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Electro-polishing kit or "how to"?

Discussion in 'General Electronics Chat' started by szzuk, Dec 26, 2010.

  1. szzuk

    szzuk Member

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    I'm looking for an electro-polishing kit. The process itself seems to be the reverse of electro-plating, so i'm looking for some kind of chemical bath with an anode, cathode and DC power supply. This is for a home project so the kit would preferably be as small and cheap as possible. I want to polish stainless steel to remove burring and imperfections. Google returns articles on industrial equipment, school supplies or jewellry suppliers but nothing that looks right.

    Does anyone know where I can get an electro-polishing kit?

    Alternatively I could have a go at making my own kit, how would I go about that?

    Thanks,

    Szzuk.
     
  2. #12

    #12 New Member

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    I loaned a power supply to a guy to do some electro-plating and he discovered that running the polarity backwards removed crud from the victim. I think that's what "electro polishing" is about...un-plating a metalic surface. Just grab a battery charger and something you can keep wet, like a metal handle flux brush and find out which polarity removes metal.
     
  3. szzuk

    szzuk Member

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    I have done some more reading and your post looks right. Not having tried before the details on how to do this are a bit hazy. I must need some sort of chemical, probably an acid, rather than only water? How much current would I need and for how long?

    Thanks,

    Szzuk.
     
  4. dave

    Dave New Member

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  5. shortbus=

    shortbus= Well-Known Member

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    Szzuk - Electro polishing won't remove burrs and imperfections, just makes them shinier.

    here is a pretty good link; Electropolishing - DIYbanter

    or this Google has a ton of information; diy elctro polishing - Google Search

    Good reading,:)

    Do you actually want to polish or passivate? If you just need to passivate small parts something called 'Bar Keepers Friend' powder works good for that.
    Bar Keepers Friend | Cleaning Products | Household Cleaning Supplies

    To remove burrs and polish a vibratory bowl or tumbling works pretty good. Different shaped parts require different types of polishing/deburring ceramic media to get all of the areas of the part.
    Tumbling Media, Deburring Media, Ceramic Media, Plastic Media, Vibratory Media
     
  6. szzuk

    szzuk Member

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    I want to polish tiny holes in stainless steel, the holes have a diameter of 20 microns or 0.02mm. The polishing may remove a burr of 2 microns which would be fine, you weren't to know I wasn't trying to remove a 1mm burr on a metal bar!

    Does anyone know of a cheap kit?

    I will start to read the DIY electropolishing articles, thanks for the link.

    Szzuk.
     
  7. atferrari

    atferrari Well-Known Member

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    There is a site dedicated to robotics explaining what you want to do. Sorry, I run across it yesterday but cannot recall the name.

    Yes, robotics.
     
  8. szzuk

    szzuk Member

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    I couldn't find the website. Thanks anyway.
     
  9. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    It sounds like you are after electrochemical deburring for a process (ECD). You may want to give this a read and then move along and give this link a read. The latter link mentions a few electrolytes you can try. On a larger scale there is tooling and fixturing involved but I guess you could keep it simple for experimenting. Generally you also have a flow with your electrolyte. Start simple with a plastic tub and maybe a sewing needle for your tool electrode. You will have to mess around with a power supply or two to get what you want. Been years but I have worked with a few EDM (Electro Discharge Machining) processes that run in a similar fashion to ECD.

    Hope That Helps
    Ron
     
  10. szzuk

    szzuk Member

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    That does help.

    * I will need a bath - plastic food container will do
    * Electrolyte - can test with salt but reckon stainless steel needs an acid of some kind
    * Power supply - a charged up lead acid I have might work, maybe need more current?
    * Cathode- can use the stainless steel part maybe
    * Anode - sewing needle maybe

    This will be interesting!

    I wonder if the electrolyte needs heating, hmmm.

    Thanks,

    Szzuk.
     
  11. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    It's going to be a trial and error affair. You can start with maybe 12 volts and salt water with various concentrations of salt. I would not be too quick to try anything acid. Just keep it safe and simple. The current draw will be a function of the electrode to the workpiece. I suggest maybe a stainless steel sewing needle only because you can get a very tiny diameter and you are, from what I see looking to deburr small holes in the workpiece. Keeping your solution moving is important. Worry about filtration later but for starters just see if things work. I would be curious as to how things go. I wouldn't worry about heating at this point.

