Metal Surface Finishing Tips


Metal Surface Finishing Tips

Surface finishes are often an important aspect in designing custom parts. Surface finishes can be used to protect your part, make it more attractive, change the friction of the surface, reflect light, absorb light, and more.

Also see our surface finish capabilities for more tips and guideliines.

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Decorative Finishes

If you need a decorative finish for a part consider these tips:

  • Metal brushing creates a texture that hides imperfections (on sheet metal parts).
  • Electroplating provides various metallic colored finishes – commonly: nickel, zinc, chrome.
  • Anodizing provides black, clear and colored finishes on aluminum.
  • Powder coating provides a durable color layer that is generally preferred to painting.
  • For Plastics, injection molding generally produces a better appearance than milling.
  • For plastics Acrylic is best for polishing.
  • Buff polishing provides a glossy finish on surfaces accessible by the polishing wheel and slightly rounded edges. For a longer lasting polished finish and/or for the brightest appearance also add chrome or bright nickel plating – otherwise you may need to brighten up the finish periodically with polishing cloths. For 2D parts cuts from sheet material we recommend specifying waterjet. For 3D parts we recommend to specify a surface and edge finish of Ra 32 or 16.
  • Milling creates a surface which may have complex patterns from the cutting process. For best appearance apply a mechanical finish. For flat parts brushing can be used. Or finish with powder coat. For non-flat parts this would usually be polishing. Prior to buff polishing we recommend to machine to Ra 32 or 16.

Compensating for Finish Thickness

Adding a surface finish can change the size of a part slightly. In some designs it is important to consider when specifying dimensions. Note:

  • Mechanical part dimensions apply after non-organic finishes (anodize, electroplate,mechanical etc.), but before organic coatings (powder coat, etc.). For example to make a powder coated one-inch cube your CAD design would need to be a few thousandth’s of an inch under one inch in size. But to make an anodized one-inch cube your CAD design should be exactly one-inch.
  • You might also want to specify whether threaded holes should be plugged to prevent finish.
  • In highly critical cases you might want to specify a tolerance on finish thickness, for example .002″ +/- .0005″.