90% of injection molding tuning defects are not due to poorly tuned parameters, but to a lack of understanding of material characteristics. The five major injection molding parameters are merely tools; the crystallization characteristics, flow characteristics, etc. of the plastic material itself are the core that determines process success or failure. This lesson thoroughly explains in one go the dedicated molding process tuning logic and defect countermeasures for the top 10 commonly used plastic materials in the workshop—even beginners can quickly master them:

• Material Properties: Amorphous high-gloss, good toughness, dimensionally stable.

• Process & Parameters: Medium temperature, medium-high speed staged injection, sufficient holding pressure. Barrel 200~240°C, mold temperature 40~50°C.

• Common Defects: Gas marks, silver streaks, weld lines, sink marks.

• Material Properties: Crystalline material, good flowability, high shrinkage prone to warping.

• Process & Parameters: Low pressure medium speed, long holding pressure for sufficient compensation, sufficient cooling. Barrel 180~230°C, mold temperature 40~50°C.

• Common Defects: Sink marks/dents, warping deformation, dimensional instability.

• Material Properties: Semi-crystalline, excellent flow, high shrinkage prone to deformation.

• Process & Parameters: Low temperature fast filling, long holding pressure compensation. Barrel 160~220°C, mold temperature 40~50°C.

• Common Defects: Flash, deformation, sink marks, drag marks.

• Material Properties: High transparency, high strength, extremely prone to moisture absorption and hydrolysis. Must be dried at high temperature with dehumidification, water-free molding throughout.

• Process & Parameters: Drying 120~130°C (3~4h); barrel 260~310°C, mold temperature 80~120°C; high mold temperature, low speed, high pressure stable filling to reduce internal stress.

• Common Defects: Hydrolysis cracking, gas marks, low-temperature stress whitening, transparency defects.

• Material Properties: High transparency, good flow, but relatively brittle material, prone to stress cracking.

• Process & Parameters: Medium temperature, high speed, sufficient venting, short holding pressure. Barrel 180~220°C, mold temperature 30~50°C.

• Common Defects: Cracking, burning, hard cracks.

• Material Properties: High hardness, wear-resistant, high shrinkage, not heat-resistant. Extremely prone to decomposition producing corrosive gases when overheated.

• Process & Parameters: Low temperature molding, low speed high pressure, long holding pressure, strong venting. Barrel 170~210°C, mold temperature 60~90°C.

• Common Defects: Burning, bubbles, sink marks, dimensional fluctuation.

• Material Properties: Super strong moisture absorption, high toughness, fast crystallization. Dimensions prone to change after moisture absorption.

• Process & Parameters: Must be thoroughly dried; high temperature fast mold filling, combined with high mold temperature for setting. Barrel 220~270°C, mold temperature 60~100°C.

• Common Defects: Bubbles, silver streaks, warping, sink marks.

• Material Properties: High transparency, super strong moisture absorption. Extremely prone to degradation and hydrolysis when exposed to water at high temperature.

• Process & Parameters: Long-time drying 150~190°C (4~6h); barrel 260~290°C, mold temperature 80~120°C; low speed high pressure stable molding.

• Common Defects: Hydrolysis whitening, bubbles, silver streaks, uneven crystallization, poor transparency.

• Material Properties: Extremely heat-sensitive, prone to decomposition at high temperature producing corrosive gases, average flowability. Divided into soft and rigid types.

• Process & Parameters: Low temperature molding, strictly control upper temperature limit, eliminate local overheating decomposition. Barrel 160~190°C, mold temperature 30~50°C; low speed, low pressure, short material storage, low back pressure molding.

• Common Defects: Decomposition blackening, burn streaks, mold corrosion.

• Material Properties: High transparency, high hardness, high brittleness, strong hygroscopicity. Extremely sensitive to process, prone to streaks and cracking.

• Process & Parameters: Sufficient drying (80~90°C, 3~4h); barrel 210~250°C, mold temperature 50~80°C; low speed high pressure, slow injection speed, stable holding pressure.

• Common Defects: Flow marks, fine lines, silver streaks, poor light transmission, stress cracking.