Optimization And Improvement Of Pet Bottle Capping Machine

With the development of China’s economy and society,the demand for packaging products continues to increase,and the application of PET bottles has become more and more extensive.Especially since the COVID-19,nucleic acid detection reagent bottles also use PET bottles,and the demand for PET bottles has reached a peak.Against this background,in combination with the project of the fully automatic filling machine of Guangdong Shunde Innovative Design and Research Institute,the PET bottle capping machine in the fully automatic filling machine is taken as the research object to optimize and improve the PET bottle capping machine.This paper first describes the composition and working principle of the PET bottle capping machine,determines the design performance requirements of the capping machine according to the requirements,and points out that the original PET bottle capping machine has problems such as damage to PET bottles,working efficiency and unqualified rate,poor durability and economy.Aiming at the problems existing in the original capping machine,the structural design and optimization of the capping machine are mainly carried out from two aspects: the capping head and the support structure.The design of the new capping head changes the capping method from a downward pressure type to a clamping type,effectively avoiding damage to PET bottles caused by the downward pressure of the capping head during the capping process;Taking the cantilever beam structure as the theoretical support,the optimal size of the support column was calculated to be 12.1 mm,and the theoretical calculation results were simulated and verified by ANSYS Workbench;Through the design of a parametric modeling process,after determining the screw size as M6,using ANSYS Workbench,it was found that the largest impact on the stress on the contact surface between the lifting cylinder mounting plate and the support column was the slot length,followed by the slot width,and a new mounting plate model was established.Through the research and test on the fixture gasket of PET bottle capping machine,it is ensured that the capping machine meets the requirements of PET bottle capping,and the test scheme with stable operation and long fatigue life is selected.According to the characteristics of the elastic materials,the stress-strain relationship of the selected rubber,silicone and polyurethane elastic materials is obtained;Based on Taguchi’s method,the orthogonal test is designed for the elastic gasket,and it is concluded that the primary and secondary order affecting the torque of the spinning cap is the cylinder pressure,gasket material,gasket thickness,and contact area;Three groups of experimental schemes with high robustness were obtained by analyzing the signal to noise ratio of the orthogonal experimental schemes,namely,group 3,group 6 and group 8;Based on the analysis of the signal-to-noise ratio,the fatigue analysis was carried out,and the optimal test scheme was determined to be Group 6,that is,when the gasket material is silica gel,the contact area is 250mm2,the gasket thickness is 1.5mm,and the cylinder pressure is 0.5MPa,the elastic gasket meets the requirements of PET bottle capping,and the scheme has the best robustness and the longest fatigue life.According to the motion planning and demand analysis of PET bottle capping machine,the control system is designed to ensure the stable operation of the capping machine.According to the requirements of the drive mechanism and the rotating cover,calculate the parameters such as the required moment of inertia,speed and torque of the servo motor,and select the appropriate servo motor;According to the functional requirements,Mitsubishi FX3U-80MT/ES-A PLC is used as the main controller to design the implementation scheme of the capping machine control system;The servo motor control system is designed based on PID control to realize the detection of the rotating cap torque and the control of the motor speed;The functions of the human-machine interface are introduced to realize the operation control,real-time monitoring and alarm of the capping machine.Finally,the production test of the optimized and improved PET bottle capping machine is carried out.The results show that the optimized capping machine has a working efficiency of more than 25/min,and the proportion of unqualified products is less than 0.3%.There is no PET bottle damage.At the same time,the equipment operates stably and the working effect is ideal,which verifies the research results of this paper.