Si3N4 is difficult to be machined due to its hard and brittle nature. In order to improve its machining quality, a new method of ultrasonic-assisted laser machining is proposed. The machining device is established including Nd: YAG pulsed laser, ultrasonic vibration stage and water flow system. Etching experiments of laser machining with and without sample vibration in anhydrous conditions and in water conditions are studied respectively. A VM-3030E two-dimensional image measuring instrument is applied to detect shape and measure dimension of the sample. Microstructure morphology of the sample is observed by a JSM-7500F scanning electron microscope. Experimental results show that there are fewer slags on inner surfaces of V-shaped grooves when laser machining with water flow. The surface quality and depth-to-width ratio of grooves machined by laser with vibration on sample are improved significantly in comparison with those without vibration. The depth-to-width ratio of groove machined by laser with 90.1W vibration power is near twice than that without vibration.
Analysis on the learning situation of the engineering drawing course in our college is carried out. The teaching method that basic object is applied to the course when students study the content of point, line, surface is proposed, and the course content is adjusted correspondently. The concrete implementation of new method is also introduced, and the teaching practice shows that the new teaching method is more conducive to improve the teaching quality.
Laser combined machining is a complex machining method which utilizes the combined effect of various forms of energy to achieve a material processing. High manufacturing quality and surface accuracy, and machining efficiency can be achieved. The research progress in the area of laser combined other machine processes is reviewed. Several methods of laser combined machining are introduced and their characteristics and applications from the point of the laser assisted liquid machining are investigated. For example, laser assisted wet etching and laser assisted jet electrochemical machining, and waterjet-guided laser machining are reported. The experimental and theoretical studies of the technologies to improve the machining performance are discussed. Finally, the existing problems and the future research directions of the laser compound processing are put forward .
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