Economic Lot Scheduling Problem with Returns

Motivated by a case study of a company that produces car parts, we study the multi‐product economic lot scheduling problem for a hybrid production line with manufacturing of new products and remanufacturing of returned products. For this economic lot scheduling problem with returns (ELSPR), we consider policies with a common cycle time for all products, and with one manufacturing lot and one remanufacturing lot for each product during a cycle. For a given cycle time, the problem is formulated as a mixed integer linear programming (MIP) problem, which provides the basis for an exact solution. The application of this model for one of the core products of the case study company indicates a 16% reduction in cost compared to the current lot scheduling policy.     

基于遗传算法的三级逆向物流网络设计模型研究

建立初始回收点以方便客户、提高回收速度以及建立集中回收中心以负责产品的收回、分拣并统一运送到相应的生产商或分销商修理地点是一种节约、有效的多层次产品回收模式。本文在即存研究基础之上,加入了考虑初始点回收成本、回收产品中再销售品的收益和可再利用品的收益等变量,提出了能够优化连接客户、集中回收中心和生产商三级逆向物流网络数学模型,最后灵敏度分析表明遗传算法对于求解这类问题是一种有效的方法。     

Forecasting Product Returns for Remanufacturing Operations

Driven by legislative pressures, an increasing number of manufacturing companies have been implementing comprehensive recycling and remanufacturing programs. The accurate forecasting of product returns is important for procurement decisions, production planning, and inventory and disposal management in such remanufacturing operations. In this study, we consider a manufacturer that also acts as a remanufacturer, and develop a generalized forecasting approach to determine the distribution of the returns of used products, as well as integrate it with an inventory model to enable production planning and control. We compare our forecasting approach to previous models and show that our approach is more consistent with continuous time, provides accurate estimates when the return lags are exponential in nature, and results in fewer units being held in inventory on average. The analysis revealed that these gains in accuracy resulted in the most cost savings when demand volumes for remanufactured products were high compared to the volume of returned products. Such situations require the frequent acquisition of cores to meet demand. The results show that significant cost savings can be achieved by using the proposed approach for sourcing product returns.     

回载可分的闭环供应链多配送中心多车辆运输策略

本文从车辆路径的角度研究了具有多个配送中心、多台车辆结合前向物流配送和逆向物流回载的闭环供应链运输策略,考虑回收产品的不同形态和可分批运输的特点,引入库存限制和成本惩罚,建立并分析了问题的数学模型.运用sweep算法把多配送中心转化为单配送中心,引入2σ原则构造了分组的启发式求解方法.算例分析表明该策略的合理有效性.     

不对称信息下的易逝品退货物流协调运作研究

退货是当前企业面临的一个重要问题,越来越多的企业开始将退货物流外包给第三方物流企业。在由第三方物流企业和制造商构成的易逝品逆向物流系统中,第三方物流企业的退货处理速度直接影响制造商退货产品的收益,因此确定合适的退货处理速度,协调两者间的利益分配成为研究的重点。本文采用排队模型求出系统最优的退货处理速度,并讨论了影响最优处理速度的各个因素;最后通过构建信息甄别模型求出了在双方对第三方物流企业的成本类型存在信息不对称时,制造商的最优协调策略。     

Optimal Policies for Recovering the Value of Consumer Returns

This study characterizes the class of Pareto optimal returns policies between a manufacturer and a retailer who receives consumer returns. The manufacturer may take a costly hidden action that reduces the expected number of products returned by consumers, which when realized is hidden information known only to the retailer. When faced with consumer returns, the retailer must decide whether to send the product back to the manufacturer, who harvests a low salvage value, or to engage in costly refurbishment that permits the returned product to be resold to consumers. We find that the optimal returns policies may be implemented through the payment by the manufacturer of a full refund to the retailer of the wholesale price for any returns as well as a bonus paid to the retailer that is decreasing in the number of returns to the manufacturer.     

Managing consumer returns in high clockspeed industries

In this study, we address control policies to manage the collection of products that have been returned by consumers to retailers after they have been sold. Specifically, we model a consumer returns process where the operational decision of interest is the frequency in which returns are picked up from a collection point and then processed at a centralized location. Returns decay in value over time according to their industry clockspeed. Hence there is an intrinsic tradeoff in the decision – a longer interval between collections not only reduces transportation cost, but also reduces the value of asset recovery.We analyze a stylized model with a single collection point and a centralized returns processing center. Given an asset decay rate and a fixed transportation cost we determine the optimal collection interval. We later expand the analysis to the case of a capacitated returns processing center. We also explore the value of information (number of returns held at the collection point) sharing between a collection point and the central processing facility. We find that the voi is quite sensitive to parametric settings ranging upwards to over 20% with a median value of 5.0%. We find that the voi increases with respect to the asset value decay rate and the rate of returns, while it decreases with respect to the shipping cost.     

