Development of working procedures of a 5 Axis CNC milling machine

Dissertação de mestrado em Mechanical EngineeringThe work developed and presented on this dissertation tends to the installation and configurations of a 5-axis CNC machine with the creation of working procedures intended to build a stable workflow that can be employed by any individual expected to use the machine. Being a large field within mechanical engineering as well as being involved in a large selection of different industrial sectors, the concept of 5-axis machining will be explored to develop knowledge in terms of CAM programming and manipulation/optimization of toolpaths. The importance/functioning of the transmission of information both from post-processor to the controller and from the controller to the actual machine is also a critical point in this work as they are directly related to the quality of the parts produced. To accomplish this, the theoretical knowledge foundations regarding CNC machining work were researched, studied, and explained. Furthermore, the machine model in question (HY-6040 5-axis CNC Router) was meticulously analysed regarding to the machines structure, post-processor, and controller. Upon assembling all this information, and through the production of some test parts, a permanent manufacture workflow for different machining approaches was established and described.O trabalho desenvolvido e apresentado nesta dissertação tende à instalação e configuração de uma máquina CNC de 5-eixos, com a criação de procedimentos de trabalho destinados a criar um fluxo de trabalho estável que possa ser empregue por qualquer individuo que pretenda utilizar a máquina. Sendo um grande campo dentro da engenharia mecânica e estando também envolvido numa grande seleção de diferentes setores industriais, o conceito de maquinagem em 5-eixos será explorado com a finalidade de desenvolver conhecimentos a nível de programação CAM e manipulação/otimização de trajetórias de corte. A importância/funcionamento da transmissão de informação quer do pôs-processador para o controlador, quer do controlador para a máquina constituem também um ponto critico neste trabalho já que estão diretamente relacionados com a qualidade das peças produzidas. Para a realização de tal, foram pesquisados, estudados e explicados os fundamentos do conhecimento teórico relativamente ao trabalho de maquinagem CNC. Para além disso, o modelo da máquina em questão (HY-6040 5-axis CNC Router) foi meticulosamente analisado quanto à estrutura da máquina, pós-processador e controlador. Após reunir toda esta informação, e través da produção de peças teste, foi estabelecido um fluxo de trabalho de manufatura (CAD/CAM/Maquinagem) para diferentes abordagens de maquinagem

A basis for the representation, manufacturing tool path generation and scanning measurement of smooth freeform surfaces

Freeform surfaces find wide application, particularly in optics, from unique single-surface science programmes to mobile phone lenses manufactured in billions. This thesis presents research into the mathematical and algorithmic basis for the generation and measurement of smooth freeform surfaces. Two globally significant cases are reported: 1) research in this thesis created prototype segments for the world’s largest telescope; 2) research in this thesis made surfaces underpinning the redefinition of one of the seven SI base units – the kelvin - and also what will be the newly (and permanently) defined value for the Boltzmann constant. Theresearchdemonstratestwounderlyingphilosophiesofprecisionengineering, the critical roles of determinism and of precision measurement in precise manufacturing. The thesis presents methods, and reports their implementation, for the manufacture of freeform surfaces through a comprehensive strategy for tool path generation using minimum axis-count ultra-precision machine tools. In the context of freeform surface machining, the advantages of deterministic motion performance of three-axis machines are brought to bear through a novel treatment of the mathematics of variable contact point geometry. This is applied to ultra-precision diamond turning and ultra-precision large optics grinding with the Cranfield Box machine. New techniques in freeform surface representation, tool path generation, freeform tool shape representation and error compensation are presented. A comprehensive technique for very high spatial resolution CMM areal scanning of freeform surfaces is presented, with a new treatment of contact error removal, achieving interferometer-equivalent surface representation, with 1,000,000+ points and sub-200 nm rms noise without the use of any low-pass filtering

A multi-objective prediction and optimisation method for additive manufacturing technology

