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Best way to make contact on parts for anodize?

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  • Best way to make contact on parts for anodize?

    I started messing around with anodizing about two weeks ago and got mixed results, so I decided to invest in basically the cheapest of the anodize kits from Caswell. I already had a few of the things, so I bought the things I needed separately. I got everything set up and made a test run today, but my parts would not take dye when finished. So, I am guessing something didn't go correctly in the anodize.

    The parts are about 5.85 sq. in. for surface area, so I simply rounded it to 6. I have (6) of them to do, so I said I had 36 sq. in. pf surface area.

    According to the 720 calculator, with a current density of 6, I should have my amps set to 1.5 and run 120 minutes.

    So when I set the power supply, I turned my voltage knob all the way up, and amps all the way down. I hooked everything up and turned my amps knob to about 1.5 and waited for 120 minutes.

    It should be noted that all of the baths are brand new, never used. I am doing SP degreaser, deoxidizer / desmut, and then anodize. All baths are heated to the proper temps and parts are rinsed thoroughly between baths with distilled water, and then neutralized after coming out of anodize before going into dye.

    So after my parts came out of dye, they looked the same as they did when they went in. No dye taking at all, which leads me to believe no anodize film is growing. I am using titanium wire, and I had a good connection as far as the leads coming off of the power supply, because the titanium wire anodized and turned purple. I thought I had a pretty good mechanical bond to my parts, but I am questioning that now. I took a multi-meter and checked continuity between the end of the hanging wire and the part and got nothing, but I am still concerned that maybe they did anodize slightly and that film is causing me to get a bad reading when I try to check. At this point, the only way I will know for sure is to check the same setup again before it goes in - before there is a possibility of an anodize film there, and then I will know I have good contact. This is an example of the type of contact the hanger has - there is a hole and a spring type wire connection.



    Scratching my head here. Really need this process to work. I have spent a lot of money and I cannot go further with this project untll these parts get good color.

  • #2
    Judging by the illustration of how you are connecting your parts there is a great potential for lose of connection part way through the ano process. Even bumping the table that your set up sits on can disrupt the connection. You need to come up with a better way to rack the parts. Something like aluminum wire wound in a coils maybe to press into the hole maybe?

    Real pics of the part would help.

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    • #3
      So after talking with Caswell Technical support, we came to the same conclusion. There was obviously some question on the way the parts were being held. Caswell recommended a better connection to the part with more of a mechanical bond, and I did even see in the manual where it said that many of the problems with anodizing can be traced back to bad connections. Just to be clear and state it again, everything else in this process has been double and triple checked. All baths are being heated to the required temps and the part is being left in them for the recommended times.

      I could not find an aluminum or titanium screw anywhere local, so I turned an aluminum screw on my lathe. I tapped a round piece of aluminum to use as a nut. So, this is a 6-32 screw with a nut passing through a 5/32 hole and sandwiching aluminum racking wire against the part.





      The temperature of the anodize bath was around 67 degrees F. The part went in and all connections were tested before hand. Everything looked good.

      At this point, there are only a handful of things that I know to question to get this process right. The first is the power requirements. The second would be possibly of the bath not being strong enough.

      For the record, I started this process trying to do six parts at once, which totaled about 36 sq. in. Since I have had all the trouble with this, I have dropped down to once part at a time until I get it right. This part was drawn as a 3D model to scale and that's how I got the surface area numbers. I have done some rough math and that all adds up. As stated before, the 3D model says the part has 5.85 sq in. of surface area. I just round this to 6 to make it easier. Since I have an aluminum bolt and nut and aluminum hanging wire on this particular piece, I bumped it up to 7 sq in. just to be safe. Using to the 720 rule calculator, with a current density of 6, I should have my amps set to .29 and run 120 minutes to get 1 mil thickness.

      Since I have been doing this, I have been keeping track of the current drop over the anodize process. I try to write down what I see every 15 minutes. Yesterday, with the latest test, I did it every 15 minutes. I started at .3 amps, and a voltage of 15 volts. This never changed over the entire 120 minutes. I never observed a drop. It stayed the same pretty much the whole time.

      When the part came out, it had a sand blasted type appearance, as do some of the other what I consider "successful" attempts. However, even after 15 minutes in 135 degree red dye, I still have only a very slight pink color.

      As I stated, I am beginning to question the bath acid strength, and possibly the power. Caswell even said that it doesn't sound like enough of an anodize film is forming on the part, because the dye is not soaking into it.

      Tomorrow I am going to try turning up the power a bit and seeing if that helps.

      I do not have one of the testers for the bath to test the acid level, but I can try to pick one up.

      If you were in this position, what would you try next? I have literally wasted an entire week of time on this trying to get it right. I know it will be worth it when I get it, but this wasted time isn't doing me any favors.





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      • #4
        Step one, and most important - know your electrolyte strength! Ask Caswell what strength it should be for the LCD method, I can't help you there as I run a different method.

        You'll need to titrate your bath which requires some lab equipment but is doable at home. For now however I'd seek the closest Ano chem supply lab to do it for you.

