The gating system is a channel for liquid metal to flow into the crankshaft casting cavity. The pouring system is mainly composed of sprue cup, sprue, sprue nest, cross sprue and internal sprue. The design of the gating system will directly affect the quality of the casting. About 30% of the waste products of the casting are caused by the unreasonable design of the gating system, and about 30% of the waste products of the casting are caused by the unreasonable design of the gating system. Basic requirements for casting gating system design:
1) The parameters of the runner in the gating system should be determined according to the solidification principle of the casting.
2) During the filling process, it is necessary to make the liquid metal flow smoothly, avoid turbulence in the flow process, and at the same time, prevent the liquid metal from getting involved in the gas, making it oxidized or producing pores.
3) When the metal liquid enters the cavity from the inner gate, the tangential velocity should not be too large, otherwise it will cause splashing, flushing the inner wall of the cavity and sand core and other phenomena.
4) The pouring system is not easy to be too large and easy to cause waste. At the same time, it needs to fill the mold cavity within the specified time to avoid the formation of defects such as sand inclusion and cold separation due to the slow rise of the metal liquid level.
5) The molding of the pouring system should be simple and easy to make, and the volume of the sand box should be reduced.
Because the crankshaft has long size, many cranks, complex structure, machining surface in the middle part of the casting, and the thickness of the crank is even but thin, so it is very important to choose the location of the pouring port of the crankshaft casting. In addition, because of the large number of cranks and the long size of the crankshaft, the feeding in the solidification process is also very important, otherwise, there will be shrinkage porosity, shrinkage cavity and other defects in the main parts of the crankshaft. Therefore, the location of the pouring port can be set on the non machining surface or the position with casting allowance, and the riser can be designed for feeding.