Cutting Through the Noise

Advances in fiber laser technology have generated significant attention in recent years. Today, when a shop considers investing in a new CNC cutting machine, the much-publicized benefits of fiber laser may make it seem like the sensible choice.

However, while the perceived benefits of fiber laser are exciting, the technology may not be the right choice for your specific needs. In some cases, plasma may be the superior cutting option. To better understand where the two technologies have advantages, you should evaluate the following elements of your fabrication process:

• The mix of material type, condition, and thickness
• Productivity and speed requirements
• Part size and movement
• Requirements for the cutting process from the next process step: welding, coating, or fastening
• Automation opportunities
• Return on investment/payback

Speed and Thickness

Much has been made of the speed of fiber laser cutting. The advantage is real when materials are thin, but as thickness increases, the benefits rapidly diminish.

For materials up to 12 mm (0.47 in.) thick, fiber laser typically cuts as much as five times faster than plasma. However, at 16 mm (0.63 in.) of mild steel, the advantage disappears for a 15-kW laser, and plasma achieves faster cutting. The trend continues, with plasma outperforming a 20-kW laser at 20 mm (0.79 in.) and a 30-kW laser at 30 mm (1.18 in.).

The latest trend in fiber lasers is ultrahigh power systems that operate above 30 kW — up to 50 or 60 kW and higher. While the specs are impressive, these very high-power systems are generally considered unproven in production, and Tier 1 manufacturers usually avoid them. Issues such as limited duty cycle, excessive heat input that distorts cutting tables, higher energy consumption, and inconsistent cut quality continue to be reported in production environments.

Modern plasma cutting systems excel at slicing through 50–60-mm (1.97–2.36-in.) mild steel and up to 120 mm (4.72 in.) of nonferrous materials with proven processes that have been perfected over the last decade. While fiber laser is catching up, plasma continues to produce excellent cut quality and production level speeds that drive profitability.

The Impact of Materials

In addition to thickness, the composition and condition of materials should be considered when choosing the best technology for a given production environment. Fiber lasers require a clean surface to cut effectively. In the past, shops working with materials containing rust, paint, scale, or coatings had to prep their plates via time-consuming cleaning processes or store raw materials in expensive indoor warehouses. Fiber laser manufacturers have responded by creating precutting vaporization passes; however, this negates much of laser’s vaunted speed and productivity advantages. Not so with plasma, which cuts materials regardless of their surface condition. If a material is conductive, plasma will cut it.

A Matter of Safety

Worker safety requirements constrain the parts that can be cut with fiber lasers. Fiber laser beams can be dangerous for operators and require enclosures to shield them. Although an enclosure can improve fume control and reduce airborne particulates, it also reduces access to the work area and restricts table size, limiting the size of the plates and parts that can be processed and typically requiring expensive material handling solutions to move parts in and out of the work area.

These limitations do not apply to plasma. The process requires only eye protection for extended viewing of the arc, and plasma cutting tables, including much larger tables reaching 50 m (164 ft) and more, are limited only by the overall factory floor. They offer uninhibited workpiece access and provide productivity enhancements that include areas to load and cut material and unload finished parts simultaneously. This makes plasma a better fit for production of a component mix that ranges from small to large. When material-handling solutions are appropriate for a production environment, they can be easily integrated with a plasma cutting table.

Manual Postprocessing

The requirements of the cutting stage are typically defined by the next step in the fabrication process, whether it’s welding, coating, or fastening. The claim to fame for fiber laser is low angularity of cuts. While this is an undeniable advantage of laser over plasma, modern plasma cutting processes produce excellent angularity, usually in the ISO 2–3 range across many thicknesses, which easily accommodates both manual and robotic welding cells with little to no cleanup. For part designs that require bevels in thicker materials, plasma cutting is often superior, producing accurate and consistent bevel angles without the common issue of parts rewelding, which can occur with fiber laser cutting. With plasma, parts are accurate, clean, and ready for the welding step without the use of hammers or other means to remove nested parts from the material.

On thicker materials, plasma cutting frequently yields smooth, weld-ready edges. Welders typically remove oxides or scale after either plasma or fiber laser cutting, as both processes can leave minor surface residue. Fiber lasers may also generate a lower-edge burr similar to the small amount of dross from plasma. Modern plasma technology, therefore, produces weld-ready parts that rival the quality of laser-cut parts.

The Edge in Automation

Automation is a fact of life for most fabricators. Whether they’re improving quality, replacing ergonomic challenges, or addressing the lack of skilled labor, robots and cobots continue to rapidly evolve, resulting in ongoing improvements to productivity, comfort, and safety. Often, fiber laser is perceived as more modern and more compatible with automation. However, the in-market offerings show that when it comes to the versatility and proliferation of services from the leading table and robotic solution providers, plasma leads in variety and ease of integration, supporting a wider range of cutting, shaping, and metal removal applications.

Pace of Innovation

Because it is a relatively mature technology, plasma is sometimes viewed as having plateaued, but it is undergoing steady, consistent improvement.

Recent years have brought significant developments to plasma machines, including next-generation control systems that streamline efficiency and improved consumables that reduce cost, waste, and training time. Ongoing investments in research and development will continue to drive advancements for years to come.

Access to Support

As a mature technology, plasma offers users instant access to a well-established network of service and support. Spare parts and consumables are easily acquired, and if a machine requires service, qualified technicians are readily available nationally and globally. In many cases, familiarity with plasma is universal, and fabricators often have in-house maintenance teams capable of servicing their own equipment.

Conversely, while fiber laser is well supported in many areas, the breadth and depth of its service network is not at the same level. This can have a substantial impact, especially given that laser cutting centers have highly technical maintenance requirements that often necessitate service from an authorized provider, resulting in downtime or expensive stocks of spare components.

The Race for ROI

Ultimately, the determining factor for most purchasing decisions comes down to the expected return on investment (ROI). With plasma, a lower cost of entry can translate into faster profitability. Currently, the price of a Tier 1 fiber laser cutting system runs anywhere from two to five times that of a comparable plasma cutting system. This raises the bar for what the machine must achieve to be profitable.

In some cases, the decision is easy. Fiber laser is an ideal option for shops working exclusively with high volumes of parts cut from materials thinner than 12 mm. At the other end of the spectrum, plasma is the obvious choice for a high-mix, low-volume environment that frequently processes thick materials with imperfect surfaces.

Most manufacturers fall somewhere in between. Many might find the ideal long-term solution is to have both technologies available, with each job being processed with the option best suited to its unique characteristics. Shops looking to invest in cutting technology should consider material variables (thickness and raw quality), operational requirements, automation readiness, service, support, and the payback period to determine whether fiber laser or plasma provides the best next step on their journey to success. 

This article was written by Kristopher Rick (Hypertherm Industrial Plasma, Hanover, N.H.) for the American Welding Society.