        Comment


        • #5
          Strange situation this morning. Have the part in. Everything is the same as stated in my last post except I am using Ti wire. I have been going back between it and aluminum, with no real difference that I can see.

          Anyway, I put the part in, and I cannot get the power supply to go any higher than about .25 amps. I was going to double the amperage, but it will not go past that. Does not matter how far up I turn the amperage wire.

          Seems like with the aluminum racking wire it would freely go past .3.

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          • #6
            I am also new to this, but am beginning to get good results.My first problem was the connections were backwards lol. the positive needs to go on the part being anodized, If you look quickly at the diagram caswell sends, it can be confusing. If the titanium wire turns purple, that means you lost your connection. When this happens, in my experience, the power supply will kick from CC to CV and this will give the bath enough voltage to anodize the titanium wire (thus it turning purpleish) [I think at least??]. What works for me, is I scotch-brite the entire titanium wire until it is shiny again prior to using it as a hangar. I also saw above that you mentioned aluminum wire... This must be stripped between uses because obviously it will anodize and lose continuity. The best way to check your connections prior to placing in the anodizing bath is to use a meter. I shoot for under 1 Ohm (but anything close wont make much of a difference) If the titanium wire is purple, you will not get continuity through it (from my experience). Also, I have a cheap power supply, and when using a small amount of area squared, I have to bump my power supply up well above the 720 rule setting until I can see the reaction coming from the GP plate. At this point, I slightly lower the current until I am at my desired current. Like I said, I have a cheap supply, and even so the current only jumps about 1 mA +/-. If it is jumping further than that, it means your connection is not secure. Also, sometimes the 720 rule will call for me to use a small amt of current, but I cannot see any reaction on the GP plate. When this happens I bump it up high until I see reaction, then lower it as low as possible, but still seeing the bubbles reacting on the GP plate. Normally this is only 30-40 mA difference than what I calculated. This could be error in the supply I use, I am not sure. But if you don't see bubbles coming from the GP plate, it is not anodizing. (I have researched at least). Sometimes you have to look closely, but you should see constant reaction. If not, bump the current up until you do. Like I said, sometimes you have to go above what you calculated to get it started, then dial it back down. I'm sure not all of this information is accurate, and these guys will probably let me know this lol, but all this has been working for me to get fairly consistent results. Also, Like gardenhackle mentioned to me a few weeks ago, I was worried about getting constant results and such when I didn't even have my process down yet. Actually getting something to anodize and getting it to take SOME dye is not hard at all. I am guessing you are doing something simple like I explained above. The hardest part for me is getting a good finish on the item so the imperfections don't show through after ano. This is where I am focusing my skills now. I would just bust out the multi-meter and check your connections prior to dropping in the ano bath and follow everything I said above and you should see some sort of results. LMK if you have any questions because I was a lost puppy just a few weeks ago myself. I have come a long way since then. Also I would practice with 6XXX aluminum, I was using 6xxx then I tried to use a "real part" that was made of 2024 and it was a total different result. The 2024 is much harder to get consistent results in my experience. Hope this helps. LMK how it goes!

            Comment


            • #7
              I just saw your last post. The problem is most definitely a poor connection or you need to clean your hangars. That is the same thing that happened to me when I had dirty hangars and/or a intermittent connection. Try out what I said above. I bet it works!! If you cannot get the amperage to stay constant or go high enough, your supply is probably kicking back and forth between cc and cv or just losing connection so often that the amperage is not constant enough to push the voltage through, thus not giving the amperage you need. Give it a try.

              Comment


              • #8
                Originally posted by Sauce118 View Post
                If the titanium wire turns purple, that means you lost your connection. When this happens, in my experience, the power supply will kick from CC to CV and this will give the bath enough voltage to anodize the titanium wire (thus it turning purpleish) [I think at least??]
                Just to keep things accurate, this is not true. If the Ti wire turns blue it is because it has a good connection with it's bus bar and has anodized. The blue/purple colour only indicates the colour spectrum consistent with the current density you provided it. How it is connected to the part is a different story though.

                Originally posted by Sauce118 View Post
                What works for me, is I scotch-brite the entire titanium wire until it is shiny again prior to using it as a hangar.
                No real need to do this as Ti remains conductive after each use. Of course it is far less conductive than aluminum to begin with so your idea of sanding between uses is not a bad idea.

                Originally posted by Sauce118 View Post
                Also, I have a cheap power supply, and when using a small amount of area squared, I have to bump my power supply up well above the 720 rule setting until I can see the reaction coming from the GP plate. At this point, I slightly lower the current until I am at my desired current.
                Not a good idea as you can burn the parts at the connection point resulting in a lost connection or produce a localized halo around the connection point. The best method is to ramp up your power slowly over 1 minute. The bubble reaction you are referring to is hydrogen gas which will start occurring when the crystal formation is at a point that is conducive to it. So you won't see it right away if you are allowing your parts to build a nice consistent coating at it's own pace as opposed to you forcing it on the onset.




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