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Anodizing calculations (720 Rule)

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  • #31
    Re: Anodizing calculations (720 Rule)

    dmiom,
    Good detailed info but you might have overlooked that his PS has a 15V max. A CD of 6ASF is the highest capable at optimum conditions. Any resistance due to connections, temperature or other parameters will max out the PS.
    SS

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    • #32
      Re: Anodizing calculations (720 Rule)

      did anyone rehost the .xls calculator? maybe this will spare someone answering the thread i just posted about wandering amperage

      though i'm not sure how to apply this to odd size parts, e.g. a tube with an irregular solid bit fused to the top. both inside and out anodize and take dye and make the math agony

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      • #33
        Re: Anodizing calculations (720 Rule)

        woop! don't remember where i found this (dang got too many tabs open) but here's the calculator, as html so you can save it and use it always.

        720 Rule Anodizing Calculator

        thx

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        • #34
          Re: Anodizing calculations (720 Rule)

          Originally posted by sswee View Post
          Yes on the area of the part. Racking very seldom needs to be considered.SS
          sorry for the noob question, but say if you were taking racking into consideration, would it only be the submerged area?


          also, with my 30v Mastech CC PS would i be able to speed up the process[where part size allows] or should i just stick w/ 6amps?


          been reading this site like a madman this past week. ive concluded youre the guy to go to for answers though i gotta tell you I really appreciate all the help youve provided me just w/ posts on other peoples threads.

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          • #35
            Re: Anodizing calculations (720 Rule)

            Yes racking needs to be considered, but only the submerged area (if any).
            If your racking is above the electrolyte and simply Ti Wire suspends your parts in the electrolyte, then do not take the racking into your calculations.

            You can speed up the process. The higher CD you have, the faster the layer will build. However, this causes more heat, higher voltage, higher amperage, and needs more agitation.

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            • #36
              Re: Anodizing calculations (720 Rule)

              Thanks Bob. I figured with only the wires submerged compensation wasnt necessary. just had to make sure.

              any recommendations on where to get Ti racking supplies online? the cheaper the better i can fab up my own racks, just have a hard time finding the stuff down here

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              • #37
                Re: Anodizing calculations (720 Rule)

                Originally posted by stayhi View Post
                sorry for the noob question, but say if you were taking racking into consideration, would it only be the submerged area?
                also, with my 30v Mastech CC PS would i be able to speed up the process[where part size allows] or should i just stick w/ 6amps? .....
                Originally posted by BobFrapples View Post
                Yes racking needs to be considered, but only the submerged area (if any).
                If your racking is above the electrolyte and simply Ti Wire suspends your parts in the electrolyte, then do not take the racking into your calculations.
                You can speed up the process. The higher CD you have, the faster the layer will build. However, this causes more heat, higher voltage, higher amperage, and needs more agitation.
                Racking - I would add that the effect depends upon what your racking is made from.

                If its from aluminium (which would have to have been stripped to ensure you got good electrical contact) then you need to take the racking surface area into account.

                If you are using Ti racks or wire, then once they've been 'pickled' (recent discussion on the board e.g. in here) then their effect is negligible and you can usually completely ignore the SA of the racking (although if the SA of of your Ti racking was say 20 times greater than the SA of your workpiece you might have to make allowance ...)

                Current Density - as Bob says, running at a higher current density than the 4.5 - 6 ASF range used in basic LCD (Low Current Density), you will introduce more heat. There will be two results - firstly, the 'bulk' heat of the electrolyte will give accelerated dissolution and a poor coating, and you'll end up with a chalky surface. Typical results are that it looks OK when pulled out and rinsed from the electrolyte tank, looks OK when pulled out from the dye tank, but as soon as you DI rinse it, you may see some dye leaching out. Then, after sealing, if you go to wipe it after spraying/dipping in WD40, you get dyed coating coming off like soot on your towel or cloth. If you cannot reduce your current density, the answer for this is both circulation and, if necessary, chilling. The second effect is increased risk of 'micro hot spots' which, as acidrain has explained on here, can lead to hydrogen bubbles building up on the surface - and for that reason, many run aeration still as well as agitation/circulation. Would suggest get your whole process working reliably using the LCD method first, and then try higher current densities etc.

                Originally posted by stayhi View Post
                Thanks Bob. I figured with only the wires submerged compensation wasnt necessary. just had to make sure. any recommendations on where to get Ti racking supplies online? ....
                Sources for Ti racking - if the items are small and suitable, 1/8" Ti rod bent into an appropriate spring shape with plenty of pressure gives great results. If you search here in the forum you'll find lots of discussion & advice on racking. For bigger items, I can do no better than recommend the range of clips from ServiSure - e.g. look at the clips of page 16+ of their online catalog (we've no connection with ServiSure - just satisfied customers). Not sure where you're situated "down here" but I imported trans-atlantic from ServiSure and it was worth every penny in terms of predictable results.

