Surface finish plays a significant role in determining the final cost of your components, especially during high-volume production. Finishing is a scaled cost (meaning it’s not amortized across your entire order), similar to machine run time, tooling, and inspections. So the bigger your part run, the more you will pay in finishing costs.
Surface finishes are applied after machining and can change the appearance, surface roughness, hardness, and chemical resistance of the produced parts. They can also have an impact on tolerances, which can result in a need for more skilled labor, tighter tolerances, and more precise machining operations.
Below is a quick summary of the most common finishes for machined components, the expected benefits, and the associated increased costs.
As-machined components maintain the highest tolerances since no additional processes are applied. However, tool path marks remain visible.
The typical surface roughness for as-machined parts is 3.2 μm (125 μin), which can be further decreased to 0.4 μm (16 μin) with additional processing.
Extra Cost: --
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Tightest dimensional tolerances No added cost (standard finish) |
Visible tool marks |
Bead blasting imparts a consistent matte or satin finish to a machined component, effectively eliminating all tool marks.
Bead blasting is primarily employed for aesthetic enhancements, as it does not ensure a specific surface roughness. Essential surfaces or features, such as holes, can be masked to prevent any alterations in dimensions.
Extra Cost: $
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Aesthetically pleasing matte or satin finish Affordable surface finish Different levels of coarseness available |
Impacts critical dimensions and surface roughness |
Powder coating applies a durable, wear and corrosion-resistant polymer paint layer to the surface of a component. It is suitable for components made from any material and comes in a variety of colors.
Extra Cost: $$
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Strong coating that's wear and corrosion-resistant Better impact resistance than anodizing Suitable for all metals |
Can't be applied to internal surfaces Less control over dimensions than anodizing Poor fit for small components |
Anodizing applies a thin, durable, non-conductive ceramic layer to aluminum surfaces, enhancing their resistance to corrosion and wear. Key areas can be masked to maintain their precise tolerances. Anodized components can be dyed, resulting in a smooth and visually appealing finish.
Extra Cost: $$
|
Durable, aesthetically pleasing coating Can be applied to internal surfaces Available in any Pantone tone |
Brittle compared to powder coating Aluminum and titanium only |
Hardcoat anodizing, referred to as Type III anodize, creates a robust, dense ceramic layer that offers superior resistance to corrosion and wear.
It's ideal for functional applications, featuring a standard coating thickness of 50 μm, typically without color. Key areas can be masked to preserve their precise tolerances.
Extra Cost: $$$
|
Excellent wear-resistance coating Can be applied to internal surfaces Excellent dimensional control |
Brittle compared to powder coating Aluminum only |
While a high-quality surface finish enhances the appearance and/or functionality of machined components, it will increase your bottom line.