Design of the optimal feeding policy in an assembly system

This paper describes an innovative and integrated approach to component management optimization within a production/assembly system. In a mixed-models assembly process the handling of parts and components for each work station represents a substantial variable that can greatly affect job duration and efficiency. This paper is strictly related to Assembly to Order/Manufacturing to Order (ATO and MTO) systems, where lead time has to be very short and flexibility is at its maximum level. In Assembly to Order (ATO) or Make to Order (MTO) systems, the production is increasingly getting more customized in response to the demand, thanks to the progresses reached in both manufacturing and information technologies. It is becoming increasingly possible to assemble or make products specifically in response to the requests of either end customers or retailers. As a consequence of such customization, the design of the whole system must take into direct account several elements: parts warehouses location, feeding policies and feeding systems. In some cases the collection of parts and components required picking activities, in other the movement of entire units load.In several instances experts have analyzed the problems about material centralization/decentralization, storage policies and assembly feeding problem in different and independent ways, while the problem needs an integrated approach. While many researches regarding components allocation problems in ATO and MTO systems, did not consider feeding policies, material picking, packing activities and vehicles optimization, this paper cover focuses on filling such gap using an integrated framework that considers both aspects of the problem: the centralization/decentralization of components in order to minimize the total storage costs and the right feeding policies.Feeding problems in assembly lines are some of the most important aspects to consider during the analysis and design of an assembly system, to allow the maximization of efficiency and flexibility. To reach such goals, a multi-factorial analysis has been carried out during this experiment and will validate the introduced framework. An industrial application of the introduced framework is illustrated to explain its real significant production implication.     

Scheduling a multi-stage fabrication shop for efficient subsequent assembly operations

Consideration is given to scheduling the operation of a multi-stage fabrication shop producing the component parts of a major commercial refrigerators producer. The objective of this scheduling problem is the determination of both production sequences and lot quantities at each stage so as to meet production targets and ensure continuous operation of subsequent assembly stations. After describing the problem within its natural context, we present an algorithm for the dynamic scheduling of the fabrication shop. This applies general planning principles adapted to the needs of the environment under consideration and makes use of existing heuristic rules for arriving at sequencing decisions. Although in no sense optimal, the algorithm can provide good feasible solutions to a previously not formally analysed problem. After being incorporated into a systematic computer-aided scheduling procedure, the algorithm has been actually implemented, demonstrating considerable improvements over previous fabrication shop scheduling practice.     

Supply chain scheduling and coordination with dual delivery modes and inventory storage cost

We study a two-echelon supply chain scheduling problem in which a manufacturer acquires supplies from an upstream supplier and processes orders from the downstream retailers. The supply chain sells a single short-life product in a single season. We consider the scenario where the manufacturer can only accept some of the orders from the retailers due to its supplier's common production time window and its own two common production and delivery time windows. The upstream supplier processes materials and delivers the semi-finished products to the manufacturer within its time window. Then the manufacturer further processes these products to produce finished products and delivers them to the retailers within its two time windows, where one window is for production and normal delivery, and the other is for production and express delivery. Having to store the materials before processing them, the supplier incurs a storage cost, which depends on the order size and storage time. The manufacturer pays the transportation cost for delivering the finished products to the retailers. Due to double marginalization, the performance of the supply chain is sub-optimal. We model the supply chain problem as a flow shop scheduling problem with multiple common time windows. We derive some dominance properties and establish some theorems that help solve the sequencing problems for the orders and eliminate the idle time among the orders. Based on these results, we develop fast pseudo-polynomial dynamic algorithms to optimally solve the problem. We prove that the problem is NP-hard in the ordinary sense only. We develop two practically relevant and robust methods for the supply chain to achieve optimal profit-making performance through channel coordination.     

Improving global spare parts distribution chain performance through part categorization: A case study

Spare parts inventory management is a complex problem and in most cases part categorization is needed to create a manageable number of control groups to focus management efforts more effectively. Usually multi-dimensional or multi-criteria classifications are used, and there are several examples of classification schemes available in the literature. The complexity increases even more when taking into consideration that a distribution chain consists of many parties. Thus, in addition to internal inventory control factors, external factors such as supplier performance, customer behavior and related demand patterns affect the controllability of the various parts.In the paper we try to expand existing classification schemes that cover only one part of the supply chain into a decision tool covering three sides of the chain: the company's distribution center with its internal processes, supplier with supply processes and customer with demand processes. The complexity that is created by the expanded view is reduced by considering two separate links: demand link and supply link. At first the links are analyzed separately considering the most relevant factors of each one and afterwards they are combined into a categorization matrix to classify the parts.The categorization scheme is tested in a large international company for improving its spare parts distribution chain performance. In the case company's demand link, part value and demand variability were used as the factors to create seven categories. In supply link, three categories are created by using availability risk of the material as the categorizing factor. The spare parts distribution chain performance is analyzed with service performance and stock-out cost key performance indicators before and after improvement actions. Finally, it is discussed how widely the insights from the case experience can be generalized towards developing a generic management tool for such a complex situation.     

The relationship between UK manufacturers’ inventory levels and supply,internal and market factors

A major survey of UK manufacturing plants was carried out to explore the relationships between certain factors and inventory levels. These factors include procurement lead time, customer delivery lead time, manufacturing lead time and levels of predictability of raw materials availability and customer demand levels. The sample for the study comprises UK manufacturing plants in different industrial sectors including engineering, process, electronics, household products and food sectors. The results of a correlation analysis show that supply chain management issues such as the procurement lead time and the frequency of raw materials delivery are significantly linked with the inventory level of manufacturing plants. Also, manufacturing lead times were found to be associated with inventory levels but there was no significant relationship between customer delivery lead times and inventory levels.     

Revenue management for make-to-order manufacturing systems with a real-life application

Abstract

Due to successful applications of revenue management in the airline industry, in recent years, there has been a growing interest to adopt revenue management in make-to-order (MTO) manufacturing systems. Several interrelated decision problems such as order acceptance/rejection, short-term capacity planning, due date assignment, and order scheduling need to be studied simultaneously in order to manage revenues effectively in MTO manufacturing systems. Both the producer’s and customer’s requirements need to be taken into account through some negotiation mechanisms that are sensitive to the service-level reputation of the manufacturing companies. In this article, we propose a new dynamic bid price–based revenue management model that considers all of the aforementioned decision problems simultaneously. A simulation optimization approach is utilized in order to determine the best possible values of control parameters for bid price, due date assignment, and price increment/reduction mechanisms. The performance of the proposed integrated revenue management model is tested on both a hypothetical example and a real problem of a bridal gown company. The computational results show that the proposed model provides significant improvements in total revenue compared to other static and dynamic bid price policies.     

REAL OPTION MODELS FOR MANAGING MANUFACTURING SYSTEM CHANGES IN THE NEW ECONOMY

The manufacturing environment is becoming increasingly dynamic with upsurges in electronic-commerce, supply chain management, forecasting, and procurement and resource planning. It also includes trends toward more process data acquisition and analysis, shorter production runs, and more stringent quality requirements. These drivers lead to an opportunity for companies to collect and use information to identify changes that will affect their manufacturing systems. In conjunction with an industry partner who produces home fashion products, we developed a case-study that highlights four major manufacturing transitions: new product introduction; moving a product from research and development (R&D) to commercialization: new plant location; and starting or restarting production of existing products. These types of changes cross many levels of the operation - including the product level, plant level, and organizational level - and typically present significant operational challenges. We use this case-study to motivate the theoretical and applied research needed to support a real option framework for system changes in manufacturing. The key elements of our framework are to quantify manufacturing changes, develop a real option model for these activities, value the options to identify the best scenarios, and integrate these elements so that we can monitor and manage the overall process. The advantage of this approach is that it allows us to directly incorporate a market driven perspective, tying the manufacturing operations with the organizational economic goals.     

