Plunge milling time optimization via mixed-integer nonlinear programming

International audiencePlunge milling is a recent and efficient production mean for machining deep workpieces, notably in aeronautics. This paper focuses on the minimization of the machining time by optimizing the values of the cutting parameters. Currently, neither Computer-Aided Manufacturing (CAM) software nor standard approaches take into account the tool path geometry and the control laws driving the tool displacements to propose optimal cutting parameter values, despite their significant impact. This paper contributes to plunge milling optimization through a Mixed-Integer NonLinear Programming (MINLP) approach, which enables us to determine optimal cutting parameter values that evolve along the tool path. It involves both continuous (cutting speed, feed per tooth) and, in contrast with standard approaches, integer (number of plunges) optimization variables, as well as nonlinear constraints. These constraints are related to the Computer Numerical Control (CNC) machine tool and to the cutting tool, taking into account the control laws. Computational results, validated on CNC machines and on representative test cases of engine housing, show that our methodology outperforms standard industrial engineering know-how approaches by up to 55% in terms of machining time

Rationalization of Machining Technology of Mold for Plastic Injection

Import 23/07/2015Diplomová práce se zabývá návrhem nové technologie obrábění dílu formy pro vstřikování plastů a porovnáním současné a navržené technologie výroby. V první části je proveden rozbor stávající technologie výroby dílu formy spolu s použitými stroji a nástroji, které byly při stávající výrobě použity. Na základě rozboru stávající technologie výroby je v druhé části proveden návrh nové technologie výroby se zaměřením na návrh produktivnějších nástrojů pro obrábění a volba obráběcího stroje. V závěrečné části diplomové práce se provádí srovnání a vyhodnocení navržené technologie výroby se současnou technologií výroby.This thesis deals of proposal of new technology machining part mold for plastic injection and comparing current and proposed technology. The first part is an analysis of the existing technology of part mold together with the used machines and tools that were used in current production. Based on the analysis of the existing technology is the second part of the design of a new technology focused on design productive tools for machining and machine tool selection. In the final part of the thesis makes a comparison and evaluation of our technology with current technologies.346 - Katedra obrábění, montáže a strojírenské metrologievýborn

Comparative and statistical analysis between the CERN conference database and three other bases

This is a comparison between three scientific conference databases and CERN data. High Energy Physics institutes DESY and SLAC databases and the STN-FIZ commercial one's are described and analysed by statistical tables. We plan to work out a co-operation policy especially with DESY for exchange or data import

Technology of CNC milling

Rozbor obecných možností na frézovacích strojích, rozbor možností při programování v dílensky orientovaném frézování v systému Sinumerik 840D ShopMill. Návrh variant technologie výroby, včetně vytvoření NC programů součásti a technicko ekonomického hodnocení pro Domek kuličkového šroubu v ose X.Common possibility analysis on milling machine, analysis possibility for programming in workshop oriented milling in system Sinumerik 840D ShopMill. Project alternative manufacturing technology including creation NC programme and technical economic valuation for part of Suspension globular screw in axis X.

Air Force Institute of Technology Research Report 2009

This report summarizes the research activities of the Air Force Institute of Technology’s Graduate School of Engineering and Management. It describes research interests and faculty expertise; lists student theses/dissertations; identifies research sponsors and contributions; and outlines the procedures for contacting the school. Included in the report are: faculty publications, conference presentations, consultations, and funded research projects. Research was conducted in the areas of Aeronautical and Astronautical Engineering, Electrical Engineering and Electro-Optics, Computer Engineering and Computer Science, Systems and Engineering Management, Operational Sciences, Mathematics, Statistics and Engineering Physics

Estudo da maquinabilidade das ligas Ti-6Al-4V e Co-28Cr-6Mo na fresagem de dispositivos biomédicos

