One Factor at a Time Analysis to Modify Potting Technique for Manufacturing of Bubble-Free High-Voltage Polyester Insulated Automotive Coils

摘要

The current study focuses on minimising the bubbles in polyester-insulated ignition coils,which were produced with a defect level of ~21–25 or 210–250 coils per 1000 batch size by usingthe potting method. This high-level rejection makes a substantial financial impact by increasingwaste material, manufacturing, and after-sales costs. Hence, to control the bubbled problem withoutusing expensive and maintenance-heavy techniques, the process parameters in the potting methodwere alternated and investigated using one factor at a time, which played a vital role in the formation/reduction of bubbles in the ignition coil insulation. Process parameters, including pre/processheating, the appropriate MEKP/cobalt naphthenate ratio, the pouring amount/increments, andthe stirring speeds, reduced the bubble formation per lot from 205 ± 30 to 146 ± 25, 108 ± 21,61 ± 17, and 10 ± 2 per 1000 lot accordingly. In addition, a comparative study was conducted interms of performance and life cycle endurance, using Japanese and Indian standards. Furthermore,an after-sale warranty claim also supports the proposed changes in the potting technique. Thismodification may reduce the after-sales rejection within two years to approximately ~85. Thismodification in the potting technique is extremely cost-effective in comparison to expensive processes,i.e., vacuum-pressure impregnation and vacuum impregnation, which require extensive labour andmaintenance.