Research On Automatic Grinding And Testing PCB Micro-drilling Technology

Since PCB drill bit is the main consumption tool for making PCBs, grinding and inspecting PCB drill are mainly realized manually. Because of the characteristics of PCB drill bit such as the mini-dimensions, the special spatial structure of the blade, the high inspecting precision requirements, various categories and sizes, large dimensional span and et al, what is more, the low quality and efficiency of manual grinding and inspection cannot meet the requirement of the PCB drill manufacturing, so it is meaningful to research and develop an automatic grinding and testing min-drill system for resolving urgent needs in PCB drill industry. According to the property of the automatic grinding and testing system, the PCB drill spatial structure of the blade, matching algorithm and radial detection are investigated in this paper.Three-dimension modeling of the min-drill blade is done, and with the software of Solidworks the mathematical model is achieved. Through researching this model and the grinding method of human way, the proper grinding point of min-drill is established. The key mechanical structure, motion control subsystem and the vision detection subsystem are designed in the paper.Image preprocessing plays an important part in vision detection. A series of image preprocessing methods for removing interference information is presented in the paper, which is consisted by median filter, iterative threshold segmentation and eight direction contour tracing method of Freeman.The feature points of the PCB min-drill is studied deeply. As for corner detection, Moravce algorithm, SUSAN algorithm and Harris algorithm are analyzed, and an improved Harris algorithm which is base on mini-drill corner detection is proposed. The experimental results show that this algorithm has high accuracy in the location on the feature point.Through sub-pixel edge position method base on Gaussian, an improved method for measuring the diameter of min-drill is put forward. The comparing experiment demonstrates that the position accuracy of the algorithm in this paper is high, which is three times of that of pixel edge position method.Finally the software of the system is implemented and tested in the platform of Visual C++. The experiment indicates that the system design of automatic grinding and testing PCB mini-drilling is feasible, which plays an important part in improving the quality and the efficiency of PCB mini-drill grind and testing.