Fiber Laser vs Plasma: 5 Things to Consider before you Invest

In this article we will break it down into the top 5 things you need to consider before you invest:

1: What is your material split now and in the future?

2: What cut edge quality do you need for your production?

3: What production rate do you need to meet?

4: What is your price range?

5: What are the main operating costs?

If your business predominately requires thinner sheets (< 10 mm) in high volumes, and profiles that require extremely high tolerances, a fiber laser machine is the obvious choice. While the acquisition and operating costs are generally higher than that of a plasma machine, the increase in productivity means, on average, you can expect to breakeven within 5 years.

Plasma machines are renowned for their high productivity rate, wide cutting range, and comparatively low acquisition costs with an average payback time of around 2-3 years. If the majority of your cutting requirements involve thicker mild steel sheets (above 10 mm) a plasma machine is the ideal solution.

Table 1 summarizes some of the key factors which we have discussed in detail below. It is advised to use this table as an indication only. We always recommend you compare the exact data and cut samples from any cutting machine you are considering purchasing.

Table 1: Summary Table

There are 2 types of CNC laser cutting machines: Fiber and CO2. In this article, we focus on fiber lasers but read our article on Fiber vs CO2 for more information. Fiber lasers use the light produced by a diode and direct it along a fiber-optic cable. In the cutting head, through a series of optical components, the beam is focused and intensified which is then used to cut through metal. The cutting gas (which ejects the molten metal from the kerf) is injected into the cutting head below the optical components and exits out the nozzle together with the laser beam.

So without further ado, let’s look in more detail at the 5 key things to consider before buying a fiber laser or plasma cutting machine.

1: What is your material split now and in the future?

In terms of material versatility, plasma and laser machines are extremely similar. The key differentiating factor is thickness range and cut quality.

Plasma machines can only cut conductive materials. Fiber laser machines are also limited to metals (the 1.06 μm wavelength of a fiber laser cannot be absorbed by non-metals). Table 2 provides a summary.

*While technically it is possible to cut reflective materials like copper and brass with a fiber laser machine, the lifetime of the consumables (specifically the protective window) will be significantly reduced and the reflections over time can cause damage to the optical components in the cutting head, therefore, cutting such materials is not advisable for prolonged periods.

Table 2: Material Summary

The exact thickness range of a plasma and fiber laser machine will vary depending on the amperage of the plasma source and power of the laser where the higher the amperage/power, the greater the cutting range.

Tables 3 and 4 give an idea of the sort of cutting ranges you can expect for a low, middle, and high amperage/power. Sometimes, particularly for plasma systems, it may be possible to go beyond the thicknesses quoted below by using special techniques such as Edge Start, although, this will produce a rough cut edge with significant dross.

Table 3: Plasma Cutting Ranges

Table 4: Laser Cutting Ranges

2: What cut edge quality do you need for your production?

● Squareness of the finished edge
● Dross adherence to the bottom of the cut
● Cut edge

Squareness

The squareness of a cut is defined as the measured deviation of a cut edge from perpendicular. This is defined by ISO 9001, where 1 indicates the least deviation and 5 the most.

Fiber lasers are able to produce an almost square cut and can be categorized into ISO 1.

Plasma cuts will always produce a cut with a slight bevel angle. The squarest cut is always achieved on the right-hand side of the plasma relative to the cutting direction (hence why internal profiles are always cut anti-clockwise and external profiles cut clockwise). The exact ISO classification will depend on the plasma system and will deteriorate alongside the consumables.

A typical plasma cut will have a slightly concave shape on the cut edge. A conventional plasma system (i.e. a Powermax) will always have some bevel angle in the range of ISO 4 – 5. Recent plasma systems (i.e. an XPR) are able to consistently achieve cuts in the ISO 2 range on thinner materials (<10 mm) and ISO 3 for anything thicker. Changing the arc voltage (and hence the torch height) can help to correct for any bevel angle i.e. if too much material is removed from the top of the cut (a positive bevel angle), the torch is too high when more material is removed from the bottom of a cut (a negative bevel angle), the torch is too low.

Dross Adherence

Dross is defined as the unwanted metal waste that has not been ejected from the kerf that forms on the underside of the cut.

