Research On The Optical Properties And Key Technologies Of A Novel Water Jet Guided Laser Processing System

With the development of precision machining and ultra-precision machining technologies, laser-hybrid processing technologies have gradually become the mainstream of manufacturing field. In terms of laser-hybrid processing technology, the combined processing technology of laser and water jet, namely the water jet guided laser processing technology, is a new direction of laser processing. Compared to traditional laser processing method, water jet guided laser processing technology, with its advantages of long working distance, small heat-affect zone, non-hot slag and high work efficiency, has been used in microelectronics, aviation machinery, medicine area, etc.However, owing to the utilization of traditional lens focus optical system in the existing water jet guided laser technology, the work of precision focusing, and the aberration of focusing optical system are unavoidable. To overcome these problems, based on the spot center characteristics of the non-diffracting beam generated by axicon, non-diffracting beam is introduced into water jet guided laser processing system for the first time, and a novel design of water jet guided laser processing system with coaxial monitoring function is proposed in this dissertation.The optical properties, and hydrodynamics characteristics, as well as the key coupling technologies between the non-diffracting beam and the water jet, have been deeply analyzed and researched. Using the transforming effect on non-diffracting beam through the water fiber, the Gaussian energy distribution of laser has been altered to a Flat-top energy distribution. This not only can improve the processing quality and satisfy the processing requirements, but also can enlarge the range of process and accomplish three-dimension process on a two-dimension platform. A coupling device is designed to solve the key technologies of coupling, such as the coupling efficiency and transmission loss between non-diffracting beam and water fiber. At the same time, a new algorithm for center location of non-diffracting beam is presented to improve the monitoring precision..The innovations of this dissertation are as follows:1. The non-diffracting beam is applied to water jet guided laser processing system for the first time. Through the research of the optical properties of the non-diffracting beam produced by axicon, a new method is proposed by use of the beam's features, such as small spot, long scope of collimation and symmetry energy distribution, and so on. In this method, an axicon is used to replace the traditional lens. The focusing problem has been resolved and the accuracy requirements of overall system design, processing, and debugging have been reduced in this way. (Patent No. accepted: 200910111326.0)Due to small divergence angle for laser beam in non-diffracting region, the non -diffracting beam can be similar to the parallel light. With the advantage of the non -diffracting beam, the coupling loss between laser and water-fiber has been reduced.3. A special three-axis coaxial optical system of processing, positioning and monitoring is designed to simplify the whole system (Patent No.: 200710009244.7). The optical system can implement the precise positioning of the laser processing indicator and real-time monitoring for the coupling of laser and nozzle, the bubble in the water, as well as the damage of the nozzle.4. Based on the sub-pixel technologies and edge detection methods, by use of the edge information of ring beam, a sub-pixel locating algorithm to the centre spot of the non-diffracting beam has been established. The experimental results show that this algorithm can achieve a high-precision positioning detection on the non-diffracting beam centre spot, and improve the precision of the system monitoring...