Sand hole is the holes by molding sand inside or on the surface of casting.

Cause:

1. Don’t have enough surface strength;

2. No round corners or small draft slopes lead to hook sand, or close the box without repair when mold damaged;

3. The sand mold is left for too long before pouring, and the surface strength decreases after air-drying;

4. Molds are damaged during box closing or during transportation;

5. When the box is closed, the floating sand in the mold is not removed. After the box is closed, the spout cup is not covered, and the broken sand falls into the mold.

Solution:

1. Increase the content of sticky sand in the sand, add new sand in time, and improve the surface strength of the sand.

2. Reasonably make draft slope and casting fillet. The damaged mold should be repaired before closing the box;

3. shorten the time of placing the sand mold before pouring

4. Be careful when packing or handling the mold to avoid damage or falling into the sand cavity

5. Remove the inner floating sand before closing the box and cover the gate.