Welding Digest

In metal fabrication, there are several cutting methods to choose from, the most predominant options being plasma and fiber laser. While there are similarities between fiber laser cutting and plasma cutting, each technology has unique characteristics, advantages, and disadvantages that best serve specific applications and business needs. Some major factors to consider when choosing between plasma and fiber laser are cut quality, material thickness and condition, initial investment, operating cost, and maintenance. 

Variables to Consider  

Fiber laser cutting uses a high-energy beam of light that creates a narrow and precise cut through the material, which can leave a thinner kerf and low angularity, making it ideal for cutting fine features, especially for thinner materials. Similarly, plasma-cutting technology produces high-energy, ionized gas that forms a plasma arc to cut through the material. While plasma is often viewed as producing a less-precise cut, the current generation of high-definition plasma cutting units produces part cut quality that far exceeds most customer requirements and rivals fiber laser. 

Cut quality considerations when making a choice between plasma and laser include the following: 

• Fiber lasers typically yield ISO 9013, Thermal cutting, range 1–2 cuts (a measure of cut angularity). High-definition plasma usually yields ISO range 2–4 cuts. This is important for companies that want weld-ready parts straight off the table. 
• Plasma-cutting processes have been perfected over the years, yielding surface finishes on cut edges that are smooth and straight with minimal oxide layers and dross. Plasma-cut parts require minimal secondary operations prior to welding. While fiber laser is improving, the cut edge surface finish is often rough, with significant dross and oxide layers, especially in thicker metals over 12 mm (0.5 in.). 
• Fiber laser provides a narrower kerf than plasma, which has the benefit of allowing for slightly better plate utilization and fine-feature capability. While this is usually an advantage, thin kerf size can cause issues with removing parts from a nest on thicker plates. For thick plates, parts can be difficult to remove from the skeleton and need to be hammered out. 

While fiber laser kerf size and angularity capabilities are compelling, plasma has advantages in cut quality to easily meet most customer requirements. 

Plasma — The Versatility Champ 

Fiber laser processes are improving with respect to imperfect materials; however, they still require either specialty-grade materials, manual cleaning, or a precut process to vaporize the coating. Plasma is highly versatile and can cut almost any conductive material, even if it’s rusty or coated. 

When it comes to plasma vs. laser cutting, additional things to keep in mind are the following: 

• Rust, mill scale, and other contaminants impact fiber laser cutting and can lead to inconsistencies and difficulty cutting.  
• Precutting operations such as bead blasting, chemical washes, and other cleanup are required to get a consistent fiber laser cut. 
• Alternatively, material to be cut with fiber laser needs to be stored indoors, which could consume shop floor space and increase costs.  
• If the material is conductive, plasma can cut it. Regardless of corrosion, coatings, or painted surfaces, plasma reliably slices through imperfect materials. 
• The greater standoff distance (the distance between the workpiece and the torch) of plasma means that material variations or tip-ups are less likely to interfere with the cutting process compared to fiber laser.  

Often overlooked, the workpiece condition can drastically affect the cycle time to perform cuts, significantly affecting overall productivity and costs. Plasma leads the pack when it comes to material cutting versatility.  

Cutting System Costs and Safety 

Fiber laser cutting systems are two to five times more expensive to purchase than comparable plasma machines, leading to longer payback periods. Plasma systems can often recover capital expenses within two years or less, freeing up cash for other investments. While fiber laser often cuts faster and at lower operating costs for thin materials, plasma holds the advantage when cutting thicker metals, offering greater productivity and lower operating costs. 

• While fiber laser is very efficient at cutting thin metals, the operating costs of plasma are lower once cutting thicknesses reach 12 to 25 mm (0.5 to 1 in.). 
• Many of the operating cost differences are driven by the cost of electricity and gas consumption. Plasma cutting processes have been refined and perfected over the years, while fiber laser is still catching up. Whether it is the direct operating cost concern or the environmental impact of electricity and gas usage, plasma is the champion for thicker metals. 
• Fiber laser requires enclosures and material handling for safety concerns. This fixed cost drives the initial investment much higher.   
• While material handling is sometimes seen as an advantage for fiber laser, plasma tables can achieve the same throughput by lengthening the cutting bed, creating the same productivity at a lower cost. 

Saving Time and Money 

Fiber laser has fewer consumable parts but higher maintenance costs due to complex cutting head and motion control components. Plasma systems are robust, often working in the most severe industrial environments, while fiber lasers may require repair only by authorized service centers.  

• Fiber laser systems are also more sensitive to dirty shop environments compared to plasma systems. Contaminants in the environment can affect the optical components and precision drives, reducing laser accuracy and uptime. Regular cleaning and maintenance are crucial for fiber laser systems to maintain their performance. 
• Plasma systems are less complex and more robust, which allows for simple, in-house maintenance.  Plasma is more suitable for harsh work environments. 
• The lure of low-cost laser manufacturers often comes with hidden costs. These companies typically keep costs low by offering limited service. It’s initially attractive but may drive downtime when the laser system breaks down. 

Conclusion 

Consider the specific requirements of your metal fabrication projects, including material types, thicknesses, production volumes, and desired finished quality, when deciding on fiber laser vs. plasma. While there are similarities between the two technologies, both methods have unique characteristics that best serve specific applications.  

Ultimately, the best choice depends on your specific needs, budget, and production requirements. Consulting with a knowledgeable supplier or industry expert can also help you make an informed decision.  

This article was written by Kris Rich (marketing director, heavy industrial business, Hypertherm Associates) for the American Welding Society.