It is composed of mixing head , nozzle, air cap, mixing pipe, stem shell and stem. It is the main mechanism to control the mixing of oxygen, combustible gas and the opening and closing of air. The bottom of the mixing head is a stem shell with a stem, oxygen, gas and air head, each with a rubber sealing film on it, and various grooves on the stem surface. It is used to control and distribute the three gases into the mixing head in order to ensure normal ignition and switch to achieve spraying purpose. When the stem wrench rotates clockwise to 90 degrees, the combustible gas head sinks slightly under the action of the spring, a small amount of combustible gas enters the nozzle, and the rest of the gas head is in the closed position, and the ignition condition is available at this time. When the point is on fire, then slowly turn the stem wrench from 90 degrees in the same direction to 180 degrees, when all the heads sink, and the air cap forms the required fire filling, and the air is ejected from the nozzle to the air cap. Dissolve the incoming metal wire into a fine mist particle (spark) in the flame and spray it onto the workpiece surface, stacking it into a coating.