How to Meet the Special Requirements of Glass Fiber-Reinforced Materials
Glass fiber-reinforced materials (GFRPs), known for their high strength, low density, and excellent heat resistance, are widely used in industrial manufacturing. However, compared to standard plastics, GFRPs have unique characteristics in the injection molding process, imposing higher demands on mold design.
1. Special Molding Characteristics of Glass Fiber-Reinforced Materials
High Abrasiveness: Glass fibers cause significant wear on mold surfaces, necessitating materials with high wear resistance.
High Flowability Requirements: GFRPs have relatively low flowability, which can lead to weld lines and air bubbles.
Warpage and Internal Stress: Uneven shrinkage during cooling can cause warpage and deformation.
2. Mold Material Selection
High-Hardness Alloy Steel: Mold steels should exhibit excellent wear resistance and hardness (e.g., H13, S136).
Surface Coating Treatments: Techniques like nitriding, hard chrome plating, or PVD coatings can enhance wear resistance and surface smoothness.
Corrosion Resistance: GFRPs may contain chemical additives; therefore, mold materials with high corrosion resistance are essential.
3. Design of the Gating System
Optimization of Gate Location and Type
Use pinpoint or submarine gates to ensure uniform material filling and reduce weld lines.
Position gates away from stress-concentration areas to minimize warpage and cracking risks.
Flow Channel Design
Design main and runner channels with circular or semicircular cross-sections to reduce glass fiber wear.
Improve uniformity in cooling channels to control material temperature differences and reduce residual stress.
4. Cooling System Design
Uniform Cooling
The cooling system should cover critical areas of the mold cavity to avoid large temperature differences that can lead to warpage.
Use high-thermal-conductivity materials (e.g., beryllium copper) for cooling inserts to enhance cooling efficiency.
Dynamic Temperature Control Technology
Employ mold temperature controllers (MTC) for precise temperature regulation to reduce warpage and stress cracks.
5. Mold Cavity Surface Treatment
Polishing and Surface Finish
The mold cavity surface should be polished to a high precision level to reduce friction and wear caused by glass fibers while improving the product's surface quality.
Surface textures should match product requirements to prevent defects during fiber filling.
