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The importance of good connections

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  • cramon1996
    replied
    How can I know what is the problem with my sulfuric bath? I dont know if my Acid is not working or maybe it has gone bad or if it is my connection but my parts are not taking any dye in, I hace replaced my cables and clamps.

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  • sandra88
    replied
    Re: The importance of good connections

    thanks for all the good suggestions

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  • torontocycles
    replied
    Re: The importance of good connections

    I use a 4 finger titanium rack as i do small parts. Titanium makes the best connection as it won't anodize or decay due to the acid. The load from such a large rack is very low.

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  • bomscho
    replied
    Re: The importance of good connections

    yeah, also, i got skimpy ano results by using titanium sheet cut into hooks put through round holes. as soon as the anodizing layer started forming, it would cut off the current flow, presumably with the reduced conductive surface area as the process takes hold. if your parts are sparking and flaring in the bath, that's the problem.

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  • elton10
    replied
    MD is correct in that last item.. The wire tends to get brittle as the process progresses. I like to use the "spring"in as deep a hole as possible to assure maximum contact area. Fortunately the parts I'm anodizing have nice deep holes with the exception of one..Not surprisingly thats the one I have the most (but still very few) problems with.

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  • M_D
    replied
    I have to agree with Fibergeek that beginners would be doing themselves a favor to stick with his connection recommended methods until basic success is achieved, then move on to alternatives if desired. If as many variables as possible are controlled, it leaves less room for failure.

    Essentially there are only a few basic steps to good anodizing:

    parts that are properly cleaned
    applying the proper current for the right amount of time
    proper electrolyte solution
    dying (if so desired)

    Like most everything else, it's the details rather than the basic steps that spell success or failure. Of all the steps, I have found the electrical part to be the most important one. I used harder aluminum wire (6061) also for a while to make bent spring clip type connections on parts that had no appropriate holes. It works if done carefully like Elton can attest, but is has more potential for failure. Except for alloys such as tempered 7075 aluminum, there isn’t a high degree “springiness” (compared to spring grade Titanium) so it is easy for a connection that starts out adequate to be degraded by handling.

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  • elton10
    replied
    Bryan

    Ahhhh OK..I just wasnt sure, and when I read my original post over I could see how easy it was to think I meant to merely hang the work in the bend

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  • Fibergeek
    replied
    Thanks, NeoMoses and Elton10.

    Elton10,
    I got the right idea from your post, I wanted to make sure that everyone else did too.

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  • elton10
    replied
    racking/hanging

    well let me clarify since some seem to have the wrong idea. When I said the parts hang fine from a J bend or U bend the bend is in the form of a 'spring' the is wedged into an opening in the part.. the part is NOT just hanging off the welding rod.. Failure rates so far are less than 1 percent.
    There indeed is no substitute for a good electrical connection.

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  • NeoMoses
    replied
    Fibergeek is 100% correct. To drive home exactly how tight the connections are between my workpiece and the wire, realize that I need pliers to squeeze the wire together. Depending on the part and the geometry, I'm getting 20-30 pounds of clamping force. There is absolutely no 'wiggle' or 'play' in the connection. Don't just think that you can loop a wire and let a part hang from it in the electrolyte bath, it's much more detailed than that.

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  • Fibergeek
    replied
    I'm going to say this one more time:

    If you don't yet have the necessary experience with the anodizing process (LCD or otherwise) so that you can tell when you have a bad connection and not some other problem, stick to tightly bolting or threading the work with soft aluminum wire. We have been through months of problems caused by beginners with lousy electrical connections, let's not go through that again.

    NeoMoses as moderator, and M_D as an accomplished anodizer, it would be appropriate you to help me amplify this.

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  • elton10
    replied
    Al welding rod

    Neo

    Saw this tread a little late but wanted to post to it. We've been using welding rod exclusively for racking and attaching it to an aluminum busbar. A lot of the parts we do suspend very nicely on the J bend or a U bend.
    I also use it to connect to my cathodes( 6"x12"plates of 6061..3/8" thick). It tends to get brittle in the anodizing bath but since its disposed of any way its no problem

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  • M_D
    replied
    Originally posted by Fibergeek
    NeoMoses,
    We highjacked your thread, my apology.
    I guess the hijacking was my fault, sorry NeoMoses. Fibergeek, thanks for the information.

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  • Fibergeek
    replied
    NeoMoses,
    We highjacked your thread, my apology.

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  • Fibergeek
    replied
    You might gain some insight by just measuring the resistance of the rack in the electrolyte (empty rack, no work). You can do this by immersing the rack and applying power, note the voltage and the current. The resistance is then R = V / I. Since it won't anodize, this resistance should remain constant if your electrolyte temp. is reasonably constant. It should not be important what current you make the measurement at.

    Servisure should be able to provide you with the SA for the rack components, but it will probably be easier to come up with a rack resistance for each rack configuration that you use.

    For a given rack, the rack resistance will appear as a resistance that is in parallel with the work, as though it was a seperate resistor across the power supply. The power it is dissapating in the electrolyte would be:

    P = V x I, or P = I squared x R, or P = V squared / R, all work equally well.

    This will tell you how much power you have to allow just for the rack.

    It will be more complicated to account for the series resistance of the rack and the contact points to the work. Maybe you could dispense with this by calculating the resistance again, this time the rack and some typical amount of work (R = V / I) when you think the work is sufficiently anodized. If you subtract the rack resistance from this total resistance, you will have the anodic resistance, plus the rack series resistance, plus the contact resistance.

    If the difference between these two calculated resistances is small; you are going to have issues with knowing what current density you are anodizing at, and keeping it constant throughout the anodizing process.

    Sorry M_D; I know you didn't want to hear this, but you might need to get good at "Kentucky Windage" anodizing. Its a PITA, but others do it successfully.

    Let me think about this a while longer.

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