了对准时生产模式的尝试，并在准时供货方面取得了一定的经验。本文介绍了在我国现有的国情下，过渡期本地化的准时供货的实践，讨论了准时供货存在的问题及相应的解决对策。     

Determining the number of kanbans: a step toward non-stock-production

Just-in-time (JIT) production is a philosophy that calls for reducing work-in-process (WIP) inventory to aid process improvement and reduce process variability. In some cases, JIT production has been misinterpreted as a method that would lead to zero or minimal WIP with a lot size of one. There are no models or theories to achieve the JIT goal, i.e. non-stock-production (NSP), and, in particular, to help determine when and where to maintain this minimal inventory. A kanban system acts as the nerve of a JIT production system whose functions are to direct materials just-in-time to workstations in stages of manufacturing, and to pass information as to what and how much to produce. Indeed, the number of kanbans between two adjacent workstations decides the inventory level of that pair of workstations. With the objective of minimizing WIP inventory level, one model dealing with three cases of production configuration is developed for deciding the optimum number of kanbans. The model is then solved using a Markov process approach which considers the demand of finished products as the departure rate and the production rates of stations as arrival rate. In this paper, the model and solution procedure are illustrated with a numerical example.     

Just-in-time purchasing: an integrated inventory model involving deterministic variable lead time and quality improvement investment

Nowadays supply chain management is a popular practice in manufacturing systems, and just-in-time (JIT) production plays a crucial role in supply chain environments. Companies are using JIT production to gain and maintain a competitive advantage. The characteristics of JIT systems are consistent high quality, small lot sizes, frequent delivery, short lead time, and close supplier ties. This paper presents an integrated inventory model to minimize the sum of the ordering/setup cost, holding cost, quality improvement investment and crashing cost by simultaneously optimizing the order quantity, lead time, process quality and number of deliveries while the probability distribution of the lead time demand is normal. This integrated inventory model is useful particularly for JIT inventory systems where the vendor and the purchaser form a strategic alliance for profit sharing.     

Implementing just-in-time philosophy to reverse logistics systems: a review

Just-in-time (JIT) and reverse logistics are two important philosophies. Coincidentally, both are related to reducing the impact on the environment. However, they are sometimes in conflict with each other. The former focuses on moving the materials smoothly which require a stable demand and supply, but the latter is weak in terms of predicting how many returned products will be processed. Therefore, there is a need to investigate the impact of JIT to reverse logistics systems. After an extensive literature review based on a model developed for this purpose, different functions, namely reverse logistics structure, process model, product life cycle, information system model, and JIT performance, have been identified that have great impact on integrating JIT with reverse logistics. In short, a process model with JIT can have a better control on cost and efficiency of reverse logistics activities, and product life cycle management with JIT helps to design the product that consider the reverse activities in various process models. An information system can support both process model and product life cycle management for JIT reverse logistics. Details are presented in this paper.     

Using V-A-T analysis for determining the priority and location of JIT manufacturing techniques

V-A-T analysis is a procedure which categorizes manufacturing operations based upon the nature of product flow via the structure of the routeings and bill of materials. The letters V, A, and T stand for the shape of the dominant product routeings and bill of material structures within a manufacturing facility. The purpose of this article is to examine the possibility of using V-A-T analysis as an aid in JIT implementation. Contained in this paper is: an examination of the evolution of JIT manufacturing in Japan, and its introduction to the United States; an analysis of the various techniques constituting JIT; implementation issues regarding JIT; and an examination of V-A-T analysis as a tool for JIT implementation.     

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.     

Logistics support for JIT implementation

It is generally believed that to maximize the full potential of ‘just-in-time’ (JIT), it must be fully integrated, system-wide. To achieve such integration, a common understanding of and appreciation for JIT is needed within various functional areas. Therefore, manufacturers and logistics executives were surveyed to determine their attitudes and understanding about JIT. The primary objective was to identify how different or similar their opinions were regarding JIT adoption and implementation. The manufacturer respondents indicated a much broader view of JIT as a management philosophy whose goal is to eliminate waste throughout an organization. In contrast, the logistics respondents were more likely to view JIT as largely an inventory reduction policy. In general, there appears to be an opportunity for logistics managers to more fully utilize aspects of JIT to achieve overall performance improvements.     

