|Lincoln Procut 80|
Plasma Cutters are pretty nifty things, and if you haven't heard of them and want to cut metallics, it is time you did learn of them. A plasma cutter is sort of an overheated welding arc with a strong force of compressed air behind it. It will cut any metallic that conducts electricity so it is usable on aluminum and stainless steel as well as iron alloys. There are typically controls for output amperage and air pressure. Plasma Cutters Cut very neatly and with a very narrow kerf. They also work exceptionally well on things that traditional 'hot wrenches' do very badly such as cutting very thin things (like exhaust pipes) or intermittent things like expanded screen.
|7/8's Vertical Cut|
The 'Business end' of a plasma cutter is a torch. The larger machines offer a process control torch (one that you can clamp in an automated cut out machine----or a hand held torch. The hand held torch is shaped not unlike a traditional OX-ACY torch with a trigger on it. Squeeze the trigger and it turns on the air and presently first off the arc. Then it works like an OX-ACY torch with the lever squeezed. There is no 'warm up' time, and indeed the metal is cut without warming it up much. If the metal is painted,for example, the paint won't be disturbed for more than half an inch from the cut.
The thickness of what you can cut is a function of the 'tip size' in the torch and the output amperage. You do need some serious electric power because as I said in many ways the plasma cutter is an over achieving arc welder. They use a DC ARC at 140 volts (compared to about 30 volts for classic DC ARC welding, and like lots of amps so as you can imagine the power in the input side has to be serious. Our first purchase of a plasma cutter was a Miller Spectrum 375. Its a cute little thing rated at 27 amps output at 90 volts. Input is 14 amps at 230 volts or 3.2kw. Consequently it will run on most all Miller engine drive welders.
The catch is that the output simply is inadequate except for really light work (muffler shops). If you read the ratings you will see it rated to cut 1/2" steel. Well, I guess it will, but so slowly that you will scream. In looking at the rating on ALL plasma cutters (not just the Miller), I suggest dividing the ratings by half and assuming that it the thickest you want to cut. Applying this rule, the 375 is usable at a reasonably speed on materials up to 1/4" thick and it cuts 1/8th inch as fast as you can move the torch. Likewise the Pro-Cut 80 is rated for 1 1/4" steel. I presume it will do it under some conditions. We have used it with 1" material with some success. It will even gouge through 1 inch material if you need to but the speed is not impressive and the problem is that you need to be very steady to do a nice job and at a slow speed being steady is a problem. If, however, you follow VanNatta's rule of plasma cutters and discount the rating by half and think of it as a machine good for 5/8" and less think steel which can be used for thicker if you have to you will be happy. You will find it faster and cleaner than an Oxy-Act system and a lot more convenient. While I have a little trouble imagining the operation of this machine on single phase power, it can be done.
I know I have digressed a bit as this is suppose to be a review of the Lincoln Pro-Cut 80. Popular sizes of the plasma cutters included the 27 amp size, a 55 amp size and an 80 amp size. After finding the 27 amp machine really unsatisfactory because we wanted to cut stuff that was too heavy for it (loggers don't fab with sheet metal), we decided to jump to the 80 amp model. Many years of experience has taught us that you never have a machine that is too big or two heavy. Rationally perhaps we should have bought the 55 amp class cutter (it is fairly happy up to about 1/2") we decided to go for broke (and about broke our pocket book). The challenge of the larger machines is that they use so much input power that you need a serious power supply. The Pro-cut 80 that we ended up with is documented for an astonishing 81 amps single phase 230 volt (18kw) or a more reasonable 44 amps 3 phase at 230 volts. (about 15kw). That is a lot of power. It is profoundly an issue if you don't have 3 phase power available. We don't, but decided to make it available by purchases a large engine drive welder.
|Ingersoll T30 Compressor|
This got us to looking at the specifications of the AC power output of the various engine drive welders. We have an older 16 horse Miller Bobcat. It did 8kw. this didn't look like it would cut it even with the 55 amp machine. The newer engine drives have 20 hp and will produce around 10kw (both the Miller and the Lincoln rangers). We considered dumping out older Bobcat for a Trailblazer, etc. but it would still be running behind the 8 ball. Of the two welders we have, the our old Miller Big 40 was the best welder for welding, but the most tired, and lamest for AC power. We decided that 35 years was enough and began shopping the choices for a big new engine drive welder with one of the requirements being a lot of AC power to drive a hummer of a plasma cutter.
