Lot-sizing for inventory systems with product recovery

We study inventory systems with product recovery. Recovered itemsare as-good-as-new and satisfy the same demands as new items. Thedemand rate and return fraction are deterministic. The relevantcosts are those for ordering recovery lots, for orderingproduction lots, for holding recoverable items in stock, and forholding new/recovered items in stock. We derive simple formulaethat determine the optimal lot-sizes for theproduction/procurement of new items and for the recovery ofreturned items. These formulae are valid for finite and infiniteproduction rates as well as finite and infinite recovery rates,and therefore more general than those in the literature.Moreover, the method of derivation is easy and insightful.product returns;recovery;lot sizing;EOQ/EPQ

Lot-sizing for inventory systems with product recovery

We study inventory systems with product recovery. Recovered items are as-good-as-new and satisfy the same demands as new items. The demand rate and return fraction are deterministic. The relevant costs are those for ordering recovery lots, for ordering production lots, for holding recoverable items in stock, and for holding new/recovered items in stock. We derive simple formulae that determine the optimal lot-sizes for the production/procurement of new items and for the recovery of returned items. These formulae are valid for finite and infinite production rates as well as finite and infinite recovery rates, and therefore more general than those in the literature. Moreover, the method of derivation is easy and insightful

Optimal manufacturing-remanufacturing policies in a lean production environment

This study analyses a production-management model that considers the possibility of implementing a reverse-logistics system for remanufacturing end-of-life products in a lean production environment (as opposed to models than use EOQ approaches). Decisions variables are identified (including manufacturing and remanufacturing capacities and return rates and use rates for end-of-life products) and optimal policies are determined. Moreover, the structure of these optimal policies is analysed. The conclusion draw is that, in may realistic scenarios, mixed policies (that is, with return rates and use rates strictly between 0 and 1) can be optimal. This conclusion is contrary to results published in earlier studies, which are based on more restrictive assumption

Diseño y desarrollo de un modelo y planificación óptima para la responsabilidad de la cadena de suministro con el medio ambiente

The responsible management of product return flows in production and inventory environments is a rapidly increasing requirement for companies. This can be attributed to economic, environmental and/or regulatory motivations. Mathematical modeling of such systems has assisted decision-making processes and provided a better understanding of the behavior of such production and inventory environments. This paper reviews the literature on the modeling of reverse logistics inventory systems based on the economic order/production quantity (EOQ/EPQ) and the joint economic lot size (JELS) settings to systematically analyze the mathematics involved in capturing the main characteristics of related processes. The literature is surveyed and classified according to the specific issues faced and modeling assumptions. Special attention is given to environmental issues. There are indications of the need for reverse logistics models' mathematics to follow current trends in ‘greening’ inventory and supply-chain models. The modeling of waste disposal, greenhouse-gas emissions, and energy consumption during production is considered as the most pressing priority for the future of reverse logistics models. An illustrative example for modeling reverse logistics inventory models with environmental implications is presented.La gestión responsable de los flujos de retorno de productos en entornos de producción e inventario es un requisito cada vez mayor para las empresas. Esto puede atribuirse a motivaciones económicas, ambientales y / o regulatorias. El modelado matemático de tales sistemas ha ayudado a los procesos de toma de decisiones y ha proporcionado una mejor comprensión del comportamiento de dichos entornos de producción e inventario. Este artículo revisa la literatura sobre el modelado de sistemas de inventario de logística inversa que se basan en la orden económica / cantidad de producción (EOQ / EPQ) y la configuración del tamaño de lote económico conjunto (JELS) para analizar sistemáticamente las matemáticas involucradas en la captura de las principales características de los procesos relacionados. La literatura se examina y clasifica de acuerdo con los problemas específicos que se enfrentan y los supuestos del modelo. Se presta especial atención a las cuestiones ambientales. Hay indicios de la necesidad de que las matemáticas de los modelos de logística inversa sigan las tendencias actuales en los modelos de cadena de suministro y inventario "ecológicos". La modelización de la eliminación de residuos, las emisiones de gases de efecto invernadero y el consumo de energía durante la producción se considera la prioridad más urgente para el futuro de los modelos de logística inversa. Se presenta un ejemplo ilustrativo para modelar modelos de inventario de logística inversa con implicaciones ambientales

Diseño y desarrollo de un modelo y planificación óptima para la responsabilidad de la cadena de suministro con el medio ambiente

