This is a liquid metal reservoir at the bottom of the sprue, which is designed to reduce the momentum of molten metal. When the metal descends from the sprue, it gains speed, some of which are lost in the sprue socket, thus reducing the corrosion of the mold. The molten liquid metal changes direction and flows into the runner in a more uniform way.
Runner
It is usually located on the horizontal parting surface connecting the sprue to the ingate to allow the metal to enter the cavity. The cross section shape of the sprue is usually trapezoidal. For ferrous metals, Guangdong Machinery Works usually open transverse gate in the upper box and inner gate in the lower box. The main reason is that in order to block the light slag on the top of the sprue, the transverse sprue should be filled. When the amount of molten metal entering from the sprue is more than that flowing through the inner gate, the transverse sprue will be filled, so as to achieve slag blocking. However, when more metal flows through the ingate than through the runner, only part of the runner is filled and the slag will enter the cavity.
Transverse gate extension end:
When the Crossgate and the ingate intersect in Guangdong machining plant, it will extend a little. This extension is to stop the dross in the molten metal. Initially, the metal and the slag floating above the ladle flow straight forward, through the inner gate and blocked by the slag at the extended end of the transverse gate.
Riser:
Most of the casting alloys in Guangdong mechanical processing plant contract during solidification. Table 10.1 shows the various volume shrinkage of typical materials. Because of this volume shrinkage during solidification, the casting tends to form shrinkage cavities unless additional liquid metal enters the area known as the hot spot because it remains hot until the end. Therefore, a reservoir of molten metal must be prepared through which the metal can flow smoothly into the casting when needed.
As shown in table 5.6, different materials have different shrinkage, so the requirements of riser vary with different materials. In gray cast iron, volume expansion sometimes occurs due to graphitization during solidification. The occurrence of this situation depends on the degree of graphitization controlled by silicon content in gray cast iron.
In order to make it effective, the riser should be designed according to the following rules
1. The metal in the riser should finally solidify.
2. The riser volume should be enough for feeding.
Table 5.6 material, shrinkage (%),
Material            Shrinkage,(%)
Medium carbon steel     2.50 to 3.50
High carbon steel         4.00
Nickel               6.10
Monel               6.30
Aluminum              6.60
Aluminum alloy (11-13% Si)   3.50
Aluminum bronze         4.10
Copper                  4.92
70-30 brass              4.50
Bearing bronze           7.3
Grey cast iron             1.90 to negative
White cast iron           4.00 to 5.75
Magnesium              4.20
Zinc                   6.50