Optimal Price and Quantity of Refurbished Products

Many retail product returns can be refurbished and resold, typically at a reduced price. The price set for the refurbished products affects the demands for both new and refurbished products, while the refurbishment and resale activities incur costs. To maximize profit, a manufacturer in a competitive market must carefully choose the proportion of returned products to refurbish and their sale price. We model the sale, return, refurbishment, and resale processes in an open queueing network and formulate a mathematical program to find the optimal price and proportion to refurbish. Examination of the optimality conditions reveals the different situations in which it is optimal to refurbish none, some, or all of the returned products. Refurbishing operations may increase profit or may be required to relieve a manufacturing capacity bottleneck. A numerical study identifies characteristics of the new product market and refurbished products that encourage refurbishing and some situations in which small changes in the refurbishing cost and quality provoke large changes in the optimal policy.     

Design of the Reverse Channel for Remanufacturing: Must Profit‐Maximization Harm the Environment?

A key attribute of a remanufacturing strategy is the division of labor in the reverse channel, especially whether remanufacturing is performed in‐house or outsourced. We investigate this decision for a retailer who accepts returns of a remanufacturable product. Our formulation considers the cost structures of the two strategies, uncertainty in the input quality of the collected/returned used products, consumer willingness‐to‐pay for remanufactured product, the extent to which the remanufactured product cannibalizes demand for a new product, and the power structure in the channel. For the profit‐maximizing retailer, the differentials in variable remanufacturing costs drive strategy choice, and higher fixed costs of in‐house remanufacturing favors outsourcing. The variable remanufacturing costs and the balance of power in the prospective outsourced reverse channel are the key drivers of environmental impact, as measured by the retailer's propensity to remanufacture. While profitability and environmental goals often conflict, they align under certain conditions. These include (a) the third party has less bargaining power; or (b) the fixed cost for in‐house remanufacturing is relatively high. All else equal, when remanufacturing is outsourced, the environment fares better if the third party has leadership power. We generalize to the cases when remanufacturing achieves a quality level less than “good‐as‐new" and when used items have non‐zero salvage value. Analysis of these extensions illuminates how relative power in the reverse channel drives the firms’ preferences, as well as the end customers’ consumption experience.     

Supply chain coordination with reverse logistics: A vendor/recycler-buyer synchronized cycles model

In this paper, we develop a synchronized cycles vendor-buyer coordination model where the single vendor is both a producer and recycler/remanufacturer, and there are multiple buyers. This model is an extension of the general single-vendor multi-buyer synchronization model to incorporate reverse logistics, and it includes costs associated with production, remanufacturing, transportation and holding inventory. The reverse logistics in the model is achieved by having the vendor pick up returned products from the buyers and then reprocess them for resale. Similar to the original synchronization model, the synchronization of our model is attained by coordinating the vendor's production cycle with both new products’ delivery cycles for transportation from the vendor to the buyers and used products’ pick-up cycles for transportation from the buyers to the vendor/recycler. A genetic algorithm is used for solving the problem. Numerical results show the benefits from this new synchronized cycles model compared to independent optimization with reverse logistics. Our findings further show that under low levels of returning products, the synchronized cycles coordination model with reverse logistics can reduce total system costs when compared with the independent optimization model without reverse logistics. Examples also show how the model with reverse logistics can perform economically better than the model without reverse logistics.     

A subsidized reverse supply chain in the Chinese electronics industry

We study a special environmental producer responsibility policy for the Chinese electronics industry that is based on awarding a per unit subsidy to qualified returned electronic products and ensuring a minimum producer collection volume while allowing larger collection volumes. Based on a real application from a Chinese electronics company that produces LCD TVs, our paper studies the optimal design of the product’s reverse supply chain when there is flexibility in settling the inspection locations of the returned products and flexibility in the volume of returned products collected. The problem is modeled as a nonlinear mixed-integer program and an efficient outer approximation-based solution approach is proposed. Analytical results and extensive numerical experiments based on this real application are conducted. Observations novel to the reverse logistics literature are related to the testing location decisions (upstream or downstream) and the optimal collection volumes of returned products. Particularly, we show how the government can stimulate the collection amount of returned products by increasing the unit subsidy and we also find that the company’s marginal benefit from improving the subsidy increases in a superlinear fashion. Furthermore, the highest collection volumes may not occur at the highest quality level of returned products for capacitated remanufacturers. The company can also be incentivized to increase the collection of returned products by permitting flexible testing locations. We also observe how the optimal testing locations vary for different levels of unit subsidy and different ratios of qualified and non-qualified returned products. Finally, conclusions and future research directions are provided.     