Doutoramento em Engenharia MecânicaOs estudos de maquinabilidade de biomateriais e outros materiais aplicados na área médica são extensos. Todavia, muitos destes estudos recorrem a modelos de geometria regular e operações elementares de maquinagem. Relativamente a estas, os estudos académicos atualmente disponíveis mostram que a tecnologia preferencial é o torneamento, opção que se fundamenta na simplicidade de análise (corte ortogonal). Saliente-se ainda que, neste contexto, a liga de titânio Ti-6Al-4V constitui o biomaterial mais utilizado. Numa perspetiva complementar, refira-se que as publicações científicas evidenciam que a informação disponível sobre a fresagem Ti-6Al-4V não é muito extensa e a do Co-28Cr-6Mo é quase inexistente. A presente dissertação enquadra-se neste domínio e representa mais uma contribuição para o estudo da maquinabilidade das ligas de Titânio e de crómio-cobalto. A aplicação de operações de maquinagem complexas, através do recurso a programas informáticos de fabrico assistido por computador (CAM), em geometrias complexas, como é o caso das próteses femorais anatómicas, e o estudo comparativo da maquinabilidade das ligas Co-28Cr-6Mo e Ti-6Al-4V, constituem os objetivos fundamentais deste trabalho de doutoramento. Neste trabalho aborda-se a problemática da maquinabilidade das ligas metálicas usadas nos implantes ortopédicos, nomeadamente as ligas de titânio, de crómiocobalto e os aços Inoxidáveis. Efetua-se ainda um estudo da maquinagem de uma prótese femoral com uma forma geométrica complexa, onde as operações de corte foram geradas recorrendo às tecnologias de fabrico assistido por computador (CAD/CAM). Posteriormente, procedeu-se ao estudo da maquinabilidade das duas ligas usadas neste trabalho, dando uma atenção particular à determinação das forças de corte para diferentes velocidades de corte. Para além da monitorização da evolução da força de corte, o desgaste das ferramentas, a dureza e a rugosidade foram avaliadas, em função da velocidade de corte imposta. Por fim, com base nas estratégias de maquinagem adotadas, analisa-se a maquinabilidade e selecionam-se os parâmetros de corte mais favoráveis para as ligas de Titânio e Crómio-cobalto. Os resultados obtidos mostram que a liga de crómio-cobalto induz maior valor de força de corte do que a liga de titânio. Observa-se um aumento progressivo das forças de corte quando a velocidade de corte aumenta, até atingir o valor máximo para a velocidade de corte de 80m/min, após a qual, a força de corte tende a diminuir. Apesar do fabricante das ferramentas recomendar a velocidade de corte de 50 m/min para ambos os materiais, conclui-se que a velocidade de corte de 65 m/min induz o mesmo desgaste na ferramenta de corte no caso da liga de titânio, e menor desgaste no caso da liga de crómio-cobalto.Studies regarding the machinability of biomaterials applied in the medical field are extensive. However, many of these studies are based on models with a regular geometry and using elementary machining operations. For these operations, the preferred technology used in academic studies is turning, due to the simplicity of analysis (orthogonal cutting). Moreover, the preferred biomaterial is the titanium alloy (Ti-6Al-4V). It should be also underlined that scientific studies published concerning the milling of Ti-6Al-4V are limited and for Co-28Cr-6Mo scarce. The present PhD Dissertation represents one more contribution to this field and aims to study the machinability of the titanium and chromium-cobalt alloys. The use of complex machining operations by means of software computer-aided manufacturing (CAM) in complex geometries such as the anatomical femoral prostheses and the study the machinability of the Co-28Cr- 6Mo and Ti-6Al -4V alloys represent the main objectives of the present work. In this study, the machining of a femoral prosthesis with a pre-defined complex geometric shape was developed, where the cutting operations were generated using the technology of computer-aided manufacturing (CAD/CAM) is performed. The study the machinability of the chromium-cobalt alloy (Co-28Cr- 6Mo) and titanium alloy (Ti-6Al-4V) is considered next. This work focuses in the determination of the cutting forces by selecting a given cutting speed and ensuring that the cross-sectional cut remains the same, as the cutting speed increases. Beyond the record of the progress of the cutting force, the tool´s abrasion, the hardness and the surface roughness were evaluated as a function of the cutting speed. Finally, based on machining strategies adopted, the most favorable cutting parameters are selected in order to carry out the machining with both alloys considered in this work. According to the results, the conclusions drawn from this thesis are the following: i) for chromium-cobalt alloy, a higher cutting force is obtained. The cutting force increases gradually, as cutting speed increases, till a maximum value at of 80 m/min, and then decreases ii) the tool manufacturer suggests a cutting speed of 50 m/min for both materials, but with a cutting speed of 65 m/min, same tool´s abrasion is obtained for the titanium alloy and less for chromium -cobalt alloy

