1 fixture design and production
1.1 Features of the fixture
The jig for anodizing is different from the jig used for electroplating. If an anodizing jig is used as a jig with a similar hook for electroplating, it is not suitable because the anodizing will quickly generate an oxide film on the surface of the jig and the workpiece. During this process, slight loosening of the fixture and the workpiece will change the position of the contact and impede the flow of current. For this purpose, the workpiece must be clamped with a flexible clamp. Only in this way can the anodizing process proceed normally.
1.2 Structure of the fixture
The fixture structure is suitable for individual type. If the assembly type is adopted, riveting or welding will be loosened after several times of use, which will hinder the normal circulation of current in the anodizing process. At the same time, the fixture should have a certain cross-sectional area. A certain section of the fixture also has enough elastic force and clamping force to keep the workpiece and the fixture in good contact, so as to ensure the normal current circulation when the workpiece is anodized. Avoid burning the workpiece due to bad heat.
1.3 Selection of Fixture Materials
The fixture is made of hard aluminum, and the hard aluminum is flexible and durable.
2 Workpiece clamping
2.1 to clean the fixture to remove the film
The fixture also produces an oxide film during anodization. For this reason, be sure to remove the oxide film before using it again before using it again. The film can be removed in aluminum degreasing solution. It is also possible to remove the oxide film at the contact area between the jig and the workpiece with a trowel, and this method can also extend the service life of the jig for some jigs.
2.2 Selection of clamping positions
The position of the workpiece to be clamped should be selected properly. Generally, it should be clamped on the secondary side of the workpiece (that is, the non-decorative part). Otherwise, the contact area between the workpiece and the fixture cannot be covered with the oxide film due to being covered by the fixture. Of course, it will not be able to be dyed. This will show obvious white spots and affect the appearance quality. In addition, the question of whether the recessed parts suspended in the solution after the workpiece is clamped in the solution, such as the generation of gas, should also be considered.
2.3 to prevent workpiece clamping deformation
Fixtures are different from one another, and clips have a certain degree of elasticity. In particular, care must be taken when clamping a deformed workpiece, and excessive deformation of the workpiece should be avoided.
2.4 To prevent over-loading
When the workpiece is clamped too loose, the current between the fixture and the workpiece will be intermittent. In this case, the workpiece is likely to be burned.
2.5 One by one clamping anodized parts to be dyed
Some units apply anodization to some small pieces using screens or other methods of dressing. Although this method can save man-hours and improve efficiency under certain conditions, it can only be used for certain anodizations with low quality requirements. Even if a small number of workpieces cannot form an oxide film at the mutual mask, they are not easily identified. But for workpieces that require black dyeing, this method of clamping is obviously not desirable. Must be installed one by one to ensure the quality of anodizing.
3 Control of Anodizing Process Conditions
3.1 The relationship between temperature and voltage of solution
The lower the temperature of the solution within the rated range, the higher the required voltage is. Because the temperature of the oxide film is relatively slow when the solution temperature is low, the film layer is dense. In order to obtain a certain thickness of the oxide film, the anodization process needs to be increased. high voltage. When the temperature of the solution is high, the dissolution rate of the oxide film increases, and the resulting oxide film is loose. At this time, reducing the voltage can properly improve the quality of the oxide film.
3.2 The relationship between temperature and time of anodizing solution
The lower the temperature of the solution, the longer the anodization time required. Because the temperature of the solution is low, the oxide film is slowly formed. As the temperature of the solution increases, the rate of oxide film formation increases. At this time to shorten the anodizing time, otherwise due to the increase of the outer layer of the oxide film resistance film layer dissolved, the size of the workpiece changes, the phenomenon of rough surface film.
The above measures are only emergency measures taken under the condition that there is no cooling device and no heating device.
4 Formulation and preparation process of dyed black solution
4.1 Formulations and Process Conditions
Acidic wool ATT 20～30g/L acid lake blue 2～3g/L Temperature 50～70°C Time 10～15min pH 3～3.5 (or 4.5～5. 5)
4.2 Boil the solution to facilitate complete dissolution of the dye and ensure it is free of defects. After the solution is cooled, it is filtered with a filter paper to remove insoluble particles and oily substances floating on the liquid surface. The pH was later measured and adjusted to process requirements with cold acetic acid or ammonia.
5 Dyeing process should pay attention to matters
5.1 Enhanced flushing before dyeing
After the workpiece is removed from the anodic oxidation tank, it must be fully flushed, especially in the slits, blind holes, etc. of the workpiece. Otherwise, the residual acid and alkali will slowly flow out during the dyeing process, causing the pH value of the dyeing solution to deviate from the normal range, and The color of the surface of the residual acid and alkali sites is clearly different from that of the clean part, and even the oxide film is etched to show white color.
5.2 Dyeing After Anodizing
Immediately dye the workpiece after anodizing. If the workpiece is anodized and exposed to air for an extended period of time, the pores of the film will shrink, and stains may get on the surface, causing difficulty in dyeing. If the dyeing tank is too small to be dyed in batches, the parts to be dyed should be soaked in clean water.
5.3 The workpieces do not overlap during dyeing
The workpieces cannot be overlapped during dyeing, especially on the flat surface, otherwise the yin and yang planes are formed due to the overlapped parts being covered.
5.4 Enhanced Dyeing After Dyeing
If the surface of the workpiece is not washed clean, residual pigments will contaminate the assembly.
6 Cleaning Work Precautions
6.1 Carefully remove the workpiece
When the fixture is removed, prevent the workpiece from being scratched. Otherwise, a round of white marks will appear. The fixture should be loosened and the workpiece should be free to fall off. Never pull the workpiece hard before the fixture is released.
6.2 Workpiece Drying Method
Drain the water in the hole of the workpiece first to avoid the residual water from contaminating the surface of the workpiece. It is better to dry the towel with a dry towel. In the rubbing process, the surface frost caused by the aluminum material or the operation process problem can also be wiped clean.
6.3 Packaging Requirements
Packing is soft, clean paper is good, and it is packaged one by one to prevent it from rubbing one another.
7 Maintenance and Maintenance of Stained Black Solutions
The maintenance and maintenance work of the dyed black solution is mainly to maintain the pH of the solution. According to relevant information, acidic ATT dyes consist of acidic blue-black 10B and acidic orange II with different diffusion properties. When the pH value of the dyeing solution is in the range of 5-6 or 3-3.5, the absorption of Acid Orange II and Acid Blue Black 10B is better, and the amount absorbed by the oxide film is also larger. The amount meets the matching requirements and the color obtained is normal black. When the pH value is around 4, the effect of the oxidation film absorbing acidic orange II increases, and the absorption naturally increases. The acid orange II in the film is larger than the normal ratio, and the color appears reddish. When the pH is restored to the range of 3-5 or 5-5. 5, the absorption of acidic orange II by the oxide film will fall again, and the dyed workpiece will show normal black color. According to this, the pH of the dyed black liquid The accurate control of the value is very important.