What is Gate?

The gate is the connection between the runner system and the molded part. The objective of the gate is to allow enough material flow for both mold filling and thermal shrinkage compensation.

Types of gating system:

There are two major classification of gates:

Manually trimmed gates

Manually trimmed gates are those that require an operator to separate parts from runners during a secondary operation. The reasons for using manually trimmed gates are:

• The gate is too bulky to be sheared from the part as the tool is opened.
• Some shear-sensitive materials (e.g., PVC) should not be exposed to the high shear rates inherent to the design of automatically trimmed gates.
• Simultaneous flow distribution across a wide front to achieve specific orientation of fibers of molecules often precludes automatic gate trimming.

The following gate types are trimmed from the cavity manually:

1. Direct (sprue) gate
2. Tab gate
3. Edge (standard) gate
4. Overlap gate
5. Fan gate
6. Disk (diaphragm) gate
7. Ring gate
8. Spoke (spider) gate
9. Film (flash) gate

Automatically trimmed gates

Automatically trimmed gates incorporate features in the tool to break or shear the gate as the molding tool is opened to eject the part. Automatically trimmed gates should be used to:

• Avoid gate removal as a secondary operation
• Maintain consistent cycle times for all shots
• Minimize gate scars

The following gate types are trimmed from the cavity automatically:

1. Pin gate
2. Submarine (tunnel, chisel) gate
3. Hot-runner (hot-probe) gate
4. Valve gate