Optimal policies in hybrid manufacturing/remanufacturing systems with product substitution

In hybrid control systems for simultaneous remanufacturing of used products and manufacturing of new ones, the two operations are not directly interconnected if remanufactured items are downgraded and have to be sold in markets different from those for new products. Sometimes a connection between these markets is given by a downward substitution property which allows the producer to offer a new item instead of a remanufactured one in case of a shortage of a remanufactured product. Thus, shortage costs can be avoided, but a loss in profit due to sale of a high-graded product at the price of a low-graded one has to be accepted. For a single-period problem with stochastic returns of used products and stochastic demands of serviceable ones, it is shown how the manufacturing and remanufacturing decisions have been coordinated in order to maximize the total expected profit. It turns out that under strictly proportional costs and revenues a medium-simple ‘order-up-to policy’ with two parameters and two parameter functions is optimal. However, optimal policies in situations where manufacturing leadtimes exceed leadtimes for remanufacturing turn out to be different from those in the opposite leadtime case. The research presented combines methods for policy analysis in stochastic manufacturing/remanufacturing problems and in stochastic inventory control problems with substitutable products.     

Optimal production–inventory strategies for a HMMS-type reverse logistics system

The aim of the paper is to find optimal inventory policies in a reverse logistics system with special structure. It is assumed that demand is a known continuous function in a given planning horizon and return rate of used items is a given function. There is a constant delay between the using and return process. We investigate two stores. The demand is satisfied from the first store, where the manufactured and remanufactured items are stored. The returned products are collected in the second store and then remanufactured or disposed. The costs of this system consist of the quadratic holding costs for these two stores and the quadratic manufacturing, remanufacturing and disposal costs.The model is represented as an optimal control problem with two state variables (inventory status in the first and second store) and with three control variables (rate of manufacturing, remanufacturing and disposal). The objective is to minimize the sum of the quadratic deviation from described inventory levels in stores and from described manufacturing, remanufacturing and disposal rates. In this form, the model can be considered as a generalization of the well-known Holt et al. (Planning Production, Inventories, and Work Forces, Prentice-Hall, Englewood Cliffs, NJ, 1960) model with two warehouses. After solving the problem, we give some numerical examples to represent the optimal path in dependence of the demand rates.     

An economic production and remanufacturing model with learning effects

Managing inventory in reverse logistics has been receiving much attention in recent years. One inventory problem that has been of interest to researchers is the production and remanufacturing model, where used items are collected and remanufactured to satisfy customer demand. The available models in the literature do not discuss the learning effects in production and remanufacturing processes. This may not be true in industries where labour costs and learning costs are expensive. By modelling these learning effects, management may use established learning models to better utilize capacity, manage inventories, and coordinate production and distribution throughout the chain.This paper extends the production, remanufacture, and waste disposal model by assuming learning to occur in both production and remanufacturing processes. However, this paper also assumes that improvements due to learning require capital investment. Mathematical models are developed, numerical examples are provided, and results are discussed.     

Optimal inventory and pricing policies for remanufacturable leased products

In this paper we consider a company which leases new products and also sells remanufactured versions of the new product that become available at the end of their lease periods. When the amount of end-of-lease items in stock is not sufficient to meet the demand for remanufactured products, the firm may purchase additional cores from a third-party supplier. We develop a dynamic programming formulation for determining the optimal price of remanufactured products, and optimal payment structure for the leased products. Our objective is to maximize the discounted system-wide profit over a finite horizon. The profit function consists of revenues that are obtained from remanufactured product sales and leasing, remanufacturing and manufacturing costs, inventory holding and shortage costs. We consider a consumer choice based demand model for mapping a potential customer into one of the product segments (a remanufactured product customer or a customer for a leased product with a particular lease period) for a given price/lease payment vector. We explore several properties of the discounted profit function and provide insight on the behavior of pricing and inventory policies. We also investigate the effect of key product characteristics such as deterioration in age, cost of shortage in remanufacturable product inventory, and key market characteristics such as relative willingness-to-pay for buying a remanufactured product and relative willingness-to-pay for leasing a new product on optimal pricing policies through a computational study.     

