Tunnel Gate Injection Molding

Tunnel Gate Injection Molding

Tunnel gate injection molding is a specialized technique within the broader scope of injection molding. It involves the creation of a discreet tunnel-like passage or gate through which the molten plastic material flows into the mold cavity. This tunnel gate is designed to minimize visible gate marks on the final molded part, providing a cleaner appearance compared to traditional dating methods.

Purpose and Benefits

The primary purpose of tunnel gate injection molding is to produce high-quality plastic parts with a superior surface finish. Utilizing a tunnel-like gate, reduces visible defects and gate marks on the finished product, enhancing its aesthetic appeal. Additionally, this technique enables the production of intricate and delicate parts while maintaining structural integrity. The benefits also encompass minimized material wastage, improved production efficiency, and enhanced consistency in the manufacturing process. Overall, tunnel gate injection molding offers a way to achieve smoother, more refined plastic components for various industries and applications.

Components of Tunnel Gate Injection Molding

Mold Design

The mold design for tunnel gate injection molding plays a crucial role in determining the final quality of the molded parts. It involves intricate planning and precise engineering to create a mold cavity that accommodates the tunnel gate structure. Factors such as part geometry, cooling channels, and gate placement are meticulously considered during the mold design phase to ensure optimal flow of the molten plastic and the formation of high-quality parts.

Tunnel Gate Structure

The tunnel gate structure is a key component that defines the tunnel-like passage through which the molten plastic material enters the mold cavity. It is intricately designed within the mold to facilitate smooth and controlled flow of the plastic, minimizing the formation of visible gate marks on the finished parts. The geometry and dimensions of the tunnel gate structure are tailored to the specific requirements of the molded part, ensuring precise filling and minimizing flow-related defects.

Injection Molding Machine

The injection molding machine used in tunnel gate injection molding is a fundamental component responsible for melting the plastic resin and injecting it into the mold cavity. It comprises several essential parts, including the hopper for resin feeding, barrel and screw assembly for melting and pressurizing the plastic, and the clamping unit to hold the mold in place during the injection process. The machine’s precision, control systems, and ability to maintain consistent pressure and temperature are critical factors that contribute to the success of tunnel gate injection molding.

Process Steps of Tunnel Gate Injection Molding

Material Preparation

The process begins with material preparation, where the raw plastic material, typically in the form of pellets or granules, is selected based on the desired properties of the final part. The material is carefully measured and fed into the injection molding machine’s hopper for melting and subsequent injection into the mold.

Mold Setup

The mold setup involves mounting the designed mold into the injection molding machine. The mold halves are securely clamped together, creating a cavity into which the molten plastic will be injected. The tunnel gate structure within the mold is aligned and positioned appropriately for the injection process.

Injection Process

The injection process commences as the plastic material is heated and melted inside the machine’s barrel. Once molten, the plastic is injected at high pressure into the mold cavity through the tunnel gate. The controlled flow of the material fills the cavity, taking the shape of the mould and forming the desired part.

Cooling and Solidification

After the mold cavity is filled, the cooling phase begins. The injected plastic starts to cool and solidify within the mold. Cooling channels within the mold assist in regulating the temperature, ensuring even solidification and minimizing warping or defects in the final part. This phase is crucial for achieving the desired part properties and dimensional accuracy.

Part Ejection

Once the plastic has sufficiently cooled and solidified, the mold opens, and the newly formed part is ejected. Ejection pins or mechanisms push the part out of the mold cavity. Post-processing, such as trimming excess material or any additional finishing steps, may be performed before the part is ready for use or further assembly. This final step completes the tunnel gate injection molding process, producing a finished plastic component with improved surface quality.

Advantages of Tunnel Gate Injection Molding

Reduced Surface Defects

Tunnel gate injection molding offers a significant advantage by minimizing surface defects on the final molded parts. The controlled flow of molten plastic through the tunnel gate structure reduces the occurrence of common defects such as flow lines, weld lines, and visible gate marks. This results in smoother surfaces and improved part quality, meeting higher aesthetic and functional standards.

Better Aesthetic Finish

One of the notable benefits of tunnel gate injection molding is the achievement of superior aesthetic finishes on molded plastic parts. By using a tunnel-like gate, this method diminishes visible gate vestiges on the finished product, enhancing its appearance. The smoother surface finish obtained through this technique contributes to a more visually appealing end product, meeting stringent design and cosmetic requirements.

Minimized Gate Marks

Tunnel gate injection molding significantly reduces or eliminates the appearance of gate marks on the final parts. Traditional injection molding processes often leave visible marks where the plastic enters the mold, affecting the overall appearance and surface quality. Tunnel gating minimizes these marks by strategically directing the flow of molten plastic, resulting in cleaner and more visually appealing parts, particularly crucial for applications demanding a pristine surface finish.

