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Just the facts...about plasma cutters

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  • Just the facts...about plasma cutters

    OK, I admit, this gets down right confusing, but the facts need to be put down on the table, written in black and white for all the world to see. What are the actually performance ratings on plasma cutters. Lets examine a few things...

    1.) You have to have good clean power. 120V single phase might run your grinder OK, but for plasma, you need more power. 240V single phase is great for the small or home shop. For power users, you may want to have 240V or 480V three phase. We know that all the plasma manufactures make different size machines and have different input power requirements for each. This is a given, depending on your application and available power sources.

    For my application, I have 240V single phase power available on a 50A 2 pole circuit breaker. Also, available Bobcat 225 NT has 10 KW of 240V 40A power on the panel.

    2.) You have to have clean, dry air at the proper input air pressure (PSIG) and cubic feet per minute (CFM) for the plasma to work properly. OK, Miller has revised its requirements on a few models to show what pressure and air flow needs to be available to the connection port on the back of the machine as opposed to what the internal regulator of the cutter will allow.

    For my application, I have 90 PSIG air available capable of flow to 5 CFM. I have a moisture trap I use with paint guns and will be purchasing a Motor Guard filter for the plasma. Adequate, clean, and dry air is not an issue.

    Now the confusion starts. Cutting capacity of specified cutting units. Esab, Thermal Dynamics, Hypertherm, Miller, Hobart, Lincoln all have plasma cutting units available in various power ranges and sizes. We have seen all the hoopla over the new 27A portable units that weigh next to nothing compared the the regular 27A unit of similar size, i.e the Miller 375 and 375 Extreme,Thermal Dynamics PakMaster 38XL, Hypertherm Powermax 380 and Powermax 30, Lincoln Pro-Cut 25, and Esab Handy Plasma 380.

    All of the above listed machines carry a rated capacity of 3/8", quality of 1/2" and sever or 5/8" inch using proper stand off from material, proper cutting technique and speed. This information is from the unit manufacturers. Some have reported what the factory reps have said or demonstrated at trade shows, the above mentioned cutting abilities.

    Then we start reading how people can't get the same above machines to do what the factory guys say or show. What is the truth? Are the factory guys lying in their product literature? Are the demo machines at the trade shows souped up compared to what we can by at the LWS? Or are people trying to do things with their machines that they should not, such as operating outside the performance envelope?

    My cutting application 90% of the time runs in the 1/8" to 3/8" range. On occasion, 5%, I will see 1/2". Cut length and duty cycle will indeed play a part in this. My cuts on the smaller sizes will be longer, 12" to 48" or more in total length. On 1/2", length will be just over 14" total run. (Hole for 4" Sch. 40 column pipe.) From the tech specs in the literature, I should be able to do my hole in the 1/2" plate within the 35% duty cycle at full 27A power on the 27A Class machine from any manufacturer. The pictured sever cut in the literature looks better than my O/A cuts in thinner metal.

    For my application a 27A machine appears to do all I would want to do. A 40A machine would be nice and a 60A would be great, but space, portablity, and budget come into play. A 15% gain in duty cycle at 50% or 100% more price doesn't compute.

    So what is the truth? Are the manufacturers ratings correct? Or are the ratings bloated by 2X, i.e. only half of what the manufacturers say? I want to hear from everybody on this. I want to hear from guys who only use their machine in the shop; those who take it everywhere with them; those who have been using the same trusty machine for years; those who get the latest toys because they have to have it; the guys that design them and build them. Lets the debate begin with input from everyone.

    Lets get input and output about plasmas for guys like me who want to get one, have been reading up on them, asking about them, has an idea at what he wants, but is still confused about what to actually get. After all, this forum is about information and education.

    Thank you and best regards to all who answer.

    '77 Miller Bluestar 2E on current service truck
    '99 Miller Bobcat 225NT for New Service Truck
    '85 Millermatic 200 in Shop

    '72 Marquete 295 AC cracker box in Shop
    '07 Hypertherm Powermax 1000 G3 Plasma Cutter in Shop
    Miller Elite and Digital Elite Hoods

  • #2
    I vote for " operator performance ".

    I purchased a 375, the heavy model. When I first used it, it cut steel but was not what maybe I thought it should be. I then went on to research in detail the requirements of the machine.

    Power was 220V , had driers inline, and flow from the compressor was overly sufficient. It was time to do some homework. Looking at what I had made me think, OK the compressor is sufficient but is the amount of air actuallty getting to the machine. I switch out the 25 foot, 3/8" airline for 1/2" airline and saw a performance improvement. The original airline was a bottleneck in air delivery.

    Now today, a couple of months later and more experience with the machine my cuts have vastly improved.

    Plasma Cutters like MIG Welders are a new machine for me.

    Remember the first time you did a TIG weld? MIG Weld? Stick weld?

