How Does Material Selection Affect Plastic Injection Molding Design?

Material selection is integral to plastic injection molding design, as each thermoplastic has unique characteristics that influence every aspect of part and mold design.

How Material Properties Affect Design:

Shrinkage:

• Different materials shrink differently (0.3% - 3%+)
• Mold cavities must be oversized to compensate
• Semi-crystalline materials (PP, PA) shrink more than amorphous (ABS, PC)
• Glass-filled materials shrink less, but anisotropically
• Shrinkage affects tolerances and assembly fit

Flow Characteristics:

• Material viscosity determines flow length
• Thin-wall designs require high-flow materials
• Gate size and runner design vary by material
• Fill pressure requirements differ significantly

Mechanical Properties:

• Strength and stiffness requirements determine wall thickness
• Impact resistance affects material choice and design
• Fatigue and creep considerations for functional parts
• Living hinge requirements (PP, PE only)

Thermal Properties:

• Heat deflection temperature for high-temp applications
• Cooling rate affects crystallinity and properties
• Thermal expansion for assembly considerations

Common Materials and Design Considerations:

• ABS: Excellent flow, low shrinkage (0.4-0.7%), good for detailed parts
• Polypropylene: High shrinkage (1.5-2.5%), excellent for living hinges
• Polycarbonate: High viscosity, requires generous radii, notch-sensitive
• Nylon: High shrinkage (1-2.5%), hygroscopic, requires drying
• Acetal: High shrinkage (2-2.5%), excellent for precision parts
• Glass-filled: Anisotropic shrinkage, abrasive to tooling

We help you select optimal materials and adjust plastic injection molding designs accordingly to ensure success.