A Small And Micro-hole Measurement Method And System Based On Coordinate Measuring Machine

Small and micro holes are widely found in various types of mechanical workpieces,and the machining accuracy of holes affects the performance of workpieces.Therefore,high efficiency and high precision instruments are needed to measure small and micro holes.The Coordinate measuring machine(CMM)is often used for contact measurement,which has the advantages of high accuracy and repeatability and is widely used for micro-feature measurement.Operators usually controlled the CMMs measurement process manually.The probe tip is difficult and inefficient to be guided to the center of the micro hole due to the part is too small.An efficient system that can guide CMM for automatic measurement micro hole is needed.In response to the above problems,a set of automatic measurement system applicable to microporosity has been proposed in this paper.The main research contents are as follows:1.The method was proposed to guide the probe tip into the center of the upper surface of the micro-hole according to the relationship between the position of the micro-probe tip and the small or micro-hole;an automatic contact measurement method of the small or micro-hole is proposed.According to this principle,a software was designed to realize the above functions,and the software has been applied to a CMM setup by laboratory.2.The method of visual guidance was analyzed,and the principle of visual guidance was elaborated.The orientation of the probe tip and hole was used to guide the CMM’s probe tip into the center of the micro hole.The principles of automatic contact measurement were described.3.The image pre-processing methods for visual guidance were analyzed and introduced.The pre-processed images were used for image recognition,two different methods were used to detect the probe tip and micro holes in the image.4.The diameter of 55 μm probe tip was guided into diameter of 100 μm pinholes using above system;the system was applied to measure small pores in a cigarette absorber cross-section by guiding diameter of 300 μm probe tip into the cigarette absorber.The best standard deviation for measuring the diameter of small pores in the cross-section of cigarette absorbers was 1.8 μm using contact measurements.