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

研究目的是研制一种光学测量系统，用于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，并提出优化控制系统，以便在一系列加工过程中充分更新后续加工条件。其测量原理是基于激光在像面上散斑的原理。构建了由斜入射激光和防水视频图像传感器组成的光学测量单元，并将其安装在常规电火花加工(EDM)的电极座上。稳功光源与电火花加工隔离，并通过光纤与测量单元相连。为了测量像面上的散斑强度分布，设计了图像传感器的光学透镜系统。由图像传感器检测到的强度分布被数字化并发送到计算机进行d…更多的数据处理。实验上不仅用对比度来评价光学信息，还用频谱来评价。人们认识到，在对比度低的情况下，光谱数据是重要的。实验还表明，检测到的光强分布受工质的影响很大，这取决于它的混浊程度或杂质。作为对其影响的一种实用补偿手段，在工作流体室中设置了两个参照面，以获得临时偏置数据。通过实验研究表明，尽管表面纹理的评定精度较低，但仍可对表面纹理进行光学评定。指出电火花加工产生的表面结构在几何上是各向同性的，其横向间距参数与平均幅度有很好的相关性。由于利用检测到的图像数据进行定位是一个复杂且耗时的过程，因此利用NC定位数据将光学测量单元与工作表面之间的相对定位改变为开环控制方法。认为电火花加工自适应控制的过程间光学检测在实际应用中是可行的，但必须考虑到单个机床的特点。较少

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