The cut quality for a fiber laser is dependent on the power of the laser and on the cutting parameters (cutting speed, cutting gas, gas pressures, nozzle size, etc.). Figure 1 shows the same shape, 10 mm Stainless Steel 304 on a 6 kW and 10 kW laser where the dross is visibly reduced as laser power increases.

Figure 1: 10 mm Stainless Steel 304 a) 6 kW vs b) 10 kW

Fiber lasers, for mild steel use both nitrogen and oxygen as the cutting gas. In general, nitrogen is used for thinner sheets (for a 2 kW laser up to 4 mm and up to 8 mm 10 kW laser). Cutting with nitrogen produces superior cut results and enables the extremely fast cutting speeds typical of fiber lasers. Cutting thicker materials with nitrogen is possible where speed and/or heat effects are a concern. Above the transition point, cutting with nitrogen will result in more dross (see Figures 2 and 3).

Figure 2: 10 mm Mild Steel 275, 6 kW a) Nitrogen vs b) Oxygen

Figure 3: 10 mm Mild Steel 275, 10 kW, a) Nitrogen vs b) Oxygen

The ideal speed range achieves a balance between productivity and a virtually dross-free cut. Even if speed is your priority, you can often still achieve dross-free cuts but the cut edge quality will be reduced. If cut edge quality is your top priority, slower cutting speeds are necessary, while the cut edge will be excellent there may be some dross formed due to the slower speed.

Cut Edge

Plasma machines will always produce smoother cut edges compared to fiber lasers due to their larger spot size. Below we have included pictures of the cut edge you can expect from both a fiber laser and a plasma for both mild and stainless steel of different thicknesses.

Fiber Laser – Stainless Steel

Figure 4: 10 mm Stainless Steel 304, 6 kW laser

Figure 5: 15 mm Stainless Steel 304, 6 kW laser

Figure 6: 20 mm Stainless Steel 304. 6 kW laser

Figure 7: 25 mm Stainless Steel 304, 6 kW laser

Figure 8: 30 mm Stainless Steel 304, 10 kW Laser

Plasma – Stainless Steel

Below we have included images of plasma cut stainless steel using a different cutting and shield gas combination (N2/N2 vs Mixed/N2). The mixed part of the gas is a combination of argon and hydrogen. This produces a cleaner cut as is shown in the pictures below, however, the gas costs are higher. To note, we wrote a separate article on everything you need to know about plasma cutting stainless steel.

Figure 9: 10 mm Stainless Steel 304, 130A a) N2/N2 vs b) Mixed/N2

Figure 10: 15 mm Stainless Steel 304, 130A a) N2/N2 vs b) Mixed/N2

Fiber Laser – Mild Steel

Figure 11: 10 mm Mild Steel 275, 6 kW

Figure 12: 15 mm Mild Steel 275, 6 kW

Figure 13: 20 mm Mild Steel 275

Figure 14: 25 mm Mild Steel 275

Plasma – Mild Steel

Figure 15: 10 mm Mild Steel 275, 130A

Figure 16: 15 mm Mild Steel 275, 170A

Figure 17: 20 mm Mild Steel 275, 300 A

Figure 18: 25 mm Mild Steel 275, 300 A

The Heat Affected Zone (HAZ) is the area near the cut surface, which is heated up during the cutting process and as it cools, the properties of the material nearby can be affected negatively. This includes surface cracking and distortion which can alter the physical size of a finished part. The size of the HAZ is dependent largely on 2 factors: the power of the laser/amperage of the plasma and the cutting speed. As power/amperage increases so does the HAZ as more heat is directed into the cut. As cutting speed decreases, the HAZ increases as there is more time for the heat to disperse away from the cut surface.

Both fiber laser and plasma machines produce a Heat Affected Zone, however, the area is smaller for fiber laser than for plasma. The HAZ can be minimized for lasers by tweaking the cutting parameters and underwater cutting on a plasma machine. Although under-water cutting comes with its own drawbacks of altering the arc voltage due to water being a conductive medium.

