WEIGHING THE BENEFITS OF PLASMA METAL CUTTING TECHNOLOGY  OVER OXYFUEL IN MANUAL CUTTING APPLICATIONS

Although oxyfuel metal cutting technology is widely used for cutting mild steel, plasma cutting technology is a rapidly growing option for many compelling reasons. Plasma technology can deliver much faster cuts with higher quality. It can cut many different types of metals, including painted, rusted or dirty materials. The same plasma system which can cut over 35 mm can also deliver excellent quality on very thin metals, down to 1-2 mm. And, since manual plasma operates on electricity and compressed air, not only are gas costs eliminated, but so are cylinder rental, pick up and drop off fees. These and other advantages mean that plasma is able to deliver significantly lower cutting costs per meter than oxyfuel in most applications. Furthermore, the ongoing and rapid evolution of plasma technology has continuously built on its fundamental advantages, making it even more viable in an ever-widening range of applications.

While plasma cutting may not fully replace oxyfuel for some applications such as heating and bending steel, or for cutting very thick (over 40 mm) mild steel, doing a total comparison between the two technologies reveals that plasma cutting is a more viable option for many jobs. Key attributes of plasma technology over oxyfuel are:

Cutting Speed
Roughly 90% of the metal cut in the world today is 25 mm thick or less, and in this range, plasma enjoys a tremendous speed advantage over oxyfuel – a minimum of 2 times, even at the thickest end of this range. As you move down in thickness, the speed increment is even more pronounced, and can easily achieve advantages of up to 12 times faster than oxyfuel. This speed advantage translates directly into a higher level of cutting output: more parts cut in less time.

Piercing Speed
For many cutting applications, inside piercing is essential. It can easily take up to 30 seconds to pierce 15 mm thick steel with oxyfuel, since the metal must be pre-heated to nearly 1000ºC; plasma can accomplish this in under two seconds. By the time you finish piercing with oxyfuel, you could have already pierced and cut several parts with plasma.

Cut Quality
Plasma generally produces better cut quality, which is also more consistent in comparison to oxyfuel. Overall, the technology produces less dross and that which is produced is very easy to remove. Also important, plasma cutting does not require as much skill to produce quality results as with oxyfuel. The most modern plasma torch technologies, for example, have nozzle shields that automatically maintain the proper height of the torch over the plate and are designed to be used with pre-cut templates, which improve operator control and hence cut quality. In addition because of its high cutting speeds, the heat input into the work piece is greatly reduced. Plasma completely avoids the problem of plate warping on thin materials (1-6 mm), which is a problem with oxyfuel cutting. In addition, modern plasma torches are easy to handle and control and offer excellent visibility to the part being cut. These factors also lead to improved cut quality.

Versatility
The ability to cut many different types of metal is essential in many operations. Because plasma is an electric arc process, it can do this easily, cutting any metal that is electrically conductive including aluminum, copper, mild steel, stainless steel, and more. Plasma can even cut rusted, painted or dirty metals. In addition, plasma can cut several plates stacked on top of one another. All of these are impossible to cut with oxyfuel. This amazing versatility opens up more opportunities and increases overall productivity.

Safety
High-pressure flammable gas and an open flame are hazards in many work environments, but nevertheless are necessary for oxyfuel cutting. In addition, because of the hazards involved with oxyfuel, a user must have expensive insurance. Special arrangements are necessary to transport the gases which also add to the costs. Plasma, on the other hand, completely eliminates these dangers and extra costs, since it does not require an open flame or any flammable gas. Plasma also uses a more focused heat (a smaller heat affected zone of 2 mm versus 12 mm on 18mm mild steel), greatly reducing  danger associated with the production of hot metals during cutting. Plasma also meets many of the government regulations and does not require the operator training that is legally mandated for oxyfuel cutting. As a result, using plasma means a safer environment with fewer regulatory issues in comparison to oxyfuel.

Costs
Many of the attributes above lead to one over-arching benefit: costs. With the overall safer cutting environment associated with plasma, and hence fewer safety regulations required and less overall chance of accidents, cost and potential losses are significantly reduced.  Faster cut speeds, better cut quality, higher productivity, increased versatility and less rework are not the only ways to reduce costs, but can help build a business with an increased array of applications available.

