Analysis and Control of Flow Field in Coat-hanger Foamed Sheet Die
|Course||Mechanical Manufacturing and Automation|
|Keywords||Coat-hanger Foamed Sheet Die uniformity velocity field damping zone pressure field Fluent|
The quality level of plastic sheet products relies heavily on the uniformity of the flow in the die. As a major component of the molding equipment, there are many abuses in the die’s design. It makes instability of plastic products and affects the product quality. On this basis, it becomes very important to research and control the uniformity in the production process of plastic sheet products.In this article, through learning the characteristics of pressure fluctuations in the entrance of the die, researchers proposed a method to decrease the pressure fluctuations. Analysis the characteristics of pressure fluctuations and the relationship between time-domain, then design an equipment to decrease the pressure fluctuations, and establish the mathematical model of the device movement. Use the FLUENT in CFD software to analysis the feasibility of the device and its’influence to pressure fluctuations at the entrance. In addition, analyzed an important factor-- damping zone which affects the flow field uniformity in the die, analyzed the influence of pressure fluctuations caused by the changes in overall height and the partial height changes.Simulate the flow in the entrance affected by the reduce pressure fluctuations equipment, it shows that this device reduced the inlet pressure fluctuation and improved the uniformity of melt flow in the entrance of the die. The research of the height adjustment in the damping zone shows that the higher the damping zone is, the worse the uniformity of extrusion. Lower the height will improve the uniformity of extrusion, but it also increased the pressure inside the die. Under the adjustment of partial height in the damping zone, the turbulence gets lower, and the uniformity of the extrusion get higher.The pressure fluctuations device reduces the pressure fluctuations on the extrusion direction relative to time. The role of damping zone is to adjust the flow uniformity in the width of the cross section of the die. With the pressure fluctuations device, pressure fluctuations in the entrance of the die get reduced, and the followed flow inhomogeneity in the width of the cross section may be improved through adjusting the damping zone. Under the combined effects of the two devices, flow field uniformity has been greatly improved.