Product variety and vertical integration

R esearch summary: In vertical relationships, the potential for scale economy in manufacturing often calls for specialization and outsourcing. Specialization, however, depends critically on the stability of the task and contractual environment. In a highly uncertain environment, the need for frequent mutual adjustments favors integration instead of outsourcing. To evaluate vertical relationships in value chains where one stage competes on product variety under great uncertainty and the other stage competes on scale, we compare operations data at about 300 distribution centers within a major soft‐drink bottler before and after it was integrated into an upstream concentrate producer. We find that vertical integration improved coordination for the integrated firm by aligning incentives and reducing strategic information asymmetry, but it worsened coordination for upstream rivals that shared the same downstream facilities. M anagerial summary: Managers make frequent decisions about outsourcing versus integration. This article helps to crystalize the costs and benefits of integration by pointing to two important factors: the potential for economies of scale and the need for coordination under uncertainty. It studies an industry where one stage of the value chain competes on product variety under great uncertainty and the other stage competes on scale. Based on operations data at about 300 distribution centers within a major soft‐drink bottler before and after it was integrated into an upstream concentrate producer, we find that vertical integration improved coordination for the integrated firm (by reducing both stockouts and inventory, and improving sales forecasts), but it worsened coordination for upstream rivals that shared the same downstream facilities. Copyright © 2016 John Wiley & Sons, Ltd.     

Designing supply chains: Towards theory development

This paper describes a typology for designing supply chains that work in harmony to design, produce, and deliver products with different characteristics and customer expectations. This research discusses supply chain types that are necessary for success across three types of products: standard, innovative, and hybrid. It develops a framework for categorizing the supply chain types according to product characteristics and stage of the product life cycle. The key success factor for a product change as the product moves through its life cycle, and this may require different supply chain characteristics and capabilities. The paper blends literature and theory development with cases study research to create the typology and develop a set of research questions for further investigation.     

Achieving Customer Satisfaction through Integrated Products and Services: An Exploratory Study

Complex products such as manufacturing equipment have always needed maintenance and repair services. Increasingly, leading manufacturers are integrating products and services to generate increased revenues and achieve customer satisfaction. Designing integrated products and services requires a different approach to new product development and a clear understanding of how customers perceive the value they obtain from actual usage of products and services—so‐called value‐in‐use. However, there is a lack of research on integrated products and services and how they impact customer satisfaction. An exploratory study was undertaken to understand customers' views on integrated products and services and the value‐in‐use derived from such offerings. As value‐in‐use and its impacts are complicated concepts, a technique from psychology—Repertory Grid Technique—was used to gather data in 33 interviews. The interviews allowed a deep understanding of customer views on integrated products and services to be obtained, and a systematic analysis identified the key attributes of value‐in‐use. In order to probe further, the data were then analyzed using Honey's procedure, which identified the impact of the attributes of value‐in‐use on customer satisfaction. Two key attributes—relational dynamic and access—were found to have the most influence on customer satisfaction. This paper contributes to the innovation field by identifying customer needs for integrated products and services and how these impact customer satisfaction. These are key points and need to be fully considered by managers during new product and service development. Similarly, the paper identifies a number of important areas for further research.     