Applications and Industries Using Tunnel Gate Injection Molding


Tunnel gate injection molding finds extensive use in the automotive industry for producing various components such as interior trims, dashboards, door panels, and intricate parts requiring high precision. The method’s ability to create parts with improved surface quality and dimensional accuracy makes it ideal for automotive applications where both aesthetics and functionality are critical.


In the electronics sector, tunnel gate injection molding is employed to manufacture intricate parts for devices such as housings, connectors, casings, and other components. The method’s capability to produce parts with minimal defects and superior surface finishes meets the stringent requirements of the electronics industry, ensuring the production of durable and visually appealing products.

Medical Devices

Tunnel gate injection molding is widely used in the production of medical devices and equipment. It allows for the creation of intricate and precise components used in medical devices, such as housings, connectors, and disposable medical tools. The method’s ability to maintain strict quality standards, produce sterile parts, and achieve exceptional surface finishes makes it crucial in this highly regulated industry.

Consumer Goods

Various consumer goods, including household items, packaging, toys, and appliances, benefit from tunnel gate injection molding. This method enables the production of parts with superior surface finishes, meeting the aesthetic demands of consumer products while maintaining structural integrity. Its versatility in creating complex shapes and designs contributes to the manufacturing of high-quality consumer goods across diverse markets. Learn more about TPU Overmolding

Recap of Tunnel Gate Injection Molding

Tunnel gate injection molding stands out as a specialized technique within the broader realm of injection molding. It involves the creation of a tunnel-like passage through which molten plastic is injected into a mold cavity, resulting in reduced surface defects, better aesthetic finishes, and minimized gate marks on the final molded parts. This method’s precision in filling complex molds while maintaining high-quality surface finishes makes it a preferred choice across various industries.

Future Potential and Developments

Looking ahead, the future potential of tunnel gate injection molding appears promising. Ongoing developments in materials, mold designs, and injection molding technologies are likely to further enhance the efficiency and capabilities of this method. Advancements in 3D printing for mold manufacturing, coupled with improvements in process control and automation, may lead to increased adoption and optimization of tunnel gate injection molding. Moreover, its continued integration with digital technologies and sustainable practices could expand its applications and contribute to more eco-friendly manufacturing processes in the future. Overall, the evolution of tunnel gate injection molding holds significant potential for advancing precision, quality, and efficiency in plastic component manufacturing.

Injection Mold Slides

Injection Mold Slides

Injection mold slides are essential elements in the injection molding process, a widely employed method for manufacturing plastic components. These slides are dynamic components within the mold that allow the creation of intricate and complex geometries, particularly in parts with undercuts or intricate details. Essentially, they contribute to the versatility of the injection molding process by enabling the production of intricate designs that would be challenging with a traditional, one-piece mold.

Importance in the Injection Molding Process

The significance of injection mold slides lies in their ability to enhance the manufacturing process by providing flexibility in design. As industries demand more sophisticated and precisely crafted plastic parts, these slides play a pivotal role in meeting such requirements. Their mobility allows for the production of parts with varying wall thicknesses, undercuts, and intricate details, expanding the possibilities for design and functionality. In essence, injection mold slides are indispensable in achieving the precision and complexity demanded by modern manufacturing. Understanding their role is key to appreciating the advancements in injection molding processes.

Basic Components of Injection Mold Slides

Mold Cavity

  1. Definition and Function: The mold cavity is a crucial component of injection mold slides, representing the void into which molten plastic is injected to form the desired part. Its function is to define the shape and features of the final product during the injection molding process.
  2. Material Considerations: The choice of materials for the mold cavity is essential for durability and effective molding. Factors such as heat resistance, wear resistance, and the ability to facilitate efficient plastic flow are key considerations in selecting the appropriate material for the mold cavity.


  1. Role in the Molding Process: The core in injection mold slides plays a pivotal role in shaping the internal features of the molded part. It complements the mold cavity by creating voids, recesses, or other interior structures, contributing to the overall design of the plastic component.
  2. Types of Cores (e.g., Floating Cores, Fixed Cores): Cores can vary in their mobility within the mold. Floating cores allow for movement to accommodate different part geometries, while fixed cores remain stationary. The choice between these types depends on the specific design requirements of the molded part.


