Theoretically And Experimentally Studying On The Pressure Feedback Dynamic Characteristics Of Extruder Based On Virtual Instrument

The virtual instruments (VI), a newly developed testing instrument was appeared as the result of the combination of computer technology and testing instruments technology. In this paper, the virtual instrument was used into the process of extrusion. Study the dynamic process of extrusion by the advanced measurement.Firstly, the virtual instrument which can automatically collect and save various data was developed by using LabVIEW software. Thus the hardware condition for real time recording various parameters changing in extrusion processing was created. Secondly, the transfer function of the single screw extruder was evaluated by analyzing its mechanism. And finally the correctness of the transfer function for single screw extruder obtained by analyzing mechanism was proved by collecting the dynamic characteristics between real rotate speed of screw and die pressure based on several materials. The most important component of the pressure close-loop control system was made up. The influence factors of extrusion processing are very complex, so the control system must be adjusted continuously to adapt the change of the extruder's condition. The pressure control of the extruder not only is the most important course for extrusion controlling but also is the most difficult problem. Until now, the most domestic extrusion systems haven't been equipped the close-loop control system between the die pressure -and screw rotate speed, due to the lack of enough theoretically research in the adjustment mechanics and stability of the close-loop control system. For the present status, the Pressure Close-loop Control System with AC speed regulation was further studied based on virtual instrument and the transfer function of the single screw extruder by using automatic control principle in this paper. Their transfer ructions was reasoned in detail. Meanwhile, the steady condition was obtained and the correctness of the theoretical derivation was proved through experiment validating.The melt pump has excellent stabilizing pressure function, but it still exist the coordination problem between the extruder and the melt pump. Finally, the PID pressure close-loop control system of the Tandem Extrusion System of Single Screw—Melt Pump was profoundly researched, and the coordination problem was solved.