| Compared with the traditional way,laser drilling has great advantages.It is widely used in industry.With the increasing application of laser drilling technology,the processed materials can be expanded from thin plates to cigarettes and sustained-release tablets,etc.the thickness of such materials is not large but the surface is curved,and the number of general processing is large,with high speed requirements,which puts forward higher requirements for laser drilling equipment and technology.The traditional laser drilling equipment can only drill on the plane greatly Because of the limitation of its wide application,this paper studies a scanning focusing method to achieve laser drilling on cylindrical surface.In order to achieve the purpose of laser drilling on curved surface and improve the quality of laser drilling,this paper presents a laser drilling system of scanning arc cylinder focusing.Firstly,the characteristics of laser and the law of the interaction between laser and matter are analyzed.The characteristics of the traditional laser drilling and focusing mode,the principle of beam shaping and the characteristics of beam transmission are studied.Based on the above points,the general scheme of laser drilling with scanning cylinder focusing is designed.In the overall scheme,the maximum output power is 250 W,For the CO2 laser with a wavelength of 10.6 ?m,the water-cooling scheme is adopted for this kind of high-power laser.The mature joint control based on arm and CPLD is applied in the control system,while the mechanical system is designed a set of smoke device based on the negative pressure suction drum.Such device will combine the optical focusing system to achieve the purpose of drilling holes on the cylinder.In the optical system,optical software is used to model and simulate two kinds of lenses used for laser cylindrical focusing.The first one is to compress the facula into a linear facula,and the second one is to focus the linear facula compressed in front into a point facula on the surface by scanning with a rotating prism.After optimization,the two kinds of lenses achieve the requirement of focusing the facula into a 0.15 mm linewidth.After that,the optical and mechanical properties of ZnSe crystal are foundto be suitable for the processing of CO2 laser focus lens,and then the processing technology is briefly described.In order to improve the efficiency of cigarette laser drilling,we usually use double laser to drill double rows of holes.At last,we use the optical software to simulate the spot of optical system,analyze the effect of double focus spot and the energy of curved spot,and get the spot with diameter of 0.15 mm and uniform light intensity distribution.The focus effect is good,which meets the requirements of cigarette laser drilling.At last,the influence of pulse width,laser power,pulse number and other laser drilling parameters on laser drilling of cigarette is studied.It is concluded that the increase of laser pulse width and power will increase the hole depth and diameter,and increase the ventilation rate of cigarette.The number of pulses was also positively correlated with the total ventilation rate.The research in this paper will provide technical support for the application of laser drilling in cylindrical surface,especially for the industrial application of laser drilling with cigarette nozzle bar. |
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