| dc.description.abstract | This study used the in-mold sensor to measure the specific volume difference in molding process as the response. The process parameters in experimental design were set to establish the relationship between the parameters and the response value.
The mold part was divided into three regions such as near, middle and far positions. The specific volume data at three positions were collected, and the variation of specific volume from freezing to equilibrium is used to estimate the volumetric shrinkage rate.
Additionally, the three positions were compared with one another. By measuring the specific volume of the three positions at freezing point, we can use the formula to quantify the non-uniformity of the specific volume, represents as an index value for predicting the possible warpage of the product.
Regarding the method of measuring the specific volume at freezing point, this study is different from the general method of estimating the freezing state of the gate through temperature or pressure. Instead, it finds the individual freezing point of the three sensing locations through the variation of pressure line.
The combination of the variation and the non-uniformity of specific volume is used as the response to conduct a two-stage experiment. First, Taguchi method is used to screen the important factors. After that, Response surface method is used to establish a mathematical model. The melt temperature, mold temperature, filling velocity, packing pressure, packing time and cooling time were selected as the control factors in the experiment. After Taguchi method experiment and analysis, packing pressure and packing time were selected as the two most significant factors.
Then adjust the packing pressure to three stages, and run a four-factor Response surface method experiment with packing pressure of three stages and total packing time. The best combination predict value is 0.0088 , and the best parameter set verified through experiment is 0.0086 , the error of prediction is 2.3%.
The experimental result of the center point group through Response surface method is 0.0125 , which is an improvement of 31.2% compared with the optimized result. Result shows that the experimental design method can effectively predict the nonlinear problem of injection molding and improve the product quality characteristics eventually. | en_US |