    How do todays welds compare to that first one?

    I recall a thread where a use was complainging his plasma cutter was not working, he took it in had it checked out and it was replaced. The new machine was not doing much better. To cut this short he was using an insufficient compressor ( low CFM ) and to add to that NO DRIERS inline. Now tack on his lack of experience and you have the recipe for dissapointment.

    Even with all this knowledge gained as a result of this forum I was not so sure. I had a neighbor who is much more experienced come over and check me out. He went over my system, checked everything and proceeded to do some cutting. Well after he was done, I knew that *I* had some learning to do. The cuts he made with my machine did not look like the cuts I had made.

    It's a new tool, and I realized it will take some time to become proficient.


    • #3
      I am new to this forum as a contributor, but have been reading it for a while.

      I believe the plasma cutters will do as the manufacturers state they will. However like any other tool each user may well see different results.

      Heck something as simple as a 20 ounce framing hammer can get different results in the hands of different users. One user may be able to bury a 3 1/2" nail in 3 strikes and another user may take 8.

      I don't think you should expect to take a Plasma Cutter out of the box and immediately duplicate results they were obtained by an experienced user. This of course assumes that all other parameters are the same.

      I cannot emphasize the need for FLOW RATE and DRYNESS of air.

      If you suspect the cutters at shows are 'juiced' to obtain unusual results, ask the demonstrator to allow you to try. I know the guys at the Miller Road Show allowed me to use the same cutter he was using, I also know his cuts were much better than mine were.


      • #4
        Thank you harcosparky and Wildweasel. Yeah, I know what you mean about it taking time to become proficient with a new tool or doing something different. My first stick welds look terrible to what I can do now and there is still room for improvement. My MIG welds are better and stronger now and not a piled up mess like they used to be and yes, there is still room for improvement and learning as I go. Much the same with my O/A cutting. The more I use it and take the time to adjust my heat and work the torch with the proper tip for the job and the right height above the work and with the right travel, my cuts do get better over time. I too suspect the same will be true with plasma. I have used one once, looked like a 125C and I was cutting expanded metal with it, it was sweet and fast. However, my first licks with it looked kinda bad. The more I cut with it and slowed down and steadied the torch handle, the better my cuts with the plasma were. This was several years ago with another employer.
        I don't think Miller or any of the other Plasma Cutter manufacturers "Juice" their machines to sell product, but you have to throw that out there to see what people will say. Its like the Magic Bullet and the Second Gunman on the Knoll. What I want to do is separate the facts from the fiction so all may learn to become more proficient with plasma. Guys thank you very much for your input. What do others have to say. Harcosparky, I will add what you said about the airline to the setup in the shop or if this thing was ever taken out on the job. Got to have air flow with less restrictions. Thank you.
        '77 Miller Bluestar 2E on current service truck
        '99 Miller Bobcat 225NT for New Service Truck
        '85 Millermatic 200 in Shop

        '72 Marquete 295 AC cracker box in Shop
        '07 Hypertherm Powermax 1000 G3 Plasma Cutter in Shop
        Miller Elite and Digital Elite Hoods


        • #5
          I can't remember the title of the thread, but we've been contemplating this for a while in this forum. Most respondents (my recollection) said they felt actual cutting performance was 1/2 the rated capacity. I've personally been posting about my usage of a 2050 which is rated to cut .875 and sever
          1.250. I felt the machine had issues just getting through .75 and cuts didn't look ANYTHING like the pictures in the ads. My machine can utilize a handheld OR machine held torch. I would not be surprised AT ALL if the companies connect their power supply to a machine held and guided torch to get the incredible cuts they show in product ads. The guy I bought the machine from professed to using it a lot (unknown actually - he had it for one year) his cuts looked nice, but that was on .125 sheet.
          I have the power for the machine.
          I have the air, but didn't try the larger diameter air hose (you can bet I will)
          I have the Motorguard (it does stop the moisture)
          I have TIG, MIG, STICK, and O/A experience at a level below the pro but above novice.
          I have much more cutting to do: Probably 40 to 60 inches combined on 1/2 steel plate, some good lengths on .25 plate, and I need to cut 6 pieces of 6" pipe .25 wall. (total combined cut length on pipe about 180 inches) and around the pipe no less which is sure to test my skill.
          I am the type of person who will come back and report on my own progress with the machine especially since I've been voicing my disappointment here.
          When I feel my technique has improved and I have more under my belt, I'll re-state my opinion good, or bad.
          Look for the previous thread where I described in DETAIL the usage of the machine and the cut. I'll even try and get pics of the cut. I will be cutting this weekend and will get back to this thread.


