Design And Research Of Precision Co-extruder And WPC Profile Coating Co-extrusion Die

The existing co-extrusion technology has some problems in practical operation,such as low precision of extruded products and difficult to achieve uniform and stable extrusion,there are also some problems such as unstable interface of coating co-extrusion and poor adhesion between core and shell,etc.Combined with the special properties of wood plastic materials,the design and processing of extruder and extruder head for co-extrusion of wood plastic profiles complicated.This topic aims at the above problems.Based on the three-dimensional modeling software of Creo,CAE simulation software is used as an auxiliary tool,on the basis of the existing co-extrusion equipment,with the guidance of precision and stable extrusion,combined with the improvement of the conventional full-thread three-stage single-screw extruder,the design of the new plastic profile co-extruder is proposed.Then,the existing coated extruder head is analyzed,the defects of the die channel are found accurately,and a new design scheme is put forward,which further solves the channel problem,completes the design optimization process of the co-extruder and the coated extruder head,improves the design accuracy and efficiency,and greatly reduces the waste of personnel and materials caused by continuous die testing.The main research contents are as follows:Firstly,the existing co-extrusion equipment was tested.By changing the process parameters,the shape and size of the cross-section of the extruded parts and the uniformity of the coating were observed under different processes,and the reasons for the non-uniformity of the extrusion coating were analyzed,which laid a foundation for the optimization design of the subsequent co-extrusion equipment.Then,Creo software was used to design a new co-extruder in order to achieve precise and stable extrusion.The extrusion system,transmission system,lifting device and heating and cooling system of co-extruder were optimized and analyzed respectively by consulting relevant data and comparing various design schemes,and improved the productivity and stability of the equipment from all aspects.After the design is completed,the finite element analysis of the screw is carried out by means of CAE simulation software,and the extrusion process of the material is further studied by establishing the screw pressure field,velocity field and shear rate field.Secondly,in order to find out the specific problems of the existing extruder head structure,through further numerical simulation of the core and shell channels of the extruder head,the uniformity of the exit velocities of the two channels is analyzed,and the corresponding problems are found out.Furthermore,several optimization schemes are proposed,and the flow field is simulated by CAE simulation software.It is determined that the main problem of the extruder head channel is at the corner near the shell exit.On the basis of trend analysis of flow field in several schemes,considering the whole channel,a new design scheme of co-extrusion channel is proposed.Finally,in order to accurately calculate the size of the extruder head structure,the rectangular encapsulated product with 50 mm *13 mm inner layer as HDPE-based wood plastic and shell as HDPE was directly taken as the research object,the extruder head size of the finalized section was obtained by reverse extrusion calculation with the simulation software,considering the results of channel optimization,the overall structure of the channel of the co-extruder head was designed.Then,the pressure field and velocity field of the new designed channel are analyzed and verified.The rationality of the new design channel and the stability of the composite interface are guaranteed by combining reverse simulation with forward simulation.