The Most Common 7 Injection Molding Gate Types
Injection Molding Gate is an integral part of the injection molding process. It is often referred to as the connecting zone between the runners and the cavity. The appearance and location of these gates can affect the overall cycle times and the cost of tooling.
What is a injection molding gate?
Injection molding involves pushing molten plastic into a mold cavity. The material stays there until it reaches a gate, which allows the plastic to enter the cavity.
Why does gate type and gate placement matter?
Gate placement is important when it comes to determining the location of a material in a mold cavity. When the gate size is too small, it can cause a buildup of material pressure to push the material into the cavity. This can result in the gate's appearance getting distorted. Another important consideration when it comes to gate placement is that they should not be placed on a visible area of the part.Gates also need to be positioned near thick-walled areas to prevent defects such as weld marks.
Injection Molding Gate placement tips:
● Away from cores and pin inserts.
● Sufficient space for degating
● Minimize flow path length
● Multiple gates consideration
Below are the most common gates types in injection molding:
● Edge Gate
● Tunnel / Submarine (Sub) Gate
● Cashew Gate
● Direct Sprue Gate
● Diaphragm Gate
● Hot Runner – Thermal Gate
● Hot Runner – Valve Gate
EDGE GATE
Edge gates are commonly used in the injection molding process due to their simple design. They are also ideal for parts that cannot be filled with thick wall sections. Due to their cross-sectional area, they allow for faster plastic flow and better hold times. An edge gate has a rectangular shape while a fan gate has a circular shape. The shape of the runner should still match the rectangular shape of the gate though its width should be wider than the height of the fan.
TUNNEL / SUBMARINE GATE
Tunnel gates are made from below the parting line and are designed to be trimmed automatically once the part is ejected. This type of gate is commonly used for injection molding. The maximum cross-sectional area is the limit for edge gates.
CASHEW GATE
Similar to a tunnel gate, the cashew one is mechanically sheared during ejection. The only difference is it has a concave shape. Unlike the tunnel gate, the cashew one has a flat surface.
DIAPHRAGM GATE
When a part has a large open diameter, diaphragm gates are used to prevent the plastic flow from getting in the way when cooling. This ensures that the part will shrink consistently as it is cooled.The diaphragm gate allows the plastic to flow into the cavity without the need for an opening. This type of gate is typically used for open-ended components.
HOT RUNNER – THERMAL GATE
Hot runner systems are designed to keep the molten resin from hitting the part or the machine barrel as it's being heated. This eliminates the need for cold runner systems.The first type of gate is the thermal gate. It functions like a normal gate except it holds the material pressure until the temperature of the cavity cools. The advantage here is that the material is saved and the process control is improved.
HOT RUNNER – VALVE GATE
The valve-gated hot runner system adds another level of control to the thermal gate. This design allows the plastic to flow into the cavity while the metal plate is turned.
Gate design is an integral part of the injection molding process. It is often used to access the various variables involved in the design process, as well as the desired production intentions. For more information, contact TEAM MFG.
Injection Molding Gate placement tips:
