Laser Cutting vs. Plasma Cutting: What’s the Difference?
Share
When we started Apex Creations, one of the biggest pieces of equipment we wanted to build our fabrication capabilities around was our fiber laser. Since then, it has become one of the most important machines in our shop. We use it for everything from signs and fire pits to custom parts, brackets, lettering, and projects that start with nothing more than an idea or a drawing from a customer.
One question that comes up when talking about cutting steel is what actually makes laser cutting different from something like plasma cutting. Both processes can take a flat sheet of metal and turn it into a finished part, but the way they cut and the type of work they are best suited for can be very different.
Plasma cutting has been used in fabrication shops for decades, and for good reason. A plasma cutter uses an electrically conductive gas to create an extremely hot plasma arc that melts through the metal. It can cut quickly, handle thick material, and is a great option for a lot of general fabrication work where extremely fine detail isn’t necessary.
Fiber laser cutting takes a different approach. Instead of a plasma arc, the machine focuses a very powerful laser beam into an extremely small area. That small cutting point is one of the biggest reasons a fiber laser can produce the level of detail that it does.
At Apex, we cut our metal on a 2,000 watt fiber laser with a 5×10’ cutting bed. One of the things that has impressed us the most as we have gotten more experience with the machine is just how precise it can be. On the right parts, we are often able to work in fractions of a millimeter when sizing laser cut holes and other features. That level of control lets us make adjustments that would be almost impossible to notice on a computer screen but can make a big difference when two parts actually have to fit together.
That has been especially useful as the projects we take on have become more complicated. Cutting a large shape out of a piece of steel is one thing. Cutting small holes, slots, tabs, detailed lettering, logos, and parts that need to fit together accurately is something completely different.
This is one of the areas where the difference between laser and plasma becomes much easier to see. A plasma arc is larger than the focused beam of a fiber laser, which generally means a wider cut and less ability to reproduce extremely small details. Depending on the part, plasma cut pieces can also require more cleanup after they come off the table.
With the fiber laser, we can cut extremely fine details while still producing clean edges. That is particularly important on something like a custom sign where small lettering or narrow sections of a design might be part of the finished product. It is also important on functional parts where the location and size of a hole, slot, or tab can determine whether everything fits together the way it was designed.
Another advantage we have seen is how little heat we can put into the surrounding material, particularly when cutting thinner carbon steel with compressed air.
Any thermal cutting process creates a heat affected zone around the cut, but the extremely concentrated beam and fast cutting speeds of a fiber laser allow the heat to remain much more localized than with plasma cutting. On thinner material, where excessive heat can contribute to distortion or warping, that can make a noticeable difference.
The assist gas we use can make a difference as well. When cutting carbon steel with oxygen, the oxygen actually participates in the cutting process through an exothermic reaction. That reaction helps the laser cut thicker material, but it also introduces additional heat into the steel.
For much of our thinner carbon steel work, we can instead use high pressure compressed air as the assist gas. Air does not provide the same oxygen assisted reaction, so we are relying more heavily on the laser itself to make the cut while the compressed air clears the molten material from the kerf. Combined with the speed of the fiber laser, this can result in considerably less overall heat input than we would typically see from plasma cutting, and less than we would generally expect when laser cutting the same material with oxygen.
That matters for more than just what the edge looks like. Less heat going into the surrounding steel can mean less distortion, a smaller heat-affected area, and parts that stay closer to the shape and dimensions we designed on the computer. When we are cutting thin signs, narrow features, small components, or pieces that need to fit together accurately afterward, keeping unnecessary heat out of the material is a major advantage.
We see that same level of control when we design parts that fit together before welding. Sometimes changing a hole or feature by only a fraction of a millimeter can be the difference between a fit that is too tight, too loose, or just right. Being able to make those adjustments on the computer and then accurately reproduce them in steel gives us a lot of flexibility when developing a new product or working through a custom project.
That doesn’t mean plasma cutting is a bad process or that a laser is automatically the better choice for every job. Plasma has its place, especially in heavy fabrication where extremely tight tolerances or intricate details aren’t required. Like most equipment in fabrication, the better process depends on what you are trying to make.
For us, the versatility of the fiber laser is what makes it such a good fit for Apex. We can cut the panels for one of our fire pits and then turn around and use the same machine to cut detailed lettering for a sign or a small custom component. We can work with a customer who already has a finished drawing, or we can start with measurements and an idea and design the part ourselves.
As we have gotten more comfortable with the laser, we have also learned that owning the machine is only part of the process. There is a learning curve to understanding how different materials cut, how designs need to be prepared, how small certain features can realistically be, and how a part should be designed when it eventually needs to be bent, welded, or assembled.
A lot of that knowledge has come from simply making things. We have had parts that worked exactly like we expected and others that went back to the computer for another revision. Each project teaches us a little more about what the machine can do and, just as importantly, how to design around those capabilities.
That is one of the things we want the Apex Journal to show. When you see a finished metal sign, fire pit, or fabricated part, the laser cutting might only take up a small portion of the entire process. Behind it are the measurements, design decisions, test fits, adjustments, and lessons that eventually turn a flat sheet of metal into the finished product.
For us, that is also one of the most interesting parts of having this capability in our own shop. We can start with an idea, make a part, see how it works, make an adjustment that might be only a fraction of a millimeter, and cut it again.
That ability to keep designing, learning, and making things more precise is a big part of what Apex Creations is about.
Interested in having something laser cut or fabricated? Whether you already have a drawing or just have an idea of what you need, reach out to us and tell us about your project.
