Advanced Materials Research Vols. 264-265

Abstract: Brittle and hard materials are problematic to mechanically micro machine due to damage resulting from material removal by brittle fracture, cutting force-induced tool deflection or breakage and tool wear. As a result, the forces arising from the cutting process are important parameter for material removal. This study was undertaken to investigate the effect of cutting conditions on cutting forces and the machined surface during the glass micro grinding using on-machine fabricated (Poly Crystalline Diamond) PCD tool. Experimental results showed that an increase in depth of cut and feed rate can result in increase of cutting forces and surface roughness as well. Among the forces in 3 axes, force along feed direction is found to be larger, which played a major role in material removal. Finally, it is observed that PCD tool exhibits promising behaviour to machine brittle material like BK-7 glass for producing micro molds and micro fluidic devices, since it has better wear resistance, experiences less cutting forces and generates smooth surfaces with Ra value of as low as 12.79 nm.

Abstract: The grinding precision of end-mill is dependent on the surface roughness of the corresponding rake face and relief face. This precision will be influential in the surface roughness of workpiece and tool life of end-mill in high-speed milling. Firstly, the experiment of high-speed milling for SKD61 tool steel has been performed in the different cutting condition, and the end-mills have the different surface roughness. From the experimental results, it has shown that small relief surface roughness will decrease tool flank wear (increase tool life). The surface integrity of end-mill is very important for high-speed milling, so the different grinding parameters of end-mill have been utilized in the grinding experiment. Finally the surface roughness analysis model of the end-mill relief could be established by a polynomial network. The predictive model of surface roughness can be used to analyze the grinding precision of end-mill.

Abstract: Predicting and modeling flank wear length in high speed hard turning by using ceramic cutting tools with negative rake angle was conducted using two different techniques. Regression model is developed by using design of expert 7.1.6 and neural network technique model was built by using matlab2009b. A set of experimental data for high speed hard turning of hardened AISI 4340 steel was obtained with different cutting speeds, feed rate and negative rake angle. Flank wear length was measured to train the neural network models and to develop mathematical model by using regression analysis. Predictive neural network models are found to be capable of better predictions tool flank wear within the range that they had been trained.

Abstract: High speed hard turning is an advanced manufacturing technology that reduces the machining time because of two reasons; reducing the manufacturing steps and increasing the cutting speed. This new approach needs an economical justification; one of the main economical factors is the machining time. The machining time was breaking down into three main parts; productive time, non productive time, and preparation time. By using matlab Simulink, a new program was developed for machining time allowing the manufacturer to find rapidly the values of cutting time parameters and gives the management the opportunity to modify the processing parameters to achieve the optimum time by using the optimum cutting parameters. Table 1: Nomenclature d Depth of cut M T total machining time pmv t Total movement time D Work piece diameter h t handling time pch t Total Tool changing time f Feed rate tc t tool changing time pre t Total preparing time z e Engagement distance on Z-axis ch t Tool changing time per piece, prg t Programming time x e Degagement distance on X-axis am t Machine allowance time su t Set up time k Number of passes ao t Operator allowance time sum t Machine set up L Tool life a t Allowance time sut t Tool set up l Work piece length o t Tool movement at the rapid speed suw t Work piece set up N Spindle speed oA t From zero point to cutting point TH Tool hardness tool n No. of tool posts in the turret p t Total productive time o X tidy of the O t point o1 p Initial position of the turret. o Z = abciss of the O t point w Work piece weigh o2 p Position of the used tool c V Cutting speed c w Width of cutting speed r Rotation speed of the turret f V Feeding speed tool n no. of tool in the turret c t Cutting time o V Rapid speed speed r : Turret rotation speed

Abstract: This study deals with the micro v-grooving of a single crystal diamond tool that is implemented on a 3-axis micro-stage. A method for monitoring the machining conditions is investigated using acoustic emission (AE) signals and cutting force signals in the micro-grooving. The AE signals and machined surface profiles are obtained under various machining conditions. The signals are acquired from an AE sensor that is attached to the tool holder and are investigated to identify the correlation with the machined surface profiles. It is found that the AE signal is an effective parameter for monitoring the texture of the machined surface.

