ingate

An ingate is the opening through which molten metal enters a casting mould during the pour. It connects the runner system, the network of channels in the mould, directly to the mould cavity itself. The term is used interchangeably with gate in foundry work, though gate can also refer to the solidified metal that remains in this channel after casting.

The ingate's location, size, and shape directly control how metal flows into the cavity. A poorly designed ingate can cause turbulence, trapping air and creating porosity defects; an ingate that is too small starves the cavity and produces incomplete castings; one that is too large wastes metal and requires extra finishing work. Ingates are typically tapered to create a gradual transition from the runner to the cavity, with typical gate velocities ranging from 3 to 5 feet per second for iron and steel.

Different casting processes use different ingate configurations. In sand casting, ingates are often rectangular or circular in cross-section and are formed as part of the mould cavity. In permanent mould casting, ingates may be carved into the metal mould itself. In die casting, they are precision-machined openings that must withstand repeated thermal cycling. The number of ingates on a single mould cavity depends on its size and complexity: a large casting may have multiple ingates positioned to fill the cavity evenly and minimize defects.

The ingate must be positioned to prevent metal from hitting the mould wall directly, which causes erosion, scarring, and sand washout in sand moulds. For this reason, the ingate often feeds into a basin or reservoir section called the well or pouring basin before the metal travels through the main runner. After solidification, the ingate and runner system are cut away from the finished casting, creating flash and scrap that must be machined or ground off.

Because the ingate is the last part of the mould to fill and the first to solidify as the casting cools, it is a natural site for shrinkage porosity. Foundry engineers often use a technique called gate feeding, where the ingate is deliberately positioned so that it remains molten longer than the main casting body, allowing it to feed liquid metal back into the cavity as it shrinks. This requires careful calculation of the ingate's thermal mass and insulation.