We looked at both Miller and Lincoln. Both manufactures offer a variety of machines that will produce 12kw 1 phase power. The 12KW machines are good for the 55 amp plasma cutters but.... the idea of 3 phase power on welders is pretty new, with Lincoln only beginning to offer it in 2005 on their new line of Vantage Welders. Miller has had it around longer but requires you to buy their Deluxe model and buy a 500 amp welder to get more than 15KW.
This led us to be the first kids on the block with a Vantage 400 from Lincoln is a brand new product first offered in the 4th quarter of 2005 (and we bought one in the 4th quarter of 2005). It has 19kw 3 phase and is reviewed elsewhere on this site. Since our plasma cutter was to be a truck mount, we stuck it in a compartment in the service body and wired power into the compartment from the welder. We left plenty of air circulation space as the Plasma cutter needs to breathe to cool itself. Since it clearly works much more efficiently on 3 phase we implemented the 3 phase wiring. Actually we had little choice. You implement 1 phase on the machine by dropping the 'red leg' and '2 phasing' the machine---but the single phase power draw was way beyond our capacity so we used the 3 phase solution (preferable anyway). We learned about NEMA 15-50P and 15-50R plugs and receptacles and made a short extension cord to run from the welder to inside the service body box. We also bought the 50 foot torch umbilical so we could get the torch 50 feet from the left front corner of the service truck where we installed this cutter. --- You can take the cutter out of the truck, but it weighs 95 lbs so removing it is not preferred.
The bottom line is that we have just assembled a service truck and it doesn't even have a bottle compartment on it. However, we have another service truck that is usually not far away that does have bottles. What you can't do with the plasma cutter is to preheat something. Likewise we don't see it as a replacement for an Carbon Air Arc where you might use it for blowing an old weld out for what ever reason. Of course, if you have an engine drive welder capable of driving this cutter it also has the horsepower to operate a formidable carbon arc.
|Ingersoll Rand Compressor electrified|
At the moment we don't have a lot of hours on this cutter, but so far so good and we really love it. We have found that for most things we have been cutting so far 1/4" to 3 /8's materials (both flats and rolled (angle iron etc) it is plenty happy turned well down from full blast to around 45-55 amps output. This tells me we could have gotten buy with a 55 amp machine but the 80 amp one gets a 100% duty cycle at 45 amps so the good news is we aren't pressing it to the wall doing what we are doing---a good thing.
Being able to run the plasma-cutter for our purposes at less than flat out all the time had another benefit. It needs Air---really clean dry air) and about 7 CFM of it to operate. This implies the need for an air compressor and a lot of filters. ON a service truck you have the issue of how to power the compressor. Compressors take a lot of power (about 1 hp per 4 CFM at best). The plasma cutter wants 7 CFM at a relatively low 70 PSI (120 MAX), but if you want to also run impact wrenches from your service truck you want lots of air with lots of pressure. (Some service trucks are using compressors as large as 70 CFM) to reduce the need for a large air tank. You can power the compressor directly from the truck PTO---or use an under the hood mount, or indirectly from the truck engine via the hydraulic system for the crane, or you can use a separate gas engine. We had a 30 CFM compressor with a 10 Hp Kohler Gas motor to mount in the service truck. However the thought of starting the gas motor every time we wanted air sort of turned us off. Noting that we had some electric power to spare, we swapped the 10 hp gas motor for a 5 hp 3 phase electric motor (and slowed the compressor down a little). This allows us to have an electric compressor on or service truck and power it off of the welder. Electric motors grab lots of amps when they start, but we worked around that by accident. Gas engine compressors don't shut down when up to pressure---so when you substitute an electric motor for the gas engine, it doesn't shut off when up to pressure, the compressor just unloads. This way when you want air you start the compressor when nothing else is going on and the motor just runs. The 12 amps 3 phase that the compressor motor may draw presents a theoretical conflict with the plasma cutter at full tilt, but since we don't run the plasma cutter at full output the potential for overload is only in theory.
