Laser beam machining (LBM) is a widely used thermal advance machining process capable of high accuracy machining of almost any material with complex geometries. CO 2 and Nd:YAG lasers are mostly used for industrial purposes. Drilling, cutting, grooving, turning and milling are the applications of LBM with different material removal mechanisms. Modeling and simulation of the LBM process is indispensable for optimization purposes. Modeling can be done by implementing analytical, numerical, experimental and artificial intelligence-based methods. This paper provides a review of the various methods used for modeling and simulation of the laser beam machining process as well as key researches done in this field so far.

A review of modeling and simulation of laser beam machining

A method for crack-free machining of deep cavity in alumina is demonstrated using a low-cost CO2 continuous wave (CW) laser. CO2 laser underwater machining has been found to result in reducing substrate defects such as recast layer, dross, cracking and heat damages that are typically found in machining in air. Finite Element (FE) modelling technique and Smooth Particle Hydrodynamic (SPH) modelling technique were employed to understand the effect of water on crack resistance and debris removal during underwater machining. Also the microstructures of machined region were demonstrated to reveal different heating and cooling processes during laser machining in water and in air. The experimental results indicated that the machined kerf width was strongly affected by the water layer thickness, whereas the kerf depth was controlled by both the laser pass number and water layer thickness. The optimal average machining rate was up to 2.95 mm3/min at a 60 W laser power.

CO2 laser underwater machining of deep cavities in alumina

A major challenge in laser fusion cutting of thick-section ceramics is to overcome the thermal-stress induced cracking, which leads to catastrophic breakdown of the material integrity. In order to achieve crack-free cutting of ceramics, it is important to understand the mechanism of the transient temperature field and resulting stress distribution effect on crack formation. In this paper, both experimental and theoretical investigations are reported to understand crack formation characteristics in fibre laser cutting of thick-section Al2O3 ceramics. A three-dimensional (3D) finite element (FE) model for simulation of the transient temperature field and thermal-stress distribution together with material removal in laser cutting was developed. Crack formation characteristics were predicted by the model and validated by experiments. The effects of four process parameters i.e. laser peak power, pulse duration, pulse repetition rate and feed rate on temperature field, resulting stress distribution and potential crack formation were also investigated in this work. The study indicates that a transition from compressive to tensile stresses can be resulted in as the laser cutting parameters change, which is beneficial to resist the crack formation. Based on the experimental and numerical investigations, the process parameters were optimised and the fibre laser crack-free cutting of 6-mm-thick alumina was demonstrated for the first time.

Experimental and theoretical investigation of fibre laser crack-free cutting of thick-section alumina

The study investigates the use of CO2 laser to induce glass strip peeling off to form microchannels on soda lime gass substrate. The strip peeling exhibits a strong dependence on the energy deposition rate on the glass surface. In spite of the vast difference in the combination of laser power and scanning speed, when the ratio of the two makes the energy deposition rate in the range 3.0-6.0 J/(cm2 s), the temperature rising inside glass will be above the strain point and reach the softening region of the glass. As a result, glass strip peeling is able to occur and form microchannels with dimensions of 20-40 μm in depth and 200-280 μm in width on the glass surface. Beyond this range, higher energy depsotion rate would lead to surface melting associated with solidification cracks and lower energy deposition rate causes the generation of fragment cracks.

Investigation on CO2 laser irradiation inducing glass strip peeling for microchannel formation

