Research On Overprint Accuracy Of Register System Of Four-color Drum Gravure Press

Gravure printing machine is a kind of equipment widely used in the modern printing industry.As the most commonly used gravure printing machine,four-color web gravure printing machine can be applied to different materials and can complete large-scale printing tasks.However,the current loss rate of gravure printing has been consistently high,and the quality problems of printing products such as color difference,flying ink,missing printing and ghosting are urgent problems to be solved in the printing industry.The registration control system is an important part of gravure printing machines,and its registration accuracy directly affects the quality of printed products.At present,the registration system of gravure press mostly uses PID controllers,which have low control accuracy,resulting in excessive printing errors and a large amount of printing product loss.In addition,PID controller is not effective in dealing with complex control problems such as nonlinear and strong coupling system in production practice,which cannot meet the development needs of higher speed,higher precision and more intelligence in printing industry.In response to the above issues,a high-precision control model for the registration system of four-color web gravure printing machine is constructed,and the overprint control scheme is designed to improve the overprint accuracy.The main research contents are as follows:(1)The mathematical model of four-color web gravure printing machine registration system is constructed.By analyzing the structure of the gravure registration system,the composition and principle of the gravure machine are clarified.We analyze the influencing factors of overprint accuracy in the actual printing process and extract tension,speed,and printing material characteristics as the main factors.Based on this,the tension mathematical model and the longitudinal registration error mathematical model of the two-color gravure printing machine are established,and the mathematical model is recursive to the four-color web gravure printing machine to establish the four-color web gravure printing machine registration system mathematical model.(2)The PID controller of registration system is modeled and optimized.According to the deduced mathematical model of the four-color web gravure printing machine registration system,the accuracy of registration error of the existing PID controller-based gravure registration system is verified to be 1mm by Simulink simulation.The error is too large,which will cause a lot of printing loss in actual production.The PID controller is optimized by introducing Smith predictor and fuzzy algorithm.Finally,it is verified by modeling and simulation that the optimized Smith-fuzzy-PID can reduce the existing PID control error to 0.8mm and improve the overprint accuracy by 20 %,which meets the requirements of three-level printing.(3)The model-free adaptive controller of four-color reel gravure registration system is designed.The nonlinear controlled system is linearized,and the influence of interference factors such as tension,speed and printing material characteristics on the register control system is reduced by estimating the pseudo partial derivative of the register system in real time.Finally,through modeling and simulation,it is verified that the model-free adaptive controller can reduce the registration error peak to 0.5mm,and the response time is 30 s,which further improves the registration accuracy of the registration system and can meet the accuracy requirements of the secondary printing.(4)A high performance ADRC model is constructed.Aiming at the problems of serious coupling between states,weak anti-interference ability and great influence on error tracking performance of four-color gravure press registration system,an active disturbance rejection control model is constructed.The tracking differentiator is constructed to arrange the transition process.The extended state observer is designed to realize the tracking estimation of the coupling interference between the states of each loop,and the error feedback controller is constructed by nonlinear combination to compensate the disturbance.Finally,through modeling and simulation experiments,it is verified that the peak value of overprint error based on active disturbance rejection controller is 0.18 mm,which greatly improves the overprint accuracy of the registration system and meets the requirements of first-level printing.By optimizing the PID control strategy,designing the model-free adaptive controller,and establishing an active disturbance rejection control model,we can improve the overprint accuracy of the gravure printing machine registration system.It has certain reference significance for reducing the overprint error of the gravure printer,reducing the loss of printed products,reducing the printing cost and improving the production efficiency.