【作者】 李灵；

【导师】 王扬；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 针对MEMS(Micro Electro Mechanical System)器件制造出现了许多新型微细加工方法,如LIGA(Lithograthie Galvanoformung Abformung)加工、电火花微细加工、电化学微细加工、激光微细加工、水导激光微细加工等。近年,随着微电子硅基材料加工业、精密医疗器械制造业的兴起,水导激光微细加工技术得到迅速的发展,其特有的加工能力能保证高加工精度、高加工速度、极小加工作用力、极小热影响区、无残余应力、无裂纹。目前,瑞士的SYNOVA公司有较成熟产品,但价格非常昂贵。基于以上现状,本文在国内外相关研究的基础上,深入开展了水导激光微细加工的理论、仿真和试验研究。建立了加工仿真模型,设计制造了完整、性能稳定可靠、成本较低的水导激光微细加工系统,通过试验得到了优化的加工工艺参数并加工出品质优异的样件。首先,在总结国内外研究基础上,研究了水束光纤的耦合原理,包括耦合对准、全反射最大入射角、多模光纤传输和激光能量在水束中的衰减、受激拉曼散射等。研制了耦合状态检测和调整系统,该系统基于CCD机器视觉采集到的耦合状态图像,采用自行开发的图像处理软件,能够实现实时、快速、准确的耦合对准和加工状态监测。对高速稳定水射流束的流体动力学原理进行研究,研究了影响水束稳定性的因素、缩流原理、空化原理,通过应用FLUENT有限元分析软件针对本文设计的高压水射流液压系统进行流体动力学仿真,得到能够形成理想射流状态的合理液压参数。应用仿真的结果,实验得到了稳定长度超过100mm、流速超过100m/s的高速水射流。对激光与固体、液体的相互作用原理进行研究,应用ANSYS有限元分析软件仿真加工过程的温度场。采用了“单元杀死技术”仿真加工蚀除情况。仿真中激光能量依照水导激光微细加工特有的非高斯分布考虑。重点研究了高速水射流的冷却、冲击作用对热影响区分布、温度梯度大小和熔融产物生成的影响。其次,从实现水导激光微细加工的各项关键技术入手,设计并研制了一套水导激光微细加工设备。由脉冲式Nd:YAG激光系统、高压水液压系统、激光与水束光纤耦合系统、CCD机器视觉耦合状态检测和监控系统、计算机数控系统、数控工作台等几部分组成。激光与水束光纤耦合装置是该系统的关键部分。耦合装置内液体腔极小,腔内流场稳定、对称,激光穿过的水层厚度仅0.2mm。齐整的喷嘴孔口边缘保证返流式缩流射流的形成。采用添加望远镜部件和扩束器部件的Nd:YAG脉冲激光系统,聚焦激光束数值孔径合理,束腰直径小、焦深大,适合于水导激光微细加工。最后,为了掌握水导激光微细加工的工艺规律,针对所设计的系统进行了试验研究。研究各项加工参数对水束稳定性的影响规律,研究加工参数对激光光斑直径影响规律,对激光能量衰减规律,不同材料的加工效率。接着采用单因素法和正交试验法进行加工参数优化试验。最后通过采用优化参数加工硅基晶片和不锈钢1Cr18Ni9Ti样件,验证了水导激光微细加工系统优异的微小零件加工性能和广泛实用性。更多还原

【Abstract】 There are many new micromachining methods developed for MEMS(Micro Electro Mechanical System) such as LIGA micromachining, micro-EDM and micro-ECM, etc. In Recent years, with the development of silicon-based microelectronic materials processing and sophisticated medical equipment manufacturing, water-jet guided laser micromachining develops quickly. It′s particular processing ability insures high machining precision, high machining speed, minimal machining force, minimal heat-affected zone, no remain stress and no crack. At present, SYNOVA Company in Sweden has mature products using this technology, but the price is quite high. Based on the situation above, this dissertation is aiming at doing research on the theories,simulation and experiments of water-jet guided laser micromachining. The simulation model was built up. The complete, steady and low cost water-jet guided laser micromachining system was designed and built up. The optimized machining parameters and high quality products were acquired from experiments.Firstly, on the bases of summing up the other researchers′work all over the world, the coupling mechanisms of water-jet guided laser micromachining were researched including the coupling alignments, the largest incidence angle of full reflection, multimode optical fiber transmission, the decay of laser energy in water and SRS(Stimulated Roman Scattering). The coupling status detecting and adjusting system was designed. This system was based on the coupling image acquired from the CCD camera machine vision. A self-developed image processing software was used. It can monitor the coupling status rapidly and accurately.The hydrokinetics principle of high speed water-jet was researched. The factors affecting the stability of water-jet, the contract flow principle and the cavitation principle were researched. The high-pressure water-jet hydraulic system was simulated by using FLUENT finite element analysis software. The reasonable parameters for creating ideal jet state were acquired. By using the simulation results high speed jet which was more than 100mm long at the speed of over 100m/s was formed in experiment. The interaction principle of laser, solid and liquid was researched. The temperature field of the machining process was simulated by using ANSYS finite element software. Meanwhile, material removal situation was simulated by using“elements killing technique”. In the simulation, the laser energy distribution is not treated as Gaussian distribution. The cooling of high speed water-jet and the impact of shock on heat-affected zone distribution, temperature gradient and melt debris were focused on.Secondly, a set of water-jet guided laser micromachining system was designed and developed to realize the key techniques of water-jet guided laser micromachining. It composed of pulsed Nd: YAG laser system, high-pressure hydraulic system, coupling unit of laser and water-jet, CCD camera machine vision coupling status detecting system, computerized numerical control system and workbench, etc.The coupling unit of laser and water-jet is the key part. It′s structure affects the machining results much. The liquid cavity in the coupling unit is quite small. Liquid field in the cavity is steady and symmetrical. The thickness of the water layer which laser goes through is only 0.2mm. Sharp nozzle orifice edge guarantees the formation of the reflux contract water-jet. By adding telescope unit and beam expanding unit on pulse Nd: YAG laser system, the numerical aperture of focusing laser beam is reasonable, waist diameter is small and the focus depth is great, which is quite suitable for water-jet guided laser microprocessing.Finally, in order to master the processing principle, the experiments were carried out using the water-jet guided laser micromachining system. The experiments were done to find the influence of machining parameters on water-jet stability, focused laser spot diameter, the attenuation of laser energy and the processing efficiency of different materials. The processing parameters were optimized by using single factor method and orthogonal experimental method. At last, silicon-based chip and stainless steel 1Cr18Ni9Ti were machined by using optimized processing parameters. The experiments results proved the excellent micro-machining ability of water-jet guided laser micromachining and its wide practicality.更多还原