McGrath Metal, 45090 Golf Center Parkway, Indio, CA 92201
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Laser vs Waterjet vs Plasma Cutting
If you need metal parts cut, you have three common CNC processes to choose from: laser, waterjet, and plasma. All three pierce metal and follow a programmed path, but they do it in completely different ways, and each one clearly wins in some situations and clearly loses in others. Choosing the right process controls your cost, your edge quality, and how much finishing work the parts need afterward. This guide explains how each one works, where it shines, and where it falls short, written from the floor of a precision metal fabrication shop rather than from a brochure. Please contact us with questions.
LASER CUTTING
The laser was invented in 1960, and the first machines were cutting hard materials by the mid 1960s. Laser cutting did not reach everyday fabrication shops until around 1980, when it was still expensive and limited to large operations that could justify the cost. Roughly 45 years later, laser cutting has become widespread, far more affordable, and available in precision shops across Southern California and the rest of the world.
A laser cuts by concentrating a beam of light onto the metal surface. The energy pierces the material and melts or vaporizes a narrow path, while an assist gas (compressed air, nitrogen, or oxygen) blows the molten material out of the cut. A CNC motion system moves the cutting head along the programmed path. Two types dominate today. Older CO2 lasers use a gas tube to generate the beam. Modern fiber lasers, which McGrath Metal runs, generate the beam in a solid fiber source, run more efficiently, and cut reflective metals like aluminum, brass, and copper that gave the older CO2 machines trouble.
Modern industrial lasers are fast. Speeds reach up to about 1,500 inches per minute on thin mild steel, and several hundred inches per minute on heavier plate such as 3/4 inch and 1 inch. Speed is only part of the story. The laser is also extremely accurate, removing a kerf (the width of material the cut removes) of only a few thousandths of an inch on thin material and slightly more on thicker plate. It produces a clean, square edge with very little of the rough material on the underside of the sheet known as dross. With the right programming and experience, that bottom edge can be reduced to the point where it is insignificant, which means less de-burring and less cleanup downstream.
Laser cutting leads every other process in speed, productivity, and the preservation of fine detail. Intricate shapes, thin webs, small letters, and decorative patterns come off the laser quickly with their resolution and crispness intact. That makes it the natural choice for laser cut metal signs, decorative metal screens, metal privacy screens, and laser cut wall panels, as well as production runs of precision parts.
The machines are still expensive, often well north of half a million dollars, but their speed and productivity offset that cost on real production work. Choose a laser for mild steel, stainless steel, and thin to medium aluminum, for the highest level of precision, for the lowest cost per part on higher volume orders, and whenever fine detail must be preserved. The main limit is thickness. Most fabrication lasers top out around one inch, and when you get above that, waterjet and plasma take over.
Waterjet Cutting
Waterjet has been around even longer than the laser. The core idea dates to the 1960s, and abrasive waterjet, the version that cuts metal, matured through the following decades.
The process pressurizes ordinary water to around 60,000 psi, with some modern systems running up to 90,000 psi. That water is forced through a very fine jewel orifice, typically around 0.010 inch in diameter (roughly one hundredth of an inch), which converts the pressure into a supersonic stream. For metal, an abrasive cutting media, almost always garnet, is drawn into the stream just past the orifice and mixed through a mixing / focusing tube. When that abrasive-laden stream hits the metal, it erodes a path straight through. As with the laser, a CNC system moves the cutting head across the table.
A waterjet produces an exceptionally clean edge with little to no bevel and excellent preservation of fine detail. Its single biggest advantage is that it is a cold cutting process. Because it cuts by erosion rather than heat, it leaves no heat-affected zone, so there is no thermal distortion, no hardening of the cut edge, and no change to the temper of the material. That matters when thick aluminum or stainless parts will go on to machining operations, or when an architectural part needs a flawless edge.