全球价值链的“空间逻辑”及其区域政策含义——基于制造组装环节与品牌营销环节空间分离的视角

本文运用一般均衡及超边际分析方法,通过建立一个包含制造组装环节和品牌营销环节的内生分工模型来探索全球价值链的"空间逻辑"。研究表明:促进制造组装环节与品牌营销环节空间分离的主要动力有两个:一是发挥各个区域的外生比较优势,最大限度地提高整条价值链的生产效率;二是充分利用各个区域的专业化经济,尽量降低整条价值链的固定学习成本。而要实现制造组装环节和品牌营销环节的空间分离,需要制造产品以及品牌服务的区域间交易效率提高到一定的临界值,其中,品牌服务在提高市场交易效率方面的"正反馈效应"对上述两个环节空间分离的实现起着促进作用。在此基础上,本文进一步分析了模型衍生的一系列区域经济政策含义。     

Permutation flowshop scheduling to minimize the total tardiness with learning effects

Scheduling with learning effects has received considerable attention recently. Often, numbers of operations have to be done on every job in many manufacturing and assembly facilities. However, it is seldom discussed in the general multiple-machine setting, especially without the assumptions of identical processing time on all the machines or dominant machines. With the current emphasis of customer service and meeting the promised delivery dates, we consider a permutation flowshop scheduling problem with learning effects where the objective is to minimize the total tardiness. A branch-and-bound algorithm and two heuristic algorithms are established to search for the optimal and near-optimal solutions. Computational experiments are also given to evaluate the performance of the algorithms.     

Inventory management in a multi-echelon spare parts supply chain

In many industrial sectors, firms are dealing with a demand which is more and more uncertain often due to the supply chain structure. One of the most critical effects of demand uncertainty is the simultaneous increase of inventories and decrease of customer service. This work describes an integrated system for managing inventories in a multi-echelon spare parts supply chain, in which customers of different size lay at the same level of the supply chain. The differences in size generate demand peaks and thus a very variable and lumpy demand pattern. The analysis presented in the paper stems from a case study in the field of durable goods spare parts. The paper contributes in three ways: on the one hand, it shows that consistency between managerial solutions and supply chain structure enables to enhance operative performances. On the other hand, it provides a new solution to a problem that characterises several different industrial contexts. Eventually, it highlights that the exploitation of a larger and more reliable set of information dramatically improves performance.     

Logistics scheduling to minimize inventory and transport costs

We study a logistics scheduling problem where a manufacturer receives raw materials from a supplier, manufactures products in a factory, and delivers the finished products to a customer. The supplier, factory and customer are located at three different sites. The objective is to minimize the sum of work-in-process inventory cost and transport cost, which includes both supply and delivery costs. For the special case of the problem where all the jobs have identical processing times, we show that the inventory cost function can be unified into a common expression for various batching schemes. Based on this characteristic and other optimal properties, we develop an O(n) algorithm to solve this case. For the general problem, we examine several special cases, identify their optimal properties, and develop polynomial-time algorithms to solve them optimally.     

Efficient location of industrial activity cells in a global supply chain

Inefficient locations for production, distribution and reverse logistics plants will result in excess costs no matter how well material requirements planning (MRP), inventory control, distribution and information sharing decisions are optimized. In this paper we study ways in which aspect of activity cell location decisions can be analyzed within an extended MRP model. This model has previously been extended by including distribution and reverse logistics components in a compact form, presented in Grubbström et al. (2007). Our aim is to demonstrate the basic differences between an approach to location problems with MRP “under the same roof” as the global supply chain, in which transportation time delays and direct transportation costs have substantial influence. We discuss possibilities of how to present location aspects in the supply chain model obtained from combining input–output analysis and Laplace transforms in four sub-systems, namely manufacturing, distribution, consumption and reverse logistics, and show how the transportation costs and lead time influenced by the location of all these activities affect the resulting net present value (NPV). Our aim is to build a model supporting decisions concerning the structure of a supply chain as an alternative to a mixed integer programming formulation. The model developed is based on the use of continuous functions describing spatial distributions of cost and customer demand. Continuous functions are embedded in the MRP extension previously introduced in Grubbström et al. (2007).Location decisions influence (i) production costs, because timing influences the cost of activities involved in creating a product, cf. (Grubbström and Bogataj, submitted for publication), and (ii) logistics costs, which refer to the procurement and physical transmission of materials through the supply chain. In this current paper we wish to combine both of these aspects into a comprehensive model, where we show the interaction between the “space of flows” and the “space of places” as Giovanni Arrighi distinguishes one from the other in his book The Long Twentieth Century.     

