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.     

基于JIT的无B/C类成品库存方法研究

针对实施JIT的现有库存控制方法进行了探讨,认为完全地追求“零库存”不适合我国制造业现状,并从供应链管理的角度引入提出了与JIT相匹配的无B／C类成品库存供应链管理策略方法,指出了应用时的实施要点。     

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.     

Transition to a JIT production system through ERP implementation: a case from the automotive industry

ERP systems provide important benefits to institutions, such as improved processes, improved data, supplier–customer integration, better planning and control, as well as real-time insight and just-in-time (JIT) management that can put a business organisation in front of the competition. In this study, the change and transformation experienced by establishing an ERP system are explained for an automotive supplier that was not using an integrated ERP system for a real-world problem. The pre-implementation situation, the problems of the existing system, the necessary reasons for such an application, the determined deficiencies of the installed system and the post-implementation situation are explained in detail. Thanks to the real-time information and integrated data generated by the reports, along with a more sophisticated business understanding, the risk to employees was lowered. As a result of a changeover to real-time Materials Requirement Planning, the decrease in inventory levels, stabilisation in delivery time and efficiency of control over the production processes were increased in addition to real-time tracking and reporting advantages. As a result of this work, the production processes were transformed into JIT. The inventory level was reduced to zero and a formerly used warehouse was no longer required.     

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.     

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。     

An analysis of manufacturers’ supply and demand uncertainty based on the dynamic customisation degree

Diverse demands regarding products are common; however, manufacturers usually cannot respond immediately to meet such changes upon demand, and thus, customer satisfaction tends to be reduced. Notebook computer manufacturers adopt a production mode of mass customisation; hence, a certain degree of dynamic customisation measurements, inherent in different supply chain models, allow manufacturers to evaluate costs and profits in advance. The application of the model, as proposed in this study, indicates that the most important factor of the customisation degree is product price. The dynamic customisation degree is adjusted based on monitoring indicators, which requires less total cost and produces greater accuracy in forecast results regarding the prediction model of customer demands. This study develops a dynamic customisation model for total product profits, inventory cost of semi-manufactured products, shortage costs and buffer inventory costs, which are affected by the degree of dynamic customisation of the products. It also analyses the supply and demand uncertainties of the Direct Shipment of the Manufactured Model, as well as the Door-to-Door Direct Shipment of the End User Model in the notebook computer industry, as the criteria with respect to a firm's customisation degree, costs, and profits in different supply chain mode operations.     

A study of an integrated inventory with controllable lead time

The Japanese experience of Just-in-Time (JIT) production has shown that there are advantages and benefits associated with the efforts to reduce inventory lead time and the associated inventory cost. The length of lead time directly affects the customer service level, inventory investment in safety stock, and the competitive abilities of a business. In most of the literature dealing with inventory problems, either a deterministic model or probabilistic model, lead time is viewed as a prescribed constant or a stochastic variable, and is not subject to control. However, in many practical situations, lead time can be reduced by an additional cost. Moreover, the successful implementation of JIT production in today's supply chain enviromnent requires a new spirit of cooperation between the buyer and the vendor (Goyal and Srinivasan 1992). A desirable condition in long time purchase agreements in such a manufacturing environment is the frequent delivry of small quantities of items so as to minimize inventory holding cost for the buyer. The vendor also needs to minimize his or her total inventory costs. An integrated inventory model that allows the two trading parties to form a strategic alliance for profit sharing may prove helpful in breaking down the traditional barriers. This paper presents an integrated inventory model with controllable lead time. The model is shown to provide a lower total cost and shorter lead time compared with those of Banerjee (1986) and Goyal (1988), and is useful for practical inventory problems.     

Original equipment manufacturers (OEM) manufacturing strategy for network innovation agility: the case of Taiwanese manufacturing networks

Manufacturing companies in newly industrialized countries contribute substantially to their global innovation networks. Those manufacturers perform not only production and physical distribution functions, but also design and engineering functions in the processes of bringing new products world-wide. This paper examines the relationship between manufacturing strategy of those original equipment manufacturers (OEM) suppliers and network innovation agility. No single best strategy can fit all OEM suppliers. They can choose either to be dedicated OEM service providers or to sell their own-brand products. Either strategy can be effective in terms of innovation agility. However, once the OEM manufacturing strategy has been chosen, a manufacturer should adopt an appropriate way to manage its product innovation process. A dedicated OEM supplier should emphasize manufacturing flexibility and pursue a product modularity strategy to enhance network innovation agility, while cross-functional integration is the key for successful manufacturers with own-brand products. For both dedicated OEM suppliers and own-brand ones, market orientation is essential for network innovation agility. Managerial implications and future research directions are discussed.     

