The technical parameters of the blasting machine operation include air pressure, blasting nozzle diameter, blasting angle, blasting distance, blasting time, blasting operation environment, and ventilation and dust removal. When alumina abrasives are used for blasting, the effect of abrasive grain size and air pressure on the surface roughness after blasting. Abrasive particle size is coarse, and the wind pressure is increased, which can increase the surface roughness; otherwise, the surface roughness is reduced. Under the condition of using the same blasting abrasive and the same wind pressure parameters, the substrate with low hardness and soft quality (such as aluminum and soft steel) has a large surface roughness after blasting.
The effect of automatic blasting time and air pressure on the surface roughness, with the increase of wind pressure, the surface roughness significantly increased; and the effect of the blasting time on the surface roughness increased linearly in the initial time of about 30 minutes The relationship, and then extended the blast time, the surface roughness is almost unchanged.
The blasting angle is 70 degrees from the horizontal line, generally 80 ~ angle is appropriate. It should not be sandblasted vertically, otherwise the power of sandblasting will decrease due to the vertical rebound of the abrasive; but it should not be less than 45 degrees, otherwise it will affect the effect of sandblasting. The blasting gun should always maintain a stable blasting angle and scan the blasting of the workpiece. Each blasting channel should cover the l of the previous blasting channel and is dominant, continuously moving from one end of the workpiece to the other. The second shot blasting should be covered with the first shot blasting, and the replacement is repeated until the required surface roughness stops.
The distance of the blasting machine is the distance from the blasting muzzle to the surface of the substrate. It depends on the type and size of the abrasive, the diameter of the blasting nozzle, and the function of the blasting machine. It generally fluctuates within the range of 102mm-304mm. For soft substrates and thin-walled parts, large blasting distances should be used; for hard substrates, thick-walled parts, large pieces, and thick coatings, shorter blasting distances should be used. After the blasting is completed, the monotonous, oil-free and clean compressed air is used to blow away the floating dust on the blasted surface. The fresh surface after sandblasting stops being contaminated by lotus, and the finger marks left by the finger touch will affect the contact of the spray coating. Spraying should be performed as soon as possible after blasting to prevent the substrate from affecting the contact function of the coating due to moisture absorption or oxidation. Regarding the steel substrate, the distance before spraying should not exceed 4h, and it should not exceed 2h in humid climate.