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Diy Anodizing...

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aeroHAWK

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I am a relatively new member here. I joined because I saw some members rebuilding their Logan 200 lathes. After joining, I was reading through some of the older threads and replied to a thread about Anodizing. At the time I thought it was only a month old thread - but I had forgotten that this is 2015 already!o_O So it is really over a year old....

Since I responded to that thread, there have been several questions asked. So instead of completely hijacking that thread, I am starting a new one here.

Background:

A few months ago I found a post on another forum where a guy (Tom) made a bench on wheels that contained his anodizing setup. He used some rectangular 5 gallon tubs for his tanks. This got me thinking, because this looked like something I wanted to be able to do.

My setup is uses 2 gallon tanks. The tanks I'm using are small (9 quart) Igloo brand coolers.
igloo.png
Years ago, a fellow named Ron Newman had a wonderful web site that spelled out how he did his anodizing. He started with 5 gallon coolers. Ron doesn't have his web site up anymore but there are remnants of it around.
newman.png
He used coolers because many of the tanks have hot solution in them and the insulated walls kept them warm.

The solution in the tanks need to be agitated to keep it "stirred" up. Typically a manifold of CPVC pipe is used (with holes in it) to pump air bubbles into it. Here is a cooler with the manifold:
manifold.png
Since the acid tank for anodizing needs to be room temperature (65 - 70 deg), and it gets warmed during anodizing, I opted for a larger tank to raise its thermal mass so it didn't heat as fast. It's about 4 gallons.
tank.png
The acid is battery acid (sulfuric acid) I got from the local auto parts store (O'Reilly's). I mixed it 50-50 with distilled water. ALWAYS ADD ACID to the water - NEVER the other way around! Some systems say to add one part acid to two parts water. I used one to one.

The power supply I used was a 65 watt 19 volt Laptop power supply/charger (I had lying around) and a Constant Current module I got from eBay. The parts I anodize are relatively small, so this works well.

To know how much current is needed, use the "Rule of 720". It states that it takes 720 amp-minutes / sq. ft. to build up .001" thickness of anodizing. In other words, 12 amps / sq.ft. for one hour will give you .001" thickness. You need to include all sides of the part when calculating area - the inside and outside of tubes, too. Since I usually model my parts in SolidWorks, I just ask it to tell me the area.

I found that, depending on surface area, the voltage needed was from 13 to 17 volts. So when using the Laptop charger of 19 volts, the Constant Current module needs to be a "Buck" converter, or step down.

Since the Laptop charger is only 65 watts, and I want a little more "headroom", I'm now "upgrading" to a PC power supply and using 12 volts. So this means I need to use a "Boost" converter to get constant current.

This is the "Boost" converter I'm using:
http://www.ebay.com/itm/300925643943?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT
boost.JPG
This is an overview of the anodizing process:

1. Submerse part in 140 degree cleaner for 5 min, rinse
2. Etch part in room temp caustic solution (lye) 10-30 seconds, rinse
3. Submerse part in 70-110 degree desmut solution for 1-3 min, rinse
4. Anodize part for 1 hour at room temp (70-75 degrees), rinse, rinse again
5. Dye part in 140 degree dye for 15 seconds to 15 min, rinse
6. Seal part in 180-200 degree Nickel Acetate Sealer for 20 min, rinse and hang part to dry

I've clear anodized over 25-30 parts with this setup - they were not dyed. I will be setting up my dye tanks soon.... I have dye for red, yellow, blue and black.

Here is a video of the process. It's from Tom, the guy that made the bench I mentioned above.


I'll keep you posted....
 
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Dracen knights

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very cool thanks for posting.. as this is something I will be getting into. can you please post some pics of your end result? I would be interested in seeing each one specially the clear one... I would like to do it to some items I have made but dont want to change the look.
 

francist

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Great write up aeroHAWK.

-frank
 

Dracen knights

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thank you... That pretty much turned out as I had hoped it would... I love the look of machining and at times I want it to stay so this could just be the ticket.
 

aeroHAWK

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Something to keep in mind if you do your own anodizing. I have found that when doing clear anodizing, getting a full .oo1" thickness makes the part fairly grey. The last part I anodized, I made the anodize no more than .0005" thick. This minimized the discoloration while still providing some extra surface durability.
 

