The quality of automotive lighting is critical to driving safety. As such, regulations worldwide impose stringent requirements on automotive lighting systems. Lamp design must not only meet safety standards but also fulfill additional criteria: it must integrate seamlessly with the vehicle's overall aesthetics, be both functional and visually appealing, comply with aerodynamic principles, and enhance driver and passenger comfort and convenience. Consequently, automotive lighting design technology has advanced rapidly alongside the development of the automotive industry.

Material and Process Characteristics of Automotive Lamps

Automotive lamps typically consist of a base and a housing. The base is commonly made from a thermoset material—BMC (Bulk Molding Compound). The housing, on the other hand, can be manufactured from materials such as PMMA, PP, or ABS, often produced using two-color or three-color molding processes.

For two-color lamp production, a critical aspect is the injection unit of the two-color injection molding¹ machine. The center distance between the two screws must correspond precisely with the center distance of the two-color mold.

Key Considerations for Lamp Manufacturing

1. Factors Affecting Stable Lamp Molding

• Control Unit Response: Long switching times, electrical noise interference, unstable command output, and temperature fluctuations.
• Hydraulic System Noise: Unstable pressure, poor valve positioning performance, hysteresis, and variations in tubing damping.
• Mechanical System Variations: Internal oil seal leakage, damping effects, friction differences, screw check ring positioning, and check valve performance.
• Inconsistent Plasticization: Variations in plasticization quality.
• Mold Temperature Control.

2. Common Issues in the Design of Specialized Barrel & Screw Assemblies for Taillights

• Screw idling without feeding material.
• Excessive required torque preventing screw rotation.
• Incomplete melting of plastic.
• Unstable screw metering.
• Poor mixing and homogenization of plastic.
• Temperature rise issues with low-temperature molding plastics.
• Bubbles within the molded part.
• Black specks or yellowing in the molded part.
• Screw corrosion, wear, and short service life.

3. Key Design Focus for Plasticizing Screw & Barrel Assemblies

The plasticizing screw and barrel assembly is the heart of an injection molding machine, responsible for feeding, melting, mixing, and metering the plastic raw material. Its performance is therefore directly linked to the quality of the final molded part. The primary goals of optimizing a plasticizing screw are:

• Enhancing shear and mixing action.
• Achieving uniform mixing.
• Improving plasticizing capacity.
• Ensuring uniform melt temperature.

4. Key Design Parameters for Specialized Taillight Screws²

• L/D Ratio: 21~23
• Finition de la surface: Extremely smooth to prevent material buildup.
• Plating: Increased plating thickness for enhanced corrosion resistance.
• Compression Ratio: 2.3
• Zone Distribution:
  • Feed Zone: Approximately 50%
  • Compression Zone: Approximately 30%
  • Metering Zone: Approximately 20%