What is the Reason why Sand Holes Appear after Oxidation of CNC Machining Parts?

When there is no problem with the material, what is the reason why sand holes appear after CNC machining and oxidation?

A customer who makes high-end equipment asked me that during his own CNC machining process, a large number of sand holes appeared on the panel after oxidation. He was not sure what caused this phenomenon. If the possibility of this kind of phenomenon is excluded from the raw materials, Generally, the reasons for this phenomenon are found to be as follows:

1. During the CNC machining process, the cutting fluid contains weak saltiness, which is caused by the lack of immediate cleaning after CNC machining.

2. The environment in which CNC parts are stored after CNC machining is highly acidic and salty. If the parts are stored for more than 7 days, there is a chance of surface corrosion.

3. The potion used in the oxidation process of the CNC aluminum parts oxidation factory contains impurities.

In order to avoid the above 3 bad causes, the PH value of the cutting fluid should be tested regularly. At the same time, the CNC aluminum parts sent to the oxidation plant should not be left for more than 7 days, especially when the weather is hot. In addition, the conditions of the oxidation process must be monitored. , can effectively prevent the sand hole defects caused by oxidation after CNC machining.

For example, if there is a problem with the material, what is the reason why sand holes appear after CNC machining and oxidation?

The presence of sandholes or porosity in CNC machined parts after oxidation can be attributed to several factors in the manufacturing process. Here are some common reasons:

1. Contaminated Material: If the material used for CNC machining contains impurities or contaminants, they can result in gas bubbles when exposed to the high temperatures of the oxidation process. These bubbles can lead to the formation of sandholes.

2. Inadequate Cleaning: Prior to oxidation, the CNC machined parts should be thoroughly cleaned to remove any residual machining oils, grease, or dirt. Failure to clean the parts properly can trap contaminants that cause porosity during oxidation.

3. Improper Surface Preparation: The surface of the machined part needs to be prepared correctly for oxidation. Any irregularities or rough spots on the surface can create areas where gas can become trapped, forming sandholes during the oxidation process.

4. Oxidation Process Parameters: The specific parameters of the oxidation process, such as temperature, time, and gas composition, must be controlled carefully. Deviations from the recommended parameters can lead to the formation of defects like sandholes.

5. Gas Entrapment: During the oxidation process, gases can become trapped within the material. This can occur if the part is not heated and ventilated properly. The trapped gases may create voids or porosity, including sandholes, when they expand during the oxidation process.

6. Poor Material Quality: The quality of the base material used for CNC machining can significantly impact the final product. If the material has inherent defects or impurities, it is more likely to develop porosity during oxidation.

7. Inadequate Cooling: After the machining process, parts should be cooled properly before undergoing oxidation. Rapid cooling can cause thermal stress and induce the formation of porosity in the material.

8. Welding or Joining Defects: If the CNC machined part has been welded or joined using a suboptimal method, it may introduce weak points in the material that are susceptible to porosity during oxidation.

To prevent sandholes and porosity in CNC machined parts after oxidation, it is crucial to follow best practices in material selection, machining, surface preparation, and oxidation processes. Additionally, maintaining proper cleanliness and controlling process parameters are essential steps in achieving high-quality, non-porous components.

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