Using simulation to analyze picker blocking in manual order picking systems

The rise of the e-commerce practice makes the warehouses be confronted with ever smaller orders that must be met ever faster, often within a 24-h period. This pressures the order picking process as the orders pickers' workload becomes higher and higher, leading subsequently to congestion in the warehouse and impacting its productivity. It is therefore crucial to determine which order batching and picking policies enhance the performance of order picking activities. This paper carries out an intensive simulation study to examine the performance of different order picking policies with batching in a wide-aisle warehouse with a low-level picker-to-parts system. The performance of the system is measured in terms of total travelled distance, number of collisions between operators (congestion) and order lead times. A full factorial design is set up and the simulation output is statistically analyzed. The results are reported and thoroughly discussed

Warehouse Safety in Order Picking

Safety in warehouse becomes one of the important factors in manual order picking process. Workplace accidents can be caused by a variety of things, including the use of incorrect tools, a lack of work processes, inadequate equipment and safety equipment, and pickers' negligence. Picker safety must come first because any workplace accidents will affect the warehouse's productivity and the time it takes to complete the picking order. Safety aims to prevent, reduce and even eliminate the risk of work accidents (zero accident). Application of safety in the order picking system will certainly increase warehouse efficiency that impact to pickers productivity. Many businesses believe that implementing safety measures is simply a waste of money, but when all the risk variables are taken into account, safety is seen as a long-term investment that will pay off for the business, which will lower costs associated with workplace accidents and improve order fulfillment accuracy, both of which have an effect on consumer satisfaction

Order picker routing with product returns and interaction delays

E-commerce companies often use manual order-picking systems in their warehouses since these systems can provide the required flexibility and scalability. Manual systems have been widely studied, but the operating policies may require significant changes for e-commerce settings. First, to maintain consumers' loyalty, it is important to maintain delivery reliability even on the busiest days. When the number of order pickers in an area increases, however, more delays due to interactions may occur. For example, travel speed may need to be lowered when order pickers pass each other in narrow aisles. Second, many products sold through e-commerce are returned by consumers. Before these returned products can be sold again, they must be reintegrated in the stock. This paper presents hybrid genetic algorithms to determine routes for simultaneous pickup of products in response to consumers' orders and delivery of returned products to storage locations. Furthermore, interactions between the order pickers are considered in the routing decisions. The developed algorithms use specific warehouse problem characteristics. We identify the mix of pickups and deliveries to realise the highest savings in practice. It is shown that order-picker interactions can be a significant cause for delay and should be accounted for in the routing

Hybrid order picking : A simulation model of a joint manual and autonomous order picking system

Order picking is a key process in supply chains and a determinant of business success in many industries. Order picking is still performed manually by human operators in most companies; however, there are also increasingly more technologies available to automate order picking processes or to support human order pickers. One concept that has not attracted much research attention so far is hybrid order picking where autonomous robots and human order pickers work together in warehouses within a shared workspace for a joint target. This study presents a simulation model that considers various system characteristics and parameters of hybrid order picking systems, such as picker blocking, to evaluate the performance of such systems. Our results show that hybrid order picking is generally capable of improving pure manual or automated order picking operations in terms of throughput and total costs. Based on the simulation results, promising future research potentials are discussed

Modello per l'ottimizzazione delle logiche di prelievo per l'asservimento di un sistema di assemblaggio

La tesi si occupa della generazione di un algoritmo multi-obiettivo in grado di ottimizzare da un lato il tempo di output degli articoli dal magazzino e dall'altro lo spazio richiesto dalle unità di carico sulle linee di produzione.ope

Análisis y valoración de flexibilidad en el enrutamiento para implementación de un sistema de vehículos de guiado autónomo en un proceso de almacenamiento industrial simulado por computador