A waterjet will also cut practically anything: metal, stone, glass (except tempered glass, which shatters), tile, composites, and rubber, in thicknesses up to several inches. The trade-off is speed, and this is the part most people underestimate. A waterjet is not just the slowest of the three, it is dramatically slower. On 3/4 inch mild steel, a quality edge comes off at roughly one inch per minute. The limit is physical, not a setting you can dial around: on one inch aluminum, for example, pushing past about one inch per minute starts to break up the water stream, which deflects the garnet and tears a broken, rough edge instead of a clean one. The machine is built for precision, not throughput, and you cannot trade one for the other.
Waterjet systems are often less expensive to buy than lasers, though premium domestic brands command a high price and earn it with build quality. The real cost is maintenance, which is far higher than laser or plasma. A mechanical pump pressurizes the water to extreme levels, and that pump needs ongoing service: wear parts, seals, and eventual replacement. Downstream of the pump, the 60,000 psi plumbing that carries water to the cutting head is prone to leaks and loose fittings that have to be chased down and repaired. Systems that use articulated high-pressure joints to feed a moving head are tidier than a fixed loop of semi-rigid tube, but those joints frequently need service even on new machines. Operators who are not mechanically inclined will not enjoy owning a waterjet.
There is more. The spent garnet collects in a catch tank below the table and builds up over time. It generally cannot be recycled easily, and a machine that runs long hours needs a monthly tank clean-out that takes several hours of labor at a minimum. Even the smallest waterjet systems typically start with a 50 horsepower motor, so the shop needs substantial electrical service, and because the machine cuts slowly, the energy bill per part is high. The garnet itself is a consumable, supplied in 50 pound bags that feed a hopper requiring frequent refills, which is another running cost. Add it all up and the picture is clear: a waterjet may cost no more than a laser to buy, and sometimes less, but once you account for how slowly it cuts, how much power it draws, how much maintenance it demands, and the constant garnet consumption, it is usually the most expensive of the three to actually run on a per-part basis. Waterjet is the right tool for thick, heat-sensitive, or non-metal work, and you pay for that versatility in throughput and operating cost.
Plasma Cutting
Plasma is by far the least expensive of the three to get into, and in exchange you give a few things up. A plasma torch forces compressed air (or another gas) through a constricted nozzle while an electrical arc ionizes it into plasma, a superheated, electrically conductive gas. That plasma jet melts the metal and blows it out of the cut. As with the others, a CNC system moves the torch along the path. One consequence of how it works: plasma only cuts electrically conductive metals. It cannot cut glass, stone, or plastic the way a waterjet can.
Plasma runs hot, and the arc is wide compared with the focused beam of a laser or the fine stream of a waterjet, so it removes a much wider kerf. Because that kerf is wide, the machine has to be programmed carefully to hold tolerances on holes and outside dimensions, more so than with either other process. An air plasma system gives its best results on mild steel roughly 1/8 inch to 3/8 inch thick. Go thicker than 3/8 inch, and the cut develops noticeable taper that grows with thickness: the kerf widens as the arc travels down through the plate and leaves a wedge-shaped, slightly undersized profile on the bottom face, pronounced by the time you reach 1/2 inch, 5/8 inch, 3/4 inch, and up. Go thinner than about 1/8 inch, and heat distortion takes over. That said, not every part needs a perfectly square edge, and a properly programmed and well set up plasma system produces a clean edge with minimal dross on mild steel inside that sweet spot.
Two limits are worth calling out. First, plasma can cut stainless steel and aluminum, but it leaves a rough, dross-heavy edge on those metals, especially as they get thicker. Second, plasma struggles with thin sheet. The heat it generates tends to burn the edges of material around 12 gauge and thinner, so while simple parts cut fine, fine detail does not survive: small points burn away, holes come out irregular, and thin sheets can warp and twist during the cut.
The upside is cost. A basic air plasma system with decent built-in functions is a perfectly acceptable way to cut basic parts of medium thickness, and it usually runs less than $50,000. Better systems, commonly called HD or high definition plasma, use different assist gases instead of plain compressed air: oxygen for mild steel, nitrogen for stainless and aluminum, and argon-hydrogen blends for thick stainless and aluminum. HD plasma improves edge results on thicker material, but the same drawbacks remain, just to a lesser degree, and there is virtually no difference in the outcome on thin metal. If you have been searching for a plasma cutting service or custom plasma cutting for medium-thickness mild steel parts, it can be a cost-effective answer. For tight tolerances, thin gauge, or fine detail, laser is the better fit.
