Plasma Cutting vs. Laser Cutting – Which cutting process should I use for my part?
There are many misconceptions about two of the most popular steel plate cutting processes today – laser cutting and plasma cutting.
Whether you are an OEM, design engineer, or a fabricator, it is very important that you use the correct cutting process for your part.
First let’s break down each process into what exactly it is and then give pros and cons of each to help you determine what is best for your application.
Plasma Cutting – What is it?
Take for example the stars, lightning, fluorescent lights, and an industrial cutting machine; they all utilize or are composed of plasma. Plasma is the fourth state of matter characterized by ionized (electrically charged) gas particles. It’s incredible that we are able to harness its energy (at 40,000 degrees Fahrenheit) to cut all types of electrically conductive metals.
In its early days, plasma cutting was largely inefficient and produced poor cuts due to low arc density and poor gas flow design. As research continued, consumable stacks were optimized to produce a tighter, more dense arc that produced a higher quality cut at a lower energy cost. Here are the current plasma systems on the market from lowest quality to the highest.
Air Plasma – Typically handheld or mounted to a hobby type CNC table.
Conventional Plasma – Use oxygen and produce a much straighter/cleaner cut than air plasma.
Hi-Definition Plasma – Have a denser, hotter arc than conventional plasma systems.
X-Definition Plasma – The newest and the best plasma technology on the market today with cut quality approaching that of a fiber laser.
All of the parts that we manufacture use the X-Definition plasma systems.
Hypertherm, a leading global brand in plasma technologies, has most of the market share and new innovations when it comes to plasma cutting. True-Hole technology (see fig. 1) is one of the best advancements we have seen in the last 10-15 years. Quality, nearly taper less holes are produced by using oxygen as a plasma AND shield gas. Variable feed rates, optimal lead ins and lead outs, as well as ramp downs are used to produce a hole ready for a bolt without the need of secondary processes and or oversizing/kerf adjustments. There are limitations however. Hypertherm currently only has factory cut parameters for hole diameter to thickness ratios of 1:1 – 2:1. Some OEMs may offer smaller ratios but for the most part, a 1:1 ratio is the minimum that true hole technology allows.
There have been advancements made in consumable longevity by using more heat resistant elements in the electrode and optimizing coolant flow to the shield. An X definition system consumable stack should easily last 2000 pierces (depending on cut length) whereas in the past, systems were doing well to get 200-300. That amounts to huge cost savings when in a production environment.
As far as cutting nonferrous materials, plasma works well. Different gas configurations can be used based on thickness and material type (Gas selection guide – plasma cutting aluminum, mild/stainless steel (hypertherm.com)). However, interior profiles such as small holes have much more taper than mild steel would.
Where plasma really shines in terms of a great balance in cost and quality is in the thickness range of 3/8” – 2”. Plasma Cutting vs. Laser Cutting – Which is best for my part?
Laser Cutting – What is it?
Laser cutting, the popular cutting process choice for thinner sheet metal has been around for decades. There are two main types of laser cutting (when we are talking about industrial metal cutting); fiber and CO2.
CO2 lasers are somewhat outdated technology as fiber lasers have been the rage in the last ten years. CO2 laser operational costs are much higher due to high gas consumption and maintenance. These systems are much more fragile than fiber systems as they use an intricate system of mirrors to deliver the laser beams. Operators had to know much more about cut parameters and how to tweak settings for the optimal cut on CO2 systems. Cut speeds were also drastically slower on a CO2 laser than a fiber laser.
However, CO2 lasers have their advantages as well. The cut edge of a CO2 is still smoother than a fiber laser (less striations). If cut settings are optimized, a mirror finish can be generated. CO2 lasers are also much more affordable than fiber lasers and have a much lower entry point. Also note that CO2 lasers do much better with cutting non metals such as glass, stone, acrylic, wood, and textiles.
Here is a comparison chart featuring Fiber Lasers vs CO2 Lasers:
Which cutting process, between laser or plasma is best for my part/product?
Now, once we have an idea of what both cutting processes are (plasma and laser), let’s talk a bit about the pros and cons of each.
Fiber lasers are great for cutting thin sheet metal parts (generally ¼” and thinner). They will hold a tight linear cut tolerance (+/- .010” is pretty standard). For plates ¼” and thinner (depending on the KW rating of the laser) they will be much faster at processing than a plasma and even more economical. Fiber lasers are great at cutting very small and intricate interior profiles. Nonferrous materials are cut with ease on a laser system. The interior and exterior edges off of a fiber laser are square, smooth, clean and straight providing the machine is set correctly.
A fiber laser is great for processing thinner sheet metal parts, but it’s not practical to laser cut thicker plates, especially when tight tolerances are not required. Lasers typically have a higher hourly rate ($200-$500 an hr.) New, these fiber laser machines cost around 3 times the cost of an industrial plasma system, sometimes much more depending on the size and level of automation. For example, a decent 6KW fiber laser with a basic pallet changer would cost between $600,000-800,000 where a hi-def plasma system may be in the $250,000 range. Maintenance cost and operational cost are also higher than a plasma system due to the complexity and nature of the machines. Lasers also require flat, clean steel, completely different than a plasma system that will burn through just about anything.
Bottom Line: If your custom steel part is thin, intricate, or requires tight tolerances, stick with a fiber laser. See fig. 2, this would not be an ideal job for a plasma.
Hi-def plasmas are optimal in the steel plate thickness ranges of 1/4“ through about 2”. For parts 5/8” and thinner, expect a +/- .025” tolerance. For steel plates ¾” and thicker, figure +/- .040” cut tolerance. Cut speeds on plasma systems are much faster on thicker plates than fiber lasers. A Hypertherm XPR300 plasma system for example, can burn through 1” A36 plate at 75 inches per minute where a 6KW fiber laser would be 20-30 inches per minute. Plasma systems hourly rates are more economical than a fiber laser. Anywhere between $150 – $300 an hour rate for a plasma system would be typical. As already stated above, industrial plasma systems have a much lower entry cost and lower operational/maintenance cost than fiber lasers.
Due to the swirl of the gas coming from the tip, all plasma cuts generate cut taper. In the last 20 years, huge improvements (including true hole technology) have been made to deal with this issue but taper angles of around 1 degree on a cut are still common. On small interior profiles, cut taper is more significant. However, for most applications, holes and slots can be oversized in order to compensate for cut taper. Plasma systems are typically in dirtier, harsher environments than laser systems and produce more smoke which has to be dealt with. Also, any holes or corner slowdowns will have slag that will need to be cleaned up downstream (we do this by default for our customers) before further secondary processes.
Bottom Line: If you are cutting a steel part that is ¼” or thicker, consider the plasma cutting process if tolerance isn’t a concern but production cost is.
The importance of selecting the right cut process for your part.
Make sure you consider both cutting processes and make the right decision for your application. Both processes have limitations and constraints. Engineers may require a laser cut when it actually isn’t necessary driving up the production cost. See more here: Laser tolerances: engineers specify them and they are costing money (hypertherm.com) In the inflationary environment today, engineers and manufacturers need to ask themselves, do these steel parts actually need to be laser cut or would an X-Definition plasma system do a satisfactory job at a lower cost?
To close, this is a cost study that we recently did on some sample parts. As you can see, the cost savings drastically increased the thicker the part. A bit below 1/4″ in thickness is a break-even point where plasma and laser meet in price.