M.Ing. / This dissertation documents the stages involved in determining the parameters that define surface integrity. Chapter one gives a basic introduction to the project; the problem statement; scope of work and project obstacles. This chapter laid down the requirements for the literature study in Chapters two and three. The literature study discusses machining, high-speed machining, titanium alloys and high speed machining of titanium alloys. Information from the literature study was used to determine the experimental program presented in Chapter 4. Two materials were investigated in this study: grade 2 titanium (commercially pure) and grade 5 titanium (an alloy containing 6% Aluminium and 4% Vanadium). A fixed feed rate of 0.25mm/rev was selected. Two depths of cut were used: 0.2mm and 1mm. Cuts were performed both lubricated and un-lubricated. Different cutting speeds were used both inside and outside recommended ranges. Surface roughness tests, optical microscopy, scanning-electron microscopy, microhardness tests and x-ray diffraction were used in the experimental program. Results obtained presented trends seen in previous work on surface integrity. Efforts were made to reduce errors in obtaining and examining data. Conclusions were drawn with regards to each surface integrity parameter tested for. It was found that different cutting speeds affect each surface integrity parameter differently.

This thesis presents numerical and experimental investigations into Electrochemical Machining (ECM). The aim is to develop a computer program to predict the shape of a workpiece machined by the ECM process. The program is able to simulate various applications of EC machining which are drilling, milling, turning and shaped tube electrochemical drilling (STED). The program has been developed in a MATLAB environment. In this present work, EC-drilling, EC-milling and EC-turning are analysed as three-dimensional problems whereas STED is simulated in two-dimensions. Experiments have been carried out to verify the accuracy of the predicted results in the cases of EC-milling and EC-turning. The ECM modeller is based on the boundary element method (BEM) and uses Laplace's equation to determine the current distribution at nodes on the workpiece surface. In 3D, the surfaces of the tool and the workpiece are discretised into continuous linear triangular element types whereas in 2D, the boundaries of the tool and workpiece are discretised into linear elements. The ECM modeller is completely self-contained, i.e. it does not rely on any other commercial package. The program contains modules to automatically discretize the surfaces/boundaries of the tool and workpiece. Since the simulation of the ECM process is a temporal problem, several time steps are required to obtain the final workpiece shape. At the end of each time step, the shape of the workpiece is calculated using Faraday's laws. However, the workpiece's shape changes with progressing time steps causing the elements to become stretched and distorted. Mesh refinement techniques are built in the ECM modeller, and these subdivide the mesh automatically when necessary.The effect of time step on the predicted 3D shape of a hole in EC-drilling is investigated. The effect of discontinuity in the slope between neighbouring elements is also studied. Results obtained from the ECM modeller are compared with 2D analytical results to verify the accuracy that can be obtained from the ECM modeller. Milling features ranging from a simple slot to a pocket with a complex protrusion were machined in order to determine the feasibility of the EC milling process. These features were machined on a 3-axes CNC machine converted to permit EC milling. The effect of tool geometry, tool feed rate, applied voltage and step-over distances on the dimensions, shape and surface finish of the machined features were investigated. A pocket with a human shape protrusion was machined using two different types of tool paths, namely contour-parallel and zig-zag. Both types resulted in the base surface of the pocket being concave and the final dimensions of the pockets are compared with the design drawing to determine the effect of tool path type on the accuracy of machining. The ECM modeller was used to simulate the machining of a thin-walled turned component. The machining parameters, i.e. initial gap, rotational speed, and applied voltage, were specified by the collaborating company. Since only a small amount of material had to be removed from the thin-walled component, the tool was held stationary i.e. a feed in the radial or longitudinal direction was not required. By taking advantage of the axi-symmetric nature of a turned component, only a sector of the component was analysed thereby reducing the computing time considerably. The accuracy of the modeller was verified by comparing the predicted time to machine the thin-walled component with the actual machining time. The initial investigations in STED were both experimental and numerical in nature and they studied the effect of applied voltage, tool feed rate and electrolyte pressure on the dimensions of the holes. Later investigations were numerical and an iterative methodology has been developed to calculate a set of feed rates which could machine a specified turbulator shape.