Owing to the properties of high-transmittance, wear-resisting and lightweight brittle, glass plays an important role in various electronic equipment screens. The laser induced thermal-crack propagation (LITP) can separate the glass with the advantage of the high-quality, high-efficiency and high-strength. However, the deviation of the separation path (which means the material do not separate in the path of laser scanning) is one of the serious problems in asymmetric linear cutting glass with LITP. In this study, a dual laser beam revision the separation path technology (DLBRP) has been developed for the first time by skillfully arranging two defocused diode pump solid state laser (1064 nm). The principle of DLBRP is expounded. This paper studied several factors's effects on the cutting quality such as Master laser power (PM), scanning speed (VM) and laser spot diameter (DM).The smaller the Master laser spot diameter, the smaller deviation of the separation path. The effects of revision factors including Accompanying laser power (PA), Accompanying laser spot diameter on the material surface (DA) and the horizontal relative distance between the Master laser and Accompanying laser (∆X) were investigated. The optimum processing parameters were presented in this paper. The cambered separation path (which means the material gets separated in the arc way) in asymmetry linear cutting glass (which means the cutting path deviating from the symmetry axis of the material in a large scale, and the area of two separated parts is varied widely) could be revised into the straight one. A numerical simulation on the thermal stress and the dynamic propagation of crack in the DLBRP for asymmetric linear cutting glass with LITP was developed to analyze the revision mechanism, which is corresponding to the theoretical analysis and experimental results. The analysis of experimental results and numerical simulation results shows that the DLBRP technology can effectively revise the deviation of the separation path in asymmetry linear cutting glass with LITP. Besides, the clean surface without any pollution and surface damage can be achieved.

Dual laser beam revising the separation path technology of laser induced thermal-crack propagation for asymmetric linear cutting glass

As a volumetric heat source, YAG laser can penetrate through the glass, and has many advantages in cutting of glass with controlled fracture compared with CO2 laser cutting of glass. This work lays great emphasis on studying the technique of YAG laser cutting of multi-layer glasses. This paper indicates the experiments of YAG laser cutting of two-layer and four-layer soda-lime glasses with controlled fracture. Optical microscope photographs of the separation surface are obtained to examine the surface quality. The impact of laser power, scanning speed and laser beam size on the cutting quality is studied and the optimum processing parameters are presented in the paper. A theoretical model of a thermal laser shock method for separation of two-layer glasses is developed, and the fracture propagation mechanism is studied by examining the temperature and stress fields using finite element software ANSYS. In YAG laser cutting of multi-layer glasses, the temperature distribution is uniform across the thickness of the glass and the fracture propagates from the top and bottom surface to middle so that better separation surface quality can be acquired and multi-layer glasses can be cut simultaneously.

YAG laser cutting soda-lime glass with controlled fracture and volumetric heat absorption

The research about laser cutting technology based on controlled fracture method has great potential to cutting ceramics. The paper investigate the controlled fracture technology to ZrO 2 ceramic irradiated with Nd:YAG laser. In the experiment, laser energy produces a thermal stress that cause ceramic to separate along the moving path of laser beam. Graphite coated ceramic surface to improve the absorption rate for laser radiation. Optical microscope photographs and SEM of the separation surface are obtained to examine the surface quality. The surface qualities of ceramic obtained by laser and mechanical cutting are compared. Fracture propagation mechanism is studied by examining the temperature and stress fields using finite element software ANSYS12.1. The results show that good cutting quality of ceramic can be acquired by continuous Nd:YAG laser cutting with controlled fracture.

Laser cutting ZrO 2 ceramic with controlled fracture technique

The research about laser cutting technology based on controlled fracture method has great potential to cutting ceramics The paper investigate the controlled fracture technology to ZrO2 ceramic irradiated with Nd:YAG laser In the experiment, laser energy produces a thermal stress that cause ceramic to separate along the moving path of laser beam Graphite coated ceramic surface to improve the absorption rate for laser radiation Optical microscope photographs and SEM of the separation surface are obtained to examine the surface quality The surface qualities of ceramic obtained by laser and mechanical cutting are compared Fracture propagation mechanism is studied by examining the temperature and stress fields using finite element software ANSYS121 The results show that good cutting quality of ceramic can be acquired by continuous Nd:YAG laser cutting with controlled fracture

Zhongguo Tian

Papers

YAG laser cutting soda-lime glass with controlled fracture and volumetric heat absorption

Laser cutting ZrO 2 ceramic with controlled fracture technique

Laser cutting ZrO2 ceramic with controlled fracture technique