The molding was first molded without air blowing at melt
temperature 220 ◦C with the GPPS. When the molding was
ejected, after cooling for 30 s in the mold, the tempera-
ture of the molding was 175 ◦C. In the main experiment,
the seventh process condition showed the lowest molding
temperature in the ejected moldings. The highest molding
temperature was measured at the eighth. In between sev-
enth and eighth, the difference of the molding temperature
was 26 ◦C. Comparing the molding temperature measured
in the seventh process condition with the molding tempera-本文来自辣%文~论!文\网，
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ture measured without air blowing, the efficiency of cooling
in molding increased approximately 50%. In the length of
molding, the longest molding occurred in the third process
condition. The eighth process condition molded the short-
est molding. Although the process conditions changed, the
weight of moldings rarely changed.
The S/N ratio for the “smaller is better” characteristic was
calculated based on the measured molding temperature in
Table 3. The Fig. 6 shows that the duration of air blowing
was the main variable affecting cooling efficiency, among
the three variables. The predicted optimum process was melt
temperature 220 ◦C, delay time for air injection 21 s and
duration of air blowing 70 s by the ANOVA.
3.3. Experiment and analysis for PP
In the experiment of PP polymer, the values of tempera-
ture, length (Fig. 5), height and gloss of the ejected moldings
were measured. Table 4 shows the measured values.
Comparing the temperature of molding measured in
the third process condition with the temperature measured
without air blowing, the efficiency of cooling in molding
increased about 45%. The length, heights and gloss of
moldings hardly changed.
The S/N ratio is calculated based on the measured mold-
ing temperature in Table 4. The Fig. 7 shows that the du-
ration of air blowing was a main variable affecting on the
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