Experiments And Mathematical Model Of Laser Cutting Aluminum Alloy Sheet Based On Vaporization-melt Ratio Controlled

Aluminum alloy slot array antenna is an important part of aircraft missile guidance. One of the key restraining factors of antenna performance is machining method of micro slot array on the antenna. The problem in laser cutting this aluminum alloy sheet lies in obtaining high surface quality, as there are micro adhering slag, recast layer and stripes on the cut. At present, some achievements in studying of process and mathematical model of laser cutting sheet have been got, and quality defects have been controlled. However, these studies did not connect the internal mechanism and cut quality together. Quality factors are depended on vaporization and melt during laser cutting, which are the two basic forms of material flows. The ratio of vaporization to melt is defined as vaporization-melt ratio and it has great influence on laser cutting process and cut quality. To establish the relations between vaporization-melt ratio and cut quality and to improve cut quality based on vaporization-melt ratio controlled, have great applied value and theoretical meaning for high-precision laser cutting.A new method of laser precision cutting based on vaporization-melt ratio controlled is presented. Evaporation and melt phenomenon during laser cutting are researched and different forms of material flows are pointed out too. By means of the analysis of influencing factors of vaporization-melt ratio, it is found that material characteristics, input laser energy and scanning speed have direct effects on vaporization-melt ratio, under the condition that the pressure of assist gas must be big enough. Applied range of this method is given too.Based on the above analysis, laser cutting of 6063 aluminum sheets,0.5 mm in thickness, is carried out on a JK701H Nd:YAG laser machining system. The effect of assist gas pressure on cut quality is firstly achieved, as it must be big enough for the following experiments. The optimized assist gas pressure is used in experiments of studying the effects of laser power and scanning speed on vaporization-melt ratio and residual molten layer. Microscopic examination is carried out to observe the adhering slag, recast layer and stripes. The results show that laser power and scanning speed affect vaporization-melt ratio by instant vaporization and constant vaporization. Vaporization-melt ratio increases and residual molten layer decreases when laser power is high and scanning speed is slow Then good cut quality can be acquired. Therefore, the processing parameters can be controlled by vaporization-melt ratio and good quality can be got at high vaporization-melt ratio. According to experiments data and theoretical research, a vaporization-melt ratio mathematical model is developed. The effects of assist gas pressure on vaporization-melt ratio and residual molten layerare are simulated, as well as laser power and scanning speed. The comparison results show good agreement between the model and experiments. So it can be concluded that this mathematical model is of good foreseeability.This thesis supplies theory analysis of laser cutting sheet metal based on vaporization-melt ratio controlled. Simulation model and experimental dates are performed. The variation of vaporization-melt ratio, residual molten layer against laser power and scanning speed is presented. Cut kerfs, with no adhering slag on the bottom, recast layer 1.28μm in thickness and improved stripe situation are obtained using parameters optimized by vaporization-melt ratio experiments. So, high vaporization-melt ratio during laser cutting can contribute to improving cut quality and this method provides reference for laser precision cutting.