Slide Mechanism

  1. Overview of Slide Functionality: The slide mechanism is the dynamic element of injection mold slides that enables movement within the mold. Its primary function is to create undercuts and intricate features by sliding or lifting during the molding process.
  2. Types of Slide Mechanisms (e.g., Straight Pull, Lifter Slides): Different slide mechanisms offer distinct advantages in molding various part geometries. Straight pull slides are simpler, while lifter slides provide more complex movement, allowing for the extraction of parts with deeper undercuts.

Design Considerations


  1. Definition and Significance: Undercuts are features in the molded part that prevent its straightforward removal from the mold. Understanding the definition and significance of undercuts is crucial for designing effective injection mold slides.
  2. Strategies for Undercut Management: Various strategies, such as incorporating complex slide movements or designing collapsible cores, are employed to manage undercuts effectively in the molding process.

Draft Angles

  1. Explanation of Draft Angles: Draft angles are inclined surfaces incorporated into the mold design to facilitate the release of the molded part. This design consideration is essential for preventing part sticking and ensuring smooth ejection from the mold.
  2. Importance in Mold Release: The proper use of draft angles minimizes friction between the mold and the part, improving the efficiency of the injection molding process.

Material Selection

  1. Impact of Material on Slide Design: The choice of material for injection mold slides is critical, considering factors such as durability, thermal conductivity, and resistance to wear. The selected material must withstand the stresses and temperatures encountered during the injection molding process.
  2. Compatibility with Molding Process:Ensuring that the material used for injection mold slides is compatible with the molding process is essential for achieving high-quality and consistent results. The material should facilitate efficient plastic flow, contribute to part precision, and withstand the rigors of repeated molding cycles.

Types of Injection Mold Slides

Standard Slides

  1. Common Applications: Standard slides are widely used in various injection molding applications. They find common use in molding parts with straightforward geometries, where complex sliding or lifting actions may not be necessary. Examples include simple containers, lids, and basic components.
  2. Design Features: Standard slides are characterized by their simplicity and ease of operation. They typically involve linear movements to facilitate mold opening and closing, making them suitable for molds with minimal undercuts or intricate details.

Hydraulic Slides

  1. Overview of Hydraulic Systems: Hydraulic slides utilize hydraulic mechanisms for their movement within the mold. These systems involve the use of hydraulic fluid to power the slide’s motion, allowing for precise and controlled movements during the injection molding process.
  2. Advantages and Disadvantages: Hydraulic slides offer the advantage of smooth and powerful movement, making them suitable for molds with complex geometries. However, they may be more complex to set up and maintain. The advantages lie in their ability to provide significant force for intricate slide actions, while disadvantages may include higher initial costs and potential maintenance complexities.

Mechanical Slides

  1. Mechanical Slide Mechanisms: Mechanical slides rely on mechanical components, such as cams and levers, for their operation within the mold. These slides are known for their simplicity and reliability, making them suitable for molds with moderate complexity.
  2. *Applications in Injection Molding:* Mechanical slides are often employed in molds where the part design requires controlled movements, but the complexity does not necessitate the use of hydraulic systems. They are versatile in various molding applications, striking a balance between simplicity and functionality.

Challenges and Troubleshooting

Sticking and Binding Issues

  1. Causes and Prevention: Sticking and binding of injection mold slides can result from factors such as insufficient lubrication, improper alignment, or material-related issues. Preventive measures include regular maintenance, proper lubrication, and precise mold design to minimize friction.
  2. Troubleshooting Techniques: Addressing sticking and binding issues involves identifying the root cause and implementing corrective measures. Techniques may include adjusting slide alignment, optimizing lubrication practices, or modifying the mold design to enhance slide movement.

Wear and Maintenance

  1. Importance of Regular Maintenance: Regular maintenance is crucial for ensuring the longevity and performance of injection mold slides. Wear can occur over time due to the repetitive nature of the molding process, making preventive maintenance essential to prevent downtime and defects.
  2. Strategies for Prolonging Slide Lifespan: Strategies for prolonging slide lifespan include implementing a robust maintenance schedule, using high-quality materials for slide components, and monitoring performance for signs of wear. Proactive measures can minimize the need for reactive maintenance and enhance the overall efficiency of the injection molding process.

Advances in Injection Mold Slide Technology

Innovative Materials

  1. High-Performance Materials: The evolution of injection mold slide technology has been propelled by the introduction of high-performance materials. These materials exhibit enhanced durability, wear resistance, and thermal properties, contributing to the longevity and efficiency of injection mold slides.
  2. Impact on Slide Performance: The adoption of high-performance materials positively impacts slide performance by improving resistance to wear, reducing maintenance requirements, and expanding the range of applications. These materials contribute to the overall advancement of injection mold technology.

