Advice on anodizing deep pockets and holes

0
J
3

Hello, I’m aware of the 720 rule for anodizing, but I’m struggling to apply it effectively to the design of my aluminum components for an optical system. These parts require Type III hard anodizing for improved wear resistance and surface hardness. The most critical component is a mounting bracket with complex geometries, including several thin walls and deep pockets.

There are several deep, narrow pockets (aspect ratio up to 5:1) that are crucial for the optical alignment. How can I ensure uniform anodizing thickness in these hard-to-reach areas? The part also has several threaded holes (M3 and M4) that need to remain functional after anodizing. What’s the best approach to protect these features while ensuring good anodizing coverage on adjacent surfaces?

Solved by JeanTech75

Two of the biggest issues with anodizing deep pockets are the lack of electrolyte flow and the low current densities near the bottom of the holes. However, with sufficient agitation in the bath and correct orientation of the part, the holes can be anodized, albeit to roughly 3 times the diameter of the hole, best case scenario. The deeper the hole, the thinner the anodizing will become towards the bottom. Your 5:1 aspect ratio will mean that there will be thinner plating at the bottom of your hole.

    • J

      Hello, I’m aware of the 720 rule for anodizing, but I’m struggling to apply it effectively to the design of my aluminum components for an optical system. These parts require Type III hard anodizing for improved wear resistance and surface hardness. The most critical component is a mounting bracket with complex geometries, including several thin walls and deep pockets.

      There are several deep, narrow pockets (aspect ratio up to 5:1) that are crucial for the optical alignment. How can I ensure uniform anodizing thickness in these hard-to-reach areas? The part also has several threaded holes (M3 and M4) that need to remain functional after anodizing. What’s the best approach to protect these features while ensuring good anodizing coverage on adjacent surfaces?

      0
    • J

      Two of the biggest issues with anodizing deep pockets are the lack of electrolyte flow and the low current densities near the bottom of the holes. However, with sufficient agitation in the bath and correct orientation of the part, the holes can be anodized, albeit to roughly 3 times the diameter of the hole, best case scenario. The deeper the hole, the thinner the anodizing will become towards the bottom. Your 5:1 aspect ratio will mean that there will be thinner plating at the bottom of your hole.

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      Reply
      • J
        JeanTech75

        Is there any way to get around this issue?

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        Reply
      • J
        Jim Elliot

        You can create custom electrodes to more evenly anodize the holes, but depending on their size, this can be impractical. Check with a local anodizing shop.

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        Reply
Advice on anodizing deep pockets and holes
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