Bernice Daniels

Anodized Aluminum - technical info

10 posts in this topic

Wow this was interesting to read. Thanks for adding the info from Grant. I really appreciate learning about the process.

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Very, very cool to read!

 

And I dunno, for a chemist, this could be a pretty fun job... If I'd gotten better marks in Chemistry in high school, this might've been something I would have considered.

 

Grant talked a little bit about the colour-matching process they use - Is it easier to match colours with the bright anodizing process than it is with the bulk anodizing process? (not sure I've got the right term, I mean whatever's used to anodize the machine cut rings).

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Definitely cool! I've always wondered about the whole process, but when you search anything on the internet, the results can be a little overwhelming. This helps a lot! (and I loved chemistry, but I was a science nerd way back when)

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Is it easier to match colours with the bright anodizing process than it is with the bulk anodizing process? (not sure I've got the right term, I mean whatever's used to anodize the machine cut rings).

 

It's my understanding that in the bulk process it's more or less impossible to perfectly match colors. It's a randomized system where the vast majority of a batch will mostly average out but there's always the likelihood of some off colored rings. That's in addition to all of the challenges with drag-out that you have to deal with in any large scale anodizing process.

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It's my understanding that in the bulk process it's more or less impossible to perfectly match colors. It's a randomized system where the vast majority of a batch will mostly average out but there's always the likelihood of some off colored rings. That's in addition to all of the challenges with drag-out that you have to deal with in any large scale anodizing process.

 

Ahh, okay. Thanks for the info :)

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Very cool to read about the process.  I completely understand the issues the have over time because I worked for years in a clinical lab staining biological specimen slides.

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I think there is a misunderstanding about how the bright dip anodizing process works that causes a concern for people trying to get the tiny 20g rings to match exactly between batches. I will try to explain in detail here. This info applies to every supplier out there who sells bright dip AA rings. You cannot avoid this problem - it is just how it is.
It is however only really noticeable on 20g (or thinner). We don't make 22g in AA partly for this reason.

The chemical process used to make the shiny (bright) anodizing removes about 2-3% of the material. This is what creates the smoother - and therefore shinier - rings. The percentage varies as I have noted <--- this is the 1st cause of a variation in wire thickness and is not preventable.
The 2nd cause is one we have more control over - and we try to minimize as much as possible. If after the 1st dip the coils come up and the color isn't quite right - its too light - then it has to be dipped a 2nd time. This 2nd dip will remove another ~2% from the wire diameter.
This process is only used on our saw cut shiny AA rings. The machine cut bulk anodized rings are not bright dipped.

We dip the coils - so the change in wire diameter has now changed the AR and ID ever so slightly.

The only time this 2%-5% is noticeable is in the 20g wire. Here is the math
20g = 0.32" = 0.81mm
best case: 2% thinner is 0.81*.98=0.7938mm (0.3136")
worst case: 5% thinner is 0.81*0.95=0.7695mm(0.304")

Now for AR - lets look at 20g 7/64"
with no loss - eg the bright aluminum rings you have:
actual ID = 2.84mm (0.112" )
wire dia: 0.81mm
Ar: 3.5

with 2% loss:
Wire dia = 0.7938mm
ID - also changed ever so slightly do to even eating away of material. This means ID has changed to 1% larger
ID = 2.84mm*1.01 = 2.8684mm
AR = 2.8684/.7938= 3.61

For the 5% loss works out to an AR of 3.78

So you would see an AR variation of 0.1 to 0.28
It is not possible for us to list the exact variation as it will vary from batch to batch. So 1 batch of purple may be a 2% batch and another may be a 5% batch.
 

calisandra, Katlee, Redbeard and 1 other like this

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Actually I think I have noticed this variation come to light on a inlay that I used 16g 5/16" rings using the marvelous bright anodizing rings.

 

In the bright dip anodizing process, is the wire coiled?  Or is it coiled after the anodizing?  If it was coiled after, there would be no ID variation.  The AR would still vary though.

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The aluminum is coiled first, and coils are placed in the racks to be dipped. Jon has indicated 200-400 coils per rack. I don't think the anodizing solution would work as uniformly into spools of bulk wire. Plus, why risk scratching anodized wire in the coiling process?

It would be nice to have bright-anodized bulk to throw onto mandrels ICE though.

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