Summary of Automotive Mold Gate Locations
In automotive mold design, approximate gate location is first determined based on experience with similar parts. MoldFlow software is then used to perform gate simulation analysis, gate shape and location are optimized based on analysis results. Since shape and structure of automotive parts are often similar, previous designs provide a reference for mold design. Using successful examples as a reference often achieves twice result with half effort.
Gating systems can be categorized as cold runner and hot runner. Gating system refers to melt channel between injection molding machine nozzle and mold cavity.
A conventional gating system is one in which melt channel between injection molding machine nozzle and mold cavity is unheated. It is suitable for applications with short runner flow paths and short product injection cycles. Advantages of a conventional gating system are simple mold part processing and low cost. However, its disadvantages are high runner pressure and heat losses, low production efficiency, and excessive runner waste.
A hot runner gating system heats melt path from injection molding machine nozzle to mold cavity, or heats a portion of runner. It is suitable for applications with long runners and large parts. Advantages of a hot runner gating system include low runner pressure and heat loss, preventing premature solidification during injection, high production efficiency, and minimal runner waste. However, disadvantages are high cost, technical complexity, high repair and maintenance costs. Automotive injection molds, due to their large size, high precision, and high lifespan, often utilize hot runner gating systems.
When designing a mold, gating and positioning are often the first hurdles that stump designers. Following lists gate locations for various automotive products for mold design reference.
Features of Submarine Gating
A submarine gate in a mold is a concealed gate structure. Its location is typically hidden inside part, on a rib, a boss, or a non-exterior surface. Gate is automatically cut off mechanically during mold opening or ejection, eliminating need for subsequent manual trimming.
Latent gates are an ideal choice for applications where "appearance prioritizes automated production." They are particularly suitable for small and medium-sized plastic parts with multiple cavities and high aesthetic requirements. However, their dependence on part structure and plastic flowability should be considered. During design, stress concentration and debris should be avoided through dimensional optimization and structural coordination.

 

Features of Hook Gates
Features: Hook gate (also known as tab gate) is a special type of gate, primarily used for highly transparent, flat-plate plastic products and those requiring minimal deformation. Its characteristic feature is that gate is located on the side of mold and features a curved portion, allowing it to automatically break during mold opening, minimizing impact on product's appearance.
Design Key Points
Location Selection: Hook gate should be located where it will not affect product's appearance, typically at the edge or in an inconspicuous location.
Dimension Control: Dimensions of hook gate must be precisely controlled to ensure a smooth break during mold opening without compromising part filling and quality.
Mold Design: Unique shape of hook gate must be considered during mold design, and specialized mold components may be required.
Material Selection: Hook gates are suitable for highly transparent plastic materials, such as PMMA (polymethyl methacrylate), which require minimal gate mark.
Advantages:
Aesthetics: Because hook gates automatically break during mold opening, they leave minimal marks on finished product, making them suitable for products requiring high aesthetics.
Applicability: They are particularly suitable for highly transparent flat-plate plastic products, maintaining high transparency and a good appearance.
Disadvantages:
Difficulty Removing: Hook gates are relatively difficult to remove, especially in high-volume production, which may increase production costs.
Mold Complexity: Due to their unique shape and location, hook gates are more complex to design and manufacture than other types of gates, potentially increasing mold costs.
In summary, hook gates offer unique advantages in injection mold design, particularly for products requiring high transparency and a good appearance. However, complexity of their design and manufacturing, as well as challenges of their removal, are also aspects that require consideration.
Bullhorn Gate

 

Features of Slope/Slide Gates
Features: A sloped/slide gate (Side Gate) is a common restrictive gate. Its main feature is its location on the side of mold, typically at parting line. As plastic melt enters mold cavity through gate, it flows down side, ultimately filling cavity. This gate design distributes melt more evenly throughout cavity, helping to reduce weld marks and air bubbles.
Advantages:
Easy to Remove: Because gate is located on the side of part and its size is small, it automatically breaks during mold opening, facilitating subsequent removal.
Reduced Residual Stress: Sloped gate design helps reduce residual stress in gate area, thereby reducing likelihood of warping and deformation.
Wide Application: This gate is suitable for a variety of plastic materials, including PVC, PE, PP, and PC.
Disadvantages:
Higher pressure loss: Compared to unrestricted gates, Lifter gates experience greater pressure loss, which may make it difficult to fully fill certain complex shapes.
Complex mold structure: Lifter gates require an additional tilting mechanism, increasing mold complexity and manufacturing cost.
Lifter gates

 

Features of side gates
Features:
Flexible location: Side gates are typically located on parting surface, allowing material to be fed from outside of cavity (plastic part).
Simple cross-sectional shape: Side gates are typically rectangular, making them relatively easy to manufacture and allowing for precise gate dimensions.
Easy to adjust: Side gates allow for easy adjustment of shear rate and gate closure time during filling, and are therefore also known as standard gates.
Easy to remove: Side gates are relatively easy to remove, leaving minimal marks.
Suitable for multi-cavity molds: Side gates are particularly suitable for two-plate multi-cavity molds.
Advantages:
Flexible gate location: Since side gates can be flexibly positioned on parting surface, they can improve filling conditions, especially in multi-cavity molds.
Easy to Remove: Side gates are relatively easy to remove and leave minimal marks, helping to maintain product's aesthetic quality.
Suitable for Two-Plate Molds: Side gates are particularly suitable for two-plate, multi-cavity molds, simplifying mold design.
Disadvantages:
Potential Surface Defects: In some cases, side gates can cause surface pitting or other defects at gate site.
Difficult to Remove: While side gates are relatively easy to remove, they can still be challenging in some cases, particularly for thin-walled or complex-shaped parts.
Application Dependency: Design and effectiveness of side gates are highly dependent on specific application, including factors such as product shape, size, material, and injection molding machine performance.
Valve Gate Direct Injection

 
Direct Injection
 
Overlap Side Gate Injection














 

Mold Flow Analysis Summary
When designing a mold, a mold analysis report, commonly known as a Design for Manufacturing (DFM) report or design proposal, must be prepared before mold development. Some large automotive or appliance mold companies typically have dedicated personnel responsible for design, manufacturing, and manufacturing (DFM). These individuals are typically team leaders or supervisors with years of mold design experience. Of course, as a qualified mold designer, ability to prepare DFM reports is essential. Below is a preliminary mold analysis report for an automotive door panel. Let's take a look!

 

Moldflow
Moldflow analysis utilizes current CAE software (Moldflow, C-Mold, Z-Mold, etc.) to perform finite element simulations of injection molding, holding pressure, cooling, and warpage processes of plastic parts.

 

Moldflow Analysis of an Automobile Bumper

 

Moldflow Analysis of an Automobile Side Skirt

 

Moldflow Analysis of an Automobile Glove Box

 

Moldflow Analysis of an Automobile Door Panel

 

Moldflow Analysis of an Automobile Instrument Panel

 

Moldflow Analysis of an Automobile Tailgate