Abstract: Cylindrical grinding is an efficient and useful method of achieving good dimensional accuracy and fine finish. Very often one of the main objectives of grinding process is to obtain very good surface finish. The present investigation takes into account the effects of common grinding parameters on surface finish obtained in cylindrical grinding. The material selected is mild steel. The grinding wheel dimensions and its specification are kept in-varied. Grinding parameters like in-feed, longitudinal feed and work speed have been varied at several levels. Surface finish parameter (Ra) has been measured and noted for evaluation of surface finish, by using the instrument Talysurf. These data have been analyzed, interpreted and discussed in the context of varied conditions of cylindrical traverse cut grinding. Apart from identifying relationships between process parameters and surface finish through graphical presentations, a number of techniques (Full Factorial Design, Response Surface Methodology (RSM) and MATLAB) have been applied on the experimental data to arrive at some conclusive remarks. The paper effectively shows how selection of process parameters may yield desirable surface finish.

Abstract: Good surface finish is one of the important demands from the outputs of a cylindrical grinding machine. Also it is expected that dimensional accuracy, including accuracy in roundness, is fine in traverse cut cylindrical grinding. Now, like any other machine tool, cylindrical grinding machines also do vibrate, and vibration will affect accuracy and surface finish of the parts produced in grinding. The analysis of vibration in cylindrical grinding is then very much important. In the present study some aspects of vibration – behavior of cylindrical grinding machine have been experimented and analyzed. The process parameters have been varied and vibration signals have been measured in different directions by positioning an accelerometer at tail stock of the machine. The data have been analyzed through various statistical techniques to identify and predict vibration at given combinations of process parameters. The results and analysis of data give useful idea about dynamic performance of cylindrical grinding machine in traverse cut cylindrical grinding operation.

Abstract: Al/SiCp-MMC’s find their use in engineering and structural components but their machining particularly finishing is a challenge for manufacturing engineers due to their heterogonous nature having abrasive particles randomly distributed and oriented in the matrix material. An abrasive flow machining (AFM) set up has been designed and fabricated with an indigenously developed alternative media to finish the internal cylindrical surfaces of Al/SiCp- MMC components. Work-pieces were prepared by lathe operations after stir casting Al/SiC-MMC, 25 mm diameter bar of 0%, 5%, 10% and 15% SiC by weight. The influence of AFM process parameters e.g. abrasive mesh size, number of cycles, extrusion pressure, abrasive concentration and AFM media viscosity grade on average surface finish improvement,
Ra and material removal, MR, mg have been analyzed. The Scanning Electron Microscopy (SEM) study also reveals the improvement in surface finish of these MMC’s.

Abstract: In this study, flank wear on CBN and PCBN tools due to cutting forces were studied. Turning tests were carried using cutting speeds of 100, 125, 150, 175 and 200 m/min with feed rates of 0.10, 0.20 and 0.30 mm/rev and constant depth of cut. The performances of tools were evaluated based on the flank wear and cutting forces. There is clear relationship between flank wear and cutting forces while turning hard martensitic stainless steel by CBN and PCBN tools. Low cutting forces leads to low flank wear formation and low cutting forces provided good dimensional accuracy of the work material including low surface roughness. Flank wear formation was mostly caused by abrasion and adhesion. The built up edges formed reduced the cutting forces and also causes the heat generated at tool tip and work interface. High cutting forces are identified and this may be due to heat and flank wear combinations. Flank and crater wear on the rake face and hard metal deposition due to diffusion of metals on the cutting tool surface are the damages occurred during process.

Abstract: This paper reports on an investigation of the relationship between the polishing force and the contact characteristics as the polishing tool approaches the boundary of a part surface during polishing. It was previous established that, for fixed abrasives, when the polishing tool is on the inner surface, the relationship between the polishing force and the pressure at the contact is approximately Hertzian and the contact is a full ellipse. The contact cannot be a full ellipse as the tool touches the boundary. The same polishing force could yield rather different pressure distribution, and thus rate of material removal, within the contact region. A model is proposed to relate the force and the pressure distribution as the tool is close to the edge of a part surface. The model takes into account changes of the contact near the edge. Experimental results are also presented to validate the proposed method.