| With the continuous development of technology,a new generation of electronic packaging technology represented by Surface Mount Technology(SMT)has emerged.SMT obtains the advantages of low cost,easy integration of manufacturing components and high degree of automation.The fixing of microelectronic components is a part of the core processes of SMT.At present,the industry mainly uses adhesive equipment to bond components.Although the existing desktop programmable dispensing system has a wide range of applications,it has the disadvantages of poor dispensing accuracy and low automation.The device relies on manually completing the clamping position of the workpiece,which affects both work efficiency and dispensing precision.The online dispensing system is an emerging high-end dispensing device that utilizes industrial cameras instead of human eyes to complete workpiece feature recognition and plan dispensing paths.It has suitable equipment flexibility,recognition accuracy and operational stability,and has become a dispensing field ideal equipment.Therefore,this paper designs a highly flexible,fully automatic online precision dispensing system with machine vision.The main contents are as follows:After comprehensive comparison of contact and non-contact dispensing technology,this paper requires a non-contact dispensing scheme and analyzes the fluid ejection process of a typical non-contact dispensing scheme.The conventional noncontact dispensing structures were described and compared.It was clarified that the knife-supported piezoelectric injection structure can achieve high-precision and highconsistency dispensing,so it is used as the dispensing scheme of the system.Depending on the non-contact dispensing injection scheme,the drive scheme based on servo motor-ball screw is designed and the key components are selected and checked.The static and dynamic simulation analysis of the drive structure is implemented by AnsysWorkbench software to obtain the inherent structure of the drive structure.The frequency and displacement frequency response curves verify the rationality of the organizational design and provide the processing and assembly basis for the subsequent production of the prototype.Machine vision technology is approved in the drive structure to improve the recognition accuracy and automation level of the equipment.The feature collection of the workpiece is completed by selecting appropriate visual hardware,and the collected features are extracted and processed by the corresponding algorithm,and the processing result is invoked as a basis for system positioning and planning path.Aiming at the problem that the driving system can not directly use the camera to collect the results,the mutual conversion relationship between the world coordinate system,the pixel coordinate system,the camera coordinate system and the image coordinate system is analyzed,and the problem is solved by the related matrix transformation.Based on the movement characteristics of the dispensing operation,the control scheme of the industrial computer and the motion control card is called upon to realize the linear and circular interpolation motion of the system.Automatic clamping and fixing device for the workpiece is developed by using the solenoid valve and the cylinder assembly,which avoids the manual clamping of the workpiece and effectively improves the working efficiency of the system.Finally,the experimental prototype was built according to the design structure,and the prototype was presented to the feature recognition accuracy,the driving system running precision and the comprehensive dispensing ability experiment.Through experiments,it is found that when the system running speed is lower than 600mm/s and the camera shooting delay time is greater than 0.05 s,the system image visual precision is sub-pixel level,and the device positioning accuracy and repeat positioning accuracy are all lower than 0.01 mm,thus proving the work of the prototype.Exceptional performance,cannot answer the need of the industry dispensing precision. |
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