스틸 인서트와 GFRP 하이브리드 볼스터의 사출성형공정 최적화 = A Study on the Optimization of Injection Molding Process for Steel Insert and GFRP Hybrid Bolster

다국어 초록 (Multilingual Abstract)

Optimization of the plastic injection molding process and the effective control of deflection are prerequisite for enhancing product quality. This necessitates an integrated methodology combining various approaches, including the utilization of PVT(Pressure-Volume-Temperature) characteristics, mold design optimization, judicious filler selection, and precise adjustment of process conditions. This comprehensive strategy ensures the manufacture of high-quality components satisfying both dimensional stability and mechanical strength specifications.
This study concentrates on optimizing the design and production process for lightweight hybrid bolsters manufactured by injection molding GFRP(Glass Fiber Reinforced Polymer) material integrated with steel inserts. The MOLDFLOW fluid analysis program was employed for the analysis and subsequent optimization of the mold design.
Initial analysis of the runner system and component moldability revealed a short shot defect. Subsequent runner system optimization augmented the filling rate from 88.4% to 92.6%, despite the inherent geometrical constraints of the part.
Subsequently, areas necessitating reinforcement were identified, and the bolster's geometry was modified. These design revisions facilitated 100% complete filling of part. S/N ratio and ANOVA(Analysis of Variance) were utilized to assess the influence of key factors based on three critical criteria: volume filled, shrinkage minimization and part weight reduction. This analysis yielded the derivation of an optimal product design. For mold fabrication, cooling line were designed, and a cooling analysis was conducted to predict whether the final product's deflection would meet the specified tolerance requirements. The simulation results were compared against a test injection utilizing actual GFRP material. The flow pattern observed in the short shot samples demonstrated good agreement with the simulation predictions, thereby confirming the accuracy and reliability of the analysis.
The deflection occurring during the production of components containing steel inserts was analyzed utilizing CCD(Central Composite Design), and RSM (Response Surface Methodology) was employed to derive the regression models for each axis. After that, the composite desirability function was applied to simultaneously optimize the multiple response objectives, specifically minimizing deflection along the X, Y, and Z axes, thereby establishing the optimal process conditions. Under these optimal conditions, the deflection in the X-axis was reduced by 0.77% to 1.940 mm, the Y-axis deflection decreased by 3.97% to 3.725 mm, and the Z-axis deflection decreased by 5.49% to 3.049 mm. The resulting value of the composite desirability function was 0.871.

목차 (Table of Contents)

• 1. 서론 1
• 1.1 연구 배경 및 필요성 1
• 1.2 국내외 연구 동향 5
• 1.3 연구 목적 및 내용 10
• 2. 이론적 배경 13
• 2.1 Bolster의 구조 및 역할 13
• 2.2 사출성형 사이클 및 주요 구성요소 18
• 2.3 유변학과 Hele-Shaw 유동 방정식 24
• 3. 유동 해석 기반 균형 충진을 위한 runner system 설계 및 평가 28
• 3.1 Mesh 생성 및 경계 조건 설정 28
• 3.2 Runner system 설계 및 소재의 선정 34
• 3.3 Runner system 유동 해석 결과 및 최적화 고찰 42
• 3.4 Runner system 형상 개선 52
• 4. GFRP 기반 bolster 형상 최적화 58
• 4.1 유동 해석 기반 bolster 형상 개선을 위한 시뮬레이션 조건 58
• 4.2 Bolster 형상 변경에 따른 유동 해석 결과 분석 64
• 4.3 S/N비 및 ANOVA 분석 71
• 5. GFRP 기반 bolster 냉각 및 변형 해석 89
• 5.1 냉각 해석을 위한 냉각수 라인 설계 89
• 5.2 냉각 및 변형량 해석 결과 94
• 5.3 금형 제작 및 시사출 샘플 유동 패턴 비교 100
• 6. Steel insert 적용에 따른 hybrid bolster 변형 최적화 104
• 6.1 경계조건 설정 및 변형량 해석 결과 104
• 6.2 반응표면법 기반 최소 변형을 위한 공정 최적화 113
• 7. 결론 128
• References 131