Automation and Industry 4.0 Integration

  1. Smart Slide Systems: The integration of automation and Industry 4.0 principles has given rise to smart slide systems. These systems utilize sensors, actuators, and data connectivity to enable real-time monitoring and control of injection mold slides. Smart slides enhance precision and responsiveness during the molding process.
  2. Increased Efficiency and Precision: The automation and Industry 4.0 integration in injection mold slides result in increased operational efficiency and precision. Smart slides can adapt to changing conditions, optimize cycle times, and provide valuable data insights for continuous process improvement.

Case Studies

Real-world Examples of Successful Slide Implementation

Real-world case studies highlight instances where advanced injection mold slide technology has been successfully implemented. These examples demonstrate the practical applications and benefits of innovative slide systems in diverse industries, showcasing their impact on efficiency, quality, and design possibilities.

Lessons Learned from Challenging Cases

Examining challenging cases provides valuable insights into potential pitfalls and issues that may arise in the implementation of advanced injection mold slide technology. Lessons learned from these cases contribute to the refinement of best practices, ensuring smoother adoption and successful outcomes in future applications. Learn more about Injection Mold Lifter Design

Recap of Key Points

Summarizing the key points underscores the importance of injection mold slides in modern manufacturing, highlighting their role in achieving intricate designs and improving efficiency. The discussion on innovative materials, automation, and real-world case studies emphasizes the dynamic evolution of slide technology.

Future Trends in Injection Mold Slide Technology

Looking ahead, the conclusion explores future trends in injection mold slide technology. Anticipated developments may include further advancements in material science, increased integration of smart technologies, and a continued focus on sustainability and efficiency. Understanding these trends is essential for staying at the forefront of the rapidly evolving field of injection molding.

injection molding phone case

PC/ABS injection molding

PP injection molding

Polypropylene PP Injection Molding

PA injection molding

PA (Nylon) Injection Molding

Information about PA6/PA66 (Nylon) Injection Molding

Basically, there are PA6 AND PA66(Nylon 6 or Nylon 66), Nylon has tenacious and wearable,  self-lubricious and smooth characteristics with non-toxic and antibiosis and high water absorbability. In addition, its tensile strength and stiffness will be sharply decreased with the moisture-absorbing. Then, the size of finished pieces changes greatly. If in the high-temperature environment for a long time, it will be resolved.

It will not soften gradually with increasing high temperature until closing to the extent of melting-point. Once reaching the proper temperature, it will flow. It is soluble in many chemicals. However, gas, lubricating oil, developer, detergent and grease have no effect on nylon.PA injection molding

It has high mechanical strength, good tenacity and high press resistance and strength of extension. Its strength of extension is close to yielding strength, which is twice stronger than ABS injection molding parts.

Nylon Injection molding parts have excellent fatigue durability with the smooth surface and minor friction coefficient and good wear resistance. It also has corrosion resistance and remarkable resistance to alkali (acid) and most of the salt solution, non-toxic, presenting inertia to biological erosion and good anti-mildew ability, heat resistance and excellent electrical features.

Its product has a lightweight and is easy to dye and molding.

It is easy to absorb water and has poor light resistance. It requires more strict plastic molding technology. It can absorb water and becomes swelling in alcohol but has no resistance to strong acid and oxidizer.

Therefore, it cannot be used as acid-resisting material.

Molding process:
We should exactly control the injection molding process to prevent problems like flashing. Meanwhile, as the faster speed of condensation quick releasing for melt, we should keep off the insufficient production caused by material blocking in orifice runner and gate (temperature and pressure increase liquidity firstly).

As the poor thermal stability, the temperature should not be too high so as not to cause yellowing of material.

The proper injection pressure can be judged by the appearance of the products. If it has higher injection pressure, products will appear the problems such as flashing; the too low temperature will bring about defects like a ripple, flow mark, weld line or insufficient producing. Therefore, the higher holding pressure should be avoided in order to prevent increasing the internal stress for products generally.

It is advisable that injection should be done with speed so as to avoid problems such as ripple or insufficient mold filling caused by the rapid cooling rate.

PA (Nylon) injection molding Technique

1, Preparation of Original Materials
PA (polyamides) absorbs humidity easily, which has an effect on the course of working, like decreasing viscosity of the melt and appearing bubbles and crazing on the surface, etc. And force property of product will also decrease obviously. Therefore, the drying process must be done before shaping up. Besides, PA is easily oxidized and color changed as well as decomposition under hot temperature, so it will be better with vacuum drying. But if there is no vacuum drying condition, atmospheric hot air drying can also be adopted. The temperature of vacuum drying is 85-95 Celsius degrees and the lasting time is 4-6H; while the temperature of hot air drying is 90-100 Celsius degrees and the lasting time is 8-10H. PA materials after being dried are not fit for locating in the air (not more than 1-3H).

