The Structure Analysis And The Computer Simulation Of The Pipe Die With Spiral Mandrel

In this paper, pipe die with spiral mandrel is designed through the open literature and existing experience. The main design method for it and how to create FEM model is also stressed. Moreover, Three-dimensional flow of polymer melt in the spiral die is simulated with POLYFLOW. The distribution of velocity, pressure and shear rate in the die is analyzed. Some inappropriate analyses of spiral die in the open literature are pointed out.Based on the original die, varying the geometric parameters, flow state under different geometric parameters is simulated. Effects of geometric parameters on the flow state in the die are analyzed, and some optimized geometric parameters are obtained.In analysis, when evaluating the distributing effect of the spiral spreader, the circumferential uniformity of velocity (flow rate) of the cross section on the common boundary between spiral spreader zone and compression zone is considered as the main evaluation factor. At the same time, a compositive method combining qualitative with quantitative isapplied to evaluating the circumferential uniformity of velocity (flow rate) from muti-aspects. In the method, the contours and profiles of velocity magnitude of the cross section, the velocity plots of the centre circle in the cross section and the statistical properties of velocities of the nodes in the centre circle are used for uniformity indexes.Through the simulation and analysis, we can draw the main conclusions:1. the flow in the spiral spreader is not a simple combination of axial flow in the annular gap and spiral flows in the spiral grooves; The number of the spiral grooves^ taper of the spiral mandreh the screw pitch and the thickness of the annular gap between the outer cylindrical die body and the mandrel is found to have significant effect on the circumferential uniformity of velocity (flow rate). They are the keys to the design;2. The pressure drop in the spiral spreader zone and molding zone is greater than that in other zones. The number of the spiral grooves > taper of the spiral mandrel n the thickness of the annular gap between the outer cylindrical die body and the mandrel has significant effect on the maximum pressure in the flow channel.3. The shear rate in the molding zone is greater than that in other zones. There is the maximum shear rate on the common boundary between the compression zone and molding zone. The taper of the spiral mandreh the thickness of the annular gap between the outer cylindrical die body and the...