Terminology (2)

Advanced Die-Casting Process Terminology

The article “Die-Casting Terminology” provided definitions for some basic die-casting process terms. This article will expand upon the earlier list to explain some of the more advanced terminology used to describe specific die-casting processes, tools, and parts. These terms may not be encountered as often by the hobbyist as the basic terms, but these definitions will provide a good understanding and appreciation of the intricacies of the die-casting process.

Biscuit – The biscuit consists of excess metal remaining in the shot sleeve of a cold chamber die casting machine. The biscuit is removed from the die with the casting after it has cooled.

Fillet – A fillet is a radius in an interior corner where two surfaces meet, rather than having a sharp corner. A fillet reduces the stresses that occur in that location when the part is bent or stressed.

Gate – A gate is a passage machined into the die that connects a runner to a die cavity.

Gooseneck – The gooseneck is the metal injection mechanism in a hot chamber die casting machine. It connects the metal chamber with the sprue hole via a nozzle.

Injection – Injection is the actual process by which the molten metal is forced into the die.

Insert – An insert is a piece of metal that is inserted into the die prior to casting. The insert then becomes part of the die-cast part.

Nozzle – The nozzle connects the gooseneck to the die via the sprue hole. The nozzle size defines the flow rate of the molten metal into the die during the casting process.

Plunger – The plunger is a piston that forces the molten metal into the die.

Port – The port is an orifice by which the molten metal enters the injection cylinder.

Runner – A runner is a passageway machined into the die that allows the molten metal to flow into the mold cavity. Molds that contain multiple cavities will have one runner directed to each cavity.

Shot Cylinder – In cold chamber die-casting, molten metal is drawn into the shot cylinder when the plunger is pulled out. In hot chamber die casting, the shot cylinder controls the plunger motion, but is not in contact with the molten metal.

Sprue – Sprue is the metal that fills the passage within the die between the part cavity and the injection nozzle after casting. This is waste metal that is removed from the part after it has cooled.

Sprue Pin – The sprue pin is a small cone-shaped part generally installed on the cover side of the die and is inserted into the sprue hole to deflect the incoming molten metal to spread it into different portions of the die. The sprue pin also makes it easier to remove the sprue after casting.

Undercut – An undercut is a feature of the die-cast part that prevents the piece from being ejected from the die after casting. Designs that require an undercut necessitate complex dies with removable slides so that the part can be extracted after casting. It is generally more cost effective to redesign the part to eliminate undercuts.

Waterline – A waterline is a channel built into the die that water can flow through. The water absorbs the heat from the die, accelerating the cooling process after the part has been cast.

Sources:
North American Die Casting Association web site - http://www.diecasting.org/
Totten, Funatani, and Xie, Handbook of Metallurgical Process Design, CRC Press, 2004.