La gestión responsable de los flujos de retorno de productos en entornos de producción e inventario es un requisito cada vez mayor para las empresas. Esto puede atribuirse a motivaciones económicas, ambientales y / o regulatorias. El modelado matemático detales sistemas ha ayudado a los procesos de toma de decisiones y ha proporcionado una mejor comprensión del comportamiento de dichos entornos de producción e inventario. Este artículo revisa la literatura sobre el modelado de sistemas de inventario de logística inversa que se basan en la orden económica / cantidad de producción (EOQ / EPQ) y la configuración del tamaño de lote económico conjunto (JELS) para analizar sistemáticamente las matemáticas involucradas en la captura de las principales característicasde los procesos relacionados. La literatura se examina y clasifica de acuerdo con los problemas específicos que se enfrentan y los supuestos del modelo. Se presta especial atención a las cuestiones ambientales. Hay indicios de la necesidad de que las matemáticas de los modelos de logística inversa sigan las tendencias actuales en los modelos de cadena de suministro y inventario "ecológicos". La modelización de la eliminación de residuos, las emisiones de gases de efecto invernadero y el consumo de energía durante la producción se considera la prioridad más urgente para el futuro de los modelos de logística inversa. Se presenta un ejemplo ilustrativo para modelar modelos de inventario de logística inversa con implicaciones ambientale

On the alignment of lot sizing decisions in a remanufacturing system in the presence of random yield

In the area of reverse logistics, remanufacturing has been proven to be a valu- able option for product recovery. In many industries, each step of the products’ recovery is carried out in lot sizes which leads to the assumption that for each of the different recovery steps some kind of fixed costs prevail. Furthermore, holding costs can be observed for all recovery states of the returned product. Although several authors study how the different lot sizes in a remanufacturing system shall be determined, they do not consider the specificity of the remanufacturing process itself. Thus, the disassembly operations which are always neglected in former analyses are included in this contribution as a specific recovery step. In addition, the assumption of deterministic yields (number of reworkable compo- nents obtained by disassembly) is extended in this work to study the system behavior in a stochastic environment. Three different heuristic approaches are presented for this environment that differ in their degree of sophistication. The least sophisticated method ignores yield randomness and uses the expected yield fraction as certainty equivalent. As a numerical experiment shows, this method already yields fairly good results in most of the investigated problem instances in comparison to the other heuristics which incorporate yield uncertainties. How- ever, there exist instances for which the performance loss between the least and the most sophisticated heuristic amounts to more than 6%.reverse logistics, remanufacturing, lot sizing, disassembly, random yield

On the alignment of lot sizing decisions in a remanufacturing system in the presence of random yield

In the area of reverse logistics, remanufacturing has been proven to be a valu- able option for product recovery. In many industries, each step of the products\u27 recovery is carried out in lot sizes which leads to the assumption that for each of the different recovery steps some kind of fixed costs prevail. Furthermore, holding costs can be observed for all recovery states of the returned product. Although several authors study how the different lot sizes in a remanufacturing system shall be determined, they do not consider the specificity of the remanufacturing process itself. Thus, the disassembly operations which are always neglected in former analyses are included in this contribution as a specific recovery step. In addition, the assumption of deterministic yields (number of reworkable compo- nents obtained by disassembly) is extended in this work to study the system behavior in a stochastic environment. Three different heuristic approaches are presented for this environment that differ in their degree of sophistication. The least sophisticated method ignores yield randomness and uses the expected yield fraction as certainty equivalent. As a numerical experiment shows, this method already yields fairly good results in most of the investigated problem instances in comparison to the other heuristics which incorporate yield uncertainties. How- ever, there exist instances for which the performance loss between the least and the most sophisticated heuristic amounts to more than 6%

Optimal and predefined policies for the static lot sizing problem in a two stage recovery system

Analyzing static lot sizing problems has always attracted a considerable interest in scientific literature. A commonly applied methodology to solve the trade-off between setup and holding costs is to order the Economic Order Quantity (EOQ) whenever the corresponding inventory is depleted. Yet, this simple proceeding can only be applied as long as there is only a single source of supply. Recovery systems, however, obtain in general two sources of supply, remanufacturing product returns and fabricating new products. Therefore, a more sophisticated approach needs to be taken into account for this kind of problem setting. This contribution focusses on extending the current knowledge in this field of research by showing that non-equal remanufacturing batches propose a significant cost reduction for some parameter classes. Furthermore, a more general optimization approach is introduced that allows to evaluate the solution quality of the preset policy structures