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Updated on 09.22, Published on 09.22
CNC Machining Surface Finishes: Polishing and Surface Treatment Options for Custom Parts
CNC Machining Surface Finishes: Polishing and Surface Treatment Options for Custom Parts
CNC machining can produce precise metal and plastic components with complex geometries and tight dimensional requirements. However, machining is often only one step in the manufacturing process.
The right surface finish can improve the appearance, corrosion resistance, wear resistance, surface texture, or functional performance of a CNC machined component.
At Akinotek, CNC machined parts can be manufactured from a wide range of metals and engineering plastics and finished according to the requirements of the final application.
Common Materials for CNC Machined Parts
Different materials respond differently to machining and surface treatment. Selecting the right material should therefore consider not only mechanical properties but also the required final surface appearance and performance.
Aluminum
Common CNC aluminum grades include:
- 6061 Aluminum
- 7075 Aluminum
- 5052 Aluminum
Aluminum is particularly suitable for anodizing, which can provide a durable oxide layer and a range of surface colors.
Stainless Steel
Common CNC stainless steel grades include:
- 303 Stainless Steel
- 304 Stainless Steel
- 316 Stainless Steel
Stainless steel can be polished to achieve a smooth, reflective appearance. Electropolishing can also be used for stainless steel applications where a smoother and cleaner surface is required.
Brass and Copper
Brass and copper are commonly machined for electrical, decorative, and functional components.
Both materials can be polished to create a brighter surface appearance. The appropriate finishing process depends on the required appearance and application.
Mild Steel
Common CNC machining grades include:
- 1018 Mild Steel
- 1045 Mild Steel
These materials can be machined into shafts, brackets, fixtures, mechanical components, and other industrial parts. Surface treatment may be selected to improve appearance or provide additional protection.
Engineering Plastics
CNC machining is also widely used for engineering plastic components.
Common materials include:
- POM / Delrin
- ABS
- Nylon
- PC
- PTFE
Plastic parts require different finishing considerations from metal parts because their hardness, thermal behavior, and surface response are different.
Common CNC Surface Finishes
1. Polishing
Polishing is used to create a smoother and brighter surface by progressively removing machining marks and surface irregularities.
It is commonly applied to stainless steel, aluminum, brass, copper, and other suitable materials.
For components where appearance is important, polishing can produce a clean and refined surface. The achievable result depends on the material, initial machining condition, geometry, and polishing process.
2. Anodizing
Anodizing is commonly used for aluminum CNC machined parts.
Available options can include:
- Clear anodizing
- Black anodizing
- Colored anodizing
Besides changing the appearance of aluminum parts, anodizing creates an oxide layer on the surface that can provide additional surface protection.
For consumer electronics, housings, brackets, knobs, and other visible components, anodizing is a commonly selected finishing option.
3. Sandblasting
Sandblasting uses abrasive media to create a uniform surface texture.
It can help reduce the appearance of machining marks and produce a matte or textured appearance.
Sandblasting is often combined with other surface treatments, such as anodizing, depending on the material and appearance requirements.
4. Brushed Finish
A brushed finish creates a controlled directional texture on the surface.
It is commonly selected for visible metal components where a consistent linear appearance is required.
Brushed finishes are frequently used on aluminum and stainless steel components for consumer products, appliances, hardware, and decorative parts.
5. Powder Coating
Powder coating applies a dry powder coating to the surface of a suitable metal component, followed by curing.
It can provide a durable colored surface and is available in different colors and textures.
Powder coating can be useful for brackets, enclosures, industrial components, frames, and other metal parts where both appearance and surface protection are required.
6. Laser Engraving
Laser engraving can be used to add permanent markings to CNC machined components.
Typical applications include:
- Logos
- Product identification
- Serial numbers
- Text
- Symbols
- Position markings
It can be used on many metal and plastic components, depending on the material and required marking effect.
7. Electropolishing
Electropolishing is commonly used for stainless steel.
The process removes a controlled amount of material from the surface through an electrochemical process, helping create a smoother and cleaner surface.
It can be considered for stainless steel components where surface quality, cleanliness, and corrosion-related requirements are important.
How to Choose the Right CNC Surface Finish
The best surface finish depends on the purpose of the part rather than appearance alone.
Surface Finish | Typical Purpose | Common Materials |
Polishing | Smooth and reflective appearance | Stainless steel, aluminum, brass, copper |
Anodizing | Surface protection and color | Aluminum |
Sandblasting | Matte and uniform texture | Aluminum, stainless steel |
Brushed Finish | Directional decorative texture | Aluminum, stainless steel |
Powder Coating | Color and protective coating | Steel, aluminum |
Laser Engraving | Identification and branding | Metals, plastics |
Electropolishing | Smooth and clean stainless surface | Stainless steel |
When requesting a quotation, it is useful to specify the material, finish type, color, surface area, appearance requirements, and any reference samples or specifications.
Surface Finish Starts with CNC Machining
The final surface treatment cannot be separated from the quality of the original CNC machined surface.
Tool selection, cutting parameters, machining strategy, material condition, and part geometry can all influence the starting surface before finishing.
For example, a component requiring a high-quality polished surface may need a better initial machining condition than a component that will receive an opaque powder coating.
For this reason, surface finishing requirements should be considered during the quotation and DFM stage rather than added only after machining.
Custom CNC Machining and Surface Finishing
Akinotek provides custom CNC machining and surface finishing solutions for prototypes, low-volume production, and production parts.
Our manufacturing process can support different materials and finishing requirements, including CNC machining, polishing, anodizing, sandblasting, brushing, powder coating, laser engraving, and stainless steel electropolishing.
Whether you need a functional prototype or production-ready CNC components, providing the 3D CAD file, material specification, required finish, quantity, and critical tolerances allows the manufacturing team to evaluate the project more accurately.
Send your CAD files and surface finish requirements to Akinotek for a CNC machining quotation.
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