A Study On The Mathematical Model Of Laser Fusion Cutting With Coaxis Double Focal Lens

The laser fusion cutting process includes knowledge of many subjects such as optics, material, thermology, fluid dynamics, mechanical control and so on. There are many factors affecting the cutting quality and efficency. It will spend much time,manpower and money in doing experiments to study the effects of these factors. Therefore, establishing a model of laser fusion cutting will make great contribution to the real laser fusion cutting process.In this dissertation, a method to design a supersonic nozzle suitable for the high pressure inert gas-assisted laser fusion cutting process had been carried out based on the theory of aerodynamics. The gas jet from a supersonic nozzle possesses the desired dynamic characteristics, which can blow away the melting material from laser cut kerf more effectively. As a result, a higher cutting quality and speed can be achieved for the metals.Under the condition of some reasonable assumptions, a model of the three-dimensional stationary geometric shape of the laser fusion cutting front adopting a lens with coaxial double focus was developed based on the theory of energy balance. Not only these parameters such as the laser power, the laser mode, the wavelength, beam polarization, the characters and thickness of the material, the cutting speed, the focus position and the structural dimension of the coaxial double focal lens, but also the effects of the multiple reflections on the absorptivity were involved in this model..A numerical solution procedure was given to calculate the geometric shape of the laser fusion cutting front of the stainless steel (304) material . The different geometric shapes of the laser fusion cutting front had been achieved under the condition of different parameters. The effects of these parameter such as the multiple reflections,, the laser power, the laser mode, the characters and thickness of the material, the cutting speed, the focus position and the dimension of the coaxial double focal lens on the geometric shape of the laser fusion cutting had been analyzed systematically and detailedly. The calculated and analyzed results coincided with the reality basically. A conclusion was achieved from the calculation of the model, which the laser cutting quality using the coaxial double focal lens was better than that using the coaxial single focal lens under the condition of the distance of two focal points within some range. The optimum parameters of the laser fusion cutting could also be obtained from the calculation of this model.This model could establish a real laser fusion cutting system to obtain the optimum process parameters.