[China Aluminum Network] paint brushing method is also an important part of the surface quality of the casting.
(1) The surface quality of the metal cavity wall before coating is extremely important for the adhesion of the paint. The new metal type must be thoroughly cleaned, de-oiled and rusted. The part with the draft angle must be polished with assorted files and fine emery cloth. (Because the taper hole of the CNC milling machine is microscopically stepped, it is not a smooth slope, and it is difficult to demold). The already used mold must also completely remove the original coating. The traditional removal method is to manually remove with a wire brush or an emery cloth, the efficiency is low, and the die wear is serious. Our company currently uses a sandblasting method that uses compressed air to blow quartz sand to the surface of the cavity. This method is not only efficient but also improves the adhesion of the paint. Recently, some merchants often introduce dry ice shot-blast cleaning methods. It is said that the effect is good, but it has not yet been promoted.
(2) Brushing method Before 2005, the brushing method adopted by our company was to use a brush to apply viscous paint to the wall of the cavity. The coating was thick and uneven, with obvious irregular texture. Later, the spraying method was used, that is, the mold was first preheated to 150-230°C, and then the spray gun was used to spray the paint to the cavity wall. When spraying, the spray gun should be kept at a cavity angle of 20 to 30 cm with an angle of 45°. The main point of the spray gun is “spotted†to avoid coating build-up and spotting. The preheating temperature can be controlled with a "handheld infrared measuring instrument". If the temperature is too low, the coating is uneven and easy to fall off; if the temperature is too high, the coating rapidly bursts, deforms, or partially falls off.
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