What are the problems in the lost foam casting process

During the pouring process in lost foam casting, in order to discharge gases and vaporized residue from the mold, the sprue must have sufficient height to provide enough pressure head for the molten metal to flow stably and rapidly, ensuring a complete and clear surface of the casting. In practice, some companies use the sprue cups originally used in sand casting. Due to their small size, uneven flow of liquid can easily occur, leading to scrap of the workpiece. To ensure sufficient flow to maintain continuous flow during the pouring process and quickly establish a dynamic pressure head, a larger sprue cup can be used; the sprue can be made hollow to reduce gas generation and back spray, increasing the pressure head at the beginning of pouring.
The lost foam casting process employs negative pressure dry sand vibrating molding, which results in a mold strength significantly greater than that of green sand. The use of negative pressure extraction enhances mold stability and promptly removes the pyrolysis and gasification products generated during mold gasification. However, in the production process, some factories only pay attention to observing the surface negative pressure before pouring, but often neglect changes in negative pressure during the pouring process, resulting in casting defects. By adjusting the negative pressure during the pouring process based on the size of the casting and the amount of pyrolysis products, this issue can be effectively resolved. Due to its characteristics of low equipment investment and low cost, the lost foam casting process has developed rapidly in recent years. Many existing small and medium-sized foundry enterprises are increasingly adopting this technology. However, some companies fail to pay attention to operational details such as molds, coatings, vibration methods, and pouring processes, leading to unstable casting quality during production.
As a near-net shape casting method, lost foam casting technology has experienced rapid development in recent years. In foreign countries, the successive establishment and commissioning of mechanized and automated lost foam casting production lines, along with the significant economic and social benefits they have generated, have demonstrated the strong vitality of this technology.
Although the application of lost foam casting technology in China has been slow in the past, it has experienced rapid development in recent years. Especially due to the low investment required for lost foam casting equipment and the short process route, many existing small and medium-sized foundry enterprises are increasingly adopting this technology. However, some enterprises have failed to pay attention to certain operational issues, resulting in problems during the production process and significantly affecting the quality of castings.