Graphite, calcium carbonate, etc. can be added to the raw material tank of the special low-pressure foaming machine for sheet to increase the flame retardant effect and save cost. The foaming machine is one of the core equipment of the entire sheet production line. This equipment is a new product independently developed by Lingxin Company and is dedicated to polyurethane sheet production line. The machine has the characteristics of high repeated injection precision, uniform mixing, stable performance, easy operation and high production efficiency.