What finishes are available for CNC machined parts?
After a part is produced through precision cutting, it often requires additional surface treatment to meet functional or aesthetic standards. A CNC Machining Service typically offers a variety of finishes to enhance appearance, durability, corrosion resistance, or mechanical properties. The type of finish chosen depends on the part’s material, application, and desired visual or structural characteristics.
As-Machined Finish
The most basic finish for CNC machined parts is the as-machined or raw finish. It retains the tool marks created during machining, offering a relatively smooth surface with a typical roughness (Ra) of 3.2 µm. This finish is ideal for functional parts where appearance is not a priority and further treatment isn’t necessary.
Bead Blasting
Bead blasting gives CNC machined parts a uniform matte or satin surface by using fine glass beads propelled at high speed. It removes tool marks and minor imperfections, creating a smooth, non-reflective finish. This is a popular option for parts where aesthetics matter, such as in consumer electronics or automotive components.
Anodizing
Anodizing is an electrochemical process used primarily on aluminum parts. It increases corrosion resistance and surface hardness while allowing for color customization. Anodizing Type II provides a decorative oxide layer with various color options, while Type III (hard anodizing) creates a thicker, more durable layer for demanding applications.
Powder Coating
Powder coating applies a dry, pigmented powder that is cured under heat to form a durable, uniform coating. It offers excellent resistance to wear, corrosion, and impact, making it suitable for parts that require both a functional and aesthetic finish. This method is available in a wide range of colors and textures.
Plating
Plating involves coating CNC machined parts with a thin layer of metal, such as nickel, zinc, or chrome. This enhances corrosion resistance, improves conductivity, or adds decorative appeal. Nickel plating, for example, is often used for its hardness and attractive appearance.
Brushing and Polishing
Brushing uses abrasive belts or pads to create a consistent directional grain on metal surfaces, giving parts a clean, industrial look. Polishing goes further, producing a mirror-like finish by removing surface defects and smoothing the part to a high gloss. These finishes are often used for cosmetic or consumer-facing components.
Custom Surface Treatments
Other specialized finishes include passivation (for stainless steel), black oxide coating, chemical conversion coating (like chromate for aluminum), and electropolishing. Each serves specific purposes, such as improving corrosion resistance or achieving precise surface tolerances.
Conclusion
CNC machined parts can be finished in various ways depending on their application and desired properties. From simple as-machined surfaces to advanced treatments like anodizing and powder coating, these finishing options help ensure the final part meets both functional and aesthetic requirements. Working closely with your CNC Machining service provider can help you choose the best finish for your project.