Zone design of specific sizes using adaptive additively weighted voronoi diagrams

Territory or zone design processes entail partitioning a geographic space, organized as a set of areal units, into different regions or zones according to a specific set of criteria that are dependent on the application context. In most cases, the aim is to create zones of approximately equal sizes (zones with equal numbers of inhabitants, same average sales, etc.). However, some of the new applications that have emerged, particularly in the context of sustainable development policies, are aimed at defining zones of a predetermined, though not necessarily similar, size. In addition, the zones should be built around a given set of seeds. This type of partitioning has not been sufficiently researched; therefore, there are no known approaches for automated zone delimitation. This study proposes a new method based on a discrete version of the adaptive additively weighted Voronoi diagram that makes it possible to partition a two-dimensional space into zones of specific sizes, taking both the position and the weight of each seed into account. The method consists of repeatedly solving a traditional additively weighted Voronoi diagram, so that each seed?s weight is updated at every iteration. The zones are geographically connected using a metric based on the shortest path. Tests conducted on the extensive farming system of three municipalities in Castile-La Mancha (Spain) have established that the proposed heuristic procedure is valid for solving this type of partitioning problem. Nevertheless, these tests confirmed that the given seed position determines the spatial configuration the method must solve and this may have a great impact on the resulting partition

Tool wear detection in dry high-speed milling based upon the analysis of machine internal signals

Unattended machining plants require intelligent monitoring systems, able to detect the different events that can happen during the machining process. In particular, the control of tool wear is an important objective of a monitoring system when dry machining is applied. This work evaluates the suitability of a tool wear monitoring system based on machine tool internal signals. It presents a sensorless monitoring procedure for the dry and high-speed milling of aerospace aluminium alloys. Dry high-speed experiments were performed using aluminium Al 7075-T6 workpieces. The sensor data from internal signals were compared and analyzed, assessing the deviation in representative variables in time and frequency domains. The signal analysis confirmed the relevance of cutting force signals for tool wear monitoring in the high-speed milling of aluminium alloys.The research was sponsored by the Basque Government project Advance Manufacturing Technologies and Coordinated by the marGUNE Cooperative Research Center. Authors wish to thank to Gorka Aramendi for the performed tests and Prof. Justino Fernández (Universidad de Navarra) for his useful help and discussions, and J.C. Yurre of Aotek for his valuable suggestions.Peer reviewe

Prediction of press/die deformation for an accurate manufacturing of drawing dies

In this work a methodological scheme for a reduction of both the try-out and lead-time of complex dies is presented. The finite element simulation of the system press/tool behaviour along the stamping process results in criteria for the best design of high-cost dies/punches. Modifications of the main geometry, components and functional parameters are so recommended. Die deflection during the pressing process is in this work investigated. With the proposed methodology die manufacturers are able to avoid errors coming from die deformation due to their asymmetrical shape. At the same time, time of manual adjustment and polishing is reduced in a 30%. Examples are deeply explained as well as experimental evidences.Peer reviewe

Machining of Large Dies Based on the Prediction of the Press/Die Deformation

This chapter presents a methodological scheme for a reduction of both the try-out and lead-time of complex dies. It describes a global methodology in order to take into account the structural behavior of the tools in the mechanical group press-die, assuming that both components are not rigid solids, and that the deformation of the press, although small, is in the order of magnitude of the manufactured part tolerance. This methodology is also tested with a sample in an industrial application, where the calculated deformation is proposed to machine the die surface. The finite element simulation of the tool behavior along the stamping process results in criteria for the best design of high-cost dies/punches. The value of the total deformation depends directly on the force for the stamping process. Using this scheme, modifications of the main geometry, components, and functional parameters are recommended. The chapter illustrates examples as experimental evidences. © 2006Peer reviewe

Analysis of ultrasonic-assisted drilling of Ti6Al4V

In this study ultrasonic vibration was applied on the drilling of Ti6Al4V workpiece samples. Several parameters of ultrasonic-assisted drilling were monitored, including feed force, chip formation by means of high-speed imaging, and temperature measurement on the drill tip by means of infrared radiation thermometry. Ultrasonic assistance offered lower feed force and higher process temperatures as compared to conventional drilling. It has also shown higher force reductions and higher temperature increments when vibration amplitude was increased.This research was sponsored by the Basque Government Project Advance Manufacturing Technologies and coordinated by the marGUNE Cooperative Research Center. Special thanks to marGUNE researches working on US, especially O. Gonzalo and R. Alberdi. Thanks are also addressed to Prof. Girot, for his valuable suggestions.Peer reviewe

