The aim of this paper is to introduce a practice-ready systematic methodology for the management of storage assignments and allocation decisions as well as an assessment of the resulting performance ...in an order picking system (OPS). Built on extant and well-known metrics of performance this method implements a double cross-analysis through an original visual tool that is easy to understand by warehousing managers and practitioners. This tool is organized in two main steps. The first step is a cross-analysis that combines multiple performance indicators to help the decision-maker understand whether an OPS provides the scope for performance improvement. A comparison with potential storage configurations is then conducted in the second step through a tailored multi-scenario cross-analysis, which attempts to identify the best combination of allocation and assignment policies capable of minimizing the overall traveling performance. The proposed methodology is applied to a significant real-world OPS. The selected case study represents a reference framework for decision-makers and practitioners.
Manual "picker-to-part" order picking takes place in a labour-intensive and time-consuming working environment where humans are the central actors and co-determine the effectiveness and efficiency of ...the process. Throughout Europe, work-related musculoskeletal disorders affect millions of workers, especially in the logistics sector, and cost employers billions of euros.
This paper studies how order pickers relate the use of technology as well as their relationship with the logistics company to their well-being, health and productivity.
To obtain data, a survey consisting of questions regarding work characteristics, health problems and the logistics company's relationship with employees was conducted in Poland, Slovenia and Croatia.
Workers who carry most items manually experience more health problems than cart and forklift users. The most common complaint is lower back pain - only 6% of order pickers (n = 221) never experienced it. The use of barcode or RFID scanner/terminal/smart phone correlates with more health problems than the use of other technologies. Participation in the selection of transport means or in training on health preservation can reduce the perceived health problems.
Workers' perception of the impact of the applied technology on health and productivity can differ from the impact that is calculated or measured. Through their relationship with employees, logistics companies can influence employees' perception of their health problems.
This paper deals with the problem of assigning warehouse space to inventory items in a low level picker-to-part system. Recognizing the importance of weights in material handling activities in ...warehouse, a linear programming model is developed with the objective of minimizing the workload required for order picking operations. It is proved that the stock location rule proposed in this paper generates an optimal solution for the model. Compared with the well known cube-per-order index (COI) rule, it is shown that the proposed rule is substantially better from the view point of human safety with some sacrifice of throughput.
•We proposed a multi-pickers-based scattered storage location assignment (MPSSLA).•Pickers’ working process are modelled as a space–time network.•A cooperative optimisation algorithm are designed to ...find the optimal solution.•MPSSLA outperforms existing storage assignment strategies under various situations.•Managerial implications of this study are derived.
Congestion always occurs in the multi-pickers picker-to-parts picking systems. In this paper, we propose a multi-pickers-based scattered storage location assignment (MPSSLA) strategy. To reduce the probability of congestion and working time of pickers, MPSSLA allows the same stock keeping units (SKUs) to be stored in multiple storage locations. Additionally, it assigns SKUs with high and middle demand correlations to storage locations that are as close as possible to each other. Moreover, a route adjustment method that considers congestion is proposed to adjust the working routes. This further improves the picking efficiency. The working process of pickers in MPSSLA is modelled as a space–time network and an algorithm is designed to determine the optimal solution. Through numerical experiments, the applicability and effectiveness of MPSSLA are analysed considering several main factors. The results show that the proposed algorithm is highly efficient and MPSSLA can achieve better optimisation results than the traditional centralised storage strategy in the multi-pickers picker-to-parts picking system. The proposed storage location assignment strategy can improve the warehouse operation efficiency of the multi-pickers picker-to-parts picking systems with high demand skewness and a large number of pickers.
The warehouse is one of the essential components of logistics and supply chains. The efficiency of the whole chain is affected by the performance of warehouse operations and, more particularly, the ...storage and retrieval of goods. This paper considers a storage and retrieval problem in a real warehouse with random storage and different types of forklifts, depending on the locations they can access. The problem deals with selecting locations to store/retrieve a predefined set of pallets, assigning an adequately skilled forklift to each operation and determining the order in which each forklift will perform its operations so that the total employed time is minimized. The problem is solved heuristically by decomposing it into three subproblems, each one handling one of the three key decisions of the problem, and taking into account congestion considerations. The paper also studies two modifications of the problem, adding secondary objective functions. Computational results compare the effectiveness of the proposed algorithms for the different problems in a stochastic environment via simulation.
