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Plasma Cutter - What Should I Look For?

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  • Plasma Cutter - What Should I Look For?

    I may want to buy a plasma cutter. I know nothing about them.

    -Do they cut better than a torch?
    -What SCFM do you need out of your compressor for plasma cutting?
    -For cutting 1/2" or less, what amperage do you need?
    -Will a cheap Chinese unit do?
    -What is the usual kerf size?
    -Do I need 220V or will 120V do?

    Are there questions I am failing to ask?
    ____________________________________________

    I don't need to find myself. I'm always at my lathe.

  • #2
    My opinions to your questions:

    1. “Better” is relative, just another method of cutting. I prefer my plasma cutter over the torch 9 times out of 10, and I can cut stainless...try that with a torch.
    2. The volume of air is not as much as you think. Even a small compressor will work. Some plasma cutters have onboard air compressors, and they’re tiny! Most plasmas are gonna have a built in pressure regulator that necks down whatever pressure you hook up to it. That’s how mine works at least.
    3. Something that is rated to cut 1/2” is not the same as severe 1/2”. No matter what plasma you get, your cutting speed will depend completely on the thickness of the metal you’re cutting. It’s rated in inches per minute. I suggest you get one size machine bigger than what you generally anticipate cutting on a regular basis. Constantly hitting your duty cycle will eventually make you sad.
    4. Not in my opinion. Buy once, cry once.
    5. Kerf size will depend on the condition of your consumables. Brand spanking new electrode and tip will make the narrowest and nicest cut. Either way, the kerf will be less than that of a torch.
    6. You will not be happy with a 120v plasma unless all you’re cutting is thin gauge sheet metal.

    Hope that helps.

    Comment


    • #3
      One thing to keep in mind is that a plasma cutter wants to cut clean material. Rusty material is much easier with a gas torch. It will cut any conductive material, like aluminum and stainless, though, which a gas torch will not. Depends on your priorities, but you'll want both eventually.

      Comment


      • #4
        If you're like me (and probably most people), you'll get a LOT more use out of an O/A cutting/welding/brazing rig.

        For a plasma cutter, one word: Hypertherm

        Comment


        • #5
          On another forum, the general consensus was 4 SCFM as a minimum for the compressor. You can have a little pancake 3 SCFM from HFT, but you'll have to stop all the time to let it catch up. I currently have a 4 SCFM 8 gallon tank compressor.

          Hypertherm. Yes, I've seen that on Youtube. Sky's the limit on price, there. $2,000 and up. The torch kit costs more than a whole Chinese unit with accessories. But I guess you get what you pay for. I would be using it half a dozen times a month Not enuff to justify $2K.

          Had an idea. My next door neighbor is always borrowing my tools. He has a Chinese plasma cutter. Maybe I can just borrow his from time to time. Then, I wouldn't have to dedicate garage space to it.

          Still, it would be nice to have my own.
          ____________________________________________

          I don't need to find myself. I'm always at my lathe.

          Comment


          • #6
            And the drier the air, the long your consumables will last. You’ll probably use your plasma cutter more than you think. You can also gouge with a plasma. I use a plasma to bevel parts before I weld them. I think the plasma cutter inputs less heat into a part than a torch does, so you’ll have less warpage. But a torch is certainly an irreplaceable shop tool for me, as is my plasma cutter.

            Comment


            • #7
              >I may want to buy a plasma cutter.

              Well good to see you said "may want". It suggests your still at the questioning stage? There may be time to stop you? Judging from your recent post, I'd say there is. But that's not stopping be from opening my big yap.

              When it comes to PAC, I'd ask lots of questions... the first and foremost would be why do I really need one?
              Notice I didn't say want? Big difference. You were given some solid advice in the previous posted replies. The solid being, you know what you plan on cutting and how much of it?

              Now, not to brag, but I'm very skilled with a cutting torch. And I don't bring it out often any more. I have never found a need to fire up the little Lincoln PAC I bought, a Lincoln Plasma 20. So when I say do you need it, well...I'm just saying?

              I'm going to add a few tidbits of commentary, more based on small piece of knowledge and insights.