A production rate control policy for stochastic repair and remanufacturing systems

We consider the control of a manufacturing system responding to planned demand at the end of the expected life of each individual piece of equipment and unplanned demand triggered by a major equipment failure. The difficulty of controlling this type of production system resides in the variable nature of the remanufacturing process. In practice, remanufacturing operations for planned demand can be executed at different rates, referring to different component replacement and repair strategies. We formulate this problem as a multi-level control problem and propose a suboptimal control policy. The proposed control policy is described by inventory thresholds triggering the use of different execution modes. Determination of the control policy parameters is based on parameter optimization of analytical cost expressions. A numerical example based on a real case is presented. Our analysis demonstrates that the use of the proposed control approach can lead to a significant reduction in the total average cost, as compared to current practices.     

The role of ambiguity tolerance in consumer perception of remanufactured products

This study examines ambiguity tolerance, perceived quality, and willingness to pay for remanufactured products. We found evidence to support a direct relationship between a consumer's tolerance for ambiguity and their willingness to pay for remanufactured products. There was also support for an indirect relationship between ambiguity tolerance and willingness to pay that is mediated through perceived quality. Extant literature often lacks an empirical justification regarding costing and quality assumptions for remanufactured products. This research provides such justification while also offering an explanation as to why consumers view remanufactured products as being of lower quality and are less willing to pay for them. Those employed in the remanufacturing industry are advised to reduce the level of ambiguity associated with their remanufacturing processes in order to command higher prices for their products in the marketplace.     

Short life-cycle deteriorating product remanufacturing in a green supply chain inventory control system

Due to global warming, environmental consciousness and shortening product life-cycles, more attentions have been paid to ecological protection and resource utilization. Green products and production process designs significantly influence the environment and resource re-usage. The relevant EU regulations, such as WEEE and EuP, have reduced negative effects by controlling the disposals and the resource re-usage. In this study, green product designs and remanufacturing efforts are investigated when we develop an integrated production inventory model with short life-cycles. A numerical example is provided to illustrate the theory. We have shown that new technology evolution, remanufacturing ratios and system’s holding costs are critical factors affecting decision making in a green supply chain inventory control system.     

考虑可持续性设计的闭环供应链差异定价研究

为了解决回收产品再制造成本增加甚至难以进行再制造的难题,制造商在产品生产的前期就要考虑后期再制造活动的可实施性,即考虑可持续性设计。在考虑可持续性设计情况下,本文针对由一个制造商和一个经销商构成的两级闭环供应链系统,分别建立经销商从事再制造和制造商从事再制造两种模式下的差异定价模型,得到了相应的最优定价策略,并主要针对可持续性努力程度,讨论其与各个最优决策变量、产品单位成本及可持续性努力程度系数之间的关系。研究给出了可持续性努力程度分别对新产品和再制造产品的最优中间价、最优销售价、最优销售量及最优利润的影响,同时论证了新产品和再制造产品的单位成本及其可持续性努力程度系数分别对可持续性努力程度的影响,并对经销商从事再制造和零售商从事再制造两种模式进行了对比分析。     

An inventory control model with consideration of remanufacturing and product life cycle

This paper investigates inventory control policies in a manufacturing/remanufacturing system during the product life cycle, which consists of four phases: introduction, growth, maturity, and decline. Both demand rate and return rate of products are random variables with normal distribution; the mean of the distribution varies according to the time in the product life cycle. Closed-form formulas of optimal production lot size, reorder point, and safety stock in each phase of the product life cycle are derived. A numerical example is presented with sensitivity analysis. The result shows that different inventory control policies should be adopted in different phases of the product life cycle. It is also found that the optimal production lot size and reorder point are not sensitive to the phase length and the demand changing rate.     

