The heat transfer medium (oil) enters into the system by I (oil tank), pumped to the mold by F (circulation oil pump ), and then back to the system. This process repeats again and again. The medium (oil) is heated up by the G (Heater), and its temperature is detected by K ( Temperature detector ). When the temperature reaches the required point, G (Heater) will stop to work. When the temperature needs to fall down, H (Cooling solenoid valve) will be open, cooling water from A to B then via H go to heater exchange, the water from heater exchange via B flow to water tower, thus descending the temperature inside the system.