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System settings Kv & UA

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  • System settings Kv & UA

    Hi Guys,
    I'm getting to the end of my larger oven build 8ft wide, 7.5ft high and 4ft deep (pics soon), so in preparation I've done some more tests on shooting powder then curing in my small oven (I'm very new to this) which is leading me to ask for help? I have 2 powder systems, Colo 610 (old but I get very good powder output) and a Gema Optiflex b where both machines have the ability to change the Kv and UA.... Which is where I hit a blank wall.... I cant find any reference to, if you increase or decrease the Kv what you should do with the UA? Also again, how the UA correlates to the Kv for second coats as well as deep corners

    Please could someone try to explain this as I'd like to know the physics of each are instead of 'just playing', otherwise I'm concerned I won't get the best from my systems?

    Thanks in advance

  • #2
    As you have discovered there is no simple easily understood explanation as to current versus voltage. If you search you will find explanations of both and their relationship to each other. That's where it starts to get complicated. If you look at the general guidelines published you will notice some differences from manufacturers. Most will recommend a high voltage setting for first pass transfer efficiency. Limiting the current is where you start to observe differences as I've seen recommendations for this setting ranging from 10 to 50.

    Then there are guns that have presets for various conditions and if you look closely these preset values can vary from the above noted settings. Also some guns will automatically adjust voltage and or current based on the opposite setting. To complicate matters further gun to part distance and from my observations even part density will vary transfer efficiency.

    I use a Parker Ionics system and here is what generally works for me. For first coats set the kV very high, 80+. Set the uA to 20 or below, especially if you have faraday areas. The lower the uA setting the closer you can get the gun into faraday cage areas. Primary and or rinsing air adjustments will also affect transfer so generally I lower the air supply for anything other than large flat areas. For second and subsequent coats many recommend a voltage setting of 30 or so, but I get better transfer keeping the voltage around 50. Bottom line is I doubt anyone can tell you a specific answer to any situation. This is where experience working with your gun will ultimately guide you to what works best for you.

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    • #3
      Ed makes a lot of great points.

      The Parker ionics and gemas Ua will adjust automatically depending how close you are to the part , with the Parker you can watch it happen , Parker also say first coats 100kv and 100Ua and on multiple coats you just lower Ua .I wouldn't lol.

      the gema has presets , I would use them if I were you. Between adjusting the fluidizing, the cloud , and learning , your hands are full enough.

      The colo will lay powder too, but it will take a little experience so you know your using it right.

      Gotta ask , do you have a booth, racks and a way to strip parts that are capable of supporting the ovens size?

      with powder you will have overspray without it you will have back ionization , and it's charged so it will stick everywhere, to everything.

      not sure if you have had the pleasure of stripping powder yet but strippers smell and not a little, the hazardous waste involved with it and the blast media ?

      you may have it all covered , I'm just asking.

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      • #4
        Originally posted by ed_denu View Post
        Bottom line is I doubt anyone can tell you a specific answer to any situation. This is where experience working with your gun will ultimately guide you to what works best for you.
        Thanks ed, I'm beginning to realise that it's really the experience which will answer my questions over time?

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        • #5
          Originally posted by powderpainter View Post
          Gotta ask , do you have a booth, racks and a way to strip parts that are capable of supporting the ovens size?

          with powder you will have overspray without it you will have back ionization , and it's charged so it will stick everywhere, to everything.

          not sure if you have had the pleasure of stripping powder yet but strippers smell and not a little, the hazardous waste involved with it and the blast media ?

          you may have it all covered , I'm just asking.
          Hi powderpainter, at the moment I'm just insulating my larger oven (build pics to follow, although I think it's a little over engineered as the inner skin and doors are 3mm laser cut/folded mild steel, with a 70mm box frame giving 75mm earthwool insulation. burner is kerosene driven off my control panel in another thread), next will be a double overhead track leading to a double turntable arragement (still to be designed and manufactured as bought ones are too expensive) allowing my pieces to be sent down a 90degree 'siding' while I work on other pieces from the oven. I've not had the pleasure of stripping powder , although I'm looking to invest in a small dustless blaster pot when I've enough £££ as I like the results of stripping powder, as well as being able to blast car/bike thin metalwork.
          OMG, I hate looking at my todo list as it's realisation of the number of long days I've got to completing my setup!!

          Thanks again guys

          Ian

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