Advanced Materials Research Vol. 576

Abstract: The majority of semiconductor devices are made up of silicon wafers. Manufacturing of high-quality silicon wafers includes numerous machining processes, including end milling. In order to end mill silicon to a nano-meteric surface finish, it is crucial to determine the effect of machining parameters, which influence the machining transition from brittle to ductile mode. Thus, this paper presents a novel experimental technique to study the effects of machining parameters in high speed end milling of silicon. The application of compressed air, in order to blow away the chips formed, is also investigated. The machining parameters’ ranges which facilitate the transition from brittle to ductile mode cutting as well as enable the attainment of high quality surface finish and integrity are identified. Mathematical model of the response parameter, the average surface roughness (R_a) is subsequently developed using RSM in terms of the machining parameters. The model was determined, by Analysis of Variance (ANOVA), to have a confidence level of 95%. The experimental results show that the developed mathematical model can effectively describe the performance indicators within the controlled limits of the factors that are being considered.

Abstract: This paper presents the thorough experimental analysis on high speed end milling of single crystal silicon using diamond coated tools. Experiments were conducted on CNC milling machine. The design of the experiments was based on the central composite design (CCD) technique of Design Expert software. Response Surface Methodology (RSM) was used to develop mathematical imperial model to establish a correlation between machining parameters (cutting speed, feed and depth of cut) and machined surface roughness in high speed end milling of single crystal silicon using 2mm diameter diamond coated tools. The optimum machining parameters were determined using the optimization tool of Design Expert software based on the desirability function. Finally, confirmation tests were performed to validate the developed model.

Abstract: This paper presents the effect of cutting parameters on surface roughness in end milling of Titanium alloy Ti-6Al-4V under the influence of magnetic field from permanent magnets. Response Surface Methodology (RSM) with a small central composite design was used in developing the relationship between cutting speed, feed, and depth of cut, with surface roughness. In this experiment, three factors and five levels of central composite with 0.16817 alpha value was used as an approach to predict the surface roughness, in end milling of titanium alloy, with reasonable accuracy. The Design-Expert 6.0 software was applied to develop the surface roughness equation for the predictive model. The adequacy of the surface roughness model was validated to 95% by using ANOVA analysis. Finally, desirability function approach was used to determine the optimum possible surface roughness given the capabilities of the end machine.

Abstract: In this investigation, the powder metallurgy (PM) electrode developed from cobalt (Co) and chromium (Cr) powders was used in electrical discharge machining (EDM). This new Co-Cr sintered electrode was used to machine mild steel workpiece with kerosene dielectric fluid. The main objective is to modify its surface characteristics and secure increased surface hardness. The EDM variables of peak current, pulse duration and pulse interval were applied to investigate these surface properties. Scanning electron microscopy (SEM) / energy dispersive X-ray (EDX) spectroscopy analysis confirmed migration of electrode materials (Co and Cr) onto the EDMed surface. Improved hardness was obtained on the mild steel, the highest being 85.3 HRB. Thus, the Co-Cr electrode introduced into the EDM has the capability of modifying the mild steel surface.

Abstract: Hard milling of hardened steel has wide application in mould and die industries. However, milling induced surface finish has received little attention. An experimental investigation is conducted to comprehensively characterize the surface roughness of AISI D2 hardened steel (58-62 HRC) in end milling operation using TiAlN/AlCrN multilayer coated carbide. Surface roughness (Ra) was examined at different cutting speed (v) and radial depth of cut (dr) while the measurement was taken in feed speed, Vf and cutting speed, Vc directions. The experimental results show that the milled surface is anisotropic in nature. Surface roughness values in feed speed direction do not appear to correspond to any definite pattern in relation to cutting speed, while it increases with radial depth-of-cut within the range 0.13-0.24 µm. In cutting speed direction, surface roughness value decreases in the high speed range, while it increases in the high radial depth of cut. Radial depth of cut is the most influencing parameter in surface roughness followed by cutting speed.

Abstract: This paper presents an alternative way of producing a hole by using a helical milling concept on a carbon fiber reinforced polymer (CFRP). Delamination is a major problem associated with making a hole by drilling on the CFRP. This study focused on helical milling technique using a vertical machining center in order to produce a hole. Various levels of cutting parameter such as cutting speed, feed rate and depth of cut have been chosen to observe the effect of trust force, delamination and surface roughness. The result will be used to determine on which cutting parameters give the best hole quality that will achieved by this new approached.

Abstract: Generate borehole by helical milling process may be used effectively since accurate location of the hole may be secured by means of the feed screw graduations. Fiber delamination which is the main defect occurred during hole making process on carbon fiber reinforced polymer (CFRP) were investigate throughout an experimental study. Effects of thrust force (F_z), delamination factor (F_d) and surface roughness are evaluated. Objective of the experiment are to find best cutting parameter and tool design suitable to performed helical milling operation on CFRP. Two types of end mill with 4 flutes were used and results are evaluated. It was found that tool design 2-1 has higher performance on CFRP.

Abstract: Powder-mixed dielectric fluid is one of the innovations of electro-discharge machining (EDM) which seeks to improve the process outputs by addition of powders to the dielectric during machining. In the present study, the influence of TaC powder in kerosene dielectric fluid on EDM process outputs was investigated. Experiments were conducted with the outputs as material removal rate (MRR), surface roughness (Ra) and micro-hardness. During the EDM, the discharge current was varied between 2.5 and 6.5 A, while powder concentration ranges between 5.0 and 15.0 g/l. Results indicate that the highest MRR of 0.38 g/min was obtained with TaC concentration of 15 g/l at the current of 6.5 A. TaC powder addition does not affect both the MRR and Ra at lower current. However, the level of micro-hardness attained was influenced by TaC powder concentration in dielectric fluid, the highest being 1,040 Hv with 5.0 g/l at the current of 2.5 A.

Abstract: Advanced ceramic materials are difficult to machine by conventional methods due to the brittle nature and high hardness. The appropriate selection of cutting tool and cutting conditions may help to improve machinability by endmilling. Performance of TiAlN and TiN coated carbide tool insert in end milling of machinable glass ceramic has been investigated. Several dry cutting tests were performed to select the optimum cutting parameters for the endmilling in order to obtain better tool life. In this work, a study was carried out on the influence of cutting speed, feed rate and axial depth of cut on tool wear.The technique of design of experiments (DOE) was used for the planning and analysis of the experiments. Tool wear prediction model was developed using Response surface methodology.The results indicate that tool wear increased with increasing the cutting speed and axial depth of cut. Effect of feed rate is not much significant on selected range of cutting condition

Abstract: A majority of the established systems for determination and optimization of cutting data are based on Woxén’s equivalent chip thickness, h_eW. In metal cutting theory and models, the equivalent chip thickness is of vital importance when the depth-of-cut a_p is in the same order or smaller than the nose radius r. Woxén made considerable simplifications in his chip area model, that form the basis for calculations of the equivalent chip thickness. Basic mathematical solutions, e.g. describing the chip area on circular inserts, are lacking. This article describes the geometrical implications when machining with round inserts. The error in Woxén’s equivalent chip thickness is largest when the depth-of-cut is less than ¼ of the nose radius and are up to 40 % wrong for some combinations of cutting data in the finishing range. The presented results explain the difficulties in getting a good validity in the models used to calculate tool life in finishing machining. The error leads to an underrating of the tool load in many machining situations