1. Gate Shape
Ear-shaped gates, also known as ear-shaped gates, are a composite gate structure consisting of two parts: First, ear-shaped gate, connected to runner, is an ear-shaped auxiliary runner protruding from side of cavity; second, secondary gate, usually a very thin side gate, connects ear-shaped gate to cavity body. Melt first enters ear-shaped gate, a buffer chamber, from runner, slows down, changes direction, then smoothly enters cavity through secondary gate. Ear-shaped gate itself is removed as scrap after demolding. Its core idea is to buffer first, then feed, changing way melt enters cavity from source.

 

2. Key Points of Gate Design
Ear-shaped gate dimensions: Length 8~15mm, width 6~12mm, thickness 1.0~1.2 times product wall thickness. Too thin and it freezes prematurely, losing its buffer; too thick and it wastes material, is difficult to remove. Secondary gate dimensions: Thickness 0.5~0.8mm, width 3~6mm, length 0.8~1.5mm. This is true gate; thin-walled design ensures an appropriate shear rate. Secondary gate location: Located on the side of ear protector rather than directly opposite cavity center, allowing melt to impact cavity wall before spreading, completely avoiding jetting. Pre-reserved removal allowance: A 2~3mm boss should be reserved at product end for easy fixture positioning and removal.
3. Advantages and disadvantages of gate
Advantages: Completely eliminates jetting and airflow marks—ear protector provides buffer space, allowing melt to enter cavity smoothly; Reduces shear stress near gate, resulting in uniform molecular orientation, significantly reduced internal stress and warpage risk; Suitable for heat-sensitive materials such as PVC and POM, reducing risk of thermal degradation; Improves flow balance in multi-cavity molds; Secondary gate is small, with removal marks far less than those from a direct side gate.
Disadvantages: Increases mold processing volume and complexity; Removing ear protector increases post-processing costs, and waste cannot be directly recycled; Occupies extra mold space, encroaching on ejector pins and cooling channels; Not suitable for small or micro products—ear protector may be larger than product itself.
4. Applicable Products for Gate
Heat-sensitive material products: PVC pipe fittings, POM precision gears, etc., to prevent material decomposition. High-transparency/high-gloss appearance parts: Acrylic display stands, high-gloss PMMA panels, etc., requiring an absolutely free surface of spray marks. Products with deep cavity shells and gate facing an open area: Ear protectors are standard solution. Precision parts: Optical lens barrels, measuring instrument housings, etc., where low internal stress is a primary requirement.

1. Gate Shape
Circular gate is a continuous gate that runs along the entire circumference of a cylindrical or annular product. Melt enters from runner and is evenly distributed along circumference, advancing synchronously into cavity like a water ring. Cross-section is a flat, narrow slit with uniform thickness and a width equal to outer circumference of product. It is typically located at the end of product to align with two-half parting surface.

 

2. Key Considerations for Gate Design
Gate Thickness: 0.5~1.5mm. Too thick and removal is difficult and freezing is slow; too thin and circumferential pressure is uneven. Parting Surface Requirements: A two-half split structure must be used. Products that cannot be radially parted require a three-plate mold or hot runner multi-point feeding. Ventilation Design: As melt propels towards center, air is pushed towards center. Sufficient venting channels must be provided in the central area; otherwise, trapped air and burning are highly likely. Removal Method: A continuous circular trace line is left after removal, usually located at a non-visible end, removed by turning or punching.
3. Advantages and Disadvantages of Gate
Advantages: Perfectly uniform circumferential feeding; melt front advances from outside to inside, resulting in excellent roundness. Continuous single-line feeding eliminates weld lines, crucial for pressure-bearing pipes and transparent cylinders. High dimensional accuracy, low internal stress, and consistent shrinkage in all directions.
Disadvantages: Extremely difficult to remove, requiring specialized turning/punching equipment. Must be split in two, limiting mold design. Significant material waste. Only suitable for products of rotation or near-rotation.
4. Applicable Products for Gate
Cylindrical Containers: Water cups, bottles, cosmetic preforms, etc., requiring high roundness and no weld lines. Pipes and Fittings: PVC/PP-R pipe fittings, valve bodies, etc., requiring high pressure resistance and no weld lines. Deep Cavity Shells: Filter housings, pen barrels, flashlight bodies, and other products with a large length-to-diameter ratio. Transparent Cylindrical Products: Transparent display tubes, lampshades, etc., with no weld lines being a core requirement.

1. Gate Shape
Horn gate is an S-shaped/C-shaped curved variant of submarine gate, with tunnel curving like a horn. Cross-section is typically circular, with a diameter of 1.0~2.5mm. It originates from runner and bypasses inner or outer structure of product. Utilizing elastic deformation and shear force of curved path, gate breaks off upon ejection.

