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Micro-end-milling is used for the fabrication of complex geometrical features with high precision on a wide variety of materials. One of the main challenges is related to chatter vibrations, which are detrimental to the productivity and overall quality of the manufactured parts. In this article, a novel chatter-detection method based on wavelet coherence functions is proposed to evaluate the stability of the micro-end-milling process. Then, the method is experimentally tested under different cutting conditions. The results show that the wavelet coherence functions of two orthogonal acceleration signals are sensitive enough and applicable for chatter detection. When chatter occurs, the two orthogonal acceleration signals are highly correlated at the chatter frequency, resulting in a sharp increase in the magnitude of the wavelet coherence functions to values approaching unity. [ABSTRACT FROM AUTHOR]

This paper presented the effect of run out on the experimental characteristic of micro-milling brass using carbide micro-end mills. A method of calculation and measurement for the run out of tool-holder-spindle assembly in micro-end mill was developed. A series of micro-milling process experiments were carried out under varying cutting parameters. The effect of run out on cutting forces, effect of cutting parameters on surface roughness, and size effect were analyzed. It was seen that the cutting force signature was seriously affected by run out in the micro-milling process. When the feed per tooth is less than the run out, the cutting force signals showed that only one cutter flute engaged in cutting process due to the effect of run out. It was also seen that the cutting force signature showed erratic variations due to the effect of tool–workpiece and the run out of tool tip at higher spindle speed. Surface roughness was affected by both cutting speed and feed per tooth. For lower cutting speed, there was increase in the surface roughness with the decrease in the cutting speed due to the effect of built-up edge. For higher cutting speed, there was increase in the surface roughness with the increase in the cutting speed due to dominance of the shearing effects. When the feed per tooth was less than the minimum chip thickness, due to the indentation and ploughing-dominated process, nonlinear increase of specific shear energy can be obtained. At lower feed per tooth, the specific energy increases with increased cutting speed. These results are used to provide strategies to optimize cutting parameters and achieve better surface quality in micro-milling brass process. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of the effects of cutting parameters of micro-end-milling process on the machined surface roughness, in order to find the optimal operation conditions for improved surface finish. Three types of metals, namely 6160 aluminium alloy, brass, and AISI 1040 steel, are used as work materials. The effect of material property on the surface roughness is investigated. It is found that under the same machining condition, the machined surface quality of aluminium alloy is the worst, while that of brass is the best. A multiple regression model for the surface roughness is developed, which includes the effects of cutting speed, feedrate, and the interaction between them. Results based on analysis of variance (ANOVA) show that the cutting speed is the most significant factor on surface roughness. The residual analysis indicates that the multiple regression model is valid and agrees with the experimental results. [ABSTRACT FROM PUBLISHER]

Building total CO 2 emissions must decline by more than 95 % from 2020 to 2050. Statistical studies affirm that 84 % of the fuel cell applications in the world are attributed to the residential market and are limited to the range of 0.5–5 kW. In this study, defining a building-based fuel cell, the first and second law of thermodynamics were approved for the hybrid system consisting of SOFC enhanced with an internal reformer and microturbine. In addition, an external reformer along with two heat recovery systems are integrated to change methane to hydrogen. Based on the exergy balance equation, 37 The installation of heat recoveries was very effective in hybrid system irreversibility reduction so they were able to reduce exergy losses by 38 %. The most irreversibility was related to chemical reactions that occurred in the external reformer (share of 37.3 %) and combustion chamber (share of 32 %) while the share of the fuel cell was only 10.7 %. The calculations of the second law showed that the hybrid system with heat recovery can convert 57.6 % of the input exergy into useful work. The environmental analysis revealed that establishing a hybrid system with a higher temperature is more effective than that with higher pressure. The CO 2 emissions of the hybrid system at the lowest and highest temperature were 1.946 kg/kW and 0.81 kg/kW. • Defining a building-based fuel cell, the first and second law of thermodynamics were approved for the hybrid system. • An external reformer along with two heat recovery systems are integrated to change methane to hydrogen. • The most irreversibility was related to chemical reactions that occurred in the external reformer and combustion chamber. • Establishing a hybrid system with a higher temperature is more effective than that with higher pressure. [ABSTRACT FROM AUTHOR]