热烈法玻璃激光切割技术综述

Review：The Influence Of Laser Scribing&Cutting Conditions In Glass Cutting,LeeHang Class：134 No:2111302042 Instructor:Baoym,Contents,Introduction,Typical Experiments& Results,Comparison& Prospect,References,Introduction,The traditional methods of glass cutting are based on scoring and snapping in which a diamond blade tool is used for scribing,which weakens the glass surface and then breaking is done by applying the mechanical force. Although the method is relatively simple, it results in the weakening of glass edges by up to 60% due to the formation of microcracks and generation of residual stresses. To reduce these defects, glass can be grounded, polished, and heat treated but these techniques can only recover only up to 30% of the glass strength.,Introduction,Different techniques of cutting glass using laser exists such as laser scribe and break, laser melting and evaporation, and the controlled fracture technique from which some are being used in industries and some are still in their developmental stages. Laser scribe and break is a two stage process and is quite similar to traditional mechanical scribe and break method. In the first stage, partially penetrating holes or deep vents at depths of onethird to one-half of the material thickness are produced using a laser. In the second stage, breaking by applying a mechanical force takes place normally with the help of vacuum chucks or by crack rollers. Several studies have been done to improve this method and the cutting quality. However, the scribing and breaking process incurs damage to the cut edge and causes damage to the glass surface. Therefore, finishing processes are required, which add extra cost to the manufacturer.,Introduction,In laser melting and evaporation method, cutting is done above glass transition temperatureTg, which results in poor surface finish and heat affected zones. Due to melting and vaporization of the glass material during cutting, microcracks and burrs are generated along the cutting profile and the requirement of grinding and polishing at the end of the process becomes inevitable. As compared with laser scribe and break and laser melting and evaporation method, the controlled fracture technique is a single stage process in which cutting is performed below the glass transition temperature Tg, which results in smooth edges and hence requires no further cleaning or grinding. Unlike the conventional cutting technique, it is a clean process without chips and coolant and it is possible to fix the workpiece on a table by a simple method because no external forces act upon it.,Introduction,In the controlled fracture technique, the cracks are initiated due to absorbed photons heating up the material. The stresses near the laser spot are compressive due to high temperature. After the passage of the laser beam, these compressive stresses relax and induce local residual tensile stresses. If these stresses exceed the failure stress f given by the critical strain energy release rate Gc for glass, crack propagates.,Typical Experiments&Results,In 2008 Koji Yamamoto et. al. conduct a three-dementational thermal analysis on laser scribing of glass.They shape a CO2 laser beam an elliptical(椭圆) profile which has a nominal power of 250W and a wave length of 10.6m to irradiate on the surface of the glass plate.,Experiments,Typical Experiments&Results,Results,The Dc max takes its maximum at d= 1416 mm. Above 18 mm,Dc max tends to decrease proportionally tod. This can be interpreted as with increasing d, the heat diffusion reduces the glass surface temperature immediately before the cooling, so that the difference decreases between the surface temperature and the inside temperature in the cooling area.,Parameters,cooling medium,There are many parameters will influence the laser cutting with controled fracture.Such as the power of laser and the thermal expansion coefficient,heat transfer coefficient and so on.,cooling point distance,thermal expansion coefficient,Typical Experiments&Results,Then Koji Yamamoto et. al. choose to study the influence of glass substrate thickness and thermal expansion coefficient in laser scribing of glass.,Glass Substrate Thickness,Thermal Expansin Coefficient,Typical Experiments&Results,Salman Nisar et. al. studied the influence of laser beam geometry in diode laser chip-free cuttiing of glass.,Typical Experiments&Results,Results,Comparison&Prospect,Stress,Typical Experiments&Results,Average Roughness,Typical Experiments&Results,Temperature,Comparison&Prospect,In the second part,many experiments are conducted by lots of researchers.We can conclude their researches that laser cutting quality will mainly depend on the maximum temperature in the surface of glass and the maximum tensile stress in the cooling area. So which parameter will affect the two factors.The thickness of glass will affect the maximum tensile stress in the cooling area,and hollows will form in the back side of the lower thickness substrate.The tensile stress generated in the cooling area decreases as the thermal expansion coefficient decreases. It is concluded that because of lower magnitudes of tensile stresses xx, the tri-f beam gives minimum cut path deviation at the leading edge and tri-r and circular beams give minimum cut deviation at the trailing edge of the glass sheet.,Comparison&Prospect,The results presented in these papers are important for the optimization of the laser cutting process of glass. However, more work is needed to study the optimum beam shape along with other laser parameters i.e., laser power, cutting speed, and beam spot size to further minimize cut path deviation at the leading and trailing edges of the glass sheet. So in the next future,we may try even more laser parameters to find he optimum beam.But it must be in a reasonable way.Such as“Orthogonal experimental design“.We can choose the main factors to do a orthogonal experimental design,then complete the exper