Injection mold design integrates product structure analysis, material adaptation, process optimization, precision control and production economy, directly determining plastic product quality, efficiency and mold life. It requires balancing adaptability, feasibility, efficiency and cost, while adopting digital/intelligent technologies for precision and green manufacturing.
Check wall thickness (0.5-4 mm, difference ≤20%) to avoid defects; align structures with mold opening direction to reduce core-pulling. Draft angles: ≥0.5° (smooth), ≥1° (fine texture), ≥1.5° (rough texture). Set fillets; blind hole aspect ratio ≤4 (draft angle if >2). Refer to GB/T 14486-2017 (grades 11-13 general, 9-10 precision). Reserve gaps for inserts/buckles; thicken plastic around inserts.
Parting Surface: Select at maximum cross-section; reserve 0.01-0.03 mm exhaust gap or grooves to prevent bubbles.
Gating System: Match sprue (taper 2-3°); circular runners (equal length/diameter for multi-cavity). Gates at thickest wall; adjust for plastic types (shorten runners for heat-sensitive, enlarge for high-viscosity). Hot runner systems for mass production (precise temperature matching).
Cooling System: Water channels 12-20 mm from cavity, spacing 3-5×diameter, flow ≥0.5 m/s. Temp: PC 8-12°C, ABS 12-18°C, PP 15-22°C; temp difference <5°C (general), <3°C (precision). Conformal channels for complex surfaces; control accuracy ±1°C.
Ejection System: Ejector pins ≥3 mm; stroke ≥5 mm over product height. Hidden ejection for appearance parts; avoid inserts to prevent deformation.
Guiding & Positioning: Guide pillars/bushings clearance 0.01-0.02 mm; locating pins accuracy ≤0.005 mm. Add auxiliary guiding for large molds.
Strength & Rigidity: Set reinforcing ribs; template ≥25 mm (small-medium); assembly gap ≤0.005 mm to prevent flash.
Mold Materials: Pre-hardened steel (30-35 HRC, ≤100k cycles); hardened steel (45-50 HRC, ≥500k cycles/precision); corrosion-resistant steel (transparent products); wear-resistant steel (glass fiber plastics). High-strength alloys for auxiliary components.
Treatment: Quench/temper key parts; nitride corrosion-resistant molds (hardness >60 HRC); mirror/electrochemical polishing for high-gloss.
Plastic-Mold Adaptation: Reserve large shrinkage for crystalline plastics (PP, PE); strict precision for amorphous (PC, ABS); optimize runners for heat-sensitive (PVC).
Process Parameters: Reserve adjustment space (reduce gate size for high-fluidity plastics; enlarge runners for high-viscosity materials). Ensure compatibility with multiple parameter combinations for stable quality.
Injection Machine Matching: Total injection volume ≤80% of machine’s maximum; calculate clamping force (projected area × pressure × 1.2-1.5 safety factor). Match mold installation dimensions with 50-2000T machines for medium molds.
Gas-assisted molds: even air channels (avoid thin walls <5 mm), thick glue roots, fill against gravity; textures to cover weld lines. Two-color molds: rotary/translational cavities, independent runners. Insert molds: anti-rotation/anti-pull structures, quick positioning; thicken plastic around inserts, control injection speed.
Use CAD/CAM/CAE for simulation to reduce mold trials (qualification rate >99.5%). 3D printing for complex surfaces/conformal channels; CNC machining (accuracy 0.001 mm). Integrate PT100 sensors (accuracy ±0.1°C) for real-time monitoring; PID algorithms for parameter adjustment. Lightweight structures, optimized cooling (cycle -30-40%), eco-friendly materials for green production.
