The first is the design technology of iron casting.
The second is to have reasonable casting process.
The third is the materials quality of the foundry.
We should control quality and measure inspection for the casting during the production process. Develop process rules and technical conditions which are from raw materials and auxiliary materials to the control and inspection of every specific product. Ensure the quality inspection on the finished castings.
We can use comparison samples to judge the casting surface roughness for the appearance quality of the professional castings. The surface of the minor cracks, we can use shading, magnetic powder to check it.