              1) The majority of erosion that occurs to plasma arc cutting consumables is when the trigger is squeezed and released. Opening and closing the door so to speak. Check those costs out. It's a power source, you need a compressor, and consumables which effect the cut quality add up and as the consumables erode, the dross you'll find still needs grinding clean up.
              2) Expense of the equipment to purchase. If you compare prices against the purchase of a hand held 5" Makita grinder and 25pks. of Walter zip discs, a 14" chop saw with a couple extra blades, and maybe a quality reciprocating saw and a jig saw with metal cutting blades, you could be further ahead with cash left over for a few more tools or better stock of consumables for cutting materials?

              >I know nothing about them.

              I do... well the process of PAC. It's principle of operation is actually very simple. But that simple, like GMAW, is simple yet complicated. I have used PAC. Cutting to gouging and quite frankly, PAC has it's place and it's grey areas of use, compared to Oxy-fuel cutting.

              How about this, you are taking and vaporizing metal in a stream of plasma erosion. The particulate is 50 times smaller then the width of a human hair. You want to talk fumes and health hazards?
              I didn't mention sparks...Most set cutting torches O2 pressures @ 40psi and PAC pressure requires minimum 90, which sparks are flying further?

              -Do they cut better than a torch?

              That depends on the the operator, the torch, it's settings and tip size as well the type and thickness of the material to be cut, quality of cut desired and resulting effects on material properties.

              Example - they allow you to use oxy-fuel cutting to remove a body panel made of HSLA materials if the cut is far enough back to allow for further removal in trimming material due to the effects of heat damaging the mechanical properties due to the broadness in it's heat effected zone, and it could be further trimmed with a zip disc? Due to the diminished heat effected zone in theory you could cut the edge.

              1) Process costs include a number of variables to be considered, but as I previously mentioned, as well others, You have to decide what you most likely to cut.

              -What SCFM do you need out of your compressor for plasma cutting?

              Look at it this way...you can learn how to plan the length of the cut better when you run out of air and it stops cutting, but that volume of air, it's cleanliness, affects the cut quality, speed of the cut, effect of heat input on the HAZ, and the efforts cleaning up of a harder dross that seems now wearing down those discs quicker?


              -For cutting 1/2" or less, what amperage do you need?

              Another good question? Lots. But why?
              I'll tell you, because while you can use a smaller unit to cut thicker materials, other factors have to be considered. It starts cutting from the top and has to travel through the thickness, that takes time. To have the cut progress you have to travel slow enough or the cut looses continuity to the stream being blown away. More current and greater air don't slow the process down. That said, while a cutting torch blows in a lamellar fashion, the stream from PAC is a circular swirl. Slowing down causes further melting and erosion on the top surface tapering the kerf wider.

              -Will a cheap Chinese unit do?

              Hmm? I'm not going to say no. How's that working out for the neighbor? I'm curious to know?
              I'm going to say, if it's Friday night and you need a new tip assembly, who's open Saturday and what do they carry?

              -What is the usual kerf size?

              I'm going to give you a perspective. The GMAW wire is small in diameter yet the bead seems to end up wider? The diameter of the orifice is reflective to the minimum width of the kerf.

              -Do I need 220V or will 120V do?

              They say no substitute for cubic inches...?
              How about this, if you got a pile of crap to place in the wheel barrel, the bigger the shovel the more you can load with each scoop.
              A burro can do most of the work of a draft horse for half the hay?
              When it comes to electrical use and PAC, higher input means more voltage out put, and pushing a bunch of skinny amps faster is easier then try to push slow fat ones? 120V equipment is always easier to resell.

              - Are there questions I am failing to ask?[/QUOTE]

              Yea...I think there is. Do I need it or do I want it? Sounds like a want?

              Comment


              • #8
                My first choice for a new shop would be aquiring a good Oxy/acetylene outfit, unless you will be working with aluminum, SS and repourposed steel that may have paint, rust and maybe grease on it. Remember, mixing Oxygen and grease is a big no-no.