An integrated optimal inventory lot-sizing and vehicle-routing model for a multisupplier single-assembler system with JIT delivery

In a manufacturing system, a just-in-time (JIT) procurement and supply system is important for reducing cost and responding to customer’s requirement quickly. Successful implementation of a JIT system needs supplier/manufacturer cooperation in small lot-size delivery and inbound logistics cost reduction. In this study, an integrated optimal model of inventory lot-sizing vehicle routing of multisupplier single-manufacturer with milk-run JIT delivery is established. A novel method for computing transportation cost is proposed. Because the integrated model is a NP-hard problem, a meta-heuristic algorithm of ant colony optimisation is developed for solving the model. Numerical examples are used to demonstrate and test the effectiveness of the model and the algorithm. The results show that integrated model with milk-run delivery can reduce the total cost and realise the JIT production and procurement philosophy which emphasises small lot-size production and delivery. The results highlight the importance of cooperation between suppliers and manufacturers in JIT production practices.     

Modelling of an automated guided vehicle system (AG VS) in a just-in-time (JIT) environment

Like other production systems, just-in-time (JIT) systems need to address the issue of material transport between workstations such as those served by automated guided vehicles (AGVs). Unlike other production systems, however, the JIT philosophy imposes strict requirements on inventory levels and supply-demand protocols which render conventional AGV delivery strategies ineffective and counter-productive. This paper describes the modelling of an AGV system (AGVS) in a JIT environment in a way that is consistent with JIT principles. The influence of a ‘JIT perspective’ is emphasized throughout the model by introducing threshold values for both input and output queues, performance measures that emphasize lower inventories in addition to transport efficiency, and a new dispatching rule that implements better inventory and transport control. The dispatching rule is shown to perform better in a JIT environment than previously developed AGV dispatching rules in both transport and logistic criteria.     

用正交试验设计法实现JIT系统的仿真优化

为降低企业推行JIT(Just-In-Time)的风险和成本,探讨了影响JIT系统性能的相关因素,运用中间变量建立了JIT系统的仿真模型;采用正交试验设计法选择仿真的优化因子,不仅考虑了因子对系统性能的影响,同时考虑了其经济性;结合企业实例,对JIT系统不同阶段优化方向的选择问题进行了进一步的探讨。     

Modular simulation tool for modelling JIT manufacturing

Since quantitative information is very helpful in implementing JIT production techniques, computer simulation can be a valuable tool in designing, implementing or changing JIT practices in a production system. Nowadays, existing simulation software incorporates modular programming and enhanced graphic systems for output representation. It enables users to generate modules that represent partial aspects of a JIT system. These modules, adequately modified and integrated, give researchers and practitioners the possibility to create complex models that can be applied to a variety of JIT systems or JIT production environments. A modular simulation tool, based on the modular capabilities of Witness, is introduced in this paper. As a module example, the feeder double-kanban line module is presented, which represents one of the core aspects of a JIT manufacturing system. Finally, module integration is illustrated by modelling a U-Shaped line. The experimentation and evaluation of the U-line allow one to appreciate how modular simulation can be a powerful tool in decision making, by enabling users to analyse systems configurations and operation rules before implementing them.     

准时生产的实施研究

从准时生产（JTT）的内涵入手，全面介绍了广州日立电梯有限公司推进JTT生产的组织，实施JTT生产所采取的具体方法、措施及其成效。结合实际，提出在制造领域实施JTT的途径及其推广价值。     

一个新的基于数量折扣的JIT采购模型

把传统采购中的数量折扣同JIT采购结合起来，建立了一个基于数量折扣的综合模型，充分发挥了两种采购方法的优势。分别研究了全单位数量折扣和累进制数量折扣两种情况下的JIT采购，给出了模型的算法和算例。算例显示，采购成本的节省明显。     

Decision model for the application of just-in-sequence

An increasing number of module variants pose a challenge for just-in-time (JIT) production systems. As a consequence of managing rising variety-driven complexity costs, sophisticated logistics concepts such as just-in-sequence (JIS) have grown in importance over the last years. Switching to JIS sourcing of modules with many variants is often indispensable in order to enable the cost-efficient production of customised products, foremost in the automotive industry. The main goal of this research is to provide a framework to determine under which circumstances switching from JIT to JIS is most advantageous. For this purpose a module selection framework as well as a logistics costs function model of the production system is developed. Often only considered as a refinement of JIT, we strive to establish JIS as a logistics concept of equal weight.     

Designing performance measurement systems for just-in-time operations

Results of a study conducted to understand how performance is evaluated in just-in-time (JIT) operations are reported in this paper. The purpose of the study was to develop a series of propositions concerning the performance criteria, standards, measurement techniques, and reporting methods that are appropriate in JIT environments. Ten propositions are provided.