Dry ice cleaning has been widely used in the foundry industry around the world. Most of the casting industry has changed to dry sand cleaning to clean the sand core mold and fixed mold. Cleaning principle: energy transfer. Dry ice hits the surface to be cleaned at a high speed, the kinetic energy of the impact dissipates, the dry ice particles and the cleaned surface undergo extremely rapid heat transfer, and carbon dioxide sublimates instantly. "Cryogenic cracking". Two different materials with different thermal expansion coefficients, the temperature difference between them will destroy the combination between the two materials. Dry ice particles (-78.5℃) impact the surface of the treated product, freezing the dirt to embrittlement and bursting, causing "cracking" and affecting the mechanical properties of the adhered dirt.