Assessing the Economic Rationality of Remanufacturing Products*

Consideration is given to the factors that affect the determination of the profitability of remanufacturing product. This results in a technique being developed and applied to assess the economic rationality of remanufacturing a variety of products. A study of price preferences from 49 subjects finds that in many cases an original equipment manufacturer (OEM) will earn greater overall profits by offering both new and remanufactured versions of their product. Differences in pricing behavior are noted between both products and individuals. There also appears to be differences in switching behavior. It is, however, reasonable to treat the transfer in preference from new product to remanufactured product as linear over some price range. This assumption allows for a relatively simple calculation of under what circumstances it is economically rational for an OEM to produce both new and remanufactured products and in such situations what the relative prices, sales, and profits should result. The remanufactured products considered are retreaded tires, auto parts, cell phones, toner cartridges, printers/copiers, and disposable cameras. In addition to the article's academic contributions, techniques and insights are offered for practitioners to assist them in understanding the opportunities and implication of pursuing remanufacturing as an addition to their current products.     

Outsourcing reverse logistics of high-tech manufacturing firms by using a systematic decision-making approach: TFT-LCD sector in Taiwan

Reverse logistics are increasingly crucial for the supply chain strategy of global high-tech manufacturing firms. As reverse logistics operations are significantly more complex than traditional manufacturing supply chains, many high-tech manufacturers are examining the feasibility of outsourcing reverse logistics activities to third party logistics providers (3PLs) from a strategic planning perspective. Internal resources and capabilities are thus examined from a resource-based perspective to identify which reverse logistics service requirements could be fulfilled in-house or outsourced. Therefore, this work presents a systematic approach using the analytical network process (ANP) not only to investigate the relative importance of reverse logistics service requirements, but also to select an appropriate 3PL. Empirical results based on the case of the TFT-LCD sector in Taiwan indicate that information technology management is of priority concern in reverse logistics services. In addition to providing a valuable reference for manufacturers concerned with service requirements for outsourcing, results of this study significantly contribute to the efforts of 3PLs in evaluating whether they comply with potential customer requirements based on their service capabilities.     

Implementation of reverse logistics as a sustainable tool for raw material purchasing in developing countries: The case of Venezuela

This study aims to analyze and understand the benefits that acquiring raw materials through the application of reverse logistics can generate, especially in developing countries. An empirical study has been carried out in the handmade sector of five municipalities in the state of Mérida, Venezuela, into the contingency factors of reverse logistics (information and communication systems, total ownership costs and life cycle of products), as well as the effect of uncertainty. A case study methodology was used to test the effect of the independent variables on the “raw materials purchasing” variable, and involved the technique of stepwise multiple regression. The results reveal that the preference for purchasing raw materials through reverse logistics is mainly determined by the “uncertainty” variable, contingency factors of “information and communication systems” and the “life cycle of products”. According to the results, firms in the handmade sector should implement an information system and be in constant communication with their customers, who play a dual role as buyers of their products and as input suppliers, therefore, greater contact can help reduce uncertainty. Handmade sector workers make products with a long average life cycle and, therefore, with greater chances of being reused, restored, repaired and to finally be subjected to recycling. National and local authorities should encourage the application of reverse logistics in other productive sectors, such as manufacturing, agriculture, services, as it can reduce the problem of acquisition of production inputs and mitigate environmental damage caused by the production of raw materials.     

Optimal control of a one product recovery system with leadtimes

In this paper a recovery system for a single product is investigated. Besides a remanufacturing and a manufacturing facility the system consists of one inventory for returned and recoverable items and one for serviceable items. Demands are satisfied from serviceable inventory, which can be replenished by remanufactured returned items, which are as good as new, or by new produced items. Additionally, there is the possibility of disposing of returned items.We determine the cost optimal manufacturing, remanufacturing and disposal rates for the system under the assumptions of a linear cost structure, a finite planning horizon and deterministic and dynamic demand and return rates. Thereby we study two classes of policies, one where backorders are forbidden and another one where they are allowed. In contrast to the existing literature positive leadtimes are considered.     

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.     

