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Anodizing calculations (720 Rule)

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  • Anodizing calculations (720 Rule)

    Hello all,

    With my past discussions with M_D and Fibergeek, I have learned about the "720 Rule" for anodizing.
    I decided to take what I had learned from the dynamic duo, and create an excel format calculator to speed up the calculations.

    Here it is. Its very simple. (hopefully M_D and Fibergeek can check it over for me)

    Two options (same info) -
    1. http://www.flamingpaperbag.com/720ru...calculator.htm
    2. http://www.caswellplating.com/720.html

    The blue cells are the cells where you plug in your known values. The green ones are the calculated values.

    I included a formula to help calculate the surface area of an unknown run. All you need to know is your peak voltage, and the amperage you had your supply set to. This calculation will also account for hanging wires and racks. (I think)

    Edited for clarity by CASWELL Inc
    Fibergeek's 10 cents worth

    The 720 Rule is: 720=ASF x minutes / mils. Where; ASF is Amps per square foot, mils is the desired coating thickness (1 mil = 0.001").

    Re-arranging to solve for time: 720 /ASF x mils = minutes

    For a current density of 20 ASF, and a thickness of 0.0005" (0.5 mils); 720 / 20 x 0.5 = 18 minutes.

    The actual current you would apply is 1.75 sq,ft. x 20 ASF = 35 Amps. The required peak voltage is 0.95 Ohms per sq.ft / 1.75 sq.ft. = .54 Ohms. .54 Ohms x 35 Amps = 18.9 Volts. This assumes no voltage drops due to bad connections, and you haven't increased the actual surface area with racking.

    Regarding Amps and Volts. Confusion occurs when the third entity is ignored, which is Ohms. Ohm's Law states that Amps = Volts / Ohms. (I=E/R) An anodizing setup is an electric circuit, as such it obeys Ohm's Law. In all things electrical; current (Amps) does the work, potential (Volts) serves to overcome the resistance (Ohms). Anodic coatings are formed by current, not voltage.

    Relating this to anodizing. An electrical resistance exists when the anodic coating is forming, it is caused by the electrolyte being restricted by the porous anodic coating from reaching the base metal. As the coating grows, this resistance increases. his resistance sets the voltage when a given current is flowing. For 20 ASF, 9.4% electrolyte concentration by volume, and 70 deg. F., this resistance is about 0.95 Ohms per square foot. Its value is inversely proportional to surface area (2 sq.ft. = 0.475 Ohms). It varies a little with alloy as well.

    Paul Yursis
    Last edited by lcaswell; 12-03-2013, 12:44 PM.

  • #2
    In addition, if anyone feels they can make the calculator work better, feel free to do so. Also, if anyone knows how to program it into a small application of its own, that would be good too.

    Comment


    • #3
      GrandSlam,

      You 720 Rule calculator works good, thanks.

      One little point; the Greek letter mu (u) is the abbreviation for micron, not mil. A mil (one thousanth of an inch) doesn't have an abbreviation.


      I'm not sure what you are doing with the second calculator, can you explain?

      Comment


      • #4
        Thanks for the feedback.

        The second calculator is for calculating the surface area of the parts, hanging wire, racks, ect. In order to perform this calculation, you have to take the known values from a previous run.
        This may seem redundant to do after the run is complete, but if you plan to run several batches of the same parts, you will be able to fine tune your surface area measurement of the anode (parts being anodized plus hanging wire or rack).
        I think it works. I have tried it several times on the same parts using different current densities to arrive at very similar results.

        For the past few months, I have been keeping very detailed logs of each anodizing run I complete. I have noticed that my peak voltages are more predictable since I have been using this formula.
        Test it out. I would like to know how it works under different acid concentrations, and different series of Aluminum.

        Formula for surface area:

        Vmax = Peak Voltage
        Ift² = Current Density
        Asys = System Current
        Sin² = Surface Area

        Sin²=(144/Vmax 0.4)Asys
        or
        Sin²=(144/Ift²)Asys

        Comment


        • #5
          Im kinda confused on how to use this...i dont know if it downloaded wrong or anything.....but wordpad is the only program that will show it...and theres lots of little things i dont understand.....all I can say is my computer does not like it....alot of stuff shows up as weird characters and symbols
          www.125customs.com - Quality custom anodizing for simple and complicated jobs.

          Comment


          • #6
            It's an .xls file, and it needs to be opened in a spreadsheet program like Excel to use it. If you don't have a spreadsheet program that accepts .xls files and you would like an *excellent* free open source spreadsheet program then I suggest you go here:
            http://www.openoffice.org/

            Comment


            • #7

              Comment


              • #8
                Re: Anodizing calculations (720 Rule)

                Originally posted by GramSlam
                ...if anyone knows how to program it into a small application of its own, that would be good too.
                Here you go. I started to write it as a standalone application, but that would limit who could use it and some people might be nervous about viruses and such. So it's written in javascript - anyone with a browser (the vast majority of them execute javascript) can use it, and the source code is out in the open for all to see.

