Research On Numerical Simulation And Application Of Micro-molding Disk Type Plasticizing Unit

The plasticizing unit of the micro-molding machine generally adopts the plunger type orthe long screw type as the mixing device,but the mixing quality and the plasticizing effect ofthe plunger type is poor,and the small plasticizing screw has obvious weaknesses of lowstability of processing?lack of structural strength?limited life-span?being difficult to transportplastic and being difficult to process thermosensitive plastic,etc.;disk-type plasticizing unit cannot be used in the traditional injection molding machine,which is because it can not establishhigh melting pressure.But it is feasible to apply disk-type plasticizing unit to the micro-moldingmachine,which doesn't require high plasticizing capacity and melt pressure.The main contents of this paper are as follows:In the first chapter,the research progress of micro-molding injection molding machine isintroduced,and the research status of disc-type screw plasticizing theory and moldingequipment at home and abroad is reviewed,the research status of numerical simulation of theplasticizing process based on Computational Fluid Dynamics(CFD),and the numericalsimulation of the three-dimensional flow of screw and the numerical simulation of theperformance of the screw mixing is included,and the content as well as the organizationalstructure of the paper is determined.In the second chapter,the geometric parameters and the end-face curve equation of thedisk-type plasticizing unit are discussed and determined.The similarity between the disk-typeplasticizing unit and the long-screw-type plasticizing unit functions,which are similar in theirfunction and motion,is calculated by the similarity and productivity.Based on the similaritybetween them,as well as the method of working out the geometrical parameters of eachfunctional segment of the long screw,this paper gives the range of the length,depth,compression ratio and the screw-flight width of each functional segment of the disk-typeplasticizing unit.Based on the diameter and the output,the curve equation of the end-face isgiven.And the three-dimensional model of the disk-type plasticizing unit is built by usingSolidworks software.The third chapter analyzes the working principle and flow model of the disk plasticizingunit,and gives the constitutive equation needed for the numerical simulation analysis accordingto the time-varying equation in the column coordinate and the rheological theory of the plastic.Considering that the the motion is too complex to simulate,the motion model is simplified.Based on the simplified model,the flowing law of the fusant in the disk plasticizing unit isanalyzed,and the velocity equation and flow equation under drag and pressure is deduced.In chapter four,the geometric model of the disk plasticizing unit is established and meshed.The material parameters and boundary conditions of the numerical simulation are defined byusing user-defined function(UDF).The numerical flowing simulation of the melt conveyingsection of the disk plasticizing unit was carried out by using FLUENT.Four cross sections of thespiral grooves were selected from the inlet to the outlet of the fusant,to analyze the distributionof the velocity,pressure,temperature and shear force of the fusant in different cross sections.Inaddition,the impact of the screw speed on the plasticity performance was analyzed.In chapter five,the geometrical models with different parameters of disk screws wereestablished by using orthogonal test method and CFD numerical simulation method,and thesimulation of these models was carried out.Using the mass flowrate,the maximum shear stressand the range of temperature as the experimental index of orthogonal test,and finally theoptimal result of the geometrical parameters of the disk screw was determined.The mixingperformance of the disk screw which includes shear rate,residence time(RTD)and mixingindex,was analyzed by using the tracer particle method(PTA).The results showed that thehigher the rotational speed,the better the RTD,the better the distributed mixing performanceand dispersive mixing performance.The sixth chapter summarized the research work in the paper,and pointed out theshortcomings in the research process.And also presented the content that needs further research.