MSEC/ICMMP2008-72258 LASER POLISHING PARAMETER OPTIMIZATION FOR DIE AND MOULDS SURFACE FINISHING MSEC_ICM&P2008-72258

ABSTRACT Final polishing operation for die and mould manufacturing represents up to 30% of the total manufacturing cost and it is a high added value operation carried out manually by qualified personnel. The work presented in this paper proposes an automated solution for this task by the process known as Laser Polishing. This process is based on the application of a laser beam melting a microscopic layer of material, which lately solidifies filling the gaps, and smoothing the overall topography. Several Laser Polishing tests have been done with CO 2 and High Power Diode Lasers (HPDL) on two different materials commonly used in die and mould industry: a DIN 1,2379 Tool Steel tempered up to 62HRC, used for injection moulds inserts, and a spheroidal graphite Cast Iron DIN GGG70L used typically on large stamping dies manufacturing. By means of the tests and Design of Experiments (DoE) technique, the operation parameters for the Laser Polishing process as well as its degree of influence in the melted surface have been defined. Starting off from an initial surface obtained by means of High Speed Milling operation, it has been possible to obtain satisfactory results with final roughness reductions higher than 80% with respect to the initial values, and mean roughness values below 0.8µm Ra. INTRODUCTION Actually the use of laser in the industry is almost limited to operations of cutting and welding. However, a new generation of lasers is extending the possible applications to fields like microtechnology, industry and other strategic areas One of the most emergent processes at the moment in the industry is the laser surface heat treatment and laser texturing. The development of new kind of lasers and the high requirements in the manufacturing of high added value parts makes the manufacturer consider the laser technology in spite of its high cost. Focusing on laser texturing process, it consists on the local vaporisation of material by means of the application of a relatively high energy laser beam, improving surface mechanical functionality, tribology or even aesthetic. The laser texturing process allows diverse types of applications, such as the friction reduction between cylinder and piston rings in combustion engine

Computation and experimental validation of the oblique cutting process in AL2024-T4 and AISI 4340

Oblique cutting is considered in this paper by implementing a numerical simulation model with ABAQUS/Explicit applied to two metallic materials, Al 2024-T4 and AISI 4340. An explicit algorithm for thermomechanically coupled problems is used. Two basic parts are considered: the workpiece and the cutting tool (a hard metal), this one being assumed also deformable. A thermoviscoplastic behavior is included for the workpiece by means of the Johnson-Cook law. An interface between the chip and machined workpiece is defined. Along this zone a cumulative damage failure criterion is applied and chip formation is brought about by the elimination of failing elements. Force components and temperature are analyzed in terms of different model parameters: the cutting velocity, the edge angle, the rake angle and the interface thickness. Several hollow cylinders have been turned for the results validation. Forces and temperature are measured by means of a piezoelectric platform and a thermographic camera, respectively. Force components in the cutting and normal direction fit well with numerical results. The effect of the cutting parameters in temperature variation is also in agreement with the numerical simulations.Peer reviewe

Effect of process parameter on the kerf geometry in abrasive water jet milling

This research work introduces a model to predict the kerf profile in abrasive water jet slot milling in aluminium 7075-T651. The experimentation allowed modelling the maximum cutting depth and the width at the half of maximum depth in terms of four process parameters: pressure, abrasive mass flow rate, stand-off distance, and traverse feed rate. It is shown that the introduction of the maximum depth and the width at the half of maximum depth in a Gaussian function is suitable to describe the kerf profile. The definition of an equivalent traverse feed rate at every instant along the jet trajectory introduces the effect of the jet acceleration in the model. Thus, the model is capable of predicting the kerf profile at constant traverse feed rate and at variable traverse feed rate due to direction changing trajectories. The variations of cutting depth along a slot are also studied in order to avoid the cutting parameters combinations which lead to low repetitiveness conditions and then irregular milling surfaces.Peer reviewe

Approximate Solutions of Delay Differential Equations with Constant and Variable Coefficients by the Enhanced Multistage Homotopy Perturbation Method

We expand the application of the enhanced multistage homotopy perturbation method (EMHPM) to solve delay differential equations (DDEs) with constant and variable coefficients. This EMHPM is based on a sequence of subintervals that provide approximate solutions that require less CPU time than those computed from the dde23 MATLAB numerical integration algorithm solutions. To address the accuracy of our proposed approach, we examine the solutions of several DDEs having constant and variable coefficients, finding predictions with a good match relative to the corresponding numerical integration solutions