ChipsAlloy!

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Interesting, so a "standard anodizing process" would add no more than .002 on the width of a plate (.001 on one side and .001 on the other). This would mean we should keep that in mind if we plan on anodizing stuff that has tight tolerances. For example you machine a recess (or groove?) in a plate for another one to slide in. The recess should be at least .oo4 wider then the intended width of the sliding piece to compensate for the added thickness on all four mating surfaces.

This example does not appear too critical as we would normally allow clearance anyway cause we dont want the slide to bind.

But it might get more critical if you plan on anodizing a part that, lets say, has been bored for a bearing to fit in. Then you should take into consideration the added thickness all around the diameter and machine the bore slightly larger. Otherwise you might have that bearing pressed too tight in.

At least this is my understanding and I guess it would be a good thing to consider before starting the process on a part.

What do you guys think?
 

aeroHAWK

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You've got the right idea, but there is something that isn't obvious you need to take into account. The anodized surface penetrates the surface .0005" and protrudes ,0005". That assumes a thickness of .001". Care must be taken to create the desired thickness (using the "Rule of 720"), but it can be hit or miss, depending upon the setup.

Also, when dying different colors, some colors work better with different surface thicknesses. So that also needs to be taken into account.

The parts in the photo I provided had some bearing bores that were held very close. When I anodized the parts, I masked the bores so I didn't have to worry about them changing. To mask them I just turned a piece of Delrin to be a press fit into the bore and pressed it in the bore during anodizing.
 

jbolt

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Cool! Nice to see someone else doing home anodizing. I got started with one of Ron's 2 gallon kits and then later bought a proper power supply. I like your air manifolds. I just use an aquarium air pump with the stone bubbler. What are you using for heaters? I use a hot plate for the sealer and submersible tank heaters for the other solutions.

One thing to mention is anodizing wont improve your finish other than adding color. What you see is what you get.

Here are some of my projects:

Rifle sight.gif sight_complete.gif Tracker_Completed.gif TrackerParts.gif
 

aeroHAWK

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I like your air manifolds. I just use an aquarium air pump with the stone bubbler.
I am considering switching over to using a pump for circulation rather than bubble aeration. I understand it can be more effective. Plus the bubbles make a little mist ab0ve the tank and it'd be nice to eliminate that.

What are you using for heaters? I use a hot plate for the sealer and submersible tank heaters for the other solutions.
I'm using these for heaters:
heater.png
However, I am using a hot plate for the sealer.

Oh, I almost forgot... Those are REALLY NICE parts! You did a good job with the anodizing too.
 

jbolt

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I am considering switching over to using a pump for circulation rather than bubble aeration. I understand it can be more effective. Plus the bubbles make a little mist ab0ve the tank and it'd be nice to eliminate that.


I'm using these for heaters:
View attachment 105427
However, I am using a hot plate for the sealer.

Oh, I almost forgot... Those are REALLY NICE parts! You did a good job with the anodizing too.
I do get some splashing with the bubbler. By pump do you mean to circulate the tank fluids?

Is that a water heater element? How are you controlling the temp? My tank heaters are some that Caswell sold years ago. They had a lot of problems with the heat controllers and finally discontinued them. I must have returned 5 or 6 before I got a good set.

Thanks on the parts. The declination drive was all done on my Smithy Granite 1324 3-in-1. Fun project

Jay
 

aeroHAWK

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By pump do you mean to circulate the tank fluids?
Yes, I have some small submersible pumps on order. I'll make a manifold to expel the fluid throughout the tank. I'm also looking at being able to adjust the flow.

Is that a water heater element?
Yes. It is a small 1440 watt unit.

