In order to avoid the defects of shrinkage cavity and porosity, the thick area of the casting needs to be fed during the solidification process, which is why the gate is set in the thick area of the casting in the actual production.
The design of the gating system needs to follow the following basic principles:
1) If the casting has multiple sections with different thickness, it is necessary to consider the design of multiple gating systems. This design is also suitable for casting large castings to shorten the filling time and avoid overheating of the molding sand at the sprue.
2) It should be avoided to place the inner gate directly opposite the sand core or mold wall. This design will cause splashing and air holes in the liquid metal.
3) The diameter ratio of sprue cup to sprue should make the whole pouring system full during the filling process.
4) The pouring system should realize the larger flow rate on the basis of ensuring the smaller flow rate of liquid metal. This will help to avoid the turbulent flow of liquid metal and reduce the involvement of gas.
5) The design of the gating system needs to ensure the sequential solidification of castings.
6) For the design of the pouring system, the sharp change of the flow direction and section should be avoided as far as possible.