High- performance amorphous thermoplastics such as polyetherimide (PEI) are widely used in aerospace applications; however, thick- walled sections are prone to internal void formation due to volumetric shrinkage and premature gate solidification. In this work, the influence of processing variables on void mitigation in thick- walled PEI components was investigated using an industrially constrained experimental design. Analysis of variance showed that thermal parameters dominated defect variation, with cooling time and mold temperature contributing 50.4% and 30.15%, respectively. Linear regression identified gate freeze time (GFT) as a practical process indicator of pressure- transmission efficiency, exhibiting a strong negative correlation with the maximum void diameter (r = −0.964, R2 = 0.930). A regression- derived threshold of 5.61 s corresponded to the aerospace specification limit of 0.75 mm, and a conservative production target of 6.5 s was recommended based on the 95% prediction interval analysis. Under optimized conditions (160°C mold temperature, 40 s cooling time), the process achieved a GFT of 8.0 s and produced no ultrasonically detectable voids (maximum void diameter < 0.1 mm). Scrap rates decreased from 18.7% to 1.1%, reducing manufacturing cost per accepted part. These findings establish GFT as a practical mechanistic indicator for process- window development in thick- walled high- performance thermoplastics.
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