Se estudia el diseño y puesta en marcha mediante la simulación de un sistema AGV (vehículos de guiado automatizado por sus siglas en inglés), en un proceso de cargue para despachos en un almacén de mercancías, donde se evaluarán las principales variables a tener en cuenta de acuerdo con los parámetros y requerimientos de funcionamiento de la operación logística, revisando la literatura y metodologías recomendadas para la implementación de un sistema de AGV, se evaluó: el tipo de vehículo, espacio de almacenamiento, ruteo de vehículos, número de vehículos, posicionamiento del vehículo, programación de vehículos, administración de la batería y la demanda de cada producto en los despachos. Finalizado el diseño del sistema AGV se procedió a la recreación de las condiciones del almacén, carga para despacho y ruteo en un software de simulación para evaluar el desempeño y las dificultades de reorganizar el despacho de pedidos dentro del sistema, al comparar AGV con montacargas tradicionales, viendo una mayor eficiencia de operación para el primer caso.Abstract: The design and start-up is studied mean of simulation of an AGV system (automated guided vehicles), in a pickup process for shipments in a freight warehouse, where the main variables are taken into account will be evaluated according to the parameters and operating requirements of the logistics operation, reviewing the literature and recommended methodologies for the implementation of an AGV system, the following was studied: the type of vehicle, storage space, vehicle routing, number of vehicles, positioning of the vehicle, vehicle programming, battery management and the demand of each product in the offices. Once the design of the AGV system was completed the conditions of the warehouse, pickup for dispatch and routing in a simulation software were analyzed to evaluate the performance and the difficulties of reorganizing the order fulfillment within the system, when comparing AGV with traditional forklifts, checking a greater efficiency of operation for the first case.Maestrí

Design and optimization of an explosive storage policy in internet fulfillment warehouses

This research investigates the warehousing operations of internet retailers. The primary physical process in internet retail is fulfillment, which typically involves a large internet fulfillment warehouse (IFW) that has been built and designed exclusively for online sales and an accompanying parcel delivery network. Based on observational studies of IFW operations at a leading internet retailer, the investigations find that traditional warehousing methods are being replaced by new methods which better leverage information technology and efficiently serve the new internet retail driven supply chain economy. Traditional methods assume a warehouse moves bulk volumes to retail points where the bulks get broken down into individual items and sold. But in internet retail all the middle elements of a supply chain are combined into the IFW. Specifically, six key structural differentiations between traditional and IFW operations are identified: (i) explosive storage policy (ii) very large number of beehive storage locations (iii) bins with commingled SKUs (iv) immediate order fulfillment (v) short picking routes with single unit picks and (vi) high transaction volumes with total digital control. In combination, these have the effect of organizing the entire IFW warehouse like a forward picking area. Several models to describe and control IFW operations are developed and optimized. For IFWs the primary performance metric is order fulfillment time, the interval between order receipt and shipment, with a target of less than four hours to allow for same day shipment. Central to achieving this objective is an explosive storage policy which is defined as: An incoming bulk SKU is exploded into E storage lots such that no lot contains more than 10% of the received quantity, the lots are then stored in E locations anywhere in the warehouse without preset restrictions. The explosion ratio Ψo is introduced that measures the dispersion density, and show that in a randomized storage warehouse Ψoo\u3e0.40. Specific research objectives that are accomplished: (i) Develope a descriptive and prescriptive model for the control of IFW product flows identifying control variables and parameters and their relationship to the fulfillment time performance objective, (ii) Use a simulation analysis and baseline or greedy storage and picking algorithms to confirm that fulfillment time is a convex function of E and sensitive to Ǩ, the pick list size. For an experimental problem the fulfillment time decrease by 7% and 16% for explosion ratios ranging between Ψo=0.1 and 0.8, confirming the benefits of an explosive strategy, (iii) Develope the Bin Weighted Order Fillability (BWOF) heuristic, a fast order picking algorithm which estimates the number of pending orders than can be filled from a specific bin location. For small problems (120 orders) the BWOF performes well against an optimal assignment. For 45 test problems the BWOF matches the optimal in 28 cases and within 10% in five cases. For the large simulation experimental problems the BWOF heuristic further reduces fulfillment time by 18% for Ǩ =13, 27% for Ǩ =15 and 39% for Ǩ =17. The best fulfillment times are achieved at Ψo=0.5, allowing for additional benefits from faster storage times and reduced storage costs

Desenvolvimento de uma metodologia baseada em um modelo exato para resolver o picker routing problem em um caso real

