1,721,482 research outputs found
Feedrate optimisation/scheduling on sculptured surface machining: a comprehensive review, applications and future directions
No full textFree-form or sculptured surface milling is one of the continually used manufacturing processes for die/mould, aerospace (especially turbine blades), precision machine design, bio-medical devices and automotive industries. Developments of machining technologies for quality enhancement of machining results have become a very important fact in current real industry. Therefore, reducing milling time, tool wear, cutter deflection and improving surface texture quality and machining operations through adaptation and optimisation of tool feedrates based on changing surface geometry in sculptured surface machining is a great step in this direction. Various feedrate optimisation strategies have different feedrate rescheduling control parameters such as chip thickness, material removal rate (MRR), min(mrr,chip,force), max(expo.Acc/dec) and resultant forces. Some commercial CAM softwares come with MRR-based feedrate optimisation algorithms which have a very short calculation time. However, commercial feedrate scheduling systems have some limitations in generating the scheduled feedrates because they use the MRR or the cutting force model which is dependent on milling conditions. However, for the processes in which machining precision/accuracy is very important, it is inevitable that mechanistic force-based feedrate optimisation approaches, for which the calculation time is improved, will be integrated into commercial CAM software packages. Here, developing only the mechanistic cutting force-based algorithm is not enough. In this paper, improvement and optimisation of machining feedrate value, which is one of the cutting parameters which has a tremendous effect on the precise machining of free-form surfaces, was discussed by using the virtual machining framework. For this purpose, the boundary representation solid modelling technique-based free-form milling simulation and feedrate optimisation system integrated with commercial CAD/CAM software is developed for three-axis ball-end milling. This review study includes the information regarding the following topics: The algorithms developed for the feedrate value optimisation, MRR calculation approaches, cutting force computation methods, details of algorithms, the effects on the surface accuracy, the effects on the machining time, the capabilities of the present commercial CAM software packages, the encountered difficulties and overcoming those difficulties, recent developments and future research directions
Identification of static surface form errors from cutting force distribution in flat-end milling processes
No full textThis paper presents a new and practical process simulation method to analyze surface errors caused by deflections of statically flexible flat-end mills. Milling force and surface error models are established to predict the surface error in various cutting conditions. The milling forces are predicted from the mechanistic model extended using the force distribution determined with an effective calibration procedure carried out by experimentally dividing the cutting part of the end mill into discs. The surface errors are modeled by establishing an analytical relationship between bending moments and deflections by means of the cantilever beam theory. These features make the present method very practical and efficient. A set of computational studies and experiments is performed to validate the effectiveness of the presented method. Comparisons of the results obtained numerically and experimentally confirm that the method is capable of accurate prediction of milling forces and surface errors. Finally, this method can be effectively applied for identifying appropriate cutting conditions in flat-end milling
Determination of Surface Qualities on Inclined Surface Machining with Acoustic Sound Pressure
No full textDie parts used in automotive and aviation industry have complicated surfaces that require multiaxis machining. In machining of inclined surfaces with ball-end milling, the process is of great significance for its correctness and accuracy. In this study, Acoustic Sound Pressure (ASP) generated during the machining of a workpiece at a vertical machining centre has been measured. The experiments have been conducted in association with cutting velocity, feed rate and step over parameters determined by using different surface forms and different cutter path strategies. Therefore, the aim of this study is to understand the relationships between the generated sound signals and surface roughness in the machining of inclined concave and convex surfaces. In the experiments, the workpiece material of EN X40CrMoV5-1 hot work tool steel, which is commonly used in the related die industry, has been chosen. The ball end mills with two indexable inserts with three different coatings of TiC, TiN, and TiAlN have been used. The results show that there is a rise at the value of surface roughness with a rise at the value of acoustic sound pressure and that surface roughness could be figured out with acoustic sound pressure level
