The Research And Development On Parison Thickness Control System Of Blow Molding Equipment

Plastic extrusion blow molding equipment is the world’s mostwidely used manufacturing hollow plastic containers of special equipment,most of the plastic hollow products are obtained by extrusion blow moldingprocess. However, the wall thickness of the extrusion blow molding productuniformity is difficult to control,especially for medium-sized plasticproducts,subject to the impact of the parison weight is more difficult tocontrol. As one of the core technology of extrusion blow molding machines,no reliable domestic product,mostly dependent on imports,making theextrusion blow molding equipment prices high.For this design the parison thickness control system, the control system isbased mainly on PLC controllers, including proportional amplifier,electro-hydraulic proportional valve, hydraulic cylinder load anddisplacement sensors. Its working principle is to use the difference betweenPLC input voltage and the feedback voltage amplified by the proportionalamplifier, acting on the electro-hydraulic proportional valve to controlhydraulic cylinder to drive the load up and do wn movement of the mandrel,to the purpose of control the thickness. And designs a wall thickness controlsystem software and hydraulic systems, reliably achieve the thicknesscontrol.Adhering to the "theory and practice" principle,a mathematical model for eachcontrol mechanism of parison wall thickness control system is built.And makes thesimulation analysis with the MATLAB simulink simulation platform and designs thePID controller to improve the control system and to improve the control effect.Simulation results show that the thickness control system strong robustness, stronganti-interference ability,is able to achieve the desired control effect.Finally, using the Bezier interpolation split to design the parison wallthickness distribution curve.This method can basically to ensure smooth transition of each transition point and achieve a certain degree of tension,hasa good local control performance.This article includes the following sections:The first chapter explains the background of the subject,summarizes theblow molding technology,and introduces the research status and developmenttrend of domestic parison thickness control system, finally proposes researchsignificance.The second chapter describes the experimental equipment and experimentalenvironment,made a brief introduction of the basic properties of extrusionblow molding equipment,mechanical structure and working methods,as theparison thickness control lay the foundation for the next chapter.The third chapter introduces the principle of parison thickness controlsystem,and proposes the overall design scheme of parison wall thicknesscontrol system,and introduces the components of the control system.The fourth chapter describes the parison wall thickness software contro lsystem and hydraulic systems.Describes the design of PLC communicationwith the computer,writes the PLC program control wall thickness,and designsthe wall thickness of the hydraulic system.The fifth chapter builds the mathematical model of the control mechanismof the parison thickness control system, by calculating the transfer functionblock diagram of the wall thickness control system.The sisth chapter builds the simulation model in MATLAB and makes thesimulation analysis according to the transfer function block diagram,anddesigns the PID controller to improve the control system, anti-interferenceability and robustness of the system are simulated.The seventh chapter proposes design method of wall thickness graphics,introduces the editing and debugging methods of thickness distribution curve.