Microelectrodes on-line measurement in micro EDM

An on-line measurement system (OMS) was proposed. It is composed of a halogen type light source, a zoom lens, a CCD camera and a bracket that has 6-degrees of freedom. It has a resolution of 1.61 μm and a magnification of 113-729. Based on the Linux operating system, an image capturing program was developed with the V4L2 API, in which the image data was acquired with the method of mmap() memory map. The conversion between the data structure of IplImage and the class of QImage was implemented. Therefore the image could be processed by using OpenCV, and showed with Qt. The contour of microelectrode can be extracted by means of Canny edge detector. Furthermore, the G code for on-line measurement was also developed. The experiment of block electrodes electric discharge machining (EDM) grinding was carried out. It shows that the relative error between OMS and scanning electron microscopy (SEM) is less than 5%. It also shows that the system can be used to deal with the difficulties in microlectrode on-line fabrication and measurement in micro EMD.