Switchgear component commonality design based on trade-off analysis among inventory level,delivery lead-time and product performance

The shortening of product delivery lead-times can usually be achieved by keeping high-level components in inventory, however in small-volume production systems, maintaining such inventories is often a costly as well as a risky business strategy. If the risk of maintaining unsold inventory can be decreased, even small-volume manufacturers may be able to justify holding more significant quantities of versatile inventory. This paper discusses a component commonality effect to breakthrough the trade-off relationship between inventory levels and delivery lead-times for such small-volume production systems. By using the same component in different products, inventory maintenance costs can be dramatically reduced, but component commonality design problems are inherently complex, since excessive module commonality may lead to lower product performances, and there are trade-off relationships between product performance and cost reductions obtained through component commonality. In this paper, such a design problem is formulated as a multiobjective component commonality design optimisation problem considering inventory level, delivery lead-time and product performance, and the optimal solutions are obtained as a Pareto optimal solution set. Detailed procedures concerning the proposed design method, including inventory simulation, are discussed and developed for a switchgear design problem. Finally, an example switchgear design problem is solved to illustrate that optimal use of component commonalities across different modules can significantly reduce inventory costs, while also shortening product delivery lead-times.     

Effect of organizational variables in JIT purchasing implementation

The paper reports empirical evidence of diverse organizational factors determining the implementation of Just-in-Time (JIT) purchasing practices. A theoretical framework distinguishing basically between operational practices, inherent in JIT environments, and complementary practices, characteristic of partnership sourcing arrangements, is proposed and used to test the relevance of a number of variables related to the interacting organizations over a sample of 152 Spanish auto components manufacturers. This approach, whose internal consistency is supported by the data analysis, reveals distinctive effects of the variables on each group of practices and helps towards the understanding of the dynamics of JIT purchasing. It also points out that the implementation of this purchasing strategy is associated to specific organizational features and requires certain attributes from suppliers.     

A continuous-review model for dual intercontinental and domestic outsourcing

When making sourcing decisions, many firms consider only the direct and most visible supply-chain costs, such as unit production costs and ocean-shipping costs. Often ignored are the hidden direct and indirect costs in long supply chains, and their impact on profitability. As supply chains lengthen, supply-chain disruptions undercut the ability of manufacturers and retailers to satisfy market demands. Supply-chain disruptions add costs by forcing companies to increase inventories, to juggle production and shipping schedules, to incur excessive backordering, and to airfreight or discount the prices of goods that were not in the right place at the right time. The question is, can higher incidence of supply-chain disruptions in intercontinental supply chains justify keeping the domestic suppliers? To address the question, this paper presents a hybrid continuous-review inventory model for dual intercontinental and domestic outsourcing. The conditions for domestic outsourcing only, for intercontinental outsourcing, and for dual outsourcing were established. The problem of minimising the long-run average cost of outsourcing was investigated, and mathematical optimisation was used to illustrate the model. It is shown that if the cost of service failure outweighs the cost differential between domestic and intercontinental outsourcing, keeping domestic suppliers may be a good option.     

Capacitated production planning with outsourcing in an OKP company

This paper addresses a dynamic capacitated production planning (CPP) problem in small to medium-sized enterprises (SMEs). These companies practise their businesses based on a manufacturing paradigm called one-of-a-kind production (OKP). Typically, they employ outsourcing in their CPP practice. Therefore, the CPP problem in this paper includes outsourcing, which is called the outsourcing CPP problem. The outsourcing strategy considered in this paper has the following features: (1) outsourcing takes place when the demand exceeds the capacity; (2) all excessive demands are outsourced without backlogging; and (3) production, inventory, and outsourcing levels all have a limit. One important difference of the problem considered in this paper from other problems is that the cost functions are considered arbitrarily time-varying. The outsourcing CPP problem is formulated into an optimization problem which captures the mentioned features. The objective of the problem is to minimize the total cost. It is very likely that there is no solution in our model so we propose a necessary and sufficient condition for feasible solutions. Dynamic programming techniques are employed in searching for a global optimal solution with a pseudo-polynomial time. This paper also presents a case study for a real-life problem in an OKP company to illustrate our approach and to show its effectiveness. The case study has shown that our approach is very effective.     