The ultimate goal in the manufacturing of a part is to achieve an economic production plan with precision and accuracy in the first attempt at machining. A physics-based comprehensive modeling of the machining processes is a fundamental requirement in identifying optimal cutting conditions which result in high productivity rates without violating accuracy throughout the part production process. This thesis presents generalized virtual simulation and optimization strategies to predict and optimize performance of milling processes up to 3-axis. Computationally efficient mathematical models are introduced to predict milling process state variables such as chip load, force, torque, and cutting edge engagement at discrete cutter locations. Process states are expressed explicitly as a function of helical cutting edge - part engagement, cutting coefficient and feedrate. Cutters with arbitrary geometries are modeled parametrically, and the intersection of helical cutting edges with workpiece features are evaluated either analytically or numerically depending on geometric complexity. The dynamics of generalized milling operations are modeled and the stability of the process is predicted using both time and frequency domain based models. These algorithms enable rapid simulation of milling operations in a virtual environment as the part features vary. In an effort to reduce machining time, a constraint-based optimization scheme is proposed to maximize the material removal rate by optimally selecting the depth of cut, width of cut, spindle speed and feedrate. A variety of user defined constraints such as maximum tool deflection, torque/power demand, and chatter stability are taken into consideration. Two alternative optimization strategies are presented: pre-process optimization provides allowable depth and width of cut during part programming at the computer aided manufacturing stage using chatter constraint, whereas the post-process optimization tunes only feedrate and spindle speed of an existing part program to maximize productivity without violating physical constraints of the process. Optimized feedrates are filtered by considering machine tool axes limitations and the algorithms are tested in machining various industrial parts. The thesis contributed to the development of a novel 3-axis Virtual Milling System that has been deployed to the manufacturing industry. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

With the increase in the application of ultra-precision manufactured parts and the absence of much participation of researchers in ultra-high precision grinding of optical glasses which has a high rate of demand in the industries, it becomes imperative to garner a full understanding of the production of these precision optics using the above-listed technology. Single point inclined axes grinding configuration and Box-Behnken experimental design was developed and applied to the ultra-high precision grinding of BK7 glass. A high sampling acoustic emission monitoring system was implemented to monitor the process. The research tends to monitor the ultra-high precision grinding of BK7 glass using acoustic emission which has proven to be an effective sensing technique to monitor grinding processes. Response surface methodology was adopted to analyze the effect of the interaction between the machining parameters: feed, speed, depth of cut and the generated surface roughness. Furthermore, back propagation Artificial Neural Network was also implemented through careful feature extraction and selection process. The proposed models are aimed at creating a database guide to the ultra-high precision grinding of precision optics.