                Not to disrespect Miller, but here is a good deal on a slightly used Demo Hyperthem 30 XP, If you are not going to be cutting much 3/8" or 1/2 " material, it may fit your needs. As your needs grow sell the 30 XP and by a bigger outfit. Do a search for 30 XP reviews and see what owners have to say about the machine.

                https://www.weldersupply.com/P/2485/...rmax30xpPlUSED

                Comment


                • #9
                  Probably more of a want. Thanks for the info. How's this for a game plan? If I have some thick steel to cut precisely, I borrow Chris's cutter, and have him show me how to use it. If I need it often, I buy one. If I need it seldom, I borrow. Probably, if I buy, it will be Chinese.
                  ____________________________________________

                  I don't need to find myself. I'm always at my lathe.

                  Comment


                  • #10
                    My luck, I borrow a tool like that, it breaks. Keep an eye on the used market too. I used to not think I needed one, until I got one. No way would I go without one now.

                    Comment


                    • #11
                      Originally posted by buffumjr View Post
                      Probably more of a want. Thanks for the info. How's this for a game plan? If I have some thick steel to cut precisely, I borrow Chris's cutter, and have him show me how to use it. If I need it often, I buy one. If I need it seldom, I borrow. Probably, if I buy, it will be Chinese.
                      The problem with borrowing a machine is you won't use it enough to learn what it will and won't do, and you won't be comfortable using it, and should it go bad while in your possesion, you'll feel obligated to get it repaired which could cost as much as a new Chinese machine. I understand your being hesitant about laying down the cash for a new machine you feel will only be used occasionally, but after a while your welding juices are going to start to stir in you and you are going to want your own machine, we all been there brother. Great fun and luck on what ever you choose to do.
                      Last edited by tackit; 07-22-2018, 09:33 PM.

                      Comment


                      • #12
                        The phrase neither a borrower nor a lender comes to mind?
                        If I was your neighbor I'd say sorry, but no, you cannot borrow my PAC. Asking to Borrow a PAC isn't
                        exactly the same as a cup of sugar? Ladder, or the phone to call the fire department.
                        No...it's something that costs more, someone sacrificed another pleasure for the ownership of and use of, and because, if it did break and you couldn't afford to buy your own, why would I think you could afford to fix mine if it chose then to crap out?
                        But before you get out of joint on that side of the coin, going in knowing what "we responding" have mentioned about the process, the cost of the equipment, and the hesitancy one has to purchase even a cheap one due to limited use, most who have the equipment enjoy the chance to make some cash pizza and beer money for being neighborly and most likely will jump in at a chance to do so.

                        I never mentioned it sooner but after reaching 1/4" in material thickness, the economic benefit of Oxy Fuel over PAC starts balancing out if you just look at carbon steels. By 1/2", comparable with oxyfuel. Above, Oxy fuel actually taking the lead.

                        Comment


                        • #13
                          Hypertherm is probably the best but like stated above. I use mine once maybe twice a year. I use oxyfuel way more often to cut parts out, heat and bend things, braze ect..... as far as size goes always buy a size or 2 bigger than you anticipate you will need. When I started in my own shop at home I made a horrible mistake and bought a MM252 and a synchrowave 200 as a pair. I quickly sold the 200 and bought a 350lx... used it a few years and sold it. Now I own a dynasty 400. The 252 is a fine machine and had residence a lot longer but I eventually sold it too and a XMT 350 with a 74dx feeder took its place. Should of bought once and cried once. Lesson learned
                          DYNASTY 400 now wireless
                          Coolmate 3.5
                          Sw320 speedway
                          Ck flex lock 230
                          2 torch buttons
                          A$$ loads of tungsten
                          XMT 350 CC/CV
                          S74DX feeder
                          Stick leads from here to China
                          A30 Spool gun that just sits there
                          Spectrum 875
                          ESAB SENTINEL
                          Old school Fibermetal
                          Acer Ultima Knee mill
                          Mazak lathe
                          Cincinnati lathe
                          Quincy 340 hp and 400 gallons of air
                          Homemade wood burner
                          A few other cool doodads and a pet Raccoon

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                          • #14
                            Amen.

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