Study On Control Mechanism And Equipment Of Precision Injection Molding Based On Polymer Pvt Property

PVT (pressure-specific volume-temperature) relationships of polymers are the theoretical basis for injection molding products mold design, flow simulation of injection molding parts, and injection molding process parameter settings. In this thesis, firstly, the experimental device for measuring polymer PVT relationships was designed and developed, the data acquisition and fit software was developed by using Matlab, and the parameters of a modified two-domain tait equation,which describes the PVT relationship of polymer,was fitted by using the multiple nonlinear regression algorithm. The PVT relationship of polymer in different temperature, pressure and different cooling rates was tested by using the manufactured PVT test instrument. Base on polymer PVT relationship research isovolumic packing pressure control mechanism, and the simulation result shows that the method of isovolumic packing pressure control can more effectively improve the molding quality of the product. The main works are as follows:1. Study the basic principles of testing polymer PVT properties, analyze and summarize the key factors that affect the testing process, and briefly elaborate the domestic and international testing device of polymer PVT characteristics. On these foundations, this paper developed and designed one testing device, which could achieve testing PVT properties of polymer in the test condition of high temperature, high pressure and high cooling rate. The testing instrument’s test temperature ranges from25℃to300℃, the maximum test pressure is100MPa, the highest cooling rate could be achieved at100℃/s, and the average heating rate of this instrument is15℃/min, and the repeated precision could reach0.35%. The testing conditions of this test instrument are in line with the polymer materials’processing conditions, so the data obtained from the test instrument could be used to guide the design of injection mold, to establish domestic materials PVT database, to update the material database of Moldflow mold flow analysis software, and to make the analysis results more in line with the actual processing.2. Studies have shown that the PVT relationship curve of polymer could be well described by the modified two-domain Tait equation. The data acquisition and fitting software was developed and designed by using Matlab GUI, that it can be used to collect data in the testing process and to fit the13parameters of the Tait equation by using the experimental data. The testing instrument ultimately get the Tait equation parameter values and the fitting data through testing the polymer PVT data, which can independently establish the domestic polymer materials PVT database, and offer the data to support the domestic CAE computer analysis software. 3. Based on polymer PVT relationship research isovolumic packing pressure control mechanism, which fully uses the temperature-time(T-t) cooling curve of the parts, and real-timely adjusts the settings of the packing pressure according to the molded product’s cooling condition, and achieves the precision injection molding of polymer product. Through studies the results of simulation, we found that the method of PVT isovolumic packing pressure can effectively improve the uniformity of the distribution of product density, and reduce the warpage amount and the volume shrinkage of product.4. The implementation of precision injection molding control technology was researched based on polymer PVT relationship research. In order to improve the molding quality of injection molding product, we should achieve the control of PVT parameters of the polymer in the injection molding process. All-electric micro injection molding machine designed and developed in our laboratory is the background of my researching, and the ILC algorithm was selected to achieve the control of the change of pressure of the PVT isovolumic packing pressure method in the. injection molding. The control flow diagram of PVT isovolumic packing pressure process was designed and the control output and control input parameters of the controlled object were determined according to schematic diagram of packing system, and ILC algorithm was demonstrated by the result of simulation, that it can quickly and accurately track the desired pressure output curve of the controlled object.