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Thread: Help on TIG / Plasma HF Start decision

  1. #1
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    Help on TIG / Plasma HF Start decision

    I'm looking to get into TIG welding and use a Plasma cutter. I'm looking at some multiprocess machines and am undecided/unclear on a few things
    a) HF start for plasma
    b) HF start for TIG
    c) HF control for AC welding of AL

    I see a lot of conversations out there that talk about (c) and HF (in general) and how it affects electronics. I grew up in a body shop and my dad was a master auto body restoration expert working on Packards; I don't hold a candle but do a decent amount of of car restorations on the weekends (read hobby) for family and am tired of using tools that would be better suited for a plasma cutter and/or TIG welder. Seeing that I don't have a lot of need for either and budgets are tight, I'm looking to make a low cost purchase and considering that I don't do it that often, I don't mind scratch starting the TIG or plasma cutter.

    With that said, if HF offers me significant advantages with minimal sacrifices (consumables aren't too much of a concern because I don't use TIG or Plasma that often) then maybe I should rethink HF starting. I've read some stories about HF screwing with electronics and the last thing I want to do is fry a $500 ECU or $400 laptop due to HF starts unless I can avoid it. How real is the risk and how great is the advantage of HF starts?

    Your thoughts?
    enmane

  2. #2
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    Re: Help on TIG / Plasma HF Start decision

    The high-frequency arc is an extremely low current arc. I have seen welders light the high-frequency only on their fingers with no harm done. As others have said, the high-frequency start is quite useful to create a very soft start with maximum control of the arc and no requirement to touch the material with the tungsten. The 2nd use is with AC current. You must have the high-frequency on continuously in order to be able to weld using AC current.
    The reason the high-frequency works for these 2 uses is the same. The main arc is a low-voltage/high current arc, while the high-frequency arc is a high-voltage/low current arc. The electrical resistance of the extremely dry shield gas is high enough that the extremely low voltage of the main arc power cannot jump the gap from the tungsten to the part and establish the main arc.

  3. #3
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    Re: Help on TIG / Plasma HF Start decision

    Great - thanks for taking the time to response. It's much appreciated.

  4. #4
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    Re: Help on TIG / Plasma HF Start decision

    Most new plasma machines are made with out HF start. They use a moving electrode or tip. They blow apart to start the arc.
    With TIG it is impossible to have a touchless start with out HF.
    With steel you can lift arc with out HF and TIG weld. Tungsten touches work then lifted off to start the arc. BUT aluminum you need HF to stabilize the arc.
    But depending of the welder type, inverter or transformer based. The amount of HF is either very small or very large. A modern inverter welder with AC output switches so fast the arc does not go out. So it uses an HF pulse to start the arc and the turns off and only fires if the arc stumbles to relight the arc. A older transformer based TIG welder has the HF on all the time you have an AC arc going. You must take precautions to control the HF. earth ground rods connected to the work piece and welder. If you are going to use any plasma or TIG or Mig process on a car. you might want to take steps to protect computer modules and displays.
    The least thing to do is keep the work clamp with in inches of the weld arc and move it as needed. Electricity follows the path of least resistance. You don't want that path to be through the computer control. High current and high voltage will damage electronics. One way to control HF is a second ground wire connected to a earth ground rod. The ground rod should have two cables. one to welder case and one to what is being welded and be with in 25 feet of the welder or closer.
    Down load the Miller syncrowave 250 owners manual and find the HF control diagram. Shows how to keep the HF out of your computer and shop. Also keeps the HF at the arc and not let it travel. And if it travels, gives it a good path back the the welder.

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  6. #5
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    Re: Help on TIG / Plasma HF Start decision

    Quote Originally Posted by enmane View Post
    ... the last thing I want to do is fry a $500 ECU or $400 laptop due to HF starts unless I can avoid it.
    I wouldn't worry much about the HF "frying" any electronics (assuming you're not welding on your laptop case) ... it's more an interference issue, like getting snow on your TV screen. The TV or computer monitor or whatever picks up the RF from the HF and it shows up as noise mostly, or the electronics might not work (somebody reported that his wife's computer monitor wouldn't work) while the HF is "on" ... but then returns to normal when the HF noise stops.

    As for multiprocess machines, I'm not a fan. Seems like they do "everything" marginally well, but nothing especially well, from what I've heard. They're also gonna be much more complicated to diagnose and fix if the Magic Smoke leaks out, as it often does.
    Last edited by Kelvin; 3 Weeks Ago at 07:49 AM.

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  8. #6
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    Re: Help on TIG / Plasma HF Start decision

    All great feedback - thanks so much for the information. I suspected some of the posts that I read were accurate from the frame of reference (older AC machines and HF) versus the newer IGBT based machines. It's great to get that confirmed. Great forum with helpful feedback - thank you all so much!

  9. #7
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    Re: Help on TIG / Plasma HF Start decision

    The one thing you don't want to do is buy a combination plasma cutter/welder. They have a very bad history of poor longevity. The design of a plasma cutter really isn't compatible with the design of a welder...different voltages and such. Welding voltages are normally well below 100 volts (usually in the 10-30 volt range for inverters), and plasma cutting voltages are usually well above several hundred volts. Any such machine is really a gamble. Some folks have good luck with them, but a lot of people report that they fail pretty quickly. If I were you I would worry much less about HF and more about getting the right tools for the job that won't waste your money. If you can't afford both a separate plasma cutter and TIG welder, I would opt for a better TIG welder. There are many tools out there that can substitute for a plasma cutter
    Syncrowave 250
    Purox Metalmaster

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  11. #8
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    Re: Help on TIG / Plasma HF Start decision

    Certainly something else to consider. I figured that the combination units would switch to different boards within for the different functions. Great feedback, thank you. I'm currently looking at the WeldPrime ones and the customer support has been great. They always answer quickly and provide great feedback with a 3 yr warranty. I've tried Amico, that took 3 days of promises to get a tech rep to call back and Lotos was good but seemed entirely web-based. The Hyperikon looks to sell one similar to the WeldPrime (different badging) and they were fast on the phone and suggest, if there are any problems, they just ship another unit which would imply that the 3 companies that sell similar units (Lotos, Weldprime, and Hyperikon) buy from China and swap out the damaged units - not a bad deal IF (a) they work ok and (b) they are around 3 yrs from now to honor the 3 yrs of warranty. The reviews (which should be taken with some measure of caution) seem pretty good. I'll look to see what separate units cost. Honestly, I'm mostly a skilled backyard mechanic (grew up in a body shop, rebuilt a number of engines, and have too much formal education in engineering) on weekends but it seems there is always 1-2 projects a year that find their way to my driveway/garage.

  12. #9
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    Re: Help on TIG / Plasma HF Start decision

    You must have the high-frequency on continuously in order to be able to weld using AC current. The reason the high-frequency works for these 2 uses is the same. The main arc is a low-voltage/high current arc, while the high-frequency arc is a high-voltage/low current arc.

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