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 alternative for many compelling reasons. The ongoing and rapid evolution of plasma technology has continuously built on its fundamental advantages, mak ing it even more viable in an ever-widening range of applications.

Breakthroughs in these technologies can deliver faster cuts with higher quality. In addition, plasma is able to cut many different types of metal, including painted, rusted or dirty metal. Plasma systems are also suitable for a range of metal thicknesses: from metal that's more than 35 mm thick to very thin 1-2 mm thick metal. Another advantage of plasma, it that is can operate solely on electricity and compressed air. You don't need to purchase bottled gas, so not only are these costs eliminated but so are cylinder rental, pick up and drop off fees. These and other advantages ensure that plasma is able to deliver significantly lower cutting costs per meter than oxyfuel in specific applications.

While plasma cutting may not fully replace oxyfuel for some applications, including heating and bending steel, a comparison of the technologies reveals that plasma cutting stands as a viable option for many jobs.

Cutting Speed 

Roughly 90% of the metal cut today is 25 mm thick or less, and in this range, plasma enjoys a significant speed advantage. At a minimum, you can expect speeds that are twice as fast as oxyfuel. And those speeds increase as thickness decreases, enabling speed advantages up to 12 times faster than oxyfuel. This increased speed translates into higher productivity which means you can cut more parts 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, because the metal needs to be pre-heated to nearly 1000ºC. Plasma, on the other hand, can pierce this in less than two seconds, greatly increasing productivity.

Cut Quality

While speed is important, quality is another driving factor when choosing metal cutting equipment. Overall, the cut quality produced by plasma is much better than oxyfuel. For example, there is less dross when cutting with plasma and the small amount of dross produced is very easy to remove. Also important, plasma cutting requires less time to master and produce quality results. Modern plasma torch technologies, for example, have nozzle shields that automatically maintain proper torch height over the plate and are designed to be used with pre-cut templates, which improve operator control and hence cut quality.

Because of its high cutting speeds, the heat input into the work piece is greatly reduced. With plasma you don't have to worry about plate warping on thin materials (1-6 mm), something that 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 several types of metal is essential in many operations. Because plasma is an electric arc process, cutting any material that is electrically conductive including aluminum, copper, mild steel, stainless steel, and more is made easier. At the same time, plasma cutting is able to cut several plates stacked atop 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. The heat produced by plasma is also more focused, greatly reducing the danger associated with the production of hot metals during cutting. It is not unusual to see a 2 mm wide heat affected zone with plasma, instead of the usual 12 mm zone encountered with oxyfuel on 18 mm thick mild steel.

Cutting Costs

Many of the attributes above directly affect one overarching benefit - cost. The combination of faster cut speeds, better cut quality, higher productivity, increased versatility and less rework is not the only way to reduce costs. Plasma can help businesses become more profitable because it allows companies to do more. Additionally, cost and potential losses are significantly reduced because businesses don't have to comply with as many safety regulations or worry as much about an operator getting hurt.

A New Generation of Plasma leads to enhanced benefits

These fundamental advantages of plasma form a baseline of benefits. In addition, 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. One company driving innovations within the industry is Hypertherm.  

For more than 40 years the company has worked to develop more compact, more efficient, and "smarter" power supplies. With a range of technologies that focus solely on plasma cutting, Hypertherm products aim to better meet the specific needs of end users.

Simple Operation

Minimizing operator training needed to properly handle plasma cutting equipment is a longtime goal of plasma system manufacturers. In mechanized applications, plasma systems can usually be integrated into existing oxyfuel control systems. This makes it fairly simple to add plasma 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 simple power supply controls, to ensure that just the right amount of power is used for the job at hand.

Higher Reliability

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 in earlier generation systems. Using fewer parts means 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 automated self-diagnostics programs designed to perform 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.

Lower Cost and 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 mentioned above, the close examination of plasma technology is a must for anyone who cuts metal.

Real-World Results

One company that has recently made the switch from oxyfuel to an automated plasma cutting system is Elmhults Konstruktion AB. The company, based in Almhult, Sweden, is a leading global manufacturer of steel transport containers. Owners and employees alike have seen increased benefits and manufacturing efficiencies since moving to a new integrated plasma system from Hypertherm.

Simplified operation, increased reliability, better torch technology, and smaller, economic systems underline the driving force behind the move and why many end users are turning to plasma.

"Prior to integrating our new Hypertherm system, we were using a normal flame torch," says Gosta Karlsson, owner of Elmhults Konstruktion AB. "While oxyfuel is a viable means of cutting metal, we found that the advantages offered by plasma provided the ideal solution for our needs."

As a leading producer of metal containers, the company utilizes more than 8 million tons of steel per annum. With such extensive usage it was important for the company to have a system that would provide high-quality cuts while also allowing for increased efficiencies. The new process is also a safer alternative. "The proximity of the flame is always a concern when using oxyfuel systems," continues Karlsson, "the new system, however, ensures that operators are not in a position to be harmed."

But what is a productive manufacturing line if efficiency is not targeted. "In the past we were forced to start and stop our system several times when using a torch. Now we have been able to increase our productivity by more than 25% and decrease our downtime significantly," comments Karlsson. With oxyfuel it took 15 minutes to cut a 12 mm thick piece of metal; now it takes 7 minutes.

Conclusion

In the end, every operation must weigh its own needs against the benefits offered by each technology before deciding which option is best for it. If a user only cuts very thick mild steel, or frequently needs to heat metal for shaping or bending it, then oxyfuel is probably a better choice. If more versatility is required, because metals other than mild steel are being cut, or if much of the metal is 35 mm thick or below, then plasma has many compelling advantages.

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.

 

 

For more information contact:
Yvette Leeflang
T: +31 (0) 165 596 932
Yvette.leeflang@hypertherm.com
www.hypertherm.com/eu

Hypertherm Europe BV

Vaartveld 9, 4704 SE ROOSENDAAL, The Netherlands

Phone: +31(0)165 596907

E-mail: yvette.leeflang@hypertherm.com

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# 2(32), 2010
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