Improving the efficiency of remanufacture through enhanced pre-processing inspection – a comprehensive study of over 2000 engines at Caterpillar remanufacturing,U.K.

Remanufacturing returns used product to an ‘as-new’ condition and is a key strategy in environmentally conscious manufacturing and waste management. However, strategies to improve the efficiency of the process are hampered by a lack of remanufacturing-specific industrial research. This paper presents the results of quantitative research, conducted in an industrial remanufacturing facility, to establish the relationship between pre-processing inspection levels and the subsequent remanufacturing process time for returned used products (known as cores). It concludes that for cores having either complex geometry (such as internal ports), a large number of sub-components or that are constructed from, or comprising of, multiple materials the remanufacturing process is shortened by increased inspection prior to processing. However, these benefits are currently limited by the amount of information that can be gained from the inspection methods used. The authors describes the practical use of these results in both a decision-making methodology for inspection and a cost assessment tool.     

Lot Sizing for Optimal Collection and Use of Remanufacturable Returns over a Finite Life‐Cycle

Reverse supply chains process used product returns to recover value by re‐processing them via remanufacturing operations. When remanufacturing is feasible, the longer the return flows are delayed during the active (primary) market demand period of the product, the lower the value that can be recovered through these operations. In fact, in order to recover the highest value from remanufactured products, the collection rates, return timings, and reusability rates should be matched with the active market demand and supply. With these motivations, this paper is aimed at developing analytical models for the efficient use of returns in making production, inventory, and remanufacturing decisions during the active market. More specifically, we consider a stylistic setting where a collector collects used product returns and ships them to the manufacturer who, in turn, recovers value by remanufacturing and supplies products during the active market demand. Naturally, the manufacturer's production, inventory and remanufacturing decisions and costs are influenced by the timing and quantity of the collector's shipments of used product returns. Hence, we investigate the impact of the timing of returns on the profitability of the manufacturer‐collector pair by developing system‐wide cost optimization models. Analyzing the properties of the optimal shipment frequency, we observe that the fastest reverse supply chain may not always be the most efficient one.     

Selling with Money‐Back Guarantees: The Impact on Prices,Quantities, and Retail Profitability

In this paper, we consider a retailer adopting a “money‐back‐guaranteed” (MBG) sales policy, which allows customers to return products that do not meet their expectations to the retailer for a full or partial refund. The retailer either salvages returned products or resells them as open‐box items at a discount. We develop a model in which the retailer decides on the quantity to procure, the price for new products, the refund amount, as well as the price of returned products when they are sold as open‐box. Our model captures important features of MBG sales including demand uncertainty, consumer valuation uncertainty, consumer returns, the sale of returned products as open‐box items, and consumer choice between new and returned products and possibility of exchanges when restocking is considered. We show that selling with MBGs increases retail sales and profit. Furthermore, the second‐sale opportunity created by restocking returned products enables the retailer to generate additional revenues. Our analysis identifies the ideal conditions under which this practice is most beneficial to the retailer. Offering an MBG without restocking increases the new product price. We show that if the retailer decides to resell the returned items as open‐box, the price of the new product further increases, while open‐box items are sold at a discount. On the other hand, customers enjoy more generous refunds along with lower restocking fees. The opportunity to resell returned products also generally decreases the initial stocking levels of the retailer. Our extensive numerical study substantiates the analytical results and sharpens our insights into the drivers of performance of MBG policies and their impact on retail decisions.     

Network design for reverse logistics

Collection and recycling of product returns is gaining interest in business and research worldwide. Growing green concerns and advancement of green supply chain management (GrSCM) concepts and practices make it all the more relevant. Inputs from literature and informal interviews with 84 stakeholders are used to develop a conceptual model for simultaneous location–allocation of facilities for a cost effective and efficient reverse logistics (RL) network. We cover costs and operations across a wide domain and our proposed RL network consists of collection centers and two types of rework facilities set up by original equipment manufacturers (OEMs) or their consortia for a few categories of product returns under various strategic, operational and customer service constraints in the Indian context.     