How are you controlling the temp?
I have a few choices. First, I have a couple simple microprocessor based temp controllers I built from a kit. I'll likely start with them. I could also make custom microprocessor based controllers. Or, somebody pointed me to some real nice controllers that are used by home-brewers. They're inexpensive on eBay, called STC-1000.
STC-1000.png
 
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aeroHAWK

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I have a lot of balls in the air right now. :rolleyes: But I did have the opportunity to do more with my anodizing setup today. ;) In my previous post, I mentioned that I was getting some submersible pumps to circulate the fluids in the tanks, in favor of using the air agitation I had been using. They sat on the shelf a few weeks, but I finally had an idea that solved a few issues. :eagerness:

One of the issues, I haven't been happy with my heater element setup. Mostly, I haven't really had a setup. :eek:

Since I am now going to use a pump with a manifold, I figured I could mount the heater element in a larger vertical pipe in the manifold. I could then pump the fluid into the top of the pipe and down around the heater and into the branches of the manifold.
Image2.png

You can see the pump is attached to the top of the standpipe. The outlet is inserted into a hole in the side of the pipe. The inlet is a short length of vinyl tube beneath the pump. I made the standpipe from PVC fittings.
Image3.png

I turned the fittings in the lathe and glued them together. One of the fittings has a female pipe thread that matches that of the heater element, one is a cap for the electrical connection. You can also see the pump in the foreground.
This is the pump and manifold in one of the tanks filled with water for testing.
Image4.png

I pointed the exit holes in the manifold in different directions in the hopes of creating a relatively random circulation. As it turns out, the pump isn't strong enough to squirt much of a 'jet' out the holes in the manifold, so it didn't matter where they were pointed.

It took a few minutes for me to figure out how to prime the pump (since it isn't submerged). The heater and pump worked well! There isn't much of a fluid stream exiting from the holes, but there is clearly some circulation. I believe it is sufficient for use in the degrease tank and also in the dye tanks.

I don't believe the circulation creates sufficient agitation for the anodizing tank, so I'll be looking into a different pump for that. I am quite pleased with this for use with the dye and degrease tanks! :encourage:
 
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aeroHAWK

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After testing in the tank with plain water, I discovered that the holes in the manifold were too large, so I made new tubes with 1/8" holes rather than the 3/16" of the old tubes. I also experimented with the temperature controller. Years ago, I got an electronics kit for a simple temperature controller.
Image3.png

I connected it to the heater element and dropped the temp sensor into the tank. It worked so well, I replaced the water in the tank with the detergent solution of the degrease tank. Here you see the temp is 57.6 degrees C (136 F).
Image2.png

You can see the holes in the manifold are smaller. They create much better agitation than the larger ones. I am very happy with the agitation instead of the aeration (the old way I did it), since it doesn't create suds in the detergent like the air bubbles did.

With this new setup, it took less than 25 minutes to heat the solution from room temp, to 140 degrees F (60 C). The temp controller is a simple thermostat so it doesn't hold temp like a PID controller, but for this it's completely adequate. It easily held the nominal temperature within 3 degrees C, and with some tweaking, I know I can reduce that to 2 degrees if I need to.

I will also need to control the temperature of the dye tanks so I'll need more controllers. I found these on fleaBay for $3 each so a grabbed four (the above controller was $20 and I still needed to build it).
Image4.png
It looks like it has the same capability as the controller above for way less money....

I'll keep you posted....
 
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aeroHAWK

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I decided to see if I could get tighter temperature regulation from the controller. I had purchased "waterproof" temp sensors as shown here:
Image1.png

I didn't originally trust the heat shrink tubing to seal the liquid, so I slid the sensor into a vinyl tube that I had made a plug for. I potted the probe end of the tubing with silicone.
Image2.png

I suspected that all this potentially thermally insulating material was a big part of the issue with controlling the temperature more tightly. So I took the sensor out of the vinyl tube to see how it would work.

Well... guess what... IT WASN'T WATERPROOF! :mad: It lasted about 10 minutes and then it was giving squirrely results. I pulled it out of the solution and the stainless steel tube fell off the end! :eek:

I filled the stainless tube with "flowable" silicone, and reassembled the probe. It now seems to be waterproof for real this time.

With the sensor fixed, I can now control the temperature within less than one degree C. :encourage:
 
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