Abstract:

In order to reduce the number of trial-and-error in the conventional bra cup molding process and to establish a quantitative analysis mehtod, and expensive scheme with 15 kinds of condition combinations (three factors and three levels) based on the Box-Behnken design (BBD) method was proposed. The soft polyurethane foams were molded to the mold cups by using the contour molding machine. According to the experimental design, the designated sectional thicknesses of molded cups generated under different mould parameters were measured by the Leica optical imaging system. Through the regression equation and the response surface plots, the relationship between molding process parameters and the section thicknesses of molded cups can be explored and the prediction can be made. The results indicate that the molding temperature has greater influence than the length of the dwell time on the section thicknesses of molded cups. From the response surfaces, even though the length of the dwell time was extended, the thickness of the mold cup cannot remain stable if the molding temperature is not high enough. For the given cup depths of different sized mold heads, the optimal molding conditions can be accurately and quickly determined. The efficiency with this approach is 3.6 times of the approach without experimental design and the results are validated by the experiment.

Key words: responding surface methodology, bra, cup thickness, molding process