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Carbon fiber-reinforced silicon carbide matrix (C/SiC) composites are typical difficult-to-cut materials due to high hardness and brittleness. Aiming at the problem of the serious high cutting force and poor surface quality in conventional milling (CM) C/SiC composite process, ultrasonic vibration-assisted milling (UVAM) and conventional milling tests with a diamond-coated milling cutter were conducted. The results showed that reducing the feed per tooth, cutting depth, or increasing the cutting speed can reduce the average cutting force, and increasing the ultrasonic amplitude, the average cutting force decreases first and then increases. With the assistance of ultrasonic vibration, the maximum reduction rates of average cutting forces Fx, Fy, and Fz were 43.7%, 29.16%, and 68.09%.The ultrasonic vibration assisting effect does not significantly improve the damage of materials such as fiber breakage during processing. The ultrasonic vibration assisting effect improves the quality of processing edges. It is found that reducing feed per tooth, cutting depth, or increasing cutting speed can reduce surface roughness and increasing the ultrasonic amplitude reduces the surface roughness first and then increases. On the whole, the surface roughness of C/SiC ultrasonic vibration milling is slightly smaller than that of conventional machining. [ABSTRACT FROM AUTHOR]

A novel micro-flank milling force prediction model is developed in this study by considering the deflection of tool and workpiece, tool run-out, and material strengthening effects during the flank milling of thin-walled parts. The model of the cutting tool applied in this study is closer to the actual structure and its deflection model is established based on Euler Bernoulli cantilever beam theory under mesoscale. The values of the workpiece deflection are obtained with an online Keyence LK-H020 laser sensor. The Johnson-Cook constitutive model is adopted to estimate the flow stress sJC, which takes in consideration the effects that strain-hardening, strain-rate, and thermal softening have on the flow stress. The mechanistic model is validated by a series of micro-thin-wall experiments with a two-flute KENNA micro-milling cutter as tool and Ti-6Al-4V titanium alloy as workpiece material. Experimental results illustrate that the proposed model performs well for the micro-flank milling forces in the x-direction, with an average error of 4.153%, while the error in the ydirection is slightly larger at 4.458%. [ABSTRACT FROM AUTHOR]

Chatter is undesirable self-excited vibrations, which always lead to adverse effects during milling process. Selecting a reasonable combination of cutting parameters is an effective way to avoid chatter. Based on the mathematical model of milling process and the Floquet theory, the stable cutting area can be determined. The stability lobe diagrams (SLD) could be obtained by different interpolationmethods. To study the effect of higher order interpolation methods on the accuracy and efficiency of milling stability prediction, the state item, the time-delayed item, and the periodic-coefficient item of the state-space equation are approximated by different higher order interpolation methods, respectively. The calculations show that when the state item is approximated by the third-order Hermite interpolation polynomial, third-order Newton interpolation of the time-delayed item can improve the accuracy of SLD, while higher order interpolation of periodic-coefficient item has negative effect on improving effectiveness and efficiency compared to high-order interpolation of the state item and the time-delayed item. In order to obtain the SLD of milling process more accurately, an updated full-discretization milling stability prediction method which based on the third-order Hermite-Newton interpolation polynomial approximation is proposed in this paper. By dividing the tooth passing period equally into a finite set of time intervals, the third-order Hermite interpolation polynomial and the third-order Newton interpolation polynomial are utilized in each time interval to estimate the state item and the time-delayed item, respectively. The comparison of convergence rate of the critical eigenvalues and the SLD of the proposed method between the existing methods is carried out. The results indicate that the proposed method show a faster convergence rate than that of other methods, and its SLD is more close to the ideal ones with small number of time intervals. [ABSTRACT FROM AUTHOR]

A new machining method for lens molds using tilt electrical discharge milling (ED milling) has been experimentally investigated. Compared with the conventional ED milling, the tilt ED milling enables efficient enlargement of discharge gap by adjusting the tilt angles of the workpiece which results in efficient chip removal and burnish surface quality. On account of this method, micro lens craters were fabricated on the tungsten carbide (WC) and silicon carbide particulate reinforced aluminum metal matrix composite (SiCp/Al) at the optimized machining parameters under various tilt angles of the workpiece. The surface morphology and material removal rate were determined with a laser scanning microscope VK-X100 (KEYENCE, Japan). Experimental results present a 60% rise in surface quality at 25° in tilt ED milling. On the basis of electromagnetic effect, the machining mechanism is analyzed in detail in tilt ED milling for lens molds. [ABSTRACT FROM AUTHOR]