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Thread: Plasma cutter ?

  1. #1
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    Default Plasma cutter ?

    Any tips on which plasma cutter is best value ?

    I am looking at cutting up to 12mm steel . A 50 amp unit may be suitable . There are cheapies on EBAY but are they total junk ? Inverter technology seems to be the current thing.

    What are the forum users using ?

  2. #2
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    I bought a Cut50 from EBay. I have no complaints. I cut some 20mm plate. I had no other way to do it. It took a number of goes at different angles and took quite a while, but I did succeed. Unfortunately when I had finished and I tried to turn off the 15A power point it was plugged into the switch would not work. The power point has clear melt marks around the slots. Plugs still fit in ok and the point works, just not the switch. New power point is on the list for Bunnings.

    I still have not had much other experience with the plasma. I should try some different thickness metals to see what it will do, properly.

    My understanding is that these units are contact arc start. Any guiding device will need to allow for this.

    I bought a circle cutter from EBay. It was quite useless as it arrived. It needs a lot of work to get it to hold properly and sit at the right height.

    I bought some expendables in a kit from EBay. They are quite different to what is on the torch now. They will fit, but are different lengths and change the torch height etc. I made a height guide from the stainless strips inside some windscreen wiper blades. This has enough flex to allow arc start. It wont work with the new bits tho. I need to make a new one. It was quite tricky and time consuming to get the correct shape etc.

    It may be that the torch as it came has the different bits on it and the replacements I bought are more standard. I don't know. That is one thing I need to work out. Maybe every time new bits are acquired the height changes again. It is difficult to work this out when you are living where I am.

    Dean

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    I was told by my local professional welding store that the ratings on Hypertherm units are the only ones you can really believe. Everyone else takes an optimistic view of their product's capabilities. If buying from ebay, their thicknesses may need to be down rated a little.

    Michael

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    Default

    I have a Cut40 that was dirt cheap off some bargain site - I had no great expectations for the price, and it's been very handy for sheet metal. Realistically once you go above 6mm things get a bit ugly - I think I may have chewed through 10mm at some point, but 12mm was a bridge too far, so a Cut50 might be fine for that.

  5. #5
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    Default

    I have one of the cheap generic 40A plasmas from eBay, it was advertised as being able to cut 12mm steel but it doesn't. 10mm is very slow and ugly, 8mm is sort of acceptable, 6mm and below is fine.

    Based on the above and assuming there is a direct ratio (I suspect it may be more of a diminishing returns ratio) between amps available and steel thickness that can be cut, a 50A plasma with an extra 25% amps over the 40A plasma will do a slow and ugly cut through 12mm.

  6. #6
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    Here's a post about cutting 12mm steel with my 50 amp plasma cutter. The results are pretty good.

    I was told by my local professional welding store that the ratings on Hypertherm units are the only ones you can really believe.
    I must admit I don't make it a habit to fully trust what a sales person tells me about what they are selling, or more correctly about what they are not selling.
    Cheers.

    Vernon.
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  7. #7
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    There must be a bit of variance in these cheap plasma cutters, as I have a Cut 40 I picked up off Ebay (an orange one branded 'Smarter Tools', for what its worth), and I've cut 16mm plate with it without much issue, although its a bit slow going. I would call the cut quality tolerable at that thickness, its neater than I expected it would have been given 16mm was its rated 'severance' cut, and the results would have been better if my travel speed had been more consistent (I'm terrible with a plasma). 10-12mm is no problem at all. If anyone cares enough, I still have the rest of the piece of 16mm plate lying around, so can take a photo of the cut edge if someone wants.

    It's worth pointing out here though that I use a 3hp compressor with a 120L tank, and have what I suspect was a fairly expensive when new inline drier (has some kind of thin membrane straws inside) on the line coming out of the tank, so its probably getting a pretty clean supply of air. Also worth noting that it WILL trip a 20A breaker on the dedicated 15A GPO circuit after a little while when the amp dial is maxed....

  8. #8
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    I suspect you are one of the lucky ones. I was wondering whether there could be some variations in capacity. The circuit my plasma connects to has 2 X 15A GPO's and a 32A breaker back at the house. I have the bits to split this circuit in my shed and fit seperate breakers. The breakers were some of the last available at our local Masters. You have reminded me of this chore.

    Dean

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    Quote Originally Posted by Jekyll and Hyde View Post
    There must be a bit of variance in these cheap plasma cutters
    I expect that this is indeed the case - while they're all called Cut40, it may well be that different units have different designs and/or components that lead to better (or worse) performance. As a reference point, Hypertherm claim their Powermax 45 will cut up to 19mm and sever 25mm. I think "sever" means the ugly cut my Cut40 does on 10mm.

    As for tripping breakers, the killer with the plasma is that you're running both the unit and an air compressor at the same time, meaning you really need to make sure your circuits are sorted out.

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    Quote Originally Posted by RustyArc View Post
    As for tripping breakers, the killer with the plasma is that you're running both the unit and an air compressor at the same time, meaning you really need to make sure your circuits are sorted out.
    I have 4 dedicated 15A GPOs in my garage, each on their own breaker, so the plasma is tripping the 20A all by itself, there is nothing else on that circuit - the compressor is on a different breaker. The length of cabling between the sub board and the 15A I use for the plasma is less than 10m, so no volt drop worth speaking of. Just an indicator of how hungry these things can be.

    To be honest though, I'm too unsteady with the plasma, and can't get a consistent neat cut (despite moments where it goes beautifully for a few hundred mm), so I spend as much time cleaning up the edge with an angle grinder or linisher as if I were to simply cut it with the grinder from the start. That, combined with the hassle of setting the thing up to use (I don't have space to have it set up ready to go all the time), and the ungodly mess it sprays all over the ground, means I rarely use the damn thing. I find it most useful for quickly dismembering some awkwardly shaped steel framing I've got as scrap into more easily stored pieces, aside from that it lives on the shelf...

  11. #11
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    Quote Originally Posted by Oldneweng View Post
    I suspect you are one of the lucky ones. I was wondering whether there could be some variations in capacity
    It could also be differences in setup and technique. While it may seem that these are "simple" machines there are still setup (and technique) variables that need to be considered.
    Cheers.

    Vernon.
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  12. #12
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    Quote Originally Posted by Vernonv View Post
    It could also be differences in setup and technique. While it may seem that these are "simple" machines there are still setup (and technique) variables that need to be considered.
    I can understand the techniques aspect, but what setup variables? I am interested because I am a complete newb with plasma and I would like to learn more.

    Dean

  13. #13
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    Quote Originally Posted by Oldneweng View Post
    I can understand the techniques aspect, but what setup variables? I am interested because I am a complete newb with plasma and I would like to learn more.

    Dean
    Air pressure and amp settings for the material being cut.
    Cheers.

    Vernon.
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  14. #14
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    And here I was, thinking you had some extra info I was not aware of.

    The amps are easy with thick steel, but the air pressure is not something I am fully conversant with. I generally run about 45 - 50 psi, but I don't know if any variation on this would be a benefit depending on metal thickness. Something I still need to learn.

    Dean

  15. #15
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    Quote Originally Posted by Oldneweng View Post
    And here I was, thinking you had some extra info I was not aware of.
    I thought it was self evident also, but I didn't want to assume.

    Quote Originally Posted by Oldneweng View Post
    I generally run about 45 - 50 psi
    For thick steel I generally run around 100psi.
    Cheers.

    Vernon.
    __________________________________________________
    Bite off more than you can chew and then chew like crazy.

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