The pre-foaming machine is one of the most important equipment of the lost foam casting white area. At present, there are two types of the machines: electric pre-foaming machine and steam pre-foaming machine. They are intermittent. The control system adopts the most advanced PLC technology. The pre-foamed beads are uniform. The steam pre-foaming machine can set stirring time and steam time in time according to process requirement. The electric pre-foaming machine can be opened by one button. The material feeding is automatic. The operation is easy and unattended.