Principles of heat. The working principle of hot-pressing die is to press by heating, so that the binder can melt quickly and coagulate and harden or semi-harden within the heat preservation time, which is a thermal principle. Hot pressing is a simple and commonly used processing method in plastic processing industry. After heating the mold, inject the sample, fix the mold on the heating plate with pressure, control the melting temperature and time of the sample, harden and cool after melting, and take out the finished model.