Principium Research Of Injection-Compression Molding

Injection Compression Molding (ICM) is a kind of processing method that the mold cavity is partly closed after the first clamping, and there is another clamping move while or after injection, before solidification, motivated by additional force. After the second clamping, the mold cavity is completely closed. At the same time, the melt is compressed and the mold cavity is fulfilled. This method can improve the molding precision of plastic parts as well as the stability property, and can also reduce the residual stress of the parts. ICM has been proved to be an effective way to produce high precision plastic products. However, there are few studies over ICM and its process principles inland. This paper went deep into the molding principles of ICM, studied on the previous research results, and took emphases on the influences of ICM process parameters caused to residual stress and weldline of the parts. The importance of the polymer P-V-T state in manufacture was taken into account as well. And a new method for polymer P-V-T state online real-time detecting, ultrasonic detecting method was discussed in this paper.The main study issues are as follows:(1) Study the ICM technique; analyze the principles of filling flow and causes of residual stress; clear-up their mathematical models; and under the help of CAE software, do simulation analysis over the impact of process parameters to the residual stress of thin-wall product. The result shows that, all of the studied parameters have influences to the part's residual stress, and the order of parameters ranked by impact, beginning with the largest one, is: compression distance> mold temperature> injection rate> compression force> compression timing> melt temperature> compression rate. Meanwhile, the optimal process parameter array with residual stress as the optimization objective was obtained.(2) Discussing the structural characteristics of injection compression molding machine as well as ICM mould; compare the residual stress results of PC lens molding by injection compression process and injection process; and work over the influences of ICM process parameters to the weldline of PC lens. Comparison experiment shows that the residual stress is much less in lens molded by injection compression process than those molded by injection process, and the conclusion that the higher the mold temperature is, the smaller the residual stress becomes, is verified at the same time. Another conclusion comes out, that the visibility of weldline is affected by process parameters such as feeding amount, compression rate, and compression distance. The visibility of weldline is lower when feeding amount gets bigger, compression rate becomes slower and compression distance gets longer.(3) Investigate the applications of polymer P-V-T state in the process of ICM and the methods of polymer P-V-T data detecting; associate the ultrasonic velocity data with polymer P-V-T data under ultrasonic online real-time detecting technique. Two calculate expressions which can well describe the relationship between ultrasonic velocity and polymer P-V-T data under constant temperature or pressure come out from the experiment. The applicability of the expressions is verified as well. Thus, the feasibility of the polymer P-V-T state online real-time detecting is proved in the abstract, and a new efficient mean for the precision plastic products molding is provided.