Hole & Cut Part Quality

Every business wants to know how the actual cut parts compare to the programmed cuts. This measure of precision is what we call cut part quality. Hole quality is the precision measure that defines how cylindrical a certain hole is, and how much difference there is between the top and bottom.

When evaluating precision, it is also important to take into account kerf width, which determines how small of an inner contour can be cut, and heat distortion, which can alter the size of a finished part.

Plasma machines have lower tolerances compared to laser machines and it is often difficult to measure tolerances as the results can vary depending on the life cycle of the consumables.

Typical tolerances for a HD plasma cutting machine can be expected to be around +/- 0.5 mm with a kerf width of around 1.7 – 2.2 mm. The effect of heat distortion will be greater than that seen with a fiber laser. With a top-of-the-range HD plasma cutter with True Hole technology, perfect holes are achievable, but only for mild steel. Without True Hole, plasma holes will have a bevel angle and also may have a “ding” (a small amount of protruding material) which is caused by the lead-in/out (see Figure 19 below). For more information on True Hole Technology, read our article here.

Figures 19 and 20 show what you can expect in terms of hole quality for stainless steel (without True Hole) and for mild steel (with True Hole).

Figure 19: 15 mm Stainless Steel 375 with a 20 mm diameter hole with no True Hole a) side, b) top, c) bottom

Figure 20: 15 mm Mild Steel 275 with a 20 mm diameter hole with True Hole a) side, b) top, c) bottom

3: What production rate do you need to meet?

Cutting speeds need to be fine-tuned. Often faster speeds can be achieved, but this comes at a cost in terms of the cut quality.

A fiber laser can cut mild steel with either oxygen or nitrogen. Thinner materials (approx. under 6 mm) will achieve faster cut speeds and a better quality cut with nitrogen. While it is possible to cut above 6 mm with nitrogen, and still achieve faster cut speeds, dross will start to form.

Approximate cutting speeds are shown in Figure 21.

Figure 21: Cutting Speeds for Fiber Laser for different materials

Figure 22: Cutting Speeds for Plasma for different materials

4: What is your price range?

Perhaps the most important factor when it comes to purchasing a new cutting machine for the vast majority of people is the initial acquisition cost.

The exact cost of a CNC cutting machine will depend on a variety of factors:

● The machine – i.e. construction of the machine, motion controls, motors, etc.
● Power Source – the higher the laser power/plasma amperage the higher the cost
● Bed Size – width/length required
● Automated Systems – load/unload systems, etc.
● Additions – i.e. additional cutting heads, gas torches (for plasma), zoom vs non-zoom cutting heads (for laser)

Table 5 shows the estimated acquisition cost for a fiber laser and plasma machine. For more information, please also check out our dedicated article on the price of a CNC plasma cutting machine.

Table 5: Acquisition Cost of a Fiber Laser and Plasma CNC Cutting Machine

Extraction units are required for both plasma and fiber laser machines. During cutting, hazardous fumes are produced which may contain chromium/nickel making them toxic. The size of the extraction system required will increase with the power/amperage of the machine and the width of the cutting bed. If you cut aluminium, a reinforced filter is needed which will also increase the cost.

The exact payback time of a machine will vary depending on the usage and tonnage. However, in general, the payback time of a plasma cutting machine is approximately 2-3 years and for a fiber laser cutting machine around 5 years.

5: What are the main operating costs?

It is very difficult to give exact operating costs for a machine as there are many factors to consider. Below we have tried to come up with some rough figures for what you can expect for both machines.

In our calculations below we have opted to focus on 3 operating costs which are discussed in more detail below:

● Power Usage
● Gas Usage
● Consumables

The below figures should only be taken as estimates. Costs will vary depending on location. All costs are estimated based on April 2021.

To get a full picture of the operating cost for each machine there are other factors that need to be considered although this list is not exhaustive.

● Labour – having a skilled machine operator can help you save money in the long run with their insights. When labour is included in operating costs, it is likely to be the highest individual component for operating costs (can be as much as 90%).
● Software – various nesting software options exist. Even if you already have experience of one, while learning a new software will take time, it could make you more productive in the long run.
● Material costs – fiber lasers are much more sensitive than plasma machines to impurities in the metal. Above 10 mm, RAEX plate is strongly recommended which can be up to 3 times more expensive than normal plate. Cutting with poor material on a fiber laser will produce an extremely poor cut with a lot of dross and can even fail to cut.
● Maintenance – preventative maintenance is key to avoid unwanted downtime for your machine. Machine manufacturers will provide you with daily/weekly and monthly checks for operators and offer regular services 1-4 times a year depending on your machine usage.

