Fuzzy Control System Design Of The Accuracy Of Forming Wire Width In MEM(FDM) And Its Application

With the rapid development of additive manufacturing,the demand of products became higher and higher.The products with low cost,short cycle,good quality and personality are favored.As the typical process of additive manufacturing,melted extrusion manufacturing possessed lots of advantages,including automation of molding process,wide range of molding materials,easy maintenance of molding equipment with small size,thus,it has been widely applied in the field of construction,light industry,archeology,military,health care,humanities,arts,aviation aerospace and so on.However,the precision of forming wire`s width is difficult to control due to the solidification of molding material from semi-solid to solid and the influence of multiple factors in molding process.Closed-loop control system possessed high control precision,strong anti-interference ability,the basis requirement was the feedback loop.Because of the larger expansion coefficient of the thermoplastic materials,it is hard to measure the width of the forming wire,which made the barrier to the design of the molding system.In order to improve the precision of the forming wire and ensure the quality of the products,the study designed the fuzzy-control system,the detailed contents are as follows:1.The indirect measurement of forming wire's width was carried out to achieve the feedback loop of the system.It's hard to measure the width of the forming wire due to the higher expansion coefficient of the thermoplastic material.The study indirectly measured the forming wire's width by detecting the scanning and extruding speed according to the matching relationship of extruding speed,scanning speed and forming wire's width.The method is reliable and easy to realize,also,it could avoid the introduction of unnecessary error.It provided a new method for the design of the system,pave a new way for similar processes in the field of additive manufacturing.2.Building approximate mathematical model of system could improve the accuracy and designing efficiency of system.The controlled object of MEM molding system is the nozzle device driven by stepper motor.As the main part of the system,the stepper motor has the typical characteristics of nonlinear,time-varying and strong coupling,which lead to the parameters even the structure of system changed along with the environment change.Thus,it brings problem for design the system.This paper stated that proper simplification of the stepper motor is able to improve the design efficiency of system and shorten the design cycle.3.Design fuzzy self-tuning PID controller to improve control precision.Conventional PID controller has the advantages of simple algorithm,good performance and high reliability,however the control effect couldn't meet the system requirement due to the limitation of the accurate mode.Fuzzy self-tuning PID controller can adjust the control parameters in real time according to the situation without the limits from the accurate model.Also,it possesses the high dynamic response quality,good adaptability and robustness as well as good control effect.4.Completing the design of hardware and software.Build the hardware circuit for forming control system.Write and debug the main program,the program of speed detection,PID controller and pulse output.Complete the design of fuzzy control system of MEM forming wire width.5.Apply the fuzzy control system to complete the manufacturing entity.Compare and analyze the molded effect.Conclusion: Fuzzy control system could effectively improve the accuracy of MEM forming wire width.The problem that wide does not meet the accuracy requirements when the nozzle scanning path less than 3mm of radius curvature has been solved.The molding accuracy has been improved by 90%,which provided the protection for the quality of the molding product.Meanwhile,it provided a useful reference for the precision control of other similar process in the field of additive manufacturing.