Study On Technology For Laser Three-dimensional Machining And Discrete Milling Of Difficult-to-machine Materials

Engineering ceramics,high-temperature alloys and other difficult-to-machine materials are widely used in aerospace,medical and electronic fields due to their excellent properties,but conventional processes are difficult to machine.Laser machining has the advantages of non-contact,adjustable energy,and can machine any material in theory.Laser machining of difficult-to-machine materials has significant advantages.Numerical control technology has the advantages of high precision and high efficiency.Combining laser machining with multi-axis numerical control and conducting research on laser three-dimensional precision machining of difficult-tomachine materials can promote the applications of laser manufacturing,which has important theoretical significance and engineering application value.This project was based on the 5+2 axis picosecond laser computer numerical control machine tool independently developed by our team,and researches on threedimensional laser machining.Firstly,the coordinate transformation equation was deduced for the post-processing of five axis laser machining,and the technical chain of transforming the geometric information in CAD/CAM software into the kinematic coordinates of the machine tool was established,which was verified by the actual machining cases,and laid the technical foundation for laser three-dimensional machining.At the same time,the application of laser three-dimensional machining in the layered machining of special-shaped holes on complex curved surfaces was studied.The process of automatic machining of special-shaped hole on complex curved surfaces was described.After analyzing the results of different incident angle machining cases,it was found that the size of the machining area after the laser tilt was not simply changed to the projection size.Then,through the experiment of laser machining of silicon nitride ceramics,the influence of laser beam being vertical,tilt and lead incidence on the processing effect was compared,and the angle effect,beam action characteristics,material removal mechanism,forming characteristics and process law of laser three-dimensional machining are explored.The experimental results showed that the machined depth and material removal rate can be controlled by adjusting the incident angle,and the machined surface quality with lead angle was better than that with vertical or negative lead angles(Under the experimental conditions,the surface roughness was 1.8 μm when the lead angle is-20° and 0.9 μm when the lead was 20°).In order to solve the problem of low efficiency in laser large-area machining,a laser hybrid machining —laser discrete milling was studied.The alumina ceramics machining experiments and finite element simulation were used to study the law of the process and material removal mechanism,it was found that the discrete machining has changed the form of mechanical energy transmission,and can achieve high feed speed and large cutting depth milling.Under the experimental conditions,the laser discrete milling can work normally when the cutting depth is 60 μm and the feed speed is 1200 mm / min,while the tool of traditional milling was seriously worn when the cutting depth is 50 μm.