Power Usage

The exact electricity cost of your cutting machine will vary from machine to machine and between manufacturers. When considering purchasing a machine, it is important to consider the current power availability in your facility to avoid unforeseen costs prior to the machine install.

For a fiber laser machine, there are 3 items needing power: the machine itself, the laser source, and a chiller. Plasma machines have 2 items: the machine and the plasma source. Both machines will require some form of extraction unit and an air compressor however, these items have been excluded from the cost calculations below.

To note, innovative features such as Esprit’s LiveRegen (present on all its Photon 5G Fiber lasers) can reduce your electricity bill.

Plasma cutters require two gases: one for cutting and a shield gas. The purpose of the shield gas is to constrict the arc. The ideal combination of cutting and shield gas depends on your priority: cut quality, cutting speed, or cost. In general, the three principal gases will be oxygen, nitrogen, and air. Other gases such as argon are common on more advanced cutting systems. Marking on a plasma can either be done with nitrogen or argon. Argon will produce superior results but also is more expensive than nitrogen.

Figure 23: Plasma Marking a) Nitrogen vs b) Argon

Fiber lasers and plasma machines both have consumable items which over time need replacing, otherwise, the cut quality of your machine will deteriorate rapidly.

The principal consumables for fiber laser and plasma machines are discussed below in Table 6 and Figure 24 respectively.

Table 6: Consumable Items for a Fiber Laser

Figure 24: Plasma Consumable Items and their purpose

For plasmas, the two most common things that will need replacing are the electrode and the nozzle. During cutting, the hafnium insert melts and small fragments are fired out of the torch, causing a pit to form in the electrode. Eventually, this deteriorates to the point where there isn’t enough hafnium left, and instead, the electrode gets burned. If either the nozzle/electrode is replaced then the other consumable should also be changed. Find out more here.

The other consumable items are most likely to be damaged by cutting debris, operator carelessness (dropping, damaged when inserting/removing, etc.), or from heat damage.

Both types of machines will have other consumable items associated with them which require changing every few months so the above list is not exhaustive.

Figure 25 shows the estimated cost per hour per meter for different thicknesses of Mild Steel 275. The cost per hour for a fiber laser is significantly higher for thinner materials as nitrogen is used as the cutting gas. However, because of the increase in cutting speed this offers, the cost per meter ends up being cheaper or similar. For thicker materials, plasma machines have the edge in terms of cut speed and hence a lower cost per meter.

Figure 25: Cost Comparison a) Cost per Hour, b) Cost per Meter

Figure 26: Breakdown of Operating Costs into Individual Components

Conclusion

When thinking about purchasing a CNC cutting machine, it is important to start your search by considering your priorities i.e. cut quality, precision, productivity, cost, etc.

Plasma and fiber laser machines both have their own unique strengths and weaknesses.

If your main concern is budget and you are mainly going to cut thicker mild steel, aluminium, and stainless steel, an HD plasma cutter will be your best choice. Plasma cutters are known for their high productivity, wide cutting range, and low acquisition cost. They offer a more than adequate cut quality for a wide range of applications and can mostly produce bolt-ready holes.

If your main concern is cutting to very high tolerances, and you mostly cut thinner (<10 mm) sheets, a fiber laser will almost always be your best option. Their only disadvantage is the relatively large investment cost and relatively narrow cutting range. However, for thinner sheets, their impeccable edge quality and speed make them an attractive option.

It is always worth gaining some expert advice from a range of manufacturers and looking at the samples.

If you have any questions about fiber laser or plasma cutters, please do not hesitate to contact us.

Our team of expert engineers can help you to identify the right CNC cutting machine for you with detailed knowledge of both fiber laser and plasma machines. They’d be delighted to talk you through your specific requirements and how Esprit Automation could help you to meet them.