A New Generation of Plasma leads to enhanced benefits
The fundamental advantages of plasma outlined above are the baseline benefits of plasma technology. In addition to those benefits, plasma technology has continually evolved to bring down costs, increase quality and become more user-friendly. This evolution is an important factor in choosing the technology today because it has evolved rapidly even over the course of the last few years. Hypertherm has driven much of this evolution by developing more compact, more efficient, and dramatically “smarter” power supplies that drive even more favorable comparisons with oxyfuel. Because the company focuses solely on plasma cutting, it is more focused and specialized with the technology can better meet the specific needs of end users. Simplified operation, increased reliability, better torch technology, and smaller, economic systems have all been hallmarks of recent improvements in plasma cutting technology.

Easier Operation
Minimizing operator skills needed for plasma cutting has been a goal of plasma system manufacturers and there have been significant strides designing systems that are simply easier to use and maintain than oxyfuel. In mechanized applications, plasma systems can usually be integrated into existing oxyfuel control systems, making it fairly simple to add a plasma station to an existing oxyfuel system, providing the equipment is able to handle the higher cutting speeds. In manual applications, plasma is easy to set up, often including pre-set gas pressure controls, and allows simple power supply control, to ensure that just the right power is used for the job at hand.

New plasma systems are also designed to use minimal consumable parts. This means that operators use less time in changing out parts, which reduces downtime. Streamlined diagnostics displays also simplify troubleshooting and service for plasma systems.  Overall, new systems are designed to reduce both the initial investment and also ongoing costs such as training, maintenance and downtime.

Easier Repair
The old adage that less is more certainly holds true for the latest generation of plasma technology. The number of component parts in the power supply has been reduced to less than half those used for the older systems on the market. As a result of using fewer parts reliability is significantly enhanced and more performance can be had for the same or even a lower initial investment.

There are also features on newer systems that reduce the time and cost of maintenance and repair, such as easy access to components as well as an automated self-diagnostics program that performs at startup and while the system is running. This ensures that the system is operating at peak levels reducing consumable costs, increasing productivity, and enhancing quality.

Better Torches
New technologies have significantly improved the overall efficiency of plasma. Torch technologies in particular have seen leaps in technological development.  For example, the quick disconnect torch for easy and quick consumable change-outs have been vastly improved. Some torches include "smart" technology that sense the lead length and torch type in either mechanical or manual systems and sets the correct pressure requirement. Operating the system at the correct pressure ensures optimal cut speed, cut quality, arc transfer, duty cycle and improves the life of the consumables.

New torches also have features such as Hypertherm's Coaxial assist jet technology that provides greater arc stability for thicker cutting and higher cutting speeds. Torches are also employing double angled nozzle design for improved nozzle life. Improved strain relief at torch head/torch lead interface makes the torch easier to handle.

Lower Cost/Better Portability
In addition, plasma technology has enabled systems to come down in weight and up in overall performance. Today, single-phase plasma systems as light as 9 kilograms, are able to easily cut 12 mm. These systems open plasma cutting to a whole new range of applications, calling for increased portability. Considering all of the attributes of plasma mentioned above, not closely examining this technology as an option against oxyfuel is no longer an option.

Conclusion
In the end, every operation has to weigh the benefits of each technology to choose which is best. If a user only cuts very thick mild steel, or frequently needs to heat metal for shaping or bending it, oxyfuel is clearly a good choice.  If more versatility is required, calling for metals other than mild steel being cut, or if much of a user’s cutting requirements are 35 mm or below, then plasma is a technology that has some compelling advantages.

Compared to oxyfuel, plasma offers many benefits that are worth considering; faster cut speeds, better cut quality, less rework, higher productivity, more material flexibility, increased efficiency and lower total costs of operation which all will lead to greater profitability. Looking at a complete picture helps to determine the true cost of cutting metal and in choosing which technology is the best for each application.

About Hypertherm
Hypertherm designs and manufactures the world’s most advanced plasma cutting systems for use in a variety of industries such as shipbuilding, manufacturing, and automotive repair. Its product line includes handheld and mechanized plasma cutters and consumables, as well as CNC motion and height controls. Hypertherm systems are trusted for fast, precision metal cutting and reliability that results in increased productivity and profitability for tens of thousands of businesses. The company’s reputation for plasma innovation dates back 40 years, to 1968, with Hypertherm’s invention of water injection plasma cutting. The company has more than 1000 associates along with regional operations and partner representation worldwide.