Gun engraving

[Scott Shepherd]

My understanding is that hard anodizing comes only in a brownish grey color, any other color and it is not hard anodized.

Then we must think the same thing Rich

[Gary Hair]

Then we must think the same thing Rich

google search "what color is hard anodized aluminum?" and you'll find that you can dye hard anodized but it's traditionally done with black.

[Bruce Page]

I have seen Type III Hard Anodizing in clear, grey(ish), black and olive green. Back in my mold making days all of our aluminum tooling was sent out to be hard anodized and always came back an OD green. That was the only time I have seen the green.

[Scott Shepherd]

google search "what color is hard anodized aluminum?" and you'll find that you can dye hard anodized but it's traditionally done with black.

Gary, what I was told by the people in the industry at the time, is that once you added the dye, it reduced the hardness. Our engineers kept specifying "hard black anodizing" and the people that did the anodizing kept saying "there is no such thing", and they told us in order to get any color to work with the hard coat, then it was done by reducing the amount of hardness of the anodizing.

Despite that, everyone called it "hard coated black". It made the guys cringe when we called it that, because they kept saying that you could't add dye to true hard coat and have it remain true hard coat.

Now, I think it's just become a term people throw around that don't know anything about the process. Having said that, I have said that things might have changed, so I have no idea in todays world, but I know years ago, it wasn't possible. I have true hard coat here and it won't mark with any CO2 laser I have, yet I see people saying they mark hard coat with a CO2. You can't even scratch the surface hardcoat with an exacto knife if it's truly hardcoat. I know I can't scratch what I have here with a knife. I've never seen any color that was that hard, but that's just what I've seen.

[Bruce Page]

We would occasionally have to resize the green hard anodized mold cores on the lathe, removing as little as .002 and it would turn the tip of a carbide tool bit red until it got under the coating. The anodizing was very hard. This was back in the 70's.

[Dave Sheldrake]

There are 6 basic methods for anodising aluminium....all of the resultant coatings have different properties.

[Tim Bateson]

I get Black, Silver/Gray, Green, Blue, and Red. That leads me to believe the gun pictured above is soft anodized. I've never seen that shine on Type III.

[Scott Shepherd]

Tim, are you saying those examples are type 3? All I can find online from companies that anodize is that only type 2 can be dyed colors where type 3 is clear or black, with the clear turning a darker color. Do you have a resurgence for type 3 dyed in colors?

[Tim Bateson]

I can check. I know my client had gone through a number of anodizing shops before one got the colors correct. Last I heard, they were working with a shop up in Dayton, Ohio. I'm told they've also nearly perfected a camouflage design. Not sure how that's done, but sounds interesting.

Once they introduced the colors I had to crack up the power for a clean White marking. These are harder than any others that I do.

[Kev Williams]

Add me to the list, only hard anodized colors I've seen is black, olive drab, and bronze.

Here some of my anodized stash-- somewhere around here is a 3x3 hard bronze plate, but as is true to form around here, I can't find it!
All three wings are hard anodized, as is the panel they're all sitting on. The disks are all just 'plain' anodized...

anodcolors.jpg

Found this website that does a good job explaining anodizing: http://www.omwcorp.com/understandingano/anoindex.html

and this is a screenshot of some of it. What I didn't know was all the "colors" of "clear" anodizing are possible!

[Dan Hintz]

I have seen Type III Hard Anodizing in clear, grey(ish), black and olive green.

Add me to the list, only hard anodized colors I've seen is black, olive drab, and bronze.

Another +1 here. I'm unaware of any Type III that isn't one of the colors listed above. The process (and thickness of the oxide) doesn't allow for much else...

[Scott Hearn]

I used to manage an aerospace finishing shop and we did MIL-A-8625, type I (chromic acid) anodizing along with chromate conversion coating (chemical film). That one is a bit different of an animal because it's primary purpose is corrosion protection. But I saw 1000's of hard anodized parts that our sister machine shop sent out to get hard anodized. Getting down to it, anodize is anodize. By that I mean it's just aluminum or aluminum alloy that has had its surface turned into an oxide layer. What is designated as "hard anodize" is different primarily in the thickness of said layer. There are different acid baths, temperatures, times, and amount of current applied to achieve the desired surface. But they are all very hard and not electrically conductive.

I never saw a type II or III coating that was dyed to a specific color for aircraft but I know in other industries it's common. It's just a dip in a dye tank after the anodize and prior to sealing. Sealing is done by a dip in boiling water. You'd be amazed at the difference in the feel between the two. Unsealed is kind of rough while sealed if very slick feeling. Also un-dyed anodize coating will vary in color between specific alloys and the temper. I've seen some 2024 alloys run almost clear with only a slight iridescence look to a greenish/gold/brown color on 7000 series. Also the color on dyed anodize will vary to a great extent depending on alloy. I'm pretty amazed that they actually get as much consistency in colors as they do.

O/P like others have mentioned, you need to experiment to get your settings. The hardness will not matter to that light beam, it doesn't cut like a cutting tool, it's the depth and color. Our machine shop had an ancient Mazak co2 1000w laser machining center that would not cut through aluminum very well at all. But it would do some really thin sheets if we painted them black. Steel, stainless steel and titanium were no problem at all.

[Dave Sheldrake]

Our machine shop had an ancient Mazak co2 1000w laser machining center that would not cut through aluminum very well at all.

I have a 7kW (actual power not interpolated) that struggles with 10mm aluminium so it's not just common to the sub 2kW machines

[Scott Hearn]

I have a 7kW (actual power not interpolated) that struggles with 10mm aluminium so it's not just common to the sub 2kW machines

Our machine was old tech when we bought it used. The owner didn't really buy it for aluminum and we made a fortune on hard metals with it. At IMTS we saw much smaller new machines flying through aluminum. I don't know what power level they were running but I just thought it was some sort of pulse modulation juju or something with the software. Didn't have time to stop and find out. We later bought a 5 axis water jet that would cut through 8.5" titanium, albeit extremely slowly, but it would do it. We were amazed. It had an 60HP motor driving the pump.

[Dave Sheldrake]

I don't know what power level they were running but I just thought it was some sort of pulse modulation juju or something with the software

Pulse shaping on ND:Yag lasers is getting right up there these days, the 4kW Yags are amazing but under 80um kerf you still get stuck with mirror delivery rather than fibre rise times are starting to be the thing that is holding technology back though