Hot runner injection methods mainly include following, suiting different injection molding needs:
1. Direct Gate (Large Gate): Nozzle passes directly through mold cavity, suitable for thick-walled parts such as buckets and basins. Its advantage is low pressure loss, but gate residue is noticeable and requires secondary trimming.
2. Point Gate (Needle Valve): Gate is small and can automatically shut off material. It is suitable for precision parts such as mobile phone cases, but it requires a three-plate mold structure and is relatively expensive. This message is a smart reply.
3. Submerged Gate (Tunnel Gate): Branch channel is submerged obliquely into side of product. Advantage is automatic gate shutoff and concealed appearance, but it may generate shear stress.
4. Fan Gate: Width is gradually changing. It is suitable for flat products and can reduce spray marks, but gate area requires subsequent processing.
5. Bull Horn Gate (Banana Gate): Branch channel has an S-shaped bend, automatic gate shutoff, and no visual traces. However, it is difficult to process and is often used for high-end products. Each of these injection methods has its advantages and disadvantages, selection process should consider factors such as product type, appearance requirements, and production costs. Advantages of hot runner systems lie in improved material utilization and production efficiency, particularly in high-volume production.
To more intuitively understand how to choose one of these five injection methods based on different product requirements, we can refer to following decision-making flowchart:

 

Figure above illustrates core logic behind selecting an injection method based on product requirements. Next, we will analyze each method in more detail.
1. Direct Gate (Sprue Gate)
Core Features: The simplest injection method, with runner opening directly into mold cavity.
Advantages: Minimal flow resistance and excellent pressure retention, suitable for molding large, thick-walled, and deep-cavity products.
Disadvantages: Large gate size, significant residual pressure (requiring secondary trimming); stress concentration, which can easily cause sink marks near gate; and significant impact on product surface aesthetics.
Suitable Applications: Large boxes, buckets, basins, and other thick-walled products with less demanding appearance requirements.
Key Design Points: Gate diameter should not be too large, typically 1.5-2 times product wall thickness.
2. Pin Gate
Core Feature: Glue is injected through a tiny, pin-shaped channel.
Advantages: Small gate footprint, automatic material shutoff, no secondary processing required; flexible location selection, and easy balanced filling.
Disadvantages: Requires a three-plate mold structure, resulting in complex mold structure and high cost; significant injection pressure loss; high plastic flow requirements.
Applications: Most surface-mount products, such as mobile phone cases, home appliance cases, and precision electronic components.
Key Design Points: Gate diameter is typically 0.8mm to 1.5mm, needs to be adjusted based on material and product size.
3. Submarine Gate (Tunnel Gate)
Core Feature: Gate is located below parting surface, cutting into side or interior of product at a certain angle (usually 30°-45°).
Advantages: Combines advantages of point gates with automatic material removal, yet requires only two mold plates, resulting in a relatively simple mold structure and high cost-effectiveness.
Disadvantages: Gate detachment generates high shear stress, potentially affecting material properties; requires high precision in gate size and angle processing.
Applications: Products with internal ribs or structures that conceal gate, such as toys, tool housings, and automotive interiors.
Design Key: Optimize entry angle and polishing quality to ensure smooth demolding and minimize shear.
4. Fan Gate
Core Feature: Gate width gradually expands into a fan shape, allowing molten material to enter mold cavity smoothly in a straight line rather than a single point.
Advantages: Effectively reduces flow orientation and internal stress, minimizes jetting, and achieves excellent product flatness.
Disadvantages: Wide gate area, resulting in a large residual area that requires subsequent trimming; prone to high holding pressure.
Applications: Large, flat products, such as LCD TV bezels, automotive dashboards, and thin panels. Design Key: Fan-shaped angle and length are crucial to ensure uniform advancement of melt front.
5. Cashew Gate (Banana Gate)
Key Features: Runner is curved in an S-shape, resembling a horn or banana, allowing for injection from inner surface or hidden areas of product.
Advantages: Gate location is extremely discreet, ensuring a virtually invisible surface finish; automatic material shutoff.
Disadvantages: Extremely difficult and costly to process; high pressure loss; prone to shear overheating, leading to material degradation.
Applications: High-end products with exceptional aesthetic requirements, such as high-end cosmetic packaging, transparent optical components, and medical devices.
Design Key: Bend radius and polishing of transition zone are crucial; runner must be smooth to minimize shear.
Summary: How to choose? All in One Form

Golden Rule:
Appearance: For Class A surfaces, valve gates or bullhorn gates are preferred; for non-appearance surfaces, consider a latent gate.
Structure: For simple shells, use a point gate; for flat parts, use a fan gate; for deep, thick-walled parts, consider direct gates.
Budget: When budget is limited and automatic demoulding is required, latent gate is the best compromise.