Earplug optimization study --- concluding phase

In the final phase of the optimization study for earplug production (Sato, 2002) a 3 factorial design was carried out to study the dependencies of the three responses, apparent density (AD), equilibrium force (EF) and retention time (RT), on the fiow rate of the reticulate solution (A) and the quantity of water in the polyol solution (B). Only these two factors were found to be important, after the execution of a 2 fractional factorial and a blocked 2 factorial design (see case studies in Sections 3A.9 and 4A.8). The other factors were fixed at levels chosen to provide the most desirable apparent densities, EFs and RTs, as well as convenient operational conditions. Table 6A.7 contains the results of the three responses for the three-level factorial experiments, which were performed in duplicate. 

The ANOVA results for these models are given in Table 6A8. Neither the linear nor the quadratic model shows significant lack of fit and both are significant at the 95% confidence level. The finear model should be preferred, because it is simpler. 

Apparent densities, equilibrium forces and retention times obtained with the duplicate 3 factorial design used to study earplug production 

The analysis of the EF data is straightforward. The AfSiof/AfSpe ratio for the linear model is 5.32, which is larger than 6,9,95 = 3.37 and so has a significant lack of fit. The same does not happen with the quadratic model. 

ANOVA table for the linear and quadratic models for the apparent density. The SS (sum of squares) and MS (mean square) values are multiplied by 10,000. df stands for degrees of freedom 

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