Which Process Should You Choose?
Here is the short version, one process at a time.
Laser cutting at a glance:
• How it cuts: focused light beam
• Best materials: mild steel, stainless, thin to medium aluminum
• Practical thickness: up to about 1 inch
• Edge quality: excellent, clean and square
• Heat-affected zone: small
• Tolerance: tightest of the three
• Fine detail: excellent
• Speed: fastest
• Cost: high machine cost, moderate to run
Waterjet cutting at a glance:
• How it cuts: pressurized water plus garnet abrasive
• Best materials: almost anything, including stone, glass, and composites
• Practical thickness: up to several inches
• Edge quality: excellent, with no heat distortion
• Heat-affected zone: none (cold cutting process)
• Tolerance: very tight
• Fine detail: very good
• Speed: very slow, about 1 inch per minute on 3/4 inch steel
• Cost: moderate to buy, but the highest operating cost per part
Plasma cutting at a glance:
• How it cuts: ionized gas arc
• Best materials: electrically conductive metals only
• Practical thickness: up to about 1.5 to 2 inches
• Edge quality: fair, with taper and dross on thick or non-ferrous metal
• Heat-affected zone: largest of the three
• Tolerance: loosest
• Fine detail: poor
• Speed: fast on medium plate
• Cost: lowest entry cost
In practice, the decision usually comes down to a few questions. If you need speed, precision, fine detail, or repeatable production on steel, stainless, or aluminum up to about an inch, laser wins. If you need very thick material, a flawless heat-free edge, or a non-metal like stone or glass, waterjet is worth its slow pace and high upkeep, but go in with eyes open: it is the slowest and, per part, usually the most expensive way to cut. If you need basic mild steel parts in the 1/8 inch to 3/8 inch range at the lowest possible cost and you can live with a wider kerf and some edge cleanup, plasma earns its place.
Frequently Asked Questions
Which is more accurate, laser or waterjet?
Laser holds the tightest tolerances on thin and medium material and preserves the finest detail. Waterjet is also very accurate and has the advantage of leaving no heat-affected zone, which matters most on thick or heat-sensitive parts.
Can a laser cut aluminum?
Yes. A modern fiber laser cuts thin to medium aluminum cleanly. For very thick aluminum, waterjet usually gives a better edge.
What is the cheapest way to cut metal?
Plasma has the lowest equipment cost and is economical for mild steel in the 1/8 inch to 3/8 inch range. For higher volumes, laser often costs less per finished part because it is so much faster and needs less cleanup. Waterjet is typically the most expensive to operate, because it cuts slowly and carries high power and maintenance costs.
Does waterjet leave a heat-affected zone?
No. Waterjet is a cold cutting process, so it does not harden the edge or distort the part with heat.
What thickness can a laser cut?
Most fabrication lasers cut steel up to around one inch. Above that, plasma or waterjet is the better choice.
Which process is best for thick stainless or aluminum?
Waterjet, because it preserves a clean, square, distortion-free edge on thick non-ferrous metals that plasma leaves rough and laser cannot reach.
About McGrath Metal
McGrath Metal is a precision CNC laser cutting and metal fabrication shop in Indio, California, serving the Coachella Valley, Palm Springs, Palm Desert, the Inland Empire, and customers across Southern California. We run high-power fiber laser cutting for sheet and plate, CNC tube laser cutting for round and structural tube, press brake forming, and in-house welding and finishing, with fast turnaround on mild steel, stainless steel, and aluminum. If you are weighing laser, waterjet, or plasma for a project, we are glad to help you specify the right process for your parts, whether the job belongs on our laser or somewhere else. Reach out for a quote on custom laser cutting, sheet metal fabrication, tube laser cutting, or your next run of laser cut metal panels and signs.