Injection Molding Encyclopedia
Injection molding revolutionized shoe manufacturing by enabling rapid, cost-effective production of complete soles and complete shoes. Understanding these processes helps optimize your sourcing strategy.
1 Injection Molding Methods
Direct Injection (DIP)
Upper placed in mold, rubber injected directly. One-piece construction. Waterproof construction.
- • No lasting required
- • Production: 200-400 pairs/hr
- • Cycle time: 8-15 seconds
Best for: Rain boots, safety boots
PU Pouring
Two-component PU injected into mold. Chemical reaction creates foam. Dual-density possible.
- • Lightweight soles
- • Production: 100-200 pairs/hr
- • Cycle time: 15-30 seconds
Best for: Athletic midsoles, work shoes
TPR Injection
Thermoplastic rubber heated and injected. Recyclable material. Versatile design.
- • Easy color changes
- • Production: 300-600 pairs/hr
- • Cycle time: 5-10 seconds
Best for: Casual shoes, children's shoes
EVA Molding
EVA pellets melted and injected. Excellent cushioning. Midsole + outsole combo.
- • Low density foam
- • Production: 150-300 pairs/hr
- • Cycle time: 10-20 seconds
Best for: Running shoes, sneakers
2 Direct Injection Process (DIP)
DIP is the most automated shoe manufacturing method. The upper and sole are fused in a single mold, eliminating separate lasting and attachment steps.
Process Steps
Upper Preparation
Lasted or unlasted upper
Mold Closing
Hydraulic clamping
Injection
Rubber/PU into mold
Demolding
Finished shoe released
Advantages
- No separate sole attachment
- Waterproof construction
- High production efficiency
- Lower labor cost per pair
Limitations
- High tooling investment
- Limited upper material options
- Design complexity limited
- Best for simple designs
3 Machinery & Equipment
Injection Machines
Rotary DIP Machine
Multiple stations rotate. Continuous production. High capacity.
12-24 stations
Linear Machine
Single station linear. Lower investment. Flexibility.
Simple operation
PU Pouring Machine
Two-component mixing. Precision dosing. Automated mixing.
Metering pumps
Tooling Specifications
4 Manufacturing & Sourcing
China Production Regions
Dongguan, Guangdong
Largest injection facility cluster. Sports shoes, casual shoes. Modern equipment.
MOQ: 500 pairs | Lead: 30-45 days
Wenzhou, Zhejiang
Rain boots, safety boots. PVC/NR injection. Traditional products.
MOQ: 1,000 pairs | Lead: 25-40 days
Quanzhou, Fujian
Athletic shoes. EVA/PU injection. Sports brand suppliers.
MOQ: 300 pairs | Lead: 35-50 days