OPTIMAL DESIGN OF MULTI-PRODUCT MULTI-ECHELON INVENTORY SYSTEMS*

Large scale inventory distribution systems typically comprise a hierarchy of retail stores and warehouses. This paper presents a model for finding the optimal design of such systems. Given the maximum number of facilities under consideration and their locations, the problem is to determine which facilities to include in the system and which products to stock at each in order to minimize the cost of the system. Demand for the products may be deterministic or stochastic. To use the model it is necessary to know the optimal inventory policies for the multi-echelon systems under consideration; however, an important feature of this work is that any multi-echelon model may be used in tandem with this design model. Included is an example to illustrate the model and the two points which are the basis for its formulation: first, there is generally no single design which is best for all products; second, the design which is optimal for a given product is not necessarily the best design to use for that product when trying to minimize the cost of the entire system.     

End‐of‐Life Inventory Problem with Phaseout Returns

We consider the service parts end‐of‐life inventory problem of a capital goods manufacturer in the final phase of its life cycle. The final phase starts as soon as the production of parts terminates and continues until the last service contract expires. Final order quantities are considered a popular tactic to sustain service fulfillment obligations and to mitigate the effect of obsolescence. In addition to the final order quantity, other sources to obtain serviceable parts are repairing returned defective items and retrieving parts from phaseout returns. Phaseout returns happen when a customer replaces an old system platform with a next‐generation one and returns the old product to the original equipment manufacturer (OEM). These returns can well serve the demand for service parts of other customers still using the old generation of the product. In this study, we study the decision‐making complications as well as cost‐saving opportunities stemming from phaseout occurrence. We use a finite‐horizon Markov decision process to characterize the structure of the optimal inventory control policy. We show that the optimal policy consists of a time‐varying threshold level for item repair. Furthermore, we study the value of phaseout information by extending the results to cases with an uncertain phaseout quantity or an uncertain schedule. Numerical analysis sheds light on the advantages of the optimal policy compared to some heuristic policies.     

The Impact of Product Returns and Retailer's Service Investment on Manufacturer's Channel Strategies*

We study the distribution channel decision of a manufacturer who considers whether to add an online channel (direct channel) to its brick‐and‐mortar retailer (indirect channel). The retailer faces the opportunity to invest in store assistance to help consumers choose products and thus reduce product returns. Special attention is given to the impact of product returns and retailer's store assistance investment on manufacturer's dual channel decision. We examine conditions under which the manufacturer uses dual channels and how various relevant factors affect its channel decision under two settings, depending on whether the retailer has its own online store or not. When the retailer does not have its online store, we find that (i) the addition of the direct channel raises the wholesale price; (ii) the direct channel addition hurts the retailer if the nonreplacement rate is low; (iii) the manufacturer has a lower incentive to add the direct channel when the retailer's service cost is lower or its returns reduction rate from service investment is higher; and (iv) the manufacturer should treat its own returns handling cost as a key factor in its channel structure decision. In addition, when the retailer operates an online store, we find that the manufacturer may have an incentive to add a direct channel such that both firms own direct channels.     

MANAGING PRODUCT RETURNS FOR REMANUFACTURING

Firms are often encouraged to offer environmentally friendly products as a demonstration of corporate citizenship. However, this may prove to be an unrealistic expectation since a rational firm will only engage in profitable ventures; those that increase shareholder wealth. We develop a framework for analyzing the profitability of reuse activities and show how the management of product returns influences operational requirements. We show that the acquisition of used products may be used as the control lever for the management and profitability of reuse activities. These activities, termed product acquisition management, affect several important business decisions. First, if a firm is to pursue reuse activities, these reuse activities must be value‐creating. Second, if a firm is to compete by offering remanufactured products, then we show how product returns management influences the overall profitability of such activities via a trial and error EVA approach. Third, we show how operational issues are strongly affected by the approach used to manage product returns. There is a need for future research specifying the mathematical relationship between acquisition price and the nominal quality of the returned product.     

Managing the Reverse Channel with RFID‐Enabled Negative Demand Information

We analyze the inventory decisions of a manufacturer who has ample production capacity and also uses returned products to satisfy customer demand. All returned items go through an evaluation process, at the end of which the decision of disposal, direct reselling, or rework is made for each unit according to a predetermined procedure. We quantify the value of information/visibility on the reverse channel for the manufacturer by making comparisons among three approaches: No information‐naive; no visibility‐enlightened; and full visibility. We find the value of visibility increases with the comparative length of the reverse channel and volume, volatility, and usability of returns. Furthermore, the smarter the manufacturer, the less benefit visibility brings to the system. By this analysis, we quantify the visibility savings of radio frequency identification (RFID) in the reverse channel as a candidate enabler technology. We also provide numerical examples to show that practical approximations in inventory management may have acceptable penalties to the manufacturer with visibility.