Making Clean air is not as easy as it seems. Air compressors do not make clean air automatically. Water, oil and crud are all things that may inhabit compressed air. You deal with this with filters and filters to the filters. The plasma cutters usually have a last chance filter or settling bowl on them, but you really want to clean up the air before it gets there. In the first photo on the right you can see our solution, or at least part of it. The air comes from the compressor in the lower hose and first goes into a dryer that is suppose to catch the water and condense it into the settling bowl. Note we have a "T" and a snap coupler before that. If we want to feed the manifold with a different compressor it can be plugged in there. Once the air goes through the water remover we then have another split. We have another snap coupler--this allows us to get dry air for filling tires, and of course the branch for the plasma cutter goes up to the black canister filter. The canister has an particulate, oil / water filter in it which exceeds the specs required for the plasma cutter. On the main manifold there is then a PIG for adding oil to the air and two more connectors. That is where you hook an impact wrench. The pig bleeds a little oil into the air to lubricate the wrench. The black tube leaving the canister filter (actually a truck air brake line) goes to the left front compartment on the service body where the Plasma Cutter is located. But Alas, we are still not done. Because the plasma cutter wants to see a maximum of 120 lbs pressure, and the air compressor over achieves we have a pressure reduction valve in there which has its own water catcher on it. From the pressure reduction valve the air then goes to the Plasma Cutter.
The second of the pair of photos shows the compressor. We have since built a steel box around it to protect it from things that might come swinging into the back of the truck via the crane. As is common the motor and compressor are sitting on a 30 gallon Air tank.
The compressor shown with the engine above the is current model of the Ingersoll Rand T30 compressor. It is a 2 stage compressor capable of 30 CFM at around 100 lbs or 24 CFM at 175 lbs. The compressor is rated at a maximum RPM of 900. The gas engine turned at 2850 and the electric motor at 1850, so we could not just move the pulley from the gas engine to the electric motor. IR usually puts a 7.5 horse single phase motor on this compressor. We only powered it with a 5 horse electric, but we compensated for this by adjusting the compressor RPM down some from the max, and we use a 3 phase motor which inherently has better starting characteristics under load than 1 phase motors.
|Lincoln plasma Torch|
|New drag cup|
|Toasted drag cup|
|New tip and electrode|
|Burned out tip|
|Tip damaged by blowback|
|Electrode eroded beyond usable|
|Abused but still usable tip|
|Drott Rear outrigger box|
One of the questions that we had in buying the plasma cutter was how well it would work in scrapping. The value of the plasma cutter in production work is well understood. They are fast, responsive to computer control, require no warm up time and have a narrow neat kerf.
We are loggers, not iron assemblers, but we have old iron that needs to take a trip (likely on a slow boat to China). The photos on the left show working on the lower unit of a DROTT 80. These things are monsters and the iron is heavy. The outrigger boxes are generally made of 1/2" with heavier here and there. The main frame is boxed 7/8"---sometimes multiple layers of it.
I had been concerned about consumable costs (torch tips) as they speak of a couple hours of life in the book---but experience of working all day with the torch was that a set of consumables would last most of a day. I don't know if that is a commentary on my work habits or what, but after 2 days of cutting on this machine I had put in two sets of consumables. That is cheaper than buying Oxygen.
I used it here on this machine set at 74 amps. --- not wide open but most of the way open. The results are satisfactory. The great thing is that it cuts the material without heating it up, so you can cut off a piece and then throw it out of the way way without getting burned (if you use just a little discretion. and in a few minutes with gloves you can even touch the recent cut.
In terms of speed, there is no delay in warming up the iron, just squeeze the trigger and go. You can move at super speeds on light material (such as 1/4" or less). Half inch cuts easily--and faster than any hot wrench I"ve used. On this machine the heavy parts are mostly made of 7/8". The manufacturer claims 11 IPM with 1" and 18" IPM with 3/4" which are numbers that I can believe.
You do run into problems when the metal is layered up 2 and 3 inches deep. With an OX-ACY you can kinds of hog though thick spots and whittle on them, but the plasma doesn't whittle well, and when you reach its capacity, well you have reached it. Obviously to do scrapping you need a portable electric supply, but we have accommodated that with the Vantage 400 which is well suited to run the Pro-Mac 80 even while powering the electric compressor to provide the air supply.
The series of photos on the left shows what happens to the Lincoln consumables over time. They are consumed. This is expected and normal. However my word of warning is about the drag cup. It is best used for clean straight cuts on thinner materials. If you have it on for heavy cutting or thick plunge cutting, or when it is in poor condition as shown in the 'used photo', it tends to catch the cut flame and reflect it back against a side of the tip. This is what happened on the tip with the side eroded out. The final photo of the tips shows a well used tip that is still usable. This was a tip used without the drag shield. My advice is to avoid using the drag cup when scrapping or working on irregularly shaped things where the risk of 'blow back' is increased. Also pay attention to the condition of the drag cup because when it is misshapen, its ability to reflect the fire back on the tip is enhanced and this is not a good thing.