Current manufacturing research aims at increasing productivity by optimal selection of process parameters. This is accomplished by understanding the fundamental physics of individual manufacturing processes. In this thesis, peripheral milling of very flexible cantilevered plates is studied. The static and dynamic deflections of the plate under periodic milling forces are modelled. A new dynamic cutting force model is developed which considers five discrete zones of relative motion between the tool and the workpiece. The kinematics of both milling and vibratory motions are modelled, which is an original research contribution in this area. It is shown that the penetration of the tool into the workpiece during vibratory cutting has a strong influence on the damping and stiffness characteristics of the milling process. A structural model of a discontinuous cantilevered plate is determined using the finite element method. A reduced order structural model at the tool-workpiece contact zone is implemented for discrete time response analysis of the plate under cutting force excitations during milling. The closed loop dynamic behaviour of the system is modelled and taken into account in the analysis. Simulations of plate machining are compared with experimental results. A model of the surface finish generation mechanism is deduced from the analysis and experimental results. Applications of this research include peripheral milling of integral jet engine impellers, computer disk drives and other flexible mechanical components. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The development of unmanned machining systems has been a recent focus of manufacturing research. Computer Numerical Control (CNC) units, which monitor and control many tightly coupled machining tasks, are inseparable parts of the unmanned manufacturing system. This thesis addresses the detailed design and analysis of a modular CNC system for a milling machine. The feed drive control system of the machine tool is thoroughly studied. The mathematical model for the feed drive control system, which consists of a motion controller, power amplifiers and DC-servo motors, is developed and experimentally verified. A method of estimating cutting forces from current drawn by feed drive motors is developed. The viability of the current sensor as a feeding-force sensing component is illustrated and experimentally tested on the milling machine. Successful application of the current sensor to tool breakage detection in milling operation is presented. The performance of the multi-axis contouring system in precision machining is discussed. The contouring errors induced by feed drive positioning systems in CNC machine tools is investigated using the state space model of the CNC system. The influence of the cutting force on the accuracy of machining is shown to be negligible for feed drives driven by ball leadscrews. Various control strategies for the improvement of machining accuracy are tested in the simulation studies. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Orientador: Anselmo Eduardo Diniz / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-28T09:40:41Z (GMT). No. of bitstreams: 1 Castanhera_IsabeladaCosta_M.pdf: 4815385 bytes, checksum: a3fe6159dcb93e0e05191d8e898977e9 (MD5) Previous issue date: 2015 / Resumo: Na década de 1970, o fresamento de materiais, sobretudo aços, endurecidos a mais de 45 HRC era desaconselhado, visto que a usinabilidade de aços tende a diminuir com o aumento de dureza. Com investimentos em máquinas-ferramenta e materiais de ferramenta, o fresamento de aços endurecidos tornou-se aconselhável, tanto para formas geométricas mais simples quanto para formas geométricas complexas, pois os centros de usinagem alcançam maiores rotações e eixos de posicionamento e usinagem. Para tanto, toda a estrutura destas máquinas-ferramentas é reforçada. As ferramentas apresentam materiais mais nobres e coberturas mais resistentes e tenazes. O fresamento do tipo high speed machining é utilizado principalmente para a usinagem de moldes e matrizes, tanto para abertura das cavidades, quanto para usinagem em acabamento fino, substituindo, quando possível, o processo de eletroerosão. Para a usinagem de uma superfície curva de aço ferramenta para trabalho a frio AISI D6, as estratégias de trajetória de ferramenta escolhidas podem afetar de modo significativo o acabamento da peça e a vida de ferramenta alcançada, sendo a estratégia descendente, que trabalha com menores diâmetros efetivos de corte, a estratégia que proporcionou as melhores vidas de ferramenta. A inclinação de ferramenta, para que se evite o contato do centro da fresa do tipo ball nose, pode apresentar grande influência no acabamento superficial, com rugosidade baixa ou rugosidade alta, sem garantia de que a simples inclinação da ferramenta apresenta contribuição positiva à rugosidade. A inclinação da ferramenta apresenta contribuição na forma de manifestação da vibração durante o corte. A vibração que resulta em diferentes forças com que cada dente corte o cavaco apresenta a maior influência na rugosidade / Abstract: In 1970 decade, milling harder than 45 HRC steels was inadvisable because of the low machinability. The investments in machining centers enabled the hardened steels milling for simple geometries or complex geometries workpieces, because the spindle speed and the extra axis for positioning and machining. The machine structure is enhanced. Tool materials are advanced, sub micrometric grain size cemented carbide and resistant tool coating. High speed machining is utilized principally in molds and dies machining for cavities opening or super finishing, reducing production time, costs reduction and EDM process substitution. In a tool steel AISI D6 hardened at 60 HRC curve surface milling, the chosen tool path strategy may affect surface finish and tool life. Downward cut, which works in lower effective diameters than upward cut, improved tool life. Tool inclination, utilized to avoid tool center in cut of tool type ball nose, may influence significantly the surface finish. Tool vibration influences surface finish because of tool bend, which promotes different cut force for each tool tooth. Tool inclination does not guarantee a good surface finish or a good vibration behavior. Tool inclination might change the manner the vibration presents itself. The vibration responsible by different cut forces in each tooth is the most influential vibration in roughness in presented cut / Mestrado / Materiais e Processos de Fabricação / Mestra em Engenharia Mecânica

The diploma thesis focuses on a conceptual design of a surface grinding machine. Aim of this work is to analyze current products and create a new design and ergonomic proposal. Result of this work is a concept of a surface grinding machine, that is defined by its progressive form and intuitive operation. The thesis brings a vision and a new solution for a current machine tool design from an ergonomic and technical perspective.

The diploma thesis concerns CNC machining of rotary part. The first part briefly introduces options of multipurpose CNC machines and robotized workplaces. The main body of the thesis analyses two production departments; one of them operated by a robotic manipulator. The conclusion summarises the accomplished results of the thesis.

This thesis is focused on a production of injection molds. It contains some analyses of the various parts of the injection molds, a description of their functions and the possibility of structural design. A summary of existing technologies for the production of these molds, their advantages and disadvantages is included. This thesis deals with design of the component parts for injection of plastics, strategy of machining and a simulation of machining.