Types of Gates for Injection Molding – A Detailed Guide

What is a Gate?

Injection Molding is a full-fledged process for manufacturing plastic components, and the entire method is fragmented through simple but crucial steps. Let’s talk about one such simple, and integral part of the injection molding called a gate.

The gate’s textbook definition is an opening through which the molten plastic material is injected into the mold. As I said earlier, the gate’s purpose is easy but crucial for the injection molding process.

Types of gates are very much dependent on the mold’s design and what purpose the mold will be used for. The shape and size of the final product being manufactured from the mold derive from the gate’s size smaller the product, smaller the gate and bigger the product, bigger and more gates.

A popular term called “Gate Freeze” is considered an extremely crucial part of the injection molding process. To run the process smoothly, gates need to be large enough to fill out the cavity properly and small enough to close the cavity.

The sealing of the gate at the exact time is called gate freeze. Gate designs are paramount features of a mold for churning out perfectly accurate products. 

Types of Gates – 

There are mainly two types of widely used gates – Manually trimmed gates and automatically trimmed gates.

Most Common Types of Gate Designs – 

When applied, there are many gate design which is utilized in injection molding for producing various products. However, we will be discussing the six most industrial-used gate designs.

1. Edge Gate
2. Sub Gate 
3. Hot Tip 
4. Valve Gate 
5. Sprue Gate 
6. Diaphram Gate 

Also Read – Injection Molding in Medical Industry | The Pros of Medical Device Injection Molding | The Importance of Plastic Injection Molding

1. Edge Gate – 

 

Edge gate is the most commonly used gate design because of its simple and flexible design. It is easy to produce and can be modified easily according to need. As the name suggests, it is located at the edge of the mold.

Utilizing an edge gate is always advisable for filling larger parts or parts in which it is improbable to avoid thicker wall sections.

Edge gate is also suitable to produce flat parts as it leaves a scar at the parting line. For the sake of understanding, If we compare fan gates and tab gates with edge gates, the circular part of the runner always tapers with the gate’s rectangular part. Whereas, in the fan gate, the shape would still be rectangular but with wider width than the runner.

The wider width helps with better plastic flow and clears some gratuitous issues. 

Talking about edge gate’s resemblance with tab gates, they are consistently thick but only for a short period of time and used mainly while producing flat parts for their ability to reduce additional stress. 

2. Sub Gate or Tunnel Gate – 

Also known as a submarine gate or banana gate, this is the only gate design that can be used automatically. It is placed just below the parting line, so when the part is ejected, the gate gets trimmed automatically.

The method is more suitable for producing small parts, high cavity molds, and wherever there’s a need for the gate to be trimmed automatically.

As the sub gate is mostly used for producing small parts, so excessive filling can leave a lot of damage and sheer heating problems, which can even result in halting the production. On the contrary, having a relatively larger tunnel gate can cause cracking. 

3. Hot Tip – 

 

The hot tip is one of many runner gate designs that are highly useful in producing conical or circular parts. Hot tip gates are located at the top of the part opposing the parting line.

The nozzle diameter here must be kept as low as possible as it is recommended to be used only in short molding cycles.

This type of gate requires the hot material to be transported directly to the part and reduces cycle times considerably.

4. Valve Gate – 

Valve gate comes with the same applications and belongs to the hot runner gate family but with a slight advantage.

It comes with a movable pin inside the hot runner tip, and when the pin is back, the plastic flows to the cavity, and when forwarded, it shuts off, giving you an extra ounce of control in the process.

5. Sprue Gate – 

Sprue gate is manually trimmed and has a straightforward design and application. It is mainly used in single cavity molds of large symmetrical fillings. It is used to produce parts that are high in strength and are low stress.

The maintenance cost is negligible. It leaves a scar on the final product at the point of contact.

6. Diaphram Gate – 

Diaphram gate is used to produce cylindrical parts or parts with large open diameters where the plastic flow is required. Plastic flow is useful in making sure that it shrinks as consistently as possible when plastic is cooling.

Utilization of a diaphragm gate is necessary to avoid any kind of mark on the final product.

Applications of Manually Trimmed Gates – 

1. As the manual gate design is quite difficult to shift automatically, it is utilized to produce high strength and low stressed parts.
2. It is also used to produce sheer sensitive parts.
3. Suitable for plastic parts that do not allow marks or welding lines on the exterior.

Applications of Automated Trimmed Gates – 

1. Gate removal is dropped as a secondary operation, thus cutting production costs.
2. Maintaining consistent cycle times for all parts becomes possible.
3. Marks or welding lines can be reduced.

Interesting Read – What is Overmolding? | Versiltality of Overmolding | Advanatges of Overmolding | Disadvantages of Overmolding

Final Thoughts – 

In the above article, I tried my best to share my knowledge about types of gates with you folks in as detail as possible.

Kindly share your thoughts in the comment box to help our team improve our articles.

Peace Out!!!