Orientador: Prof. Dr. Cassius Tadeu ScarpinDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Sociais Aplicadas, Programa de Pós-Graduação em Gestão de Organizações, Liderança e Decisão. Defesa : Curitiba, 14/10/2022Inclui referênciasResumo: Neste trabalho apresenta-se uma aplicação real de um modelo exato para o Problema de Roteamento de Separadores de Pedidos, também conhecido com Picker Routing Problem (PRP), em uma Rede varejista do setor supermercadista. O estudo de caso feito na pesquisa foi no Centro de Distribuição desta rede supermercadista. O PRP consiste em determinar a menor rota a ser percorrida por um separador em um Centro de Distribuição (CD) de forma a coletar manualmente todos os produtos contidos em um determinado pedido. Tem-se como objetivo a aplicação de um modelo de Programação Linear Inteira Mista (PLIM), encontrado na literatura, e a comparação dos resultados obtidos com o atual método utilizado na empresa, a heurística SShape. Para isso, dados reais de pedidos de um determinado período foram coletados e algumas suposições relativas ao tamanho do problema e ao leiaute do CD foram feitas para gerar os 65 cenários de testes estabelecidos. Para atingir o objetivo almejado, foi necessário elaborar um algoritmo em três etapas, em linguagem de programação C#. A primeira etapa é o tratamento de dados e ajuste do leiaute para a elaboração do modelo Matemático. Com uso do solver GUROBI para a resolução dos testes, realizou-se a segunda etapa. A terceira etapa consistiu na aplicação da heurística S-Shape para possibilitar a comparação entre os métodos. As comparações entre o modelo aplicado e a heurística da empresa foram avaliadas em termos de economias (em metros) do trajeto gerado e tempo de resolução. Em 81,54% dos testes, o modelo obteve melhores resultados, gerando rotas com distâncias menores. Os outros 18,46% ambos os métodos retornaram o mesmo resultado. A melhoria média geral ficou em 8,41%. O modelo com parâmetro alterado resolveu 87,69% dos testes em até 30 minutos, considerado como tempo aceitável em termos práticos operacionais. Para os 12,31% dos testes resolvidos acima de 30 minutos, uma manipulação nos dados para contornar essa situação foi sugerida. Dessa forma, foi considerada como vantajosa a aplicação do modelo para o problema real de roteamento de pickers.Abstract: This work presents a real application of an exact model for the Picker Routing Problem (PRP), in a retail chain in the supermarket sector. The case study done in the research was in the Distribution Center of this supermarket chain. The PRP consists of determining the shortest route to be taken by a picker in a Distribution Center (DC) in order to manually collect all the products contained in a given order. The objective is to apply a Mixed Integer Linear Programming (MILP) model, found in the literature, and to compare the results obtained with the current method used in the company, the SShape heuristic. For this, actual order data for a given period was collected and some assumptions regarding the size of the problem and the CD layout were made to generate the 65 established test scenarios. To achieve the desired goal, it was necessary to develop an algorithm in three steps, in C # programming language. The first step is the data treatment and adjustment of the layout for the elaboration of the Mathematical model. Using the GUROBI solver to solve the tests, the second step was performed. The third step consisted of applying the S-Shape heuristic to make it possible to compare the methods. The comparisons between the applied model and the company's heuristic were evaluated in terms of savings (in meters) of the generated route and resolution time. In 81.54% of the tests, the model obtained better results, generating routes with shorter distances. The other 18.46% both methods returned the same result. The overall average improvement was 8.41%. The model with an altered parameter solved 87.69% of the tests within 30 minutes, considered an acceptable timeframe in operational practical terms. For the 12.31% of the tests resolved over 30 minutes, a manipulation of the data to get around this situation was suggested. Thus, it was considered advantageous to apply the model to the real problem of picker routing

Proposta de um modelo heurístico para a roteirização de empilhadeiras em um armazém de grande porte

TCC (graduação) - Universidade Federal de Santa Catarina. Campus Joinville. Engenharia de Transportes e Logística.Em um cenário econômico cada vez mais competitivo, cadeias de suprimento são desafiadas a se tornarem mais produtivas, agregando valor às atividades e assim, os custos se mantém, ou até mesmo, são reduzidos. Neste contexto, a logística deixa de ser uma área com potencial para redução de custos e passa a ser vista como capaz de ser um diferencial estratégico para as empresas. Os armazéns são um dos mais importantes nós logísticos em uma cadeia de suprimentos, não apenas pela representatividade nos custos, mas também por sua importância no equilíbrio que este pode gerar entre as demandas de vendas e a capacidade produtiva. Quando se busca maior produtividade nas atividades de um armazém, a movimentação de produtos são as que recebem maior atenção, porque representam grande parte dos custos operacionais. Este trabalho busca, por meio de um modelo heurístico baseado no algoritmo de Clark & Wright, analisar as rotas das empilhadeiras de um armazém de grande porte, procurando reorganizar as tarefas de picking e armazenamento de forma conjunta. Os resultados obtidos mostram que, dentro do modelo de trabalho empregado no armazém, não é possível captar redução nos custos com a implantação do modelo proposto