Lockout/tagout and operational risks in the production control of manufacturing systems with passive redundancy

This paper addresses problems associated with production control and occupational safety in a manufacturing system prone to failure involving two machines working in passive redundancy. Machines turning out one part experience two modes of failure and repair: firstly, where failure occurs when a machine remains in fair condition; and, secondly, where such failure results in outright breakdown. Accordingly, we examine both modes of failure for their impact on a flexible manufacturing system (FMS) with respect to production control in terms of costs associated with lockout/tagout procedures and corrective maintenance. This study seeks to identify optimal costs related to backlogs, inventories and maintenance over an infinite planning horizon, along with levels of occupational risk where production control includes efficient planning of lockouts/tagouts. Our study offers numerical methods which may be employed to achieve optimal conditions in setting control policies. A numerical example and sensitivity analysis support this approach.     

Integrating noncyclical preventive maintenance scheduling and production planning for a single machine

This paper deals with the problem of integrating noncyclical preventive maintenance and tactical production planning for a single machine. We are given a set of products that must be produced in lots during a specified finite planning horizon. The maintenance policy suggests possible preventive replacements at the beginning of each production planning period, and minimal repair at machine failure. The proposed model determines simultaneously the optimal production plan and the instants of preventive maintenance actions. The objective is to minimize the sum of preventive and corrective maintenance costs, setup costs, holding costs, backorder costs and production costs, while satisfying the demand for all products over the entire horizon. The problem is solved by comparing the results of several multi-product capacitated lot-sizing problems. The value of the integration and that of using noncyclical preventive maintenance when the demand varies from one period to another are illustrated through a numerical example and validated by a design of experiment. The later has shown that the integration of maintenance and production planning can reduce the total maintenance and production cost and the removal of periodicity constraint is directly affected by the demand fluctuation and can also reduce the total maintenance and production cost.     

Considering stochastic lead times in a manufacturing/remanufacturing system with deterministic demands and returns

In this paper we study a manufacturing/remanufacturing system with stochastic lead times and a constant demand. We base our approach on previous research in which we have developed models to describe an inventory system with stochastic lead times. In this paper, we first adopt this method to manufacturing/remanufacturing situations, where there are essentially two supply sources for replenishing serviceable inventory. We then provide a solution procedure when a cycle ordering policy is used. Secondly, we investigate the possibility to use a dual sourcing ordering policy in which each order is split between a manufacturing and a remanufacturing process. Finally, we compare the two ordering policies and illustrate how the lead-time patterns influence the economic consequences.     

Remanufacturing decision and sustainability under product life cycle uncertainty

Abstract

For a single type of product, we study a firm's remanufacturing decisions for the product under demand uncertainty from a real options approach. Specifically, we assume that the product life cycle consists of a growth regime with the expected product demand and volatility increasing with respect to time and a decay regime with the expected product demand and volatility decreasing with respect to time while the timing of regime change itself is uncertain as well. Under this framework, this study aims to derive and analyze the demand threshold above which the firm establishes a remanufacturing process in its production system. Moreover, the number of products being remanufactured throughout the life cycle is numerically studied to assess the degree of sustainability due to remanufacturing.     

Designing a reverse logistics network for optimal collection, recovery and quality-based product-mix planning

This study proposes an integrated, reverse logistics supply chain planning process with modular product design that produces and markets products at different quality levels. A mixed integer programming (MIP) model formulates the overall planning process required to maximize profit by considering the collection of returned products, the recovery of modules and the proportion of the product mix at different quality levels. This paper proposes the collection of returnables (end-of life, defective, product under warranty) through retail outlets combined with the recovery of modules from the collected products using a network of recovery service providers. The proposed modular product design approach would create a design criterion that provides an improved recovery process at a lower cost. This study uses a total supply chain view that considers the production, transportation and distribution of products to customers, while a numerical problem illustrates the applicability of the models.     

政府补贴对再制造闭环供应链的影响研究

本文在考虑消费者支付意愿存在显著差异、消费者和制造商存在不同政府补贴分配比例下,建立再制造博弈模型,探讨政府补贴再制造品对产品价格、需求以及对消费者、制造商、社会总收益的影响。结论表明,政府补贴有利于促进再制造品的需求,消费者剩余效用、制造商收益以及社会总收益都增加;政府补贴时应不允许制造商涨价,在考虑制造商积极性下尽量补贴给消费者;提高消费者环保意识才是促进再制造的根本途径。