Surface treatment is a crucial process in CNC machining, as it not only enhances the appearance of the parts but also improves their performance, such as corrosion resistance, wear resistance, and hardness. However, various issues may arise during the surface treatment process, affecting the quality of the final products. This article will discuss some common problems and their corresponding solutions.
One of the common problems is poor adhesion of the coating. This means that the coating applied to the surface of the CNC machined part is easy to peel off or fall off, which greatly reduces the protective effect of the coating. The main reasons for this problem may be insufficient surface cleaning before coating, presence of oil stains, rust, or other contaminants on the surface, or improper surface roughness. For example, if there is oil on the surface, the coating cannot firmly attach to the part. To solve this problem, first, we need to strengthen the surface cleaning process. We can use professional cleaning agents to remove oil stains and rust, and then perform processes such as sandblasting or pickling to increase the surface roughness, which helps to improve the adhesion between the coating and the part. In addition, ensuring that the coating material is compatible with the base material of the part is also an important measure.
Another problem that often occurs is uneven coating thickness. Some parts may have thicker coatings in some areas and thinner in others, which not only affects the appearance but also leads to inconsistent performance of the part. This is usually caused by factors such as uneven current distribution during electroplating, improper placement of parts in the coating equipment, or unstable parameters of the coating process. For instance, in electroplating, if the parts are placed too close to each other, the current density in the adjacent areas will be higher, resulting in thicker coatings. To address this issue, we can adjust the placement of parts to ensure uniform current distribution. At the same time, strictly controlling the parameters of the coating process, such as temperature, time, and concentration of the coating solution, can also help to obtain a uniform coating thickness. Regularly calibrating the coating equipment is another effective way to ensure the stability of the process.
Surface discoloration is also a troublesome problem in surface treatment. The surface of the treated part may show abnormal colors, such as yellowing, darkening, or spots, which seriously affects the appearance quality. This problem may be caused by factors such as contamination of the treatment solution, excessive treatment time, or improper post-treatment. For example, if the plating solution is contaminated by impurities, it will react with the part surface during electroplating, resulting in discoloration. To solve this problem, we need to regularly replace and filter the treatment solution to ensure its purity. At the same time, strictly controlling the treatment time and temperature, and performing proper post-treatment such as cleaning and drying in a timely manner can also prevent surface discoloration.
In addition, pinholes or bubbles on the coating surface are also common defects. These small holes or bubbles will reduce the corrosion resistance of the coating and affect the service life of the part. The main reasons for this problem include the presence of gas in the coating solution, improper pretreatment of the part surface (such as incomplete removal of oxide layers), or too fast coating speed. For example, if the part surface has an oxide layer, the coating cannot be well combined with the base material, and gas will be trapped between them, forming bubbles. To solve this problem, we can take measures such as degassing the coating solution, strengthening the pretreatment process to remove oxide layers and impurities, and adjusting the coating speed to ensure that the coating is formed evenly and without gas entrapment.
In conclusion, the surface treatment of CNC machined parts may encounter various problems, but as long as we find out the causes of the problems and take corresponding solutions, we can effectively improve the quality of surface treatment. Strengthening process control, optimizing operation procedures, and regularly maintaining equipment are the key to ensuring the quality of surface treatment.