Order picking is a time-intensive and costly logistics process as it involves a high amount of manual human work. Since order picking operations are repetitive by nature, it can be observed that ...human workers gain familiarity with the job over time, which implies that learning takes place. Even though learning may be an important source of efficiency improvements in companies, it has largely been neglected in planning order picking operations. Mathematical planning models of order picking that have been published earlier thus provide an incomplete picture of real-world order picking, which affects the quality of the planning outcome. To contribute to closing this research gap, this paper presents an approach to model worker learning in order picking. First, the results of a case study are presented that emphasize the importance of learning in manual order picking. Subsequently, an analytical model is developed to describe learning in order picking, which is then evaluated with the help of numerical examples. The results show that learning impacts order picking efficiency. In particular, the results imply that worker learning should be considered when planning order picking operations as it leads to a better predictability of order throughput times. In addition, the effects of learning are relevant for the allocation of available resources, such as the allocation of workers to different zones of the warehouse. The results of the numerical analysis indicate that it is beneficial to assign workers with the lowest learning rate in the workforce to the fastest moving zone to gain experience.
This paper investigates manual order picking, where workers travel through the warehouse to retrieve requested items from shelves. To minimise the completion time of orders, researchers have ...developed various routing procedures that guide order pickers through the warehouse. The paper at hand contributes to this stream of research and proposes an optimal order picker routing policy for a conventional warehouse with two blocks and arbitrary starting and ending points of a tour. The procedure proposed in this paper extends an earlier work of Löffler et al. (2018. Picker routing in AGV-assisted order picking systems, Working Paper, DPO-01/2018, Deutsche Post Chair-Optimization of Distribution Networks, RWTH Aachen University, 2018) by applying the concepts of Ratliff and Rosenthal (1983. "Order-picking in a Rectangular Warehouse: a Solvable Case of the Traveling Salesman Problem." Operations Research 31 (3): 507-521) and Roodbergen and de Koster (2001a. "Routing Order Pickers in a Warehouse with a Middle Aisle." European Journal of Operational Research 133 (1): 32-43) that used graph theory and dynamic programming for finding an optimal picker route. We also propose a routing heuristic, denoted S*-shape, for conventional two-block warehouses with arbitrary starting and ending points of a tour. In computational experiments, we compare the average order picking tour length in a conventional warehouse with a single block to the case of a conventional warehouse with two blocks to assess the impact of the middle cross aisle on the performance of the warehouse. Furthermore, we evaluate the performance of the S*-shape heuristic by comparing it to the exact algorithm proposed in this study.
•The paper concerns the decision on how to store items within the forward area.•The choice is between carton from pallet picking and carton from rack picking.•The mathematical model proposes a ...convenience condition applicable at item level.•The convenience condition is part of the carton picking convenience decision-making method.•The methodology is also applied in a real industrial case study.
In a manual picker-to-parts picking warehouse, a usual approach is to divide the whole stocking area in two different zones, the reserve and the forward areas. The dimensioning of the forward area, which is dedicated to picking activities, has an important impact on the overall performance of the picking system. Indeed, its size as well as the item allocation deeply influence the travel time of the operators on one side and the frequency of the refilling activities on the other. The present paper aims to provide a new method that can be easily used to assess the most suitable way of storing a product in the forward area, considering the possibility of keeping a product directly in a pallet or storing it in racks. Starting from simple data, such as the picking orders of the items to pick and their physical dimensions, as well as the characteristics of the warehouse, the method focuses on the comparison of the total times to define the Carton Pick from rack Convenience Condition (CPCC). The CPCC formulation and its application methodology allow to quickly establish which items should be stored on pallets and which on racks, with interesting impacts on space and time savings. This is shown also in the reported case study, the results of which prove the effectiveness as well as the easy and full applicability of the methodology, also in different warehouse contexts.
Online order picking has become one of the key issues for ensuring the service level of modern retail e-commerce. This paper studies the online order batching and batch assignment problem (OOBBAP) ...with multiple pickers of picker-to-parts warehouses. First, we establish a biobjective optimization model that minimises the total picking time and order response time. Then, an online order batching algorithm embedded with the sequencing algorithm and optimal path algorithm is designed to solve the model. Finally, we use retail e-commerce from China with data on 87,277 orders of an online shopping festival to examine the optimization results of the model. The optimization results of the key indicators are satisfactory. The optimization rates of the maximum order response time, average order response time, total picking time, average picking time of picking posts, picker total walking distance and average walking distance are between 7.45% and 30.20%. The model demonstrates an excellent ability to solve the OOBBAP in multiple picker warehouses, which can provide a reference solution for similar picking problems in picker-to-parts retail e-commerce warehouses.
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