供应链可靠度管理中的模糊QFD应用

在供应链管理（SCM）中,人们更关注于寻找一种系统的方法,能够在计划阶段对可靠度进行评估。提出了一种模糊QFD模型,使其能够在供应链管理的过程中,传达用户需求与设计参数间的模糊关系;同时提出一套模糊的决策程序：模糊多准则决策．用来寻找一组CRT设计中可靠度需求性能的最优解。主要目的是找出合适的可靠性测试等级,以便使每一条供应链中模糊需求与产品生产参数之间的关系更加合理,以满足用户的需求。     

Ordering and pricing policies in a manufacturing and distribution supply chain for fashion products

In the paper, we develop a model of manufacturing and distribution supply chains that are operating to meet price-sensitive random demand for products with short life cycles such as fashion products. Two specific scenarios are considered. The manufacturer-controlled scenario is one where the distributor shares price-sensitive random demand with the manufacturer, and the manufacturer controls the supply chain stocking decisions and bears the risk of overstocking costs. The distributor-controlled scenario works in the opposite direction. Prevailing wisdom suggests that the manufacturer should control supply chain decisions (e.g., via vendor-managed inventory). Our results indicate that such an arrangement is against the interest of a distributor selling short life-cycle products. Furthermore, we find that the total supply chain profit is generally higher when the distributor controls the supply chain stocking decisions and bears the risk of overstocking costs.     

The bullwhip effect in capacitated supply chains with consideration for product life-cycle aspects

This paper presents an analysis of the bullwhip effect and net-stock amplification in a three-echelon supply chain considering step-changes in the production rates during a product's life-cycle demand. The analysis is focused around highly complex and engineered products (e.g., automobiles), that have relatively long production life-cycles and require significant capital investment in manufacturing. Using a simulation approach, we analyze three stages of the product life-cycle including low volumes during product introduction, peak demand, and eventual decline toward the end of the life-cycle. Parts of the simulation model have been adopted by a major North-American automotive OEM as part of a scenario analysis tool for strategic supply network design and analysis. The simulation results show that performance of a system as a whole deteriorates when there is a step-change in the life-cycle demand. While restriction in production capacity does not significantly impact the bullwhip effect, it increases the net stock amplification significantly for the supply chain setting under consideration. Furthermore, a number of important managerial insights are presented based on sensitivity analysis of interaction effect of capacity constraints with other supply chain parameters.     

流水工序调度与生产效率的关系模型分析

提出一种基于粒子群算法的流水工序调度任务优化模型。利用流水工序调度任务的特点得到流水工序时间约束条件,利用粒子群算法的原理建立流水工序调度任务优化模型,利用粒子群算法对模型进行求解。仿真实验表明,利用该算法能够得到流水工序调度问题的最优解,提高生产效率。     

A model for supply management of agile manufacturing supply chains

This paper addresses the configuration problem of Manufacturing Supply Chains (MSC) with reference to the supply planning issue. Assuming that the manufacturing system is composed of different stages, we present a technique for the strategic management of the chain addressing supply planning and allowing the improvement of the MSC agility in terms of ability in reconfiguration to meet performance. More in detail, we enhance a previous design method by some of the authors that employs digraph modeling and integer linear programming to optimally design the MSC. The original approach avoids supply chain disruption and stock out and, at the same time, can manage spare parts distribution. In order to take into account the level of demands and maximum production capacities with single/multiple sourcing, in this new formulation we introduce supplier capacity constraints. A case study is presented describing the optimal MSC configuration of an Italian manufacturing firm. The obtained results show that the design method provides managers with key answers to issues related to the supply chain strategic configuration and agility, e.g., choosing the right location for distributors and retailers for enhanced MSC flexibility and performance.