What are the different types of flow channels in casting?

1, Direct pouring channel
Direct runner is the most basic and common type of runner in casting. It extends directly from the sprue cup or sprue basin vertically downwards to the parting surface or deeper, providing the main metal liquid supply channel for the casting. The design of the sprue is simple and easy to manufacture, making it particularly suitable for the production of large, thick walled castings. However, the sprue occupies a large area, and the flow speed of the molten metal in it is fast, which can easily generate vortices and gas entrapment. Therefore, it is necessary to control the pouring speed and gate size reasonably to reduce the occurrence of defects.
2, Horizontal pouring channel
A transverse runner is a channel connected to a straight runner and arranged horizontally or obliquely on the parting surface. It mainly plays the role of distributing and guiding the molten metal, evenly distributing the molten metal in the sprue to each inner sprue or cavity. The design of the runner needs to consider factors such as the flow resistance of the molten metal, temperature loss, and gas discharge to ensure that each cavity is filled simultaneously or in the predetermined order. The use of transverse runners improves the forming quality and production efficiency of castings, especially suitable for the production of multi cavity molds and complex shaped castings.
3, Internal pouring channel
The inner runner is the last section of the flow channel that connects the transverse runner (or straight runner) with the mold cavity, and it is also the direct channel for molten metal to enter the mold cavity. The design of the sprue has a great impact on the quality of the casting, and its shape, size, and position need to be accurately calculated and arranged according to the structural characteristics, wall thickness differences, and shrinkage laws of the casting. The common shapes of sprues include circular, rectangular, trapezoidal, etc. The design principle is to ensure that the molten metal enters the mold cavity smoothly and quickly, while reducing gas entrainment and the generation of inclusions.
4, Special channel
In addition to the common types of flow channels mentioned above, there are also some special flow channels in the casting process to meet the production needs of specific castings. For example:
Multi layer flow channel: In the production of large or complex castings, in order to reduce the temperature loss and flow resistance of the metal liquid in the flow channel, multi-layer flow channel design is often used. This design divides the flow channel into multiple layers, with each layer connected by connectors to form a complex metal liquid transport network.
Insulated flow channel: In casting processes that require maintaining the temperature of the metal liquid for a long time or preventing premature solidification of the metal liquid, insulated flow channel design can be used. By setting insulation materials or heating elements around the flow channel, the molten state of the metal liquid in the flow channel is maintained to ensure the smooth formation of the casting.
Slanted flow channel: For certain castings with special shapes or positions, a tilted flow channel design can be used to ensure smooth filling of the molten metal and reduce gas entrapment. This design adjusts the inclination angle and position of the flow channel to allow the molten metal to flow along a predetermined path under the action of gravity.
5, Considerations for Channel Design
When designing the flow channel, the following factors need to be considered comprehensively:
Casting shape and size: Determine the layout and size of the flow channel based on the complexity and size of the casting.
Metal liquid performance: The flowability, solidification characteristics, and thermophysical properties of different metal liquids have a significant impact on channel design.
Casting process requirements: including the constraints of process parameters such as pouring temperature, pouring speed, and pouring pressure on the design of flow channels.
Economy and feasibility: Minimize the complexity and manufacturing cost of the flow channel system while ensuring the quality of the castings.