 

2. Key Points of Gate Design
Bending Radius and Angle: Bending radius R is 3~8mm, and the total bending angle is 90°~180°. Too small a radius results in high resistance and difficult processing; too large a radius increases mold thickness and reduces tensile strength. Ejection Design: A special ejector pin is required to eject solidified material from tunnel entrance. Ejector pin diameter is 2~3mm larger than gate diameter, and head is beveled or stepped to grip solidified material. Manufacturing Method: Curved tunnels cannot be drilled using traditional methods; therefore, EDM (Electrical Discharge Machining) or 3D printing of conformal water channel inserts is typically used. Shape of each cavity in a multi-cavity mold must be strictly consistent. Exit Location: Ideally, it should be located on inner wall, at base of reinforcing ribs, or at a rounded corner, avoiding outer surface. Exit diameter should be slightly smaller than inlet diameter to create a taper for easy breakage.
3. Advantages and Disadvantages of Gate
Advantages: Excellent concealment of gate marks—no trace on the outer surface; Automatic cutting and runner detachment, suitable for fully automated production; Can bypass reinforcing ribs, clips, etc., to feed material from optimal position; Can be achieved with a two-plate mold, eliminating need for a three-plate mold.
Disadvantages:
High processing difficulty and cost – requires EDM or 3D printing; High flow resistance in curved paths, requiring higher injection pressure; Improper design can easily lead to breakage or surface damage; High flow rate erosion + glass fiber materials easily wear down tunnels; Not suitable for high-viscosity materials such as PC and PMMA.
4. Applicable Products for Gate
Consumer electronics high-profile casings: mobile phone frames, tablet back covers, etc., with gate hidden on inner wall or behind clips. Transparent thin-walled products: transparent storage boxes, lampshades, etc., where inner gate marks are not visible. Products with complex internal structures: appliance casings with multiple reinforcing ribs and clips, where gate can bypass ribs for feeding. Products with fully automated production and zero appearance defects: precision medical consumables, high-end cosmetic packaging, etc.

1. Gate Shape
Needle valve gate is an actively controlled gate for hot runner systems. Hot runner nozzle has a movable valve needle at its end, driven by pneumatic, hydraulic, or servo motor technology to precisely control opening and closing timing of gate. Product surface appears as a circular feed point with a diameter of 1.5~3.0mm, surrounded by a small countersunk area. Gate lacks traditional narrow throttling section; flow rate is adjusted by degree of valve needle opening, and gate is physically cut off as valve needle advances.

 

2. Gate Design Considerations
Timing Control: The biggest advantage—precisely controlling opening and closing time of each gate guides melt front line along a predetermined path, driving weld lines to non-critical areas or even eliminating them completely. Gate Diameter: 1.5~3.0mm. Too small a diameter leads to wear and blockage; too large a diameter leaves residual studs after closure. Gate Zone Temperature Control: Independent heating coils and thermocouples are essential to ensure uniform temperature and prevent freezing or thermal degradation. Valve Needle Closing Timing: Too early leads to insufficient shrinkage and shrinkage; too late results in residual studs or overflow. Determination needs to be made through trial molding and mold flow analysis. Signage control: Create a 0.05~0.1mm deep recess around gate to completely hide signature after valve pin closes. System compatibility: Requires a complete hot runner system (hot nozzle, manifold, temperature controller, timing controller). Installation space and wiring channels should be reserved during mold design stage.
3. Advantages and disadvantages of gate
Advantages: Completely eliminates runner waste, achieving near 100% material utilization, which is significant for expensive engineering plastics; Excellent gate quality—valve pin is physically cut off, resulting in no stringing or residual studs, providing ultimate solution for a high-quality appearance; Timing control makes weld lines completely controllable or even eliminated; Optimal holding pressure effect—optimal timing for cut-off prevents backflow; Suitable for almost all materials; No runner cooling, resulting in the shortest molding cycle.
Disadvantages:
Extremely high mold cost – hot runner systems cost tens to hundreds of thousands of yuan; Complex maintenance, requiring high operational and environmental standards; Only suitable for mass production (usually only cost-effective after 100,000 molding cycles); Temperature control failures may lead to material thermal degradation and system contamination; Increased mold thickness places higher demands on injection molding machine's mold opening stroke.
4. Applicable Products for Gates
Large automotive interior and exterior parts: Bumpers, dashboards, door panels, etc., large in size and expensive in materials, hot runner + sequence valve is standard. High-end consumer electronics casings: Laptop A-sides, mobile phone casings, etc., with minimal gate marks and controllable weld lines. Multi-color/multi-material injection molding: Two-color automotive headlight lenses, soft and hard plastic overlays, etc., requiring precise control of injection timing. Expensive engineering plastic products: PEEK medical implants, LCP connectors, etc., with quick return on investment due to material cost savings. Mass production of automated standard parts: bottle caps, thin-walled packaging containers, etc., hot runner systems + high-speed machines achieve ultimate efficiency.

Gate selection is a multi-dimensional decision-making process: product structure, material properties, appearance requirements, mold costs, production volume, injection molding machine capabilities—each variable affects final solution. We hope this series can serve as a quick reference guide for gate selection in your plastic parts, providing solid technical support during product reviews and mold handover.