Post Processing and Finishing for CNC Machined Aluminum

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CNC machining produces parts with excellent dimensional accuracy, but the raw milled surface often requires further treatment to meet final application requirements. For aluminum, a wide range of postprocessing and finishing techniques are available to enhance the part's appearance, durability, and functionality, ultimately adding significant value to your project.


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Why Finish Aluminum Parts?

Aluminum naturally forms a protective oxide layer, but it is thin and can be easily compromised. Postprocessing addresses this by:
Enhancing Corrosion Resistance: Protecting parts from oxidation and harsh environmental conditions.
Improving Aesthetics: Creating a specific visual appeal, from a matte to a mirrorlike shine.
Modifying Surface Properties: Increasing surface hardness for wear resistance or altering texture for grip.
Preparing for Assembly: Ensuring proper surface characteristics for painting, adhesive bonding, or other assembly processes.

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Common Finishing Options for Aluminum

1. Bead Blasting: This process uses fine glass beads to create a uniform, satinlike matte surface. It is excellent for removing minor tool marks and providing a clean, nonreflective finish that is ideal for visual parts.



2. Anodizing (Type II & III): This is the most prevalent finishing method for aluminum. The part is electrolytically oxidized to create a hard, porous, and corrosionresistant surface layer.
Type II (Decorative): Offers good corrosion and wear resistance and can be dyed in various colors (black, red, blue, etc.) for part identification or branding.
Type III (Hard Coat): Creates a much thicker and harder layer, offering superior abrasion resistance and is commonly used in military, aerospace, and highwear applications.

3. Powder Coating: This involves applying a dry polymer powder electrostatically and then curing it under heat to form a thick, durable, and decorative coating. It provides excellent corrosion resistance and is available in a vast array of colors and textures (e.g., glossy, matte, wrinkled).

4. Chemical Film (Chromate Conversion Coating): Often known by its trade name, Alodine, this coating provides a thin, conductive layer that offers good corrosion resistance and serves as an excellent primer for paint. It is widely used in the aerospace and electronics industries.

5. Polishing and Buffing: These mechanical processes progressively refine the surface to a highgloss, mirrorlike finish. This is typically used for decorative components or applications requiring reduced surface friction.

Choosing the Right Finish for Your Project

Selecting the optimal finish depends on your part's function, environment, and cosmetic requirements. For instance, an internal gear might only need a simple abrasive finish, while a consumer electronics housing would benefit from a colored anodize or a sleek powder coat.

Partnering with a manufacturer that offers a comprehensive suite of these services, like ours, ensures your CNC machined aluminum parts are not only precisionmade but also finished to the highest standard, ready for immediate use. This endtoend capability streamlines your supply chain, reduces lead times, and guarantees a final product that excels in both performance and appearance.