<p style="text-align: center;"><img src="/ueditor/php/upload/image/20260113/1768281187422658.png" title="1768281187422658.png" alt="1.png"/></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 12px;">Geometric quality assessments were conducted on three gear specimens from each material group using a Zeiss Coordinate Measuring Machine (CMM) equipped with a Zeiss VAST XXT scanning probe (Fig. 3). The evaluation encompassed critical gear parameters, including profile deviation, lead variation, pitch error, and runout, all measured in accordance with the ISO 1328 standard for gear quality inspection (Ref. 10). The quantified parameters and their corresponding quality grades are summarized in Table 2. As the quality grades among the polymer gear sets exhibited minimal variation, it was assumed that geometric quality had a negligible effect on the observed NVH behavior during testing. Although the steel gears demonstrated superior geometric precision, they were included in the experimental matrix to enable quantification of NVH differences attributable to material substitution.</span></p>