The surface roughness of castings is related to the following factors:
1) The material of the sand mold. For example, castings made of resin sand and clay sand have different surface roughness. The casting surface of resin sand is smoother.
2) Humidity of sand mold
3) The technological level of making sand molds
4) The speed of pouring. If the speed is too fast, the sand surface will be damaged and the casting will be rough.
5) The size of the casting