Gates, Risers and Cores in Casting

What are gates, risers and cores in casting? The passage-way which serves to deliver the molten metal into the mould cavity is known as gating system. A gating system consists of a pouring cup, a down gate or sprue, a runner and an ingate. There are various types of gates such as parting line gates, bottom gates, horn gate, branch gate and top gate.

A riser (or feed head) is an opening through the cope. Its main purpose is to feed the molten metal to the casting as it solidifies i.e., to compensate for the shrinkage. The risers also serve as a large vent for generated steam and gases and afford a place for collecting loose sand or slag.

The cores are defined as sand bodies used to form the hollow portions or cavities of desired shape and size in a casting. In addition to forming internal cavities in the casting, the cores serve a number of purposes as follows:

1. The cores may be used to construct a complete mould.

2. The cores may be used to form a part of a green sand mould.

3. The cores strengthen or improve a mould surface.

4. The cores may be used as a part of the gating system.

The various types of cores, depending upon their position are horizontal cores, vertical cores, balanced cores, drop cores and cover cores or hanging cores.

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