Operational Research Commons^™

Optimizing The Rearrangement Process In A Dedicated Warehouse, Hector J. Carlo, German E. Giraldo

11th IMHRC Proceedings (Milwaukee, Wisconsin. USA – 2010)

Determining the optimal storage assignment for products in a dedicated warehouse has been addressed extensively in the Facility Logistics literature. However, the process of implementing a particular storage assignment given the current location of products has not received much attention in the existing literature. Typically, warehouses use downtime or overtime to remove products from their current location and move them to the suggested location. This work presents the Rearrange-While-Working (RWW) policy to optimize the process of rearranging a dedicated warehouse. The RWW policy seeks to relocate products in a warehouse from the initial arrangement to the optimal arrangement while serving …

A New Milp Approach For The Facility Layout Design Problem With Rectangular And L/T Shaped Departments, Yossi Bukchin, Michal Tzur

11th IMHRC Proceedings (Milwaukee, Wisconsin. USA – 2010)

In this paper we propose a new approach for the facility layout problem (FLP) and suggest new mixed-integer linear programming (MILP) formulations. The proposed approach considers simultaneously the location of the departments within the facility and the internal arrangement of the machines. Two models are suggested, where the first addresses the rectangular department case and the second allows nonrectangular departments defined by an L/T shape. New regularity constraints are developed to avoid irregular department shapes.

Strategic Design Of A Robust Supply Chain, Marc Goetschalckx, Edward Huang

11th IMHRC Proceedings (Milwaukee, Wisconsin. USA – 2010)

The strategic design of a robust supply chain has as goal the configuration of the supply chain structure so that the performance of the supply chain remains of a consistently high quality for all possible future scenarios. We model this goal with an objective function that trades off the central tendency of the supply chain profit with the dispersion of the profit as measured by the standard deviation for any value of the weights assigned to the two components. However, the standard deviation, used as the dispersion penalty for profit maximization, has a square root expression which makes standard maximization …

Evaluating The Effect Of Operational Conditions And Practices On Warehouse Performance, Andrew L. Johnson

11th IMHRC Proceedings (Milwaukee, Wisconsin. USA – 2010)

Analyzing warehouse performance across different environments is critical to improving overall productivity and reducing costs. Although two-stage DEA estimators have been shown to be statistically consistent, the finite sample bias of DEA in the first stage carries over to the secondstage regression, which causes bias in the estimated coefficients of the contextual variables. The bias is particularly severe when the contextual variables are correlated with inputs. To address this shortcoming, we apply insights from Johnson and Kuosmanen (2010), who demonstrate that DEA can be formulated as a constrained special case of the Convex Nonparametric Least Squares (CNLS) regression to develop …

Comparing Transport Policies In A Full-Scale 300mm Wafer Manufacturing Facility, J. E. Kiba, S. Dauz`Ere-P´Er`Es, C. Yugma, G. Lamiable

11th IMHRC Proceedings (Milwaukee, Wisconsin. USA – 2010)

Research in semiconductor manufacturing ideally wants to determine the “best” transport policy to ensure continuous production. Determining such a policy is difficult because it depends on many factors such as the layout, the product types, the equipment, etc. Most of the transport policies found in the literature combine dispatching policies (scheduling of transport requests) and routing policies (selection of the path to move from one point to another). This paper investigates a policy called "minimum service" which consists in keeping a minimum number of available vehicles in bays, so that they can quickly answer transport requests and empty travel times …

The Human-Centric Warehouse, Kevin R. Gue

11th IMHRC Proceedings (Milwaukee, Wisconsin. USA – 2010)

In theory and in practice, the objective of warehouse design has long been to meet operational requirements of throughput and service performance at minimum cost. A natural product of this “bottom line” approach has been warehouse buildings and operations ill-suited to the humans who spend their working lives interacting with them. We offer an explanation for the current approach, and argue that a new approach— a new paradigm —is needed. We then describe a comprehensive approach to warehouse design that includes human well-being as a primary goal.

Forklift Routing In Warehouses Using Dual-Commands And Stackable Pallets, Ahmed Hassan, Bill Ferrell

11th IMHRC Proceedings (Milwaukee, Wisconsin. USA – 2010)

This research determines time optimal routes for loading and picking pallets that can be stacked on top of each other during transport in a manual warehouse that only contains full pallets and utilizes single deep storage. This research was motivated by the fact that we are seeing this situation on an ever increasing basis, particularly in warehouses that supply parts to automotive assembly. In practice, forklift drivers have developed strategies to take advantage of this opportunity but to our knowledge there is no literature that addresses this problem rigorously. The important features of this work are that a time based …

Plug-And-Work Material Handling Systems, Kai Furmans, Frank Schonung, Kevin R. Gue

11th IMHRC Proceedings (Milwaukee, Wisconsin. USA – 2010)

One disadvantage of automated material handling systems is their relative Inflexibility: once racks are installed and conveyors are laid, making even mi-nor changes to a system can be cumbersome and expensive. However, recent progress in the capabilities and cost of basic system components, such as controllers, drives, and sensors, has made possible a new class of material handling systems having a much higher degree of flexibility. We propose underlying de- sign principles for such systems and describe several prototype plug-and-work" systems, which feature decentralized control and ease of reconfiguration.

Control Policies For A Dynamic Storage System With Multiple Lifts And Shuttles, Iris F.A. Vis, Hector J. Carlo, Paloma Diaz, Maria E. Laboy, Bruno Vanwijgaarden

11th IMHRC Proceedings (Milwaukee, Wisconsin. USA – 2010)

New types of Automated Storage and Retrieval Systems, able to achieve high throughput levels, are continuously being developed and require new control polices to take full advantage of the developed system. In this paper we study a dynamic storage system as developed by Vanderlande Industries consisting of a conveyor, two lifts, multiple transfer shuttles, and a storage rack. One of the decision problems for this system is the scheduling problem of the two lifts. In other words, which lift is going to handle which request and in which order. In this paper, we derive an integrated look-ahead heuristic based on …

Optimization Models And Algorithms For Spatial Scheduling, Christopher J. Garcia

Engineering Management & Systems Engineering Theses & Dissertations

Spatial scheduling problems involve scheduling a set of activities or jobs that each require a certain amount of physical space in order to be carried out. In these problems space is a limited resource, and the job locations, orientations, and start times must be simultaneously determined. As a result, spatial scheduling problems are a particularly difficult class of scheduling problems. These problems are commonly encountered in diverse industries including shipbuilding, aircraft assembly, and supply chain management. Despite its importance, there is a relatively scarce amount of research in the area of spatial scheduling.

In this dissertation, spatial scheduling problems are …

Investigating An Optimal Decision Point For Probability Bounds Analysis Models When Used To Estimate Remedial Soil Volumes Under Uncertainty At Hazardous Waste Sites, Charles O. Dankwah

Walden Dissertations and Doctoral Studies

Hazardous waste site remediation cost estimation requires a good estimate of the contaminated soil volume. The United States Environmental Protection Agency (U.S. EPA) currently uses deterministic point values to estimate soil volumes but the literature suggests that probability bounds analysis (PBA) is the more accurate method to make estimates under uncertainty. The underlying statistical theory is that they are more accurate than deterministic estimates because probabilistic estimates account for data uncertainties. However, the literature does not address the problem of selecting an optimal decision point from the interval-valued PBA estimates. The purpose of this study was to identify the optimal …