Allocation of manufacturers through internet-based collaboration for distributed process planning

The pursuit of lower cost, shorter time-to-market, and better quality has led to a shift toward global production in today's competitive business environment. This shift however, forces manufacturing enterprises to have separate design houses and manufacturing facilities. In general, design houses are located in the same regions as customers to enable them to respond to the rapidly changing demands of customers. By contrast, manufacturing facilities can be placed in regions in which production costs are lower. However, this physical and logical separation between designers and manufacturers (or between upstream manufacturers and downstream manufacturers) raises various integration issues. The present paper addresses two of these issues: the framework for representing the data necessary to communicate requirements and objectives of the designer, and the methodology for utilizing such data to optimize the business objectives related to production cost and quality. The proposed representation, collaboration framework, and methodology will enable design houses and manufacturing facilities to realize the benefits of global production and to accommodate the management of loosely integrated supply chains.     

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.     

基于系统动力学的乳制品冷链库存与终端收益仿真

为了有效控制乳制品冷链的库存温度和运作效率,依据系统动力学原理,引入了第三方物流,建立了由生产商、供应商和零售商组成的乳制品冷链系统动力学模型,并使用Vensim软件进行仿真分析。模拟了系统在阶跃需求、随机需求等不同需求模式下的表现,以及在不同温度与运作效率下的库存水平与终端销售状况。结果表明：在同样的需求模式下,当温度控制在0℃时的终端收益高于温度保持在-4℃时的终端收益;同时提高冷链的运作效率即缩短订货提前期和到货延迟,有助于减少质量损失成本,增加零售商利润,这对构建良好消费环境和减少食品安全问题提供了理论参考。     

Ex-post inventory control

Classical inventory control, using an ex-ante optimization approach and tending to recommend large stockholdings, has been criticized over recent decades. As a result, just in time (JIT) based inventory systems, which exhibit sensitivity to customer requests (rather than production plans based on demand forecasts) are increasingly recommended. In such inventory control schemes, orders are made once the demand is revealed. As a result, ex-ante classical and ex-post JIT inventory schemes can be compared and analysed through: (a) the valuation and the management of demand uncertainty and (b) the time phasing of information and its relationship to the (inventory) control policy. The purpose of this paper is to elaborate and compare such approaches and devise an approach to inventory control based on regret decision making. Examples are used to show how we may be able to value flexibility explicitly in supplies and construct robust inventory policies which can respond to predictable and unpredictable demands (such as using options in inventory control and increased reactivity through JIT controls).     

基于双渠道联合库存策略的生鲜品产销

生鲜厂商采用“线上”“线下”两种销售渠道时,采用联合库存策略可以有效降低库存节约成本。考虑影响各渠道需求的各种因素和消费者的选择行为,建立了基于生鲜产品双渠道联合库存策略下的多周期产销最大收益模型。已知线下渠道销售价格,假设库存优先满足线下渠道销售,从生鲜厂商的角度给出了最优线上销售价格和最优生产量。算例表明,该策略下保质期短的生鲜农产品线上定价较高,选择线下自提取货的消费者比例越高则收益越大,需求不确定性增大则会使得利益受损,为生鲜产商通过双渠道销售生鲜农产品提供理论支持。     

基于供应链的企业库存成因及优化控制的研究（一）

基于企业全面库存的管理思想,对库存成本、库存控制、库存系统优化等管理经验与前人研究成果进行分析,借鉴先进企业的库存管理理念和方法,以大型制造企业为核心研究对象,在集供应商、制造商、经销商为一体的供应链作为研究框架的基础上,运用供应链系统理论作为研究方法,分析了库存管理现状、影响因素及产生原因,从优化生产管理、整合企业内部供应链和跨企业供应链的角度提出了库存控制的相应对策,以实现全面的库存优化,提高经营效益。     

基于供应链的企业库存成因及优化控制研究（二）

基于企业全面库存的管理思想,对库存成本、库存控制、库存系统优化等管理经验与前人研究成果进行分析,借鉴先进企业的库存管理理念和方法,以大型制造企业为核心研究对象,在集供应商、制造商、经销商为一体的供应链作为研究框架的基础上,运用供应链系统理论作为研究方法,分析了库存管理现状、影响因素及产生原因,从优化生产管理、整合企业内部供应链和跨企业供应链的角度提出了库存控制的相应对策,以实现全面库存优化,提高经营效益.