          • #6
            I have a Cutmaster 50, have had it about 4 years.
            I've also used a larger machine a few hours.
            My take is the machines will do about what the mfgs.
            claim under ideal conditions ( like most tools ).
            If I were buying another unit I'd figure about
            85-90% of the mgfs. rating and would not be unhappy
            in the "real world".
            I've been very satisfied with the unit I have, It was
            delivered to me as a demo....if it didn't do what I wanted,
            I could return it for something else.
            One of the advantages of dealing with a local dealer...
            Dave P.
            Edit.....just saw you wanted to pierce and cut 1/2in
            material. That would make me vote for a 40amp machine.
            I don't think you will be happy with the smaller units.


            • #7
              I've spoken to really nice guys at Miller three times on my cutter. According to Miller, the machine won't pierce better than about 1/2 the rated cut. So, for my machine (spectrum 2050) Scott said I shouldn't try and pierce more than .40 (about 1/2 of .875).

              This is a different topic from the people in the posts saying they thought actual cut performance was 1/2 the stated capacity. That was their opinion of regular cutting.


              • #8
                i think the key here is "under ideal conditions". If you plan on using it daily and time matters to you, go bigger. If your OK with the extra time and effort learning what "ideal" means then follow the manufacturers. I bought my 375 for my self as a toy, i stuck to my budget and got the best machine for me. if i were doing this for a living i would go at least a step bigger maybe 2. You don't buy a dynasty 200 with the intention of welding 1/4" plus alluminum all day, but with the the right gas and preheat its doable on occasion, same applies to the PC.
                Dynasty 200 DX
                Millermatic 175
                Spectrum 375
                All kinds of Smith OA gear


                • #9
                  FM117, thank you for the information on piercing a hole. My dad has told me, even with O/A, in thick plate, i.e. 1/2", mark off your hole, drill a hole with a drill as a start point and cut from there. It sounds like the same rule applies for the smaller plasma units as well. I can understand needing more power for piercing but there are ways to work around the issue. From what I have read, the smaller machines will start a cut from an edge without trouble, O/A is the same way. It is all a matter of time, patience, and technique. Thank you for you input.

                  This is a good start guys, everyones input and experience is needed and greatly appreciated. When my dad gets the plasma cutter for our shop, I will post what we got, how well it works, and how the learning curve goes.

                  Drewworm, I had read somewhere that one person was running a moisture trap on his air line, a moisture filter at the tap point on the air line where his hose to the machine connected and then two motor guard filters/dryers at the plasma machine itself. I think local weather and humidity dictates the amount of moisture removal gear one has to have to do the job. Here in semi-arid West Texas Panhandle-South Plains I will not need the moisture traps and filters that someone in Houston might require. Also, I don't need compressor oil getting into the plasma either. We are planning on using a moisture trap and the Motor Guard filter. If we need to get more drying capacity, we will add it where it is most effective and will let everyone know what we have to do, for our conditions here. Again, Drewworm, thank you for your input.

                  '77 Miller Bluestar 2E on current service truck
                  '99 Miller Bobcat 225NT for New Service Truck
                  '85 Millermatic 200 in Shop

                  '72 Marquete 295 AC cracker box in Shop
                  '07 Hypertherm Powermax 1000 G3 Plasma Cutter in Shop
                  Miller Elite and Digital Elite Hoods


                  • #10
                    Even without needing to pierce, I'd still want a
                    40 amp unit for cutting 1/2 in material.
                    Take a piece of material to a dealer and ask for
                    a demo, that will answer the question to your
                    Good Luck
                    Dave P.


                    • #11
                      I don't know much about water molecules, but I suspect the molecule is the same size everywhere. It's probably the amount of molecules present that changes.
                      My Sears water trap on my compressor only catches molecules down to 80 microns. I consider that my first line of defense for nailers, sanders, and plasma.
                      The Motorguard goes down to .05 micron and catches everything. Hint: The water will trap in the Motorguard and there is no way to let it out. (My Sears trap has a pet****). I open my Motorguard and let it dry out. The manufacturer recommends replacment of the filter media WEEKLY under regular use.
                      Different compressors make more/less water than others. My sears jobbie runs at high RPM and makes loads of water. The nice, professional, US made "real" compressors make air at much lower RPM and don't heat the air quite as much which makes much less water in the first place. I also add tool oil at the tool and don't introduce it into the air line.
                      Good luck.


                      • #12
                        Miller edited out pet**** - I guess I should have tried something like "petrooster"???? HAHAHAHA
                        Anyway, the thingy with the lever that lets water drain out.
                        Anyone got a pic of a "petrooster"?


                        • #13
                          Now that's funny!
                          Maybe you could call it a pet*****?
                          I wonder if that will get by?
                          Sorry I just couldn't help myself.
                          Dave P.


                          • #14
                            Didn't get by. I'm thinking you wrote pu$$y. See if that works.


                            • #15
                              petc0ck should work.

                              for that matter so should petcöck, petcõck, petcôck, petcóck, petcòck and pet

                              sorry I'm done now