The riser can store a certain amount of liquid metal and can feed sand castings. The purpose of feeding is to prevent shrinkage porosity and casting defects. The riser also has the function of gas outlet and slag collection. Of course, the main function of riser is feeding sand casting. There are certain design principles for sand casting riser. Therefore, the following principles should be followed when designing Riser:
- During solidification of sand castings, there should be feeding channels between the riser and the Fed part;
- The riser of sand casting should solidify later than the feeding part of sand casting, so as to form feeding channel;
- Enough liquid metal shall be stored in the riser of sand casting to supplement the shrinkage of sand casting and the volume due to the expansion of mold cavity after pouring;
- The volume of sand casting riser should be as small as possible and as convenient as possible for modeling.
According to the riser design principle, the riser of hydraulic turbine blade is designed according to the thermal modulus method, as shown in the figure. The riser root size is 2500mmx650mm and the riser height is 1000mm. Place the riser at the water inlet edge and lower ring of the blade, which can make the blade contract freely to the greatest extent and avoid the obstruction of the riser to the blade contraction to a certain extent. In order to ensure that the blade sand castings can solidify in sequence, keep the riser feeding channel unblocked and prevent the blade from shrinkage cavity and porosity, a riser subsidy is set at the back of the blade, which can make the riser feed the blade sand castings smoothly, And ensure the internal quality of blade sand casting.