The conflict of choosing between laser cutting and plasma cutting always arises when precision cuts are needed.
Both methods give excellent results in cutting and can be used for a variety of materials.
Although both are used for performing similar functions, they have different working principles and applications.
In this article, I go through the important aspects of both techniques to explain the difference between them and help you understand which one to choose for your application.
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What is Laser Cutting?
Laser cutting is a non-contact machining technique that uses an amplified beam of light to cut through a material.
This beam of laser light is passed through an optical arrangement to focus it on the material.
The highly focused beam raises the temperature at the focus point and melts, burns, or vaporizes the material.
For cutting thick materials, the laser beam is accompanied by pressurized gas which blows away the slag from the cutting slot and produces cuts with smoother edges and a good surface finish.
Applications of Laser Cutting
Laser cutting provides great flexibility in terms of the materials it can work on.
It is primarily used for cutting thin sheet material with high precision and high speed.
The power of a laser cutter can be controlled and at low powers, it can be used to perform laser engraving.
With the advancement in technology, now you can even find small desktop laser cutters that can cut through very thin sheets of metal.
What is Plasma Cutting?
Plasma cutting is a comparatively older technique that cuts the material using a jet of hot plasma.
The hot plasma is created by forcing a jet of gas (nitrogen, oxygen, argon, etc.) through a nozzle and generating an electric arc between the workpiece and the electrode of the plasma cutter.
This electric arc raises the temperature of the gas and transforms it into the fourth state of matter called plasma.
The high temperature of plasma melts the metal, and its high velocity blows the molten metal away to produce the required cut.
Plasma cutter was initially introduced as handheld equipment, but it is now available in CNC as well as portable-handheld equipment form.
Avid CNC has introduced Avid CNC PRO4896, which offers an add-on Pro CNC plasma kit option that can transform the Avid PRO series CNC router into a CNC plasma cutter.
Applications of Plasma Cutting
Plasma cutting is a relatively cheaper machining process used for cutting metal workpieces.
When working with thick workpieces, further grinding may be required to smoothen the edge of the cut and improve the surface finish of the workpiece.
The cuts produced by plasma cutting have a bevel angle of around 0.5° to 3° with the vertical cross-section, making it an ideal choice for operations where bevel cuts are to be made, thus eliminating the need for a secondary operation.
Laser Cutting vs Plasma Cutting
Here’s a quick summary of the differences between the two cutting techniques.
| Cutting Parameter | Laser Cutting | Plasma Cutting |
|---|---|---|
| Cutting Material | Can be used to cut wood, plastics, leather, glass, ceramics, metals, etc. | Can be used only for cutting metals with good electric conductivity. |
| Cutting Thickness | Can cut thin sheets (approximately up to 1” of mild steel) | Can cut comparatively thicker sheets (approximately up to 3” of mild steel) |
| Quality of cut | Produces cut with a smooth edge, good surface finish, and very little slag formation. | Produced cut might need further machining to improve the surface finish. |
| Cutting speed | Laser cutting is comparatively faster when cutting thin metals. | Plasma cutting has a slower cutting speed but is comparatively faster when cutting thicker metals. |
| Precision | It produces cuts with a very narrow slot width and high precision of around ±0.15mm. | The slot width is comparatively more and has a precision of around 0.5 – 1mm. |
| Cost-effective | Has an operational cost of around $20/hour and also has a high set-up cost. | Has an operational cost of around $15/hour with a comparatively less initial cost. |
Laser Cutting vs Plasma Cutting
Laser Cutting – Advantages and Disadvantages
Laser cutting can be used to cut a variety of materials, including metals and non-metals.
However, it can be challenging to cut reflective metals because they reflect the laser beam, which results in loss of laser energy, and the reflected laser beams can be dangerous.
Laser cutting is comparatively faster, more precise, and produces cuts with a better surface finish than plasma cutting.
It can produce cuts with a narrow slot width of less than 0.015” and perform other detailed operations like making small holes and engraving a material.
The highly focused nature of the laser beam allows it to have a minimal heat zone and produce cuts with smooth edges and minimum heat distortion in the material being cut.
While cutting thin metals, it can achieve a fast cutting speed of around 1000 inches per minute, but with the increase in thickness of the metal being cut, the cutting speed can drop to 20 inches per minute.
This slow cutting speed for thicker metals can increase heat distortion, which makes it unsuitable for cutting very thick workpieces.
Plasma Cutting – Advantages and Disadvantages
Plasma cutting can be used to cut through any metal with good electric conductivity and can perform comparatively better than laser cutting when the thickness of the metal exceeds ¼”.
