Study Of Vision Automatical Tool-Setting Technology For CNC Machine Tools

With the rapid development of machine tool manufacturing, the demand to improve the machining accuracy is higher and higher for production. Because tool-setting is the first step for machine tool parts processing, so the accuracy and efficiency of tool-setting will directly affect the subsequent processing quality of products. Due to the influence of manual factors, the traditional operation has some defects such as big errors and lower efficiency, in addition, the high precision automatic tool setting device mainly rely on imports, its price is more expensive. Therefore, it is necessary for us to develop a new automatic machine tool setting device and to solve these problems. In this paper, we apply the technology of machine vision positioning to the field of tool-setting of CNC machine tools on the basis of the traditional study, in order to achieve automatic tool-setting.Firstly, according to the principle of tool-setting in CNC machine tools, we design the overall structure of the system, after that we calculate some parameters of hardware devices and select its type, and then we set up a three degree of CNC platform for visual automatic tool-setting, which can move freely in its work space. DMC-2143 motion controller and magnetic grid sensor are used in the motion control of machine tools, on the basis of this, the AC servo motor and the moving parts of the machine can form the whole closed loop of the numerical servo position control system, which can improve the accuracy of the motion control of CNC machine tools.Secondly, we use different methods to complete the camera calibration of two industrial cameras, which is based on the LabVIEW Vision Development Module Calibration Training tools and Matlab script nodes, and on the basis of the established nonlinear model of the camera imaging, the internal and external parameters matrix of the camera are solved, at the same time, we do the digital image processing for the acquired workpiece, extract the knife point coordinates and calculate the distance of the knife, while we compare and improve the image processing algorithms, and then we choose the optimal processing scheme through the experimental verification, so that it can improve the accuracy and stability of the knife positioning system. In order to improve the effect of workpiece edge detection, in this paper, we have improved the algorithm of the workpiece contour edge detection on the basis of the Canny operator, which uses the Canny operator and the morphology of fused image processing. In the algorithm of cutter setting coordinate extraction, we use the improved Hough transform algorithm to extract the center coordinate of rectangular workpiece and circular workpiece, which can reduce the complexity of the algorithm. In the algorithm of calculating the tip to the knife point distance, we use the optimization principle of point to the straight line distance to determine the tool tip, through which we can determine the knife tool drop distance, so as to complete the extraction of 3D machine tool coordinates of the knife point.Finally, we use LabVIEW as software development platform, and the software of visual positioning is developed, which can be used in the field of CNC machine tools automatic tool-setting. At the same time, on the basis of camera calibration, using the software algorithm of visual positioning to extract the machine tool coordinates of workpiece of tool-setting point and to calculate the distance of knife tool falling, after that,using the PC to send the information to the motion controller, and then, we can control the actuator movement and adjust the moving distance of the three axis machine tool, at last, it can complete the workpiece automatic tool-setting, which improves the intelligence and automation of CNC machine tool setting technology. After the debugging of the system and automatic tool-setting experiment, the result proves that the system operation is stable and reliable. By using the developed system of automatic tool setting, the time of automatic adjustment is only one third of manual cutter and the error of visual automatic tool-setting is within the 0.02 mm, which can meet the requirements of the actual machining.