                Comment


                • #9
                  Re: Anodizing calculations (720 Rule)

                  Thanks for the Java Version! Good job.

                  Well. I know have the .exe version ready for download.
                  I scaned it with Norton, but if it makes you feel safer, run a scan before you download it.

                  There will be more versions to follow. The next version that will require the beta testing will have data logging to keep records of all your information. It will also graph out your voltages, time, resistance, and temperature.

                  You can download it here

                  link removed - site no longer available

                  Enjoy, Please post any comments here.

                  Graham Skjenna
                  aka. GramSlam
                  Last edited by sswee; 09-18-2008, 11:16 PM.

                  Comment


                  • #10
                    Re: Anodizing calculations (720 Rule)

                    I am new to anodizing, and I had no clue what all the terms and electrical settings. So I used your 720 rule program to set my settings. I was amazed at the quality of the anodize after color and sealing. I believe the parts I have done on my first day of using the LCD kit are better than the stuff I just picked up form my local anodize house. I will be posting pictures soon.

                    Comment


                    • #11
                      Re: Anodizing calculations (720 Rule)

                      When I first introduced to 720 Rule to this website in January 2004 it was a response to help in color consistancy. I am very impressed in how far the 720 Rule has progressed on this web site. I have not been able to visit or respond to forums on this website due to contract obligations with an employer, but that is now completed and I have been reading the forums again on Caswell and again I am impressed by the knowledge passed along. Please keep it going!
                      And just a side note on the firguring of rack size and the 720 Rule- Yes, you will need to figure in rack size only if you are doing eletrolytic color. Some of our rack designs have been over 1,000 ft2 alone per 30' load bar.

                      Comment


                      • #12
                        Re: Anodizing calculations (720 Rule)

                        Hi,
                        I have put up with a new plant of hard anodizing.
                        Please can u guide me in how to get the best results for my anodizing.
                        I am anodizing utensils but i am getting gray color anodized. I need jet black.
                        please guide me on the bellow question: -

                        1. What temperature shoult i anodize.
                        2. What should be my acid mixture(and how pure should be my acid).
                        3. What volts and amps should i anodize .
                        4. What other chemicals can i us.
                        5. How should i do the sealing.

                        my tank size is:- length=13ft
                        Width= 3ft
                        Hight=3.5ft

                        please guide me.
                        thanking you
                        manish

                        Comment


                        • #13
                          Re: Anodizing calculations (720 Rule)

                          Hi,
                          I have put up with a new plant of hard anodizing.
                          Please can u guide me in how to get the best results for my anodizing.
                          I am anodizing utensils but i am getting gray color anodized. I need jet black.
                          please guide me on the bellow question: -

                          1. What temperature shoult i anodize.
                          2. What should be my acid mixture(and how pure should be my acid).
                          3. What volts and amps should i anodize .
                          4. What other chemicals can i us.
                          5. How should i do the sealing.

                          my tank size is:- length=13ft
                          Width= 3ft
                          Hight=3.5ft

                          please guide me.
                          thanking you
                          manish n jain

                          Comment


                          • #14
                            Re: Anodizing calculations (720 Rule)

                            Originally posted by manishnjain View Post
                            Hi,
                            I have put up with a new plant of hard anodizing.
                            Please can u guide me in how to get the best results for my anodizing.
                            I am anodizing utensils but i am getting gray color anodized. I need jet black.
                            please guide me on the bellow question: -

                            1. What temperature shoult i anodize. 32*F
                            2. What should be my acid mixture(and how pure should be my acid). 1:1 or 1:2 by volume
                            3. What volts and amps should i anodize . Depends on if using CC or CV
                            4. What other chemicals can i us.
                            5. How should i do the sealing. Distilled water boil if for eating utensils

                            my tank size is:- length=13ft
                            Width= 3ft
                            Hight=3.5ft

                            please guide me.
                            thanking you
                            manish n jain
                            Your questions are out of the scope of this forum. The answers I gave are from my study of the anodizing procedure and are not from this forum. What you are asking about is Type III Hard anodizing. It is not a DIY project.
                            SS

                            Comment


                            • #15
                              Re: Anodizing calculations (720 Rule)

                              WHAT IS CC AND CV RIGHT NOW I AM ANODISING AT 90 VOLTS AND 500 AMPS.
                              What should be the level of sulphuric acid in my tank the capacity of my tank is 3000 lts.

                              Comment

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