Reliability training

Discussed here is failure physics, the study of how products, hardware, software, and systems fail and what can be done about it. The intent is to impart useful information, to extend the limits of production capability, and to assist in achieving low cost reliable products. A review of reliability for the years 1940 to 2000 is given. Next, a review of mathematics is given as well as a description of what elements contribute to product failures. Basic reliability theory and the disciplines that allow us to control and eliminate failures are elucidated

1991-1992 Bulletin

Volume 102, Number 4. Scanned from the copy held in the Registrar\u27s Office.https://ecommons.udayton.edu/bulletin/1035/thumbnail.jp

Effect of elevated strain rates on the mechanical performance of polyethylene structures

The theme of this research was the development of an integrated approach to establish how the stiffness of a thermoplastic material could be measured and modelled for use in impact simulations. By undertaking this an understanding was obtained of how thermoplastic materials behave and the structures that are made from them perform when subjected to mechanical impact loads. A series of tensile tests was undertaken using three control methods to establish a tensile test control method suitable for a wide range of strain rates. The effect of applied strain rate on the mechanical performance of High Density Polyethylene (HDPE), as illustrated by the tensile stress-strain curve, was investigated. Tests were performed at various elongation rates and temperatures to simulate different practical operating conditions. Extensive use of the finite element method was made in simulating the mechanical impact performance of various beam, disc and automotive fuel tank structures with the predictions of these analyses being correlated with experimental test data. The research is novel and of direct practical relevance as indicated by the prediction and correlation with experimental data, of the impact performance of a HDPE fuel tank, which to the author's knowledge has not been previously done. The demonstrated methodology thus provides a significant advance in the prediction of the impact performance of components made from polymers, whose mechanical performance is strain rate sensitive

An Investigation into the Analysis of Truncated Standard Normal Distributions Using Heuristic Techniques

Standard normal distributions (SND) and truncated standard normal distributions (TSND) have been widely used and accepted methods to characterize the data sets in various engineering disciplines, financial industries, medical fields, management, and other mathematic and scientific applications. For engineering managers, risk managers and quality practitioners, the use of the standard normal distribution and truncated standard normal distribution have particular relevance when bounding data sets, evaluating manufacturing and assembly tolerances, and identifying measures of quality. In particular, truncated standard normal distributions are used in areas such as component assemblies to bound upper and lower process specification limits. This dissertation presents a heuristic approach for the analysis of assembly-level truncated standard normal distributions. This dissertation utilizes unique properties of a characteristic function to analyze truncated assemblies. Billingsley (1995) suggests that an inversion equation aids in converting the characteristic functions for a given truncated standard normal distribution to its corresponding probability density function. The heuristic for the inversion characteristics for a single doubly truncated standard normal distribution uses a known truncated standard normal distribution as a probability density function baseline. Additionally, a heuristic for the analysis of TSND assemblies building from the initial inversion heuristic was developed. Three examples are used to further demonstrate the heuristics developed by this dissertation. Mathematical formulation, along with correlation and regression analysis results, support the alternate hypotheses presented by this dissertation. The correlation and regression analysis provides additional insight into the relationship between the truncated standard normal distributions analyzed. Heuristic procedures and results from this dissertation will also serve as a benchmark for future research. This research contributes to the body of knowledge and provides opportunities for continued research in the area of truncated distribution analysis. The results and proposed heuristics can be applied by engineering managers, quality practitioners, and other decision makers to the area of assembly analysis