| Injection molding gears have the advantages of lightweight,low noise,low cost,high production efficiency,large batch and so on.However,in the production process of injection molding gears,due to the unstable manufacturing process,mold deterioration,impurities within raw material and other reasons,it is easy to produce size out-of-tolerance,burr,black spots,warping deformation,teeth deficiency and other defects.These factors seriously affect the transmission accuracy,appearance quality,service performance and service life of injection molding gear.In order to ensure product quality and production efficiency,for injection molding gear production site inspection need,a workshop-oriented rapid visual inspection system for injection molding gears is developed.The system is combined with the production line and used conveyor belt for loading,glass rotary for transmission,pneumatic device for sorting.The basic parameters such as the tip diameter,the hole diameter and the concentricity are measured by machine vision method,and to compare with its tolerance range,so as to judge the product quality.Through the algorithms such as image segmentation,edge extraction,curve fitting,feature extraction and defect identification,the surface defects such as burr,black spots,warping deformation and teeth deficiency are inspected.Finally,good and bad products are automatically sorted according to the test results.The system has the characteristics of fast,online,automatic and non-contact.The practices show that the measurement repeatability of the system is less than 0.005 mm,the fastest inspection speed is 170 pieces/minute,the defect identification and sorting functions are correct.The inspection system has been put into use in the production site and has withstood the test of long-term stable operation.It can meet the on-line inspection demand of mass,high efficiency and high reliability of injection molding gears.The main research contents include:(1)Overall program determination and hardware system construction.According to the inspection requirements and the characteristics of injection molding gear,the overall scheme of the system is developed.The inspection system consists of optical imaging subsystem,mechanical control subsystem and software subsystem.The selection of camera,lens and light source is determined through calculation and experiment,and the design of optical imaging system is completed;the overall structure of mechanical control system is designed and the working principle of detection system is introduced.(2)Research on digital image processing technology.The median filtering method is used for denoising the image.The maximum variance between classes method is used for segment the image.The dual threshold algorithm based on canny operator is used for extracting the pixel level edge.The Lagrange quadratic polynomial interpolation method is used for extracting the sub-pixel level edge.The lattice calibration plate is used for calibrating the system,etc.(3)Inspection algorithm development.The algorithms of image preprocessing,edge extraction,target point extraction,curve fitting,parameter calculation,feature value extraction and defect determination used for the visual inspection of injection molding gear are designed and developed.(4)Software development.The software development process is planned;using C# language,the detection software based on Windows platform is developed,which has the functions of camera control,system calibration,parameter input,real-time display of inspection results,data analysis,image saving setting,automatic alarm and so on.(5)Inspection practice.The dimension measurement repeatability practice,speed practice,contrast practice and defect discrimination accuracy practice are carried out on the developed injection molding gears rapid visual inspection system.The practice results show that the inspection system can meet the testing requirements and is stable and reliable in the long run. |
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