Application of Taguchi methods in the optimization of cutting parameters for surface finish and hole diameter accuracy in dry drilling processes
No full textThe aim of the work reported here was to utilize Taguchi methods to optimize surface finish and hole diameter accuracy in the dry drilling of Al 2024 alloy. The parameters of hole quality are analyzed under varying cutting speeds (30, 45, and 60 m/min), feed rates (0.15, 0.20, and 0.25 mm/rev), depths of drilling (15 and 25 mm), and different drilling tools (uncoated and TiN- and TiAlN-coated) with a 118A degrees point angle. This study included dry drilling with HSS twist drills. The settings of the drilling parameters were determined by using Taguchi's experimental design method. Orthogonal arrays of Taguchi, the signal-to-noise (S/N) ratio, the analysis of variance (ANOVA), and regression analyses are employed to find the optimal levels and to analyze the effect of the drilling parameters on surface finish and hole diameter accuracy values. Confirmation tests with the optimal levels of machining parameters are carried out in order to illustrate the effectiveness of the Taguchi optimization method. The validity of Taguchi's approach to process optimization is well established
Halkla İlişkiler Faaliyetlerinde Kullanılan Dil: TC Aile ve Sosyal Politikalar Bakanlığı Örneği
Full text linkBu çalışmada halkla ilişkiler faaliyetlerinde kullanılan dilin özellikleri ve unsurlarının ortaya konulması, bu dilin çeşitli yaklaşımlar açısından incelenmesi ve bu doğrultuda halkla ilişkiler faaliyetlerde kullanılan dilin genel karakteristiğinin tespit edilmesi amaçlanmıştır. Çalışmanın amacına ulaşabilmesi ve sorulara cevap verilebilmesi için halkla ilişkiler faaliyetlerinde kullanılan dil; retorik, söylem ve argümantasyon kuramı yaklaşımları bağlamında ele alınmıştır. Araştırma bölümünde ise literatür ışığında halkla ilişkilerde dil kullanımının incelenmesi için örnek olarak seçilen T.C. Aile ve Sosyal Politikalar Bakanlığı’na ait farklı halkla ilişkiler metninin analizi yapılmıştır
A Methodology for Cutting Force Prediction in Side Milling
No full textThis article describes a methodology based on force distributions for predicting cutting forces in side milling 7075-T651 aluminum. The methodology includes a practical mechanism for gathering experimental data. Milling forces on each disc are measured by experimentally dividing the cutter into discs for determining the milling coefficients. Force distributions are characterized as functions of cutting and edge forces, including cutter geometry and cutting parameter effects. In contrast to previous researches, the coefficients are determined considering relations between load and shear. Owing to its high performance, this methodology can be effectively used to improve machining accuracy in side milling
Preference Based on Reasons of Vocational and Technical Secondary Schools in Turkey
No full textIt is considered that choosing a career is one of the most important decisions in human life. Because of many reasons such as family, environment, school etc. Industry and technical occupation high school to be preferred by students' educational system is very important to adoption of developments in the world, catch up with information society and develop its international competitiveness. The education system must train qualified manpower in order to decrease unemployment and increase social welfare. Policy of educational system is important at this stage. Industry technical occupation high schools educate qualified manpower and various non-formal education institutions continuously give the employers the skills needed by sector. A survey was done among the 503 students of 10th classes in industry and technical high school in Uskudar, Istanbul, Turkey. The data was collected with survey method. It is understood that the students of educated in industry technical high school choose their school according to their own wishes abilities and gender. They also think they couldn't get enough points for university entrance exam. In addition industry technical occupation high schools give them a chance to find a job easily. It is the shortest way for job opportunities and they bring off in their life. (C) 2014 The Authors. Published by Elsevier Ltd
Sustainable machining of the magnesium alloy materials in the CNC lathe machine and optimization of the cutting conditions
No full textIn this study, MQL turning performance was compared to dry conditions. The magnesium based material will be formed by applying the orthogonal cutting. The CNC Lathe shall be used for both cutting processes. The experiment used MINITAB 16 software to establish the experiment plan. In this study, workpiece was turned at cutting speeds of 230, 330 and 430 m/min, feed rates of 0.20, 0.35 and 0.50 mm/rev and cutting depth of 1, 2 and 3 mm. Taguchi experimental design method was used for determining the settings of turning parameters. Orthogonal arrays of Taguchi, the signal-to-noise (S/N) ratio, the analysis of variance (ANOVA) were carried out to determine the optimum levels and to analyze the influence of cutting speed, feed rate, cutting depth on surface roughness, temperature and cutting forces during dry and MQL turning
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