Optical Measurement of Surface Texture for Practical use in working fluid of an Electric Discharge Machine and Optimization of its Machining Conditions

本研究的目的是开发一种光学测量系统，通过该系统可以在工作液中对电火花加工产生的相对光滑表面的表面纹理进行实际评估，并提出一种优化控制系统，通过该系统可以在一系列加工过程中充分更新后续的加工条件。测量原理是基于激光散斑成像原理。光学测量单元主要由倾斜入射的激光束和防水的视频图像传感器组成，并连接到传统的电火花加工机（EDM）的电极保持器。功率稳定的激光源与电火花加工机隔离，并通过光纤与测量单元连接。设计了图像传感器的光学透镜系统，使其能够测量像面上的散斑强度分布。由图像传感器检测到的光强分布被数字化并发送到计算机进行数据处理。 ...更多信息 数据处理。实验中不仅用对比度值，而且用频谱来评价光学信息。认识到在低对比度的情况下光谱数据是重要的。研究还表明，检测到的强度分布受工作流体的影响很大，这取决于其浑浊或杂质。作为一种实用的补偿方法，在工作流体腔中设置两个参考面，以获得临时的偏差数据。通过实验研究表明，尽管表面纹理的评定精度较低，但可以用光学方法进行评定。有人指出，电火花加工产生的表面纹理是几何各向同性和其横向间距参数的相关性相当好的平均振幅。光学测量单元和工作表面之间的相对定位被改变为通过NC位置数据的开环控制方法，因为通过使用检测到的图像数据的定位是复杂且耗时的过程。据判断，过程间的光学检查的自适应控制的电火花加工是可行的，实际使用，虽然个别机器的特点，必须考虑到。少

The research purposes are to develop the optical measurement system by which the surface texture of relatively smooth surfaces generated by electric discharge machining can be assessed practically in working fluid and to propose the optimizing control system by which the succeeding machining conditions are adequately renewed during a series of machining processes. The measuring principle is based on laser speckling on image plane. The optical measurement unit composed mainly of an oblique incident laser beam and a waterproofed video image sensor was constructed and attached to the electrode holder of a conventional electric discharge machine (EDM). The power stabilized laser source is isolated from the EDM and connected with the measurement unit by light fiber. The optical lens system of image sensor was designed so that the speckle intensity distribution on an image plane can be measured. The intensity distribution detected by the image sensor is digitized and send to a computer for d … More ata processing. The optical information was evaluated experimentally by not only contrast value but also frequency spectrum. It was realized that spectrum data is important in case of low contrast value. It was also demonstrated that the intensity distribution detected is considerably affected by the working fluid depending on its muddiness or impurity. As a practical compensation means of its influence, two reference surfaces were set in a working fluid chamber to obtain temporary bias data. Through the experimental study it was made clear that the surface texture can be assessed optically in spite of its low accuracy. It was noted that the surface texture generated by EDM is geometrically isotropic and its lateral spacing parameters are correlated fairly well with averaged amplitude. The relative positioning between an optical measurement unit and a work surface was changed to an open-loop control method by NC location data because the positioning by use of detected image data is a complicated and time-consuming process. It was judged that the inter-process optical inspection for adaptive control of electrical discharge machining is feasible for practical use although individual machine characteristics must be taken into account. Less