What factors on the workpiece surface will affect the processing effect of automatic sandblasting machine?

surface roughness

Influence of initial roughness: the initial roughness of the workpiece surface will have an impact on the sandblasting effect. If the surface of the workpiece itself is rough, for example, the roughness (Ra) of the metal surface after rough machining may reach more than 12.5 μ m.. In this case, the sandblasting machine needs to adjust the sandblasting parameters according to the actual roughness. If the sand particles are not properly selected, such as the particles are too fine, the surface roughness may not be effectively improved and the expected processing effect may not be achieved; If the particles are too large, the surface may be too rough and even damage the surface of the workpiece.

Target roughness requirements: Different application scenarios have different requirements for surface roughness after sandblasting. For example, in the coating industry, proper surface roughness can enhance the adhesion between coating and workpiece surface. Generally speaking, the surface roughness (Ra) is between 3-7μm, which is favorable for coating adhesion. If the workpiece is used for high-precision machining, such as aerospace engine parts, the surface roughness after sandblasting may need to be controlled at a low level to ensure the dimensional accuracy and surface quality of the parts.

surface hardness

Hardness and sand selection: the surface hardness of the workpiece determines the choice of sand and the setting of sandblasting pressure. For workpieces with higher hardness, such as quenched alloy steel and hard ceramics, sand with higher hardness, such as corundum sand, can be used. Because these sand materials can effectively remove impurities and roughen the surface of the workpiece. On the contrary, for workpieces with low surface hardness, such as soft metals such as aluminum and copper or some plastics, it is necessary to choose relatively soft sand materials, such as quartz sand or plastic sand, and reduce the sandblasting pressure. Otherwise, it may cause excessive wear, deformation and even scratches on the surface of the workpiece.

Effect of hardness inhomogeneity: If the surface hardness of the workpiece is uneven, for example, the surface hardened metal workpiece has high hardness in the quenched area and low hardness in the non-quenched area. In the process of sandblasting, this difference in hardness may lead to inconsistent machining effect. In areas with high hardness, sand may not be able to fully remove surface impurities or achieve the expected roughness, while in areas with low hardness, there may be over-processing.

Surface cleanliness

Influence of oil stain and grease: When there are pollutants such as oil stain and grease on the surface of workpiece, it will affect the processing effect of sandblasting machine. Oil pollution will form an isolation layer on the surface of the workpiece to prevent direct contact between sand and the surface of the workpiece. For example, on a machined metal workpiece, the residual cutting oil will make it difficult for sand to effectively remove impurities such as scale and rust on the surface of the workpiece. Moreover, oil pollution may also lead to the bonding of sand materials, affect the recycling of sand materials and reduce the efficiency of sandblasting.

Influence of dust and impurities: Dust and other solid impurities on the surface will also interfere with the sand blasting process. If there is a lot of dust on the surface of the workpiece, these dust may be mixed with the sand during sandblasting, which will affect the spraying direction and impact force of the sand, and then affect the machining effect. In addition, some impurities embedded in the surface of the workpiece, such as metal chips and sand particles, may lead to bumps or unevenness on the surface of the workpiece after sandblasting.

Surface shape and contour

Influence of shape complexity: the complexity of workpiece surface shape has a significant influence on sandblasting effect. For the plane or cylindrical surface with simple shape, the spray gun of the sandblasting machine can easily keep the uniform sandblasting angle and distance, thus obtaining a relatively uniform machining effect. However, it is difficult to ensure the uniformity of sandblasting for workpieces with complex cavities, deep holes, grooves or curved surfaces. For example, when the mold with complex internal channels is sandblasted, it is difficult for sand to penetrate into all corners and gaps, which leads to the processing effect in these areas is not as good as that in other areas.

Influence of contour change: the change of workpiece surface contour will also affect the sandblasting effect. If there are large protrusions or depressions on the surface of the workpiece, the protrusions may be impacted by too much sand during sandblasting, resulting in excessive machining; The concave part may be under-processed because the sand is difficult to reach. In this case, it is necessary to adjust the position, angle and blasting time of the spray gun to minimize the machining difference caused by the contour change.