Cost Reduction in Material Selection: From Material Substitution to System Optimization – A Case Study of Automotive B/C Pillar Trim Parts

Against the backdrop of continuously rising prices of plastic and metal raw materials, material optimization has become a crucial strategy for companies to reduce costs and improve efficiency. However, many engineers still perceive "cost reduction through material selection" as simply switching to domestic alternatives or cheaper suppliers, overlooking deeper cost-saving opportunities. In reality, cost reduction in material selection encompasses multiple dimensions, including material type changes, process optimization, and performance balancing. Among these, changing the material type, though technically challenging, often yields more significant cost-saving results.  

This article takes automotive B/C pillar trim parts as an example to detail how cost reduction can be achieved through material type substitution. In this case, a company adopted high-gloss, paint-free PC/ASA/PMMA material to replace traditional painting or two-shot molding solutions. This not only addressed the pain points of conventional processes but also achieved an annual cost saving of 20 million RMB.  

1. Analysis of Traditional Material Solutions for Automotive B/C Pillar Trim Parts  

Currently, the mainstream manufacturing solutions for automotive B/C pillar trim parts are: PC/ABS painting and ABS+GF/PMMA two-shot molding. Both have advantages and disadvantages but also come with cost or process limitations.  

1.1 PC/ABS Painting Solution  

Advantages:  

- Excellent scratch resistance and weather resistance after painting, meeting long-term durability requirements for automotive exterior parts.  

Disadvantages:  

1. Low painting yield: The painting process is prone to defects such as pinholes, orange peel, undercut, and particles, leading to high rejection rates and increased rework and scrap costs.  

2. Complex process: Additional painting steps after injection molding increase labor, equipment, and energy costs, extending the production cycle.  

3. Environmental pressure: Painting involves VOC emissions, which are strictly regulated, requiring additional investment in exhaust treatment.  

1.2 ABS+GF/PMMA Two-Shot Molding Solution  

Advantages:  

- Paint-free, stable appearance, and good scratch resistance.  

- Two-shot molding integrates two materials in one step, reducing post-processing.  

Disadvantages:  

1. High equipment investment: Two-shot molding requires specialized molds and large injection machines, resulting in high upfront costs.  

2. Long production cycle: The molding cycle is over 50% longer than single-shot injection, reducing efficiency.  

3. Design limitations: Complex part geometries are difficult to achieve with two-shot molding, restricting design flexibility.  

2. Innovative Solution: High-Gloss, Paint-Free PC/ASA/PMMA Material  

To address the drawbacks of traditional solutions, some companies have adopted high-gloss, paint-free PC/ASA/PMMA alloy material, enabling the production of B/C pillar trim parts through single-shot injection molding. The key advantages of this solution include:  

2.1 Process Optimization & Cost Reduction  

- Paint-free: Direct injection molding achieves a high-gloss surface, eliminating painting steps and reducing defect rates and environmental compliance costs.  

- Single-shot molding: Compared to two-shot molding, it requires less complex molds and smaller machines, shortening the production cycle by over 30%.  

2.2 Performance Enhancement & Expanded Applications  

- Better heat resistance: 20°C higher than traditional PC/ABS.  

- Higher impact strength: Suitable for harsher environments.  

- Customizable appearance: Supports different textures and colors, meeting diverse design needs.  

2.3 Implementation Challenges & Solutions  

Despite its advantages, the following issues must be addressed in practical applications:  

1. Slightly lower weather resistance: Enhanced with UV stabilizers to ensure long-term color retention.  

2. Higher material cost: Though the unit price is slightly higher, the overall cost (eliminating painting/two-shot molding expenses) remains advantageous.  

3. Stricter process control: Requires optimized mold design and injection parameters to avoid flow marks or weld lines.  

3. Economic Benefit Analysis  

In a real-world application for a specific vehicle model, the high-gloss, paint-free PC/ASA/PMMA solution delivered significant cost savings:  

- Cost reduction per vehicle: 101 RMB (for 6 trim parts, compared to traditional painting).  

- Annual savings: 20 million RMB (based on 200,000 units/year).  

Additionally, this solution offers extra value:  

✅ Shorter production cycles, improved capacity utilization  

✅ Reduced painting pollution, aligning with green manufacturing trends  

✅ Greater design freedom, enabling more innovative appearances  

4. Conclusion: Key Success Factors for Cost Reduction Through Material Selection  

Material substitution is not merely about "changing materials" but requires systematic evaluation and optimization:  

1. Performance matching: Ensure the new material meets core product requirements (e.g., weather resistance, scratch resistance).  

2. Process compatibility: Optimize molds and injection parameters to avoid surface defects.  

3. Cost calculation: Consider material costs, processing costs, yield rates, and other factors holistically.  

4. Supply chain collaboration: Work closely with material suppliers to ensure stable supply and quality consistency.  

This case demonstrates that with a scientific material selection strategy, companies can achieve substantial cost and efficiency gains without compromising product performance. As new material technologies advance, more innovative solutions will help manufacturers overcome cost barriers in the future.