                Dave

                (p.s. If you've any more questions on the racking, aeration etc. itself , can I suggest posting a fresh question rather than here in the 720-rule thread).
                Last edited by dmiom; 09-12-2009, 11:00 AM.

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                • #38
                  Re: Anodizing calculations (720 Rule)

                  that pretty much covers what i was looking for, posted here as everything asked applied to the thread and wasnt covered yet.[for noobs like myself]

                  "here" is honolulu so Mahalo for the help, ill go check out airgas tomorrow, but i dont think they stock Ti rod. Mastech arrives wednesday so my annoying noob threads in the weeks to come

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                  • #39

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                    • #40
                      Re: Anodizing calculations (720 Rule)

                      Start a new thread. What kind of gun receiver? Can you post a pic? Most of the calculations are basic. Can get you in the ball park.
                      SS

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                      • #41
                        Re: Anodizing calculations (720 Rule)

                        ok i read a bunch but havent found the info i was looking for.... i am anodizing a bunch of small, similarly sized parts. I have a 7-8 gallon tank, and i am using an Astron vs-50m power supply. With one of the parts in there, the amp meter barely moves. Maybe .5A max. With 12 pieces in there, it goes up to approx 5 amps. So what do i use to calculate the 720 rule? It's a 50amp power supply, but it doesnt seem like it'll put out any more amps than the parts will draw.
                        Also, if i'm anodizing a bunch of different sized parts, and the current goes up because of the larger parts, how to i know what the amperage is for the smaller parts?

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                        • #42
                          Re: Anodizing calculations (720 Rule)

                          Firstly, have a read of this thread

                          The 720 rule is not about setting the current.

                          The 720 rule tells you how long to anodise for at a chosen current density.

                          All of your parts should be racked so that, electrically, they are wired in parallel - i.e. each one connects back to the positive tank bar or however you're racking them - never try daisy-chaining the parts.

                          The constant current you set on the supply is based on the total wetted area of all your parts times your chosen current density. A good current density to start from is 6 Amps per square foot. If all your parts add up to, say, 72 square inches (half a quare foot) and you wish to use a CD of 6 ASF, then the constant current limit you should set on your supply would be 3.0 Amps. If your power supply struggles to maintain that constant current, or you are generating more heat than you can take out of the tank, maybe reduce the CD to 4.5 ASF

                          Dave

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                          • #43
                            Re: Anodizing calculations (720 Rule)

                            Originally posted by dmiom View Post
                            Firstly, have a read of this thread

                            The 720 rule is not about setting the current.

                            The 720 rule tells you how long to anodise for at a chosen current density.

                            All of your parts should be racked so that, electrically, they are wired in parallel - i.e. each one connects back to the positive tank bar or however you're racking them - never try daisy-chaining the parts.

                            The constant current you set on the supply is based on the total wetted area of all your parts times your chosen current density. A good current density to start from is 6 Amps per square foot. If all your parts add up to, say, 72 square inches (half a quare foot) and you wish to use a CD of 6 ASF, then the constant current limit you should set on your supply would be 3.0 Amps. If your power supply struggles to maintain that constant current, or you are generating more heat than you can take out of the tank, maybe reduce the CD to 4.5 ASF

                            Dave
                            i guess i didnt explain what i was asking clearly... i understand what the 720 rule is.
                            My power supply is a 50amps. It should have no issues anodizing the small parts i'm doing. There is a current meter on the front of the power supply, and also an adjustment knob. The current meter's reading seems dependant on the load, so the smaller the parts i am doing, the lower the meter sits. I cannot turn up the current with the adjustment knob, i can only turn it down. Now what i dont understand is what amperage do i go by when calculating the 720 rule... the 50amps my power supply is capable of, or the .5amp load that is on the meter, or neither? I cant set it to 4 or 6asf to my knowledge.

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                            • #44
                              Re: Anodizing calculations (720 Rule)

                              Daniel, please carry this to a new post I started for you.
                              Thanks
                              SS

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                              • #45
                                Re: Anodizing calculations (720 Rule)

                                Hi,

                                I have a question about this 720 rule. Can this rule be applied to all acid concentrations for one preset ASF? I know that high acid concentration makes larger pores at the same ASF than low concentrated acid... and also dilute the oxide layer much quicker. So I presume that for the same ASF the duration of anodizing should be longer because of the dilutation, that fights back the anodiziation process. Therefore for higher concentration the ASF is set higher. Is this correct or maybe I am thinking in the wrong way.

                                Thanks.

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