Without sophisticated glue feed design, even the best molds cannot produce perfect products.
Like human body's vascular system, it determines how plastic melt is injected into mold cavity, directly affecting product's appearance, strength, and production efficiency.

Core Function: It is melt delivery channel connecting injection molding machine nozzle to product cavity. It consists of three parts: main runner, branch runner, and gate.
Analogy:
Main channel= Aorta (from nozzle to parting surface)
Branch channel= Branching blood vessel (distributes melt to each cavity)
Gate= Capillary (final gateway for melt to enter cavity)

1. Direct Gate (Large Gate)

 

Features: Large diameter (Ø3-8mm), low pressure loss
Advantages: Suitable for thick-walled parts (such as buckets and basins)
Disadvantages: Significant gate residue, requiring secondary trimming
Examples: Plastic benches, storage boxes
2. Point Gate (Needle Valve Type)

 

Features: Small gate size, automatic material shutoff
Advantages: Smooth appearance, suitable for precision parts
Disadvantages: Requires a three-plate mold structure, high cost
Examples: Mobile phone cases, digital products
3. Submerged Gate (Tunnel Gate)

 

Features: Gate hidden on the side or bottom of product
Advantages: Automatic gate break, discreet appearance
Disadvantages: Prone to shear stress
Examples: Appliance buttons, toy joints
4. Fan Gate

 

Features: Gradual width (5-30mm), gradually decreasing thickness
Advantages: Smooth melt spread, reducing jetting
Disadvantages: Gate area requires subsequent processing
Examples: Flat products (keyboards, instrument panels)
5. Bullhorn Gate (Banana Gate)

 

Features: Curved flow channel design
Advantages: Automatic gate break + no visual traces
Disadvantages: High processing difficulty
Examples: Automotive headlight lenses, high-end cosmetics packaging

1. Art of Balancing Gate Size
Oversized gate: Excessive residue, insufficient pressure transfer → shrinkage
Undersized gate: Excessive shear heat → burning or snake marks
Calculation formula: Gate thickness ≈ Product wall thickness × 0.6-0.8
(Example: 2mm wall thickness product, gate thickness 1.2-1.6mm)
2. Location Selection Strategy
Golden Area: Thickest part of product or non-exterior surface
Forbidden Zone: Weak structural area (prone to deformation)
High stress area (causing cracking)
Assembly surface (affecting dimensional accuracy)
3. Fluid Mechanics of Runner Design

Scientific Verification: Circular runners are 30% more efficient than trapezoidal ones because they have the smallest surface area for same cross-sectional area.

1. Hot Runner Revolution
Needle Valve Sequencing Control: Multiple gates open on demand (Example: 3-stage sequential glue feed for a car bumper)
Temperature Control Accuracy: ±0.5℃ (PID algorithm)
Energy Savings: 30% less material than cold runners
2. In-Mold Sensing Technology
Pressure Sensor: Real-time Monitoring of Gate Pressure
Automatic Adjustment: 5% Speed Reduction When Pressure Exceeds Limit
Case Study: Medical Syringe Mold Yield Increased to 99.9%

Fractal Tree Flow Channel: A diversion design that mimics tree branches, reducing pressure loss by 22%
Shark Skin Effect: Microgrooves on the gate surface reduce flow resistance (inspired by shark skin)
Vascular Network Model: A multi-stage diversion system based on human capillaries
A Dialogue Between Industry and Nature: The best injection molding designs often lie within evolutionary wisdom of nature
Conclusion: Small Gates, Big Questions
Injection mold injection systems are culmination of science, art, and experience:
Science: In fluid dynamics calculations
Art: In visual balance of defects
Experience: In accumulation of millions of mold trials