Pondering plasma?

As a business grows, new needs inevitably arise. Some fabricators will need to bring their cutting capabilities in-house while others…

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As a business grows, new needs inevitably arise. Some fabricators will need to bring their cutting capabilities in-house while others will need to expand on their pre-existing operations. In these instances, fabricators are often faced with the dilemma of choosing between fiber laser or plasma cutting technologies. Making the right choice hinges on a handful of important factors and each individual situation is unique, which means there is no universally accepted, dead-set solution to choosing one over the other.

The two predominant options for the production cutting of metal up to 2.5 in. thick are fiber laser and plasma. While there are similarities between fiber laser and plasma cutting, each technology has unique characteristics that best serve specific applications. When the decision is finally made, it typically comes down to material type, cut quality requirements, productivity and cost.

The piece cut with plasma (top) shows a much cleaner edge than the piece cut with fiber laser (bottom).

Cut quality and angularity

Fiber laser uses a concentrated beam of light that creates a narrow and precise cutting line through the material. Lasers leaves a thin kerf (width of cut) and low angularity, making it ideal for cutting fine features, especially in thinner materials.

Plasma, on the other hand, cuts material by producing high-energy, ionized gas that forms a plasma arc. While older plasma systems typically produce a wider kerf and greater angularity than fiber laser, the latest high-definition plasma technology produces accuracy and angularity far better than previous generations and is well-suited for most applications.

While the angularity with a laser is about 1 degree tighter than plasma, Hypertherm’s XPR line of “expanded” high-definition plasma systems delivers a cut quality that is smooth and consistent. The result is perfect for any next step, whether it’s welding, coating or painting.

According to Kristopher Rich, director of product management and marketing for heavy industrial business at Hypertherm Associates, while the typical plasma systems tend to lose that tight angularity and edge quality as the machine ages, Hypertherm’s technology avoids such problems.

“With our XPR family of plasma cutting systems,” he says, “your first cut and 500th cut are indistinguishable. Along with our other proprietary technologies that extend consumable life and protect the system under adverse conditions, that’s one of the greatest advantages with XPR – the consistent cut quality over life means you can confidently cut knowing the end result and move to the next workstation with minimal clean up. That means your productivity soars and operating cost is driven down.”

For many fabricators, edge quality determines the success of downstream processes. For plasma, the surface finish of the cut edge is typically very smooth, with few of the striations or “coin edges” that laser cut parts can sometimes display. A smooth cut surface finish can be important for perception of quality, exposed edges, or the ability to go straight to paint or weld stations.

“If a part has an undulating, striated cut surface,” Rich says of the outcome of some laser cuts, “that has to be cleaned up so you can butt the parts together well.”

Everything from angularity to the smooth-cut edge is important for the success of downstream processes. The “expanded” high-definition plasma cutting technology from Hypertherm offers consistency from the 1st to 500th cut.

Cost considerations

Although fiber laser processes are improving, plasma outperforms laser when cutting materials that are imperfect due to paint, oxidation or mill scale. Rich says that most fab shops and metal service centers must store their materials outdoors, where it is prone to rust and corrosion. To accommodate fiber laser tech, the alternative is purchasing laser-grade materials, which are expensive, or storing the materials indoors, which is also cost-prohibitive for most shops.

Otherwise, to cut material that may have some of these surface imperfections, it must go through a manual cleaning process or a laser vaporization pass, both of which drive up cycle time, negating any cutting speed advantage that laser technology might offer.
That added cycle time can be a real dealbreaker for some shops.

“As long as the material is conductive,” Rich says, “plasma cuts it. It doesn’t matter what’s on the material – plasma eats right through it. That is not always true for laser.”

Return on investment is also a topic to consider when making the decision between fiber laser and plasma. Fiber laser cutting systems can be two to five times more expensive to purchase than a comparable plasma cutting system, driving payback periods for that investment to be many times more than a plasma system. Plasma systems see an ROI in 12 to 24 months, freeing up cash to make other investments.

But what about material thickness in the plasma versus fiber laser debate? Rich says in Hypertherm’s calculations, lasers can be as cost efficient or better than plasma when the material thickness is 0.39 in. or thinner. However, once the thickness begins to ramp up, the cost advantage quickly changes to plasma.

“We know that for people who are cutting medium thick to thick mild steel or non-ferrous metal,” he says, “plasma makes sense almost 100 percent of the time, in part because the laser is a gas and power hog. It uses an enormous amount of gas and electricity in those thicker metals, and that is what drives operating costs higher.”

Often, the costs associated with fiber lasers tend to sneak up on new owners. Therefore, it’s important to determine if they have the infrastructure to power a laser and if they have the appropriately sized tanks to store the gas or must buy a gas generator.

“Some of our customers have had to invest in a new tank farm to ensure the right amount of hydrogen or nitrogen is on hand,” Rich says. “Or, they had to go buy a gas generator. These are hidden costs that people don’t think about up front.”

The XPR line of high-definition plasma cutting machines brings advancements that make plasma a true contender with fiber laser technology, especially with thicker metals.

Matters of maintenance

Fiber laser users benefit from having fewer consumable parts involved in the cutting process. For example, lasers don’t have torch heads like plasma technology does, and these include numerable parts that must be replaced. While this drives down the number of components to potentially replace during regular operations, consumables tend to be only a small portion of the total operating costs. Fiber laser maintenance costs tend to be higher overall than plasma due to the highly technical nature of the repairs. Rich says fiber lasers are highly sophisticated with high-accuracy motors, precision process heads and delicate optical lenses.

“The training level of technicians has to be higher,” he says. “Basically, you need to be an electrician to work on a fiber laser, and unless it’s a huge company, most can’t afford to have those people on staff. That’s why most fiber laser users often contract with a service organization for regular maintenance.”

Rich also points out the fact that the low-cost laser companies, often from China and Eastern Europe, present even more maintenance challenges.

“We hear a lot of reports that service is either spotty or non-existent,” he says. “Buyer beware.”

Plasma systems, however, are highly robust, often working in the world’s most severe industrial environments. When Hypertherm surveys its customers, Rich says a common response is that they “love plasma because it sits there and runs – the technology is reliable and robust.”

Also, should parts need to be replaced on a plasma machine, rather than having to take it to a “clean room” that is free of dust particles in a dedicated service center, “in-house maintenance teams can fix plasma.”

See how Hypertherm’s XPR plasma technology was used to cut materials for one of the world’s largest track and field arenas.

Making choices

Given the percentage of production facilities that have fiber laser and plasma technology on the floor, there’s obviously no reason to go completely laser or completely plasma. As Rich says of the metal fabricators he’s spoken to, “almost 100 percent of them say ‘plasma will always have a place in our shop.’”

“One of the things I really like about this company is we take the time to really understand our customers,” he says. “We believe in recommending the right thing for the customer. Look at your situation and work with teams that can help you think through the costs as well as your upstream and downstream requirements before you make that decision.”

Hypertherm Associates

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