Multi-objectives process optimization in end milling process of aluminium alloy 6061-T6 using genetic algorithm

Manufacturing industries are business driven and profits are generated by increasing annual revenue and reducing total manufacturing costs. The cost involves multiple resources such as raw materials, manpower, equipment and even manufacturing time. Thus, every manufacturing process from the frontline to the backline must run up to the maximum capacity and effectiveness without compromising products’ yield and quality. End milling is one of the crucial processes to produce geometry shape products mainly in the automotive and aerospace industries. Therefore, this paper aims to obtain optimum conditions of ethe nd milling process for three cutting inserts with multi-objective parameters using a combination of mathematical modelling and genetic algorithm. The responses studied are surface roughness, cutting temperature, cutting force and flank wear. The target is to obtain the lowest value of all the responses studied by considering both input and response parameters simultaneously at one time. The process involved multi parameters and responses, thus in this study, multi-objective optimization genetic algorithms (MOGA-II) were applied. The optimization process parameters of end milling were obtained using response surface methodology, mathematical models and the MOGA-II approach. The optimum parameters were determined according to the design flow, constraints value and mathematical algorithm. Based on MOGA-II analysis, every workflow generated 1600 feasible solutions for optimization that meet the design space requirement. However, only a final solution was selected according to the multi-objective optimization of each insert used in the experiments. Subsequently, multi-criteria decision-making is required to choose the final optimization of the machining performance. Based on the parallel coordinates plot in MOGA-II and the multi-criteria decision-making approach, the final iteration number representing a single combination of optimum parameters was obtained for each cutting insert. The results of end milling process parameters with optimised machining conditions are presented and discussed. In the confirmation analysis, all the results are less than 10% of marginal error, thus, indicating that the model that was developed for the response studied is reasonably accurate. All the actual values are within a 95% prediction interval. Therefore, it can be concluded that the process was optimized which regards the lowest value obtained for the responses studied. In addition, the process was enhanced significantly with a combination of the MQL technique and the application of tri-hybrid nanofluids in end milling even for the low-cost cutting insert like uncoated tungsten carbide. For future study, other methods or algorithms can be applied in other machining processes to obtain optimum machining parameters

Wear Behaviour of Tungsten Carbide in End Milling Process of Aluminium Alloy 6061-T6 with Minimal Quantity of Tri-hybrid Nanofluids

Nowadays, using nanotechnology in science and industry improves the yield of different processes. The machining process using hybrid nanofluids requires further research to better understand the mechanism of tool wear and the fundamental aspects are not yet ventured. In machining, tool wear is common problems that exist for quite some time. In addition, milling process of Aluminium Alloy was challenged due to a strong adhesion particularly in higher temperature. Deposition of chips material during the process at the tool edge may induce several tool failures such as build-up edge, chipping and flaking. Eventually, tool life, manufacturing cost and product quality were the factors that normally effects by tool wear. However, the severity of tool wear can be reduced by applying a cutting fluid to the tool-workpiece interface. This paper intends to discover the effects of tri-hybrid nanofluids in end milling process of Aluminium Alloy 6061-T6 mainly on wear conditions of uncoated and double-layered PVD coated inserts. In this research works, three different nanoparticles SiO2-Al2O3–ZrO2 were dispersed in 60:40 of deionized water and ethylene glycol. The concentration was prepared between 0.06 and 0.12 wt.%. The MQL system with assisted air pressure was employed to deliver newly developed tri-hybrid nanofluids. During metal cutting process, the metal working fluid was supplied intermittently based on flow rate setting in the MQL system to the cutting zone with a very minimal quantity. A single insert was used and changed for every 100 mm of cutting length at different machining parameters. The effects on wear mechanisms were closely examined at the flank area using scanning electron microscope. Through comprehensive investigation, the wear mechanisms consist of attrition, flaking, abrasion and coating delamination. Other phenomenon such as thermal crack was observed in the wear region. The tool failures have a relationship with machining parameters and cutting tool condition itself. It can be concluded that, coating delamination and abrasion quite severe for coated inserts. While, uncoated tools were severe with attrition mode of failures. At extreme machining condition, higher temperature and friction forces at the tool-workpiece interface have a significant effect on the tool failures. For further investigation, the effects of tri-hybrid nanofluids on wear behaviour of tungsten carbide inserts can be examined for other machining process with different workpiece material

Emitter Profile Tailoring to Contact Homogeneous High Sheet Resistance Emitter

AbstractIn this work we report on successful direct contacting of high sheet resistance (RSH) emitter at 100Ω/sq by emitter profile manipulation. The formation of lightly doped emitter via POCl3 diffusion was investigated and optimized by the variation of temperature, time and gas fluxes. Sheet resistance mapping and emitter profile analysis have been done by four-point-probe and Electrochemical Capacitance Voltage (ECV) measurements. By increasing the depth of the n++ layer and at the same time reducing the peak concentration of inactive phosphorous doping, an efficiency gain of up to 0.7% absolute was achieved for multicrystalline silicon (mc-Si) solar cells. Suns-VOC measurements show an even higher gain of up to 1% absolute. In this work five different silver pastes are analysed accompanied by three different simulated grid designs. Electroluminescence imaging technique was used to characterize the spatially-resolved electrical properties of the solar cells. Based on these investigations we evaluated a 160Ω/sq emitter and could demonstrate by laser doping that the minimum n++ layer depth for high fill factors is approx. 25nm leading to 0.4%abs efficiency gain

SiliconPV 2012 generation of defect-related acceptor states by laser doping

In this work we report for the first time on the creation of thermal acceptors after laser irradiation of a phosphorous doped p-type silicon substrate in ambient atmosphere. The concentration of these defects up to 1020 cm−3 is leading to a conductivity change from n- to p-type just beneath the surface. Electrochemical capacitance voltage (ECV) measurements followed by resistivity measurements confirm this conversion of conductivity. Secondary ion mass spectrometry (SIMS) measurements show significant oxygen incorporation after laser irradiation. The comparison of saturation current density and lock-in thermography measurements of processed wafers in ambient and in nitrogen atmosphere reveal that these defects are electrically active recombination centres that disappear in absence of oxygen. In simulations of the temperature profile during laser processing a correlation between the pulse energy density (EP) and the appearance of thermal acceptors has been observed. The influence of these laser induced acceptor defects on solar cell parameters has been finally investigated. An efficiency loss of 1.3% absolute pertinent to pulse energies usually applied in laser doping process under ambient atmosphere could be avoided by laser processing in nitrogen atmosphere