    Ron
     
    Last edited: Dec 27, 2010
  12. codex653

    codex653 New Member

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    wow! this is a very interesting thread! i think i may start trying this with some of my steel pieces i have for some of the parts to my amp case! :D
     
  13. szzuk

    szzuk Member

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    It is interesting that you mentioned keeping it simple and safe at first, acid and large currents with equipment being made off the cuff has potential for unwanted outcomes. I imagined myself getting too familiar with the setup and trying to alter it when I shouldn't. From what you've mentioned I need to worry about the acid moreso, so I will leave that for now and just make sure I have everything else working.

    I'd be willing to pay £50 ($100) for a setup but from what I can gather they start at about 4 times this much. I have reserved an electroplating/polishing book at the library which should fill in some gaps. It looks simple in theory but it won't be until I've made a few mistakes!

    How long does the process take? Could I stir the electrolyte by hand? The part I want to polish is a stainless steel disc of 15mm diameter and thickness 0.3mm, it is the holes through the thickness that need polishing so water can pass through them more easily.

    Thanks,

    Szzuk.
     
    Last edited: Dec 27, 2010
  14. szzuk

    szzuk Member

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    I would like to know how it goes!
     
  15. shortbus=

    shortbus= Well-Known Member

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    Hi again, I don't want to be a stick in the mud, but, this isn't a easy or simple as you guys a trying to make it to be. I worked for a very large corp that had parts that need to be polished/deburred all the time. they had the resources to by just about any machine or process needed.

    But two of the few things they always sent out was plating and electropolishing. Electropolishing sounds good in theory but in practice it's not what it seems to be. Before E/P is done the area is most times mechanically polished. The E/P process takes material from across the whole surface. If there is a ridge or pit it doesn't eliminate either one just makes them shinier.

    One thing they did buy at work for this, before sending out for final finishing was a 'Extrude Hone'. This will remove burrs and prepolish, before the E/P. But you need to fixture all the areas to be honed.

    Here is a company that caters to DIY polishing and plating needs. read what they have to say about electropolishing.


    electropolishing - Google Search
     
  16. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    It's hard to say how long? Just think initially patience and good things come to those who wait. :)

    Think of it this way. You are using an electrical process to remove material. The reason for circulation is as we remove material we want it to go somewhere even though they are micro particles. If the electrolyte doesn't flow then the material will begin to build up on our electrode. You will be plating sewing needles. :) Not a big deal but eventually you will want to circulate the electrolyte and filter it.

    As to the electrolyte? Yes, I suggest boring stuff like salt water and try a few concentrations. Electrolytes like this can also be acids or caustics at which point if something goes wrong you can be really hurt! Things like safety goggles and rubber gloves come into play. Just a tiny splash of acid or caustic can take away your vision for life. High price to pay for an experiment huh? I won't be the one to tell you just fill a beaker with 50% sulfuric acid and water and shove a few electrodes in it.

    More advice, buy a small mountain or paper and a box of sharp pencils. When you try different electrolyte solutions take notes as to the salt added and volume of the solutions. Note currents and voltages, hell note everything as you muddle along. Collect and save your data. You are refining a process for your parts, your application.

    When you get a process going look for tiny bubbles, they will be an indicator something is going on. :)

    Just be safe!!!!!!

    Ron
     
  17. codex653

    codex653 New Member

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    yah i'll probably end up trying it sometime this week, i'm gotta finish building the rest of the pre-amps and SMPS circuits first :p
     
  18. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    Oh absolutely and I strongly agree. I have my share of time around plating processes. However, on a tiny scale and not looking for a super micro-finish I don't figure it will hurt using safe chemicals like salt to screw around a little. Maybe learn a little. That is how I am trying to keep things anyway. Yes, in reality complex jigs and fixturing is used with very tight tolerances and control. Your input is much appreciated also.

    Ron
     
  19. szzuk

    szzuk Member

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    I think it is simple to start, but doing it well is difficult. I expect to spend several weeks, perhaps longer, getting it all working. There is no particular timescale so if it takes longer that is ok. It doesn't look like a cheap plating/polishing kit exists and I don't want to send this to a contractor to do for me because I will need a few every month so the cost would quickly add up. The link is very good, thanks.
     
  20. szzuk

    szzuk Member

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    That is good advice. I'm thinking I will have to circulate the electrolyte through the holes, it will be tricky. Lots to do. Thanks!
     
  21. szzuk

    szzuk Member

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    I have to use either concentrated sulphuric acid or perchloric acid (super acid). My guess is that anything else won't work or will take too long, so I could only experiment but not actually do the job. It's just too dangerous to do at home. I couldn't even store the stuff safely with kids around etc, never mind dodging the toxic fumes. I'll have to find a contractor. Live and learn! Thanks for the input on this thread.
     

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