Problemas de conformación de lotes con ruteo en el acomodo y la preparación de pedidos considerando K equipos heterogéneos

Esta tesis doctoral tiene como objetivo modelar problemas de conformación de lotes con ruteo en el acomodo y la preparación de pedidos. En la preparación de pedidos, se modeló un problema que considera K equipos de materiales (EMMateriales) heterogéneos, n productos, m posiciones de almacenamiento y la condición de disponibilidad del inventario, lo cual permite superar las limitaciones detectadas en la literatura científica. De otra parte, al revisar el estado del arte del acomodo no se identificaron problemas que abordan la formación de lotes con ruteo, sino que únicamente solucionan el problema de asignación de posiciones de almacenamiento (Slotting). Para solucionar la conformación de lotes en cada uno de los problemas modelados, se desarrollaron reglas de prioridad y metaheurísticos basados en búsqueda local inteligente. En tanto, para resolver el ruteo se modelaron metaheurísticos de búsqueda tabú híbridos con estrategias de intensificación y diversificación. Las reglas y metaheurísticos para cada problema, se integraron a un WMS (Warehouse Management System) y fueron modelados considerando las características y restricciones particulares de estas operaciones del Centro de Distribución (CEDI). Diseños de experimentos (Designs of Experiment_DoE) de parcelas divididas no sólo fueron implementados para validar los problemas modelados sino también para realizar un análisis numérico exhaustivo que permitió identificar las combinaciones de niveles de los factores significativos que generan los menores tiempos promedios totales y la mayor eficiencia en el acomodo y la preparación de pedidos. El uso de diseños de parcelas divididas puede considerarse un aporte metodológico al estado del arte, ya que este enfoque no fue detectado en la literatura para resolver este tipo de problemas. A partir del análisis experimental se identificó que los metaheurísticos para la formación de lotes, INS (Intelligent Neighboorhood Search) y PNS (Picking Neighboorhood Search), generaron las mejores soluciones para el acomodo y la preparación de pedidos. De otra parte, los metaheurísticos híbridos RABTIN (Ruteo acomodo búsqueda tabú intensificación) y RUPBTDI (Ruteo preparación de pedidos búsqueda tabú diversificación) 3-Opt Inserción produjeron las mejores soluciones para el ruteo de estas operaciones.Abstract: The aim of doctoral thesis is to model and valid the order batching and routing problem in the putaway and picking operation. In the picking operation was modelled a problem, took in account K Material Handling Equipment, n products, m storage locations and a condition of available inventory. This approach contributed to overcome the gaps detected in the scientific literature. On the other hand, a significant contribution to the knowledge was achieved in the putaway operation since the batching and routing problems had not been detected in the systematic literature review (SLR) results. This is raised because the slotting problem was only approach identified for the putaway operation in the scientific literature. Priority rules and metaheuristics based on intelligent local search were developed to solve the order batching component in each modelled problem. Meanwhile, hybrid tabu search metaheuristics with intensification and diversification strategies were implemented to sort out routing component in the putaway and picking problem. In addition, the priority rules and metaheuristics developed not only were integrated a WMS (Warehouse Management System) but these were modelled considering the specific characteristics and constrains of the putaway and picking operation. A DOE (Design of Experiment) named Split Plot not only was implemented to valid the modelled problems but also performed an exhaustive numeric analysis, enabled to identify the combination of significant factors levels that generated the shortest average times and the higher efficiency in the putaway and picking operation. Split plot design could be considered a methodological contribution to the state of the art since this approach was not identified in the scientific literature for solving is kind of problems. Based on results of experiments it was detected that INS (Intelligent Neighboorhood Search) and PNS (Picking Neighboorhood Search) metaheuristics generated the best solutions for solving the order batching component in the putaway and picking operation. Meanwhile, the hybrid metaheuristics called RABTIN (Putaway routing using intensification strategy with tabu serach) and RUPBTDI (Picking routing using diversification strategy with tabu search) 3-Opt produced the best solution for sorting out the routing component of these operations.Doctorad