Unlike laser cutting, plasma cutting can be used to cut through highly reflective metals with ease.
Plasma cutting can cut through metal with a part accuracy greater than 0.008” even at high cutting speeds.
The cuts produced by plasma cutting are comparatively less precise and have a slot width (kerf) greater than laser cutting.
While cutting a thin sheet of mild steel (approximately 0.06”), some plasma cutters can achieve a cutting speed of up to 400 inches per minute.
When cutting through a 1” thick mild steel plasma cutters can achieve around 40 inches per minute.
The ability to cut through thick metal gives plasma cutting an edge over laser cutting, making it an ideal machining process for applications involving metal cutting.
As an older technique, plasma cutting has gone through many developments and offers a cost-efficient operation.
Plasma cutting has an average operating cost of $15 per hour, which is comparatively cheaper than a laser cutter’s $20 per hour operating cost.
Also, Industrial plasma cutters, with a cost of around $50k to $100k, are much cheaper than laser cutters of the same caliber which can cost you above $300k.
Which one to Use-Laser or Plasma?
The answer to this depends upon the work material, the thickness of the work material, and the precision required for the application.
Based on the Type of Material
For an application where metal cutting is the main objective, plasma cutting always has the upper hand over laser cutting because of its ability to cut through almost any metal with a wide range of workpiece thicknesses.
On the other hand, laser cutting is preferred for applications where a variety of materials are to be cut, including both metals and non-metals.
Based on the Thickness of the Metal
Although laser cutting can be used to cut metal sheets (up to 1″ for mild steel), plasma cutting is more efficient when the thickness of the metal workpiece exceeds ¼”.
Therefore, plasma cutting is preferable for applications where thick sheets of metal are to be cut (up to 3″ for mild steel).
Based on the Surface Finish
If the workpiece consists of thin metal that can be cut by both laser cutting and plasma cutting, then laser cutting is the better option because it provides higher precision with less machining time.
The cuts performed by laser have smoother edges with better surface finish and minimal slag formation.
However, when cutting thick metals, the quality of cut produced by a plasma cutter is far better than a laser cutter.
If a high quality surface finish is the main priority of your application, Water jet machining and Wire EDM can provide a far superior quality at the expense of cutting speed.
Based on the Precision and Accuracy
If narrow slot width and precise cut are your primary requirements, laser cutting is recommended.
Laser cutting can make very precise cuts with a slot width of around 0.6mm, whereas plasma cutting produces cuts with a minimum slot width of around 1mm.
Based on the Cost of Operation
The initial and operational cost of a laser cutter is higher than an equally capable plasma cutter.
Although plasma cutting might seem like the winner here, with an average operational cost of $15/hour compared to $20/hour for laser cutting, the speed of cutting is also a factor.
Thus, for thin metals (under ¼”), laser cutting finishes the process faster, thereby reducing the overall machining cost.
However, for thicker metals (above ¼”), plasma cutting gives better performance with lesser operational costs.
Final Thoughts
Both laser cutting and plasma cutting are better than most conventional cutting techniques and can produce cuts with high precision and a good surface finish.
As discussed, both have their ideal use cases.
Selecting the appropriate cutting technique, based on your application is the way to go here.
Frequently Asked Questions (FAQ)
Can you use laser cutting to cut a thick metal?
Yes, you can use laser cutting to cut a thick metal, but you will have to do it in multiple passes.
This will increase the overall cost of operation and can also result in heat distortion of the material being cut due to excessive exposure to the high-temperature laser.
Can plasma cutting be used to engrave metal?
Yes, a plasma cutter can be used to engrave metal. However, the quality of engraving produced by a laser is far superior to that of a plasma cutter.
What kind of material cannot be cut by a plasma cutter?
Materials with poor electric conductivity like wood, rubber, plastics, ceramic, etc., cannot be cut using a plasma cutter. The list also includes some metals like tin, lead, tungsten, and manganese that have poor electrical conductivity and resist the generation of electric-arc.
Why is plasma cutting only applicable for materials with good electric conductivity?
Plasma cutting is based on the principle of melting and cutting the material by a high temperature and high-velocity plasma created by an electric discharge between the workpiece and the electrode of the plasma cutter.
In order to have a successful electric discharge, a potential difference is to be generated between the electrode (cathode) and the workpiece (anode), which is not possible if the workpiece has poor electric conductivity. Thus, plasma cutting is only applicable for materials with good electric conductivity.