2, Melting Temperature
The choice of the machine barrel is mainly based on the melting point of PA Material. At the same time, it is also related to the type of injection molding machine, type of product and size. Generally, under 220-320 Celsius degrees, PA6  220-300 Celsius degrees; PA66:260-320 Celsius degrees, as the processing temperature of PA is narrow, so the temperature of machine barrel must be controlled strictly, in order to avoid decomposition of melt thus to make the product go bad. The setting of the machine barrel has a large effect on plasticizing and speed of melt. The temperature of the middle section of the machine barrel should be higher than the melting point of 20–40 Celsius degrees and lower than the decomposition of 20-30 Celsius degrees. The temperature of the front section is lower than the middle section of 5-10 Celsius degrees. The temperature of back-end (loading section) is lower than the middle section of 20-50 Celsius degrees. Cooling of the charging hole must be effective. If the temperature of the middle section is too low and the screw changes its speed too fast, then jamming phenomenon will appear. If the temperature of the posterior section is too high, then the delivering capacity will be affected. A lower speed of screw will affect production efficiency.

3, Injection Pressure
Injection pressure has a small effect on the force of PA. Choosing of injection pressure mainly depends on the type of injection molding machine, machine barrel temperature, type and size of the product, and mold structure. And there are also some factors like injection speed, injection time and injection time, etc.

4, Injection Speed
Choosing of injection speed is related to the thickness of the product, the temperature of the melt, the size of the gate, etc. The injection speed cannot be so fast. Otherwise, the excess temperature will be caused due to over cutting thus to create decomposition, causing color changing of product and decrease of force property. Too fast injection speed will also create defects like bubble and scorching, etc.

5, Revolving Speed of Screw
Intermediate speed should be adopted. The too-fast speed may cause decomposition of plastic due to excessive cutting, causing color changing and decrease of property and too slow of revolving speed, which may affect the quality of melt and production efficiency due to a long period of melting.

6, Back-pressure
On the premise to guarantee the quality of the product that the lower of the back-pressure is the better. High back-pressure may decompose due to the excessive cutting of melting.

7, Mold temperature for PA injection molding

The high temperature of mold improves hardness, density, tensile strength and modulus of elasticity of the product. Mold temperature is related to the property of the product. As to those thin products which require elongation and good transparency, it will be better with lower mold temperature; while as to those thick molds which require high strength, good abrasion resistance and transformation less, and then higher temperature of mold temperature is better. The specific is as follows.

The thickness of product temperature of mold: Less than 3mm, mold temperature use 50 -70 Celsius degrees, 3-6mm, mold temperature use 70-90 Celsius degrees, 6-10mm, mold temperature use 80-100 Celsius degrees, and wall thickness is more than 10mm, 100 Celsius degrees Mold temperature has a big effect on contractibility rate of product. The higher of the mold temperature, the bigger of the contractibility, otherwise, the smaller of the contractibility rate.

8, Molding Cycle
It mainly depends on the thickness of the product. As to thin wall product, the injection time, pressure maintaining time and cooling time can all be shorter; while as for thick wall product, in order to avoid the appearance like shrinkage transformation, sink mark and bubbles, etc., then injection time and pressure maintaining time should be lengthened and high mold temperature should be adopted. The cooling time should be longer.

9, Post-processing of Product
Crystallization of the process of molecular orientation and cooling process while in the process of cooling creates some internal stress in the product. The size and shape of the product will change while in the future storage and using process. Therefore, annealing and humidifying processing are required.

10, Annealing
It adopts a product that is 80 Celsius degrees higher of the temperature and accurate precision. The product is taken out after being demoulded, putting in oil or paraffin for annealing. The temperature of annealing is higher than the usage temperature of 10-20 Celsius degrees and time is 10-60 minutes. (Depending on the thickness of product)

11, Humidifying
While in the process of shaping up, a product that is used in humanity or aqueous solution must be put into boiling water or potassium acetate solution for 1-2 days after taken out.

12, Residence Time
While in the process of manufacturing, if the temperature of glue is above 300 Celsius degrees, then the long residence time of melting in the machine barrel must be avoided (20 minutes), otherwise decomposition will be caused due to overheating, causing the color change of product or brittleness. If a temporary stoppage for more than 20 minutes is required, then the temperature of the machine barrel can be lowered to 200 Celsius degrees. When in a long time of residence, polymer with higher viscosity must be used to clean the machine barrel. For example, HDPE or PP can be used for cleaning.

Contact us to get a price for your PA injection molding (PA6, PA66, PA12) or any other custom injection molding projects.