The Numerical Simulation For Single-Screw Extrusion Processing

In this paper, the author adopted the software MathCAD to analyze the classical theories for different stages of single-screw extrusion, in order to offer facilities for readers to investigate the influences of different parameters on extrusion processing, and check the screw parameters, polymer characteristics and operating conditions. At the same time, the picture and chart form for pressure distribution, temperature distribution, etc. were also achieved by the powerful functions of MathCAD, so readers could have an intuitionistic understand. The theory foundations of this paper were Darnell-Mol solid conveying theory for the feeding stage, Tadmor melting theory for the compressing stage, and liquid dynamics theory for the metering stage. The main contents of this paper were as follows:1.The author generally introduced the three-stage and seven-section model for the whole single-screw extrusion, in order to provide an instruction to the followers.2.During the analysis for the Darnell-Mol solid conveying theory, the author considered the friction coefficient's real time changes with pressure and temperature, and applied the Laplace transform method to solve the energy equation. On the basis of the MathCAD programs, the pressure and temperature distributions along the screw were also gained to optimize parameter settings, thus, enhance solid conveying efficiency.3.During the analysis for the Tadmor melting theory, the author calculated velocity distribution and solid-bed width distribution for the Newton and Datwald-de wale model separately. On the basis of the MathCAD programs, the solid-bed width distribution curve and the melting length were gained to optimize design.4.During the analysis for the liquid dynamics theory for the metering stage, the author calculated the leaking-flow rate in the gap between barrel and screw, applied latter-day analysis method to calculate the energy consumption, and employed the Laplace transform method to solve the energy equation again.The velocity distribution, temperature distribution and accordingly viscidity changes were also achieved by the MathCAD programs.5.By considering the pressure flow and the dragging flow separately, the author also presented a new method to analysis the Datwald-de wale model for the metering stage, which could be the theory foundation for the assistant small screw's design for precision extrusion with the help of MathCAD programs.