The mark on the mold is not clear enough (the reason for the mold); 2. The markings on the mold are not clear. You can analyze whether the particle size of the following molding sand is fine enough and whether the strength is high enough; 3. The refractoriness of the mold and coating is not enough. 4. Another factor that is easily overlooked is the casting location of the casting mark. When determining the casting position, try to keep the casting mark on the bottom or side to avoid being on the top surface.