Cleaner production in a sustainable and customised industrial environment has gradually become the focus of attention in industrial manufacturing. Additive manufacturing (AM) proposes a revolutionary paradigm for customised engineering design and manufacturing, attributed to its design freedom with limitless structural constraints. As an emerging manufacturing technology, most manufacturers and researchers are dedicated to the innovation of AM’s manufacturing mechanism and the improvement of part quality. However, the understanding of this emerging manufacturing technology is not yet sufficient in the resource efficiency perspective, which includes three environmental dimensions, namely production time, electrical energy consumption and material usage. In order to improve AM’s resource efficiency, this thesis aims to provide a general modelling scheme to predict time, energy and material consumptions of the AM process, utilise meta-heuristic algorithms to optimise the process parameters of AM, and minimise the three consumptions (i.e. time, energy and material). A hybrid data-driven and physics-based modelling method is proposed to build up the predictive models of AM’s time, energy and material consumptions. To start with, all consumption-related components of the existing AM technologies are classified into five types of module: axis movement, material processing, material feeding, component heating and auxiliary components. Then, hybrid modelling is performed on each module to obtain the relationships between the consumptions and process parameters. In physics-based modelling, the time, distance of axis movement and amount of material usage are calculated from the computer numerical control (CNC) programming language (also named G-code). In data-driven modelling, the remaining parameters are measured through experiments. A power meter is used to measure the apparent power and time of each module under different process parameters. The relationships between the measured parameters and process parameters are derived through regression analysis methods. In addition, some parameters in the predictive models are affected by the characteristics of machine and material in a practical manufacturing context. For example, the actual speed of axis movement is affected by the high loads of stepper motors during high-speed printing. To further improve the prediction accuracy, additional experiments are conducted to test the actual values of affected parameters. The nature of additional experiments is determined by the machine characteristics. Meta-heuristics are developed to approximate the Pareto front of process parameters that consume the least time, energy and material. The predictive models are used as three objective functions to evaluate the performance of each solution of process parameters. Since the non-dominated sorting genetic algorithm (NSGA-II) has been widely used to solve optimisation problems with two or three objectives in industrial manufacturing, this study improves and applies NSGA-II to this optimisation problem. Experiments are designed to perform the optimisation under different combinations of optimisation parameters. A set of Pareto fronts is obtained. Hypervolume (HV) indicator is used to compare all obtained Pareto fronts before finally selecting the optimum solution sets of process parameters. In a practical manufacturing context, the optimisation result can provide guidance and a trend for selecting a feasible solution of process parameters. To validate the effectiveness of the prediction and optimisation method, two case studies are conducted on two different types of fused deposition modelling (FDM) 3D printers. The predictive models of time, energy and material consumptions for each printer have been built by following the proposed prediction method. To improve the prediction accuracy, additional experiments are performed on both FDM 3D printers, including testing the actual speed of axis movement and the actual density of thermoplastic material. According to the prediction results and experimental results, the feasibility of prediction models has been proved, which achieves an acceptable prediction accuracy. The consideration of machine characteristic has also been proved to further improve the prediction accuracies. The effectiveness of the optimisation method using NSGA-Ⅱ are also verified in two case studies. To evaluate and compare the qualities of obtained Pareto fronts, the hypervolume (HV) indicator has been used as the response of each optimisation test. The non-dominated iv solutions of the Pareto front that has the maximum HV indicator are the optimum solutions for the AM task. This result can provide guidance for setting a feasible combination of process parameters in the prefabrication stage. The optimal solutions of process parameters are compared with the default setting of process parameters. The comparison results prove that the consumptions of optimal solutions are significantly reduced. Furthermore, the significances of optimisation parameters (i.e. population size, number of generations, crossover probability and mutation probability) for the response are analysed by using the range analysis and analysis of variance (ANOVA) methods. According to the analysis results, the significances of optimisation parameters for the HV indicator are not found to be consistent in these two cases. Since the predictive models are customised, there is no general rule to recommend the setting of process parameters and optimisation parameters for general AM technologies. The proposed prediction and optimisation methods provide a modular, customisable and flexible interface to personalise the predictive models, the optimisation objectives and the process parameter to be optimised. The method fully considers the characteristics of AM machine and material, process parameters, production environment, and customer demands. The use of manufacturing information provided by G-code significantly reduces the workload of the modelling process and achieves an acceptable prediction accuracy. Furthermore, the proposed method is unrestricted to any AM machine, task or complex structure of CAD design, and is also applicable to any other manufacturing technologies that fabricate through numerical control (NC) programming

Chemical Symmetry Breaking

This book entitled “Chemical Symmetry Breaking” is a collective volume of state-of-the-art reports on unique nonlinear chemical and physical symmetry-breaking phenomena that were experimentally observed upon a thermally or photochemically induced phase transition in various organic condensed phases, such as metastable liquid crystals, crystals, amorphous solids, and colloidal polymer materials, only under nonequilibrium conditions. Each author summarizes the introductory section in simple terms but in detail for beginners in this field. We wish that many readers familiarize themselves with the general concepts and features of nonlinear and nonequilibrium (or out of equilibrium) complexity theory, which govern a variety of unique dynamic behaviors observed in chemistry, physics, life science and other fields, so that they may discover novel symmetry-breaking phenomena in their own research areas

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen

Proceedings of the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008

This volume contains full papers presented at the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008, held in Braga, Portugal, between September 4th and 6th, 2008.FC