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Laser vs. Waterjet

Technical advances have led to some overlap between these two processes, but the fundamental advantages of each remain intact. This comparison by two experts reviews the basics and updates the range of applications for laser and waterjet.

Fabricators in today’s marketplace are faced with many challenges. Those challenges include maintaining flexibility while controlling costs. With an incredible range of equipment available and various technologies, it can be difficult to keep track of the latest machine developments and how those developments can help to meet current and future operational needs. Complicating matters, as technology gets better and better, there may be several ways to solve any one problem. The challenge is to fully understand each of those solutions and the unique advantages offered to remain competitive.

Being competitive in today’s market usually requires high levels of precision. Two of the most common processes for producing high precision parts are waterjet and laser cutting. Both processes are well established in modern manufacturing, and technology for each process continues to develop. Many of the
advantages of each process have remained the same over many years. Waterjet is able to produce parts with no heat affected zone(HAZ), and can process an incredibly large range of materials. including metal, glass, stone, ceramic, plastic, wood, and even food. The thickness range capability of waterjet is equally impressive, topping out at around12 inches! Conversely, lasers can produce sheet metal parts at an astounding pace and offer good capability up to 1-in. thick mild steel. Furthermore, laser can do so with unattended operation and low operating costs. In many ways these technologies are complimentary and many fabricators have both options at their disposal. However, the latest trends in technology have started to increase the overlap regions for these solutions.

Trends in laser

For many years laser has been an indispensable tool for flexible manufacturing. The speed in thin materials and the precision in thicker ranges has opened the doors to new affordable possibilities in manufacturing industries, ranging from kitchen equipment to earth moving monsters. The biggest trend in industrial laser processing over the last five years has been the evolution of fiber delivered lasers, the two primary technologies being the fiber laser and the disc laser. There are many similarities between these two laser types:

– Both utilize diode lasers as the method to convert electrical power to optical power
– Both use another medium to increase the brightness of the optical power
– Both have a similar wavelength, which is about 10 times shorter than CO2
– Both deliver the beam through an optical fiber

Regardless of the technology utilized in the laser, the end results are the same – higher productivity in many materials and lower operating costs. These advantages have resulted in the adoption of fiber based lasers and enabled growth from almost nothing five years ago to about 25 percent of all laser systems delivered last year. Every major laser supplier has an option for a fiber based system and many new smaller OEMs have developed laser cutting systems centered on the fiber solution, because of the ease with which the laser power can be delivered. The increase in volume production of the lasers and associated components has helped drive down costs to further improve the position of fiber based lasers relative to the incumbent CO2 technology.

At the heart of the fiber laser advantage is the solid state technology. The diode lasers are highly efficient at converting electricity to light and have no moving parts. This eliminates many of the traditional operating costs associated with CO2 lasers. There is no lasing gas consumable, no resonator optics to replace, no turbines to rebuild, and no beam delivery mirrors to clean and align. Flip a switch and the laser is on. There is no more worrying about a resonator pump being down or a lengthy warm up time eating into production time. The higher efficiency of a fiber laser means lower electrical costs for both the laser and chiller, and the shorter wavelength focuses to a smaller spot while also coupling more effectively into material when nitrogen is used as the assist gas. These factors can add up to straight line cutting speeds nearly three times faster than an equivalent power CO2 in certain material types and thickness ranges. Additionally, materials with higher reflectivity such as brass and copper are more efficiently processed.

The pace of fiber laser development and associated machines has been impressive. Not too long ago a 2 kW fiber laser was the maximum power level you could get. Today, however, many machine builders are offering 5 and even 6 kW machines that operate at 6 g’s of acceleration. While fiber laser was initially recommended for thin material, there are now systems with variable beam configurations that can maintain thin material speed and also reconfigure for thicker plate processing. All of this happens automatically when a specific material type is called up or a certain contour is detected in the part program. If the budget allows, add in automatic nozzle changers and material handling systems to make lights-out system operation a reality.

AluminumCopper

Trends in abrasive water jet

Waterjet is widely recognized as a complementary tool to other cutting processes. Waterjet systems use a combination of water and an abrasive, normally garnet, to cut material using an erosion process. Waterjets are a flexible tool that can cut virtually any material at any thickness, and expand the breadth of projects that a job shop or other business can take on. This is because waterjet can cut stainless steel one minute and plastic the next. Waterjet can also be used on laminated material.

At the extremely high pressures used in waterjet cutting—60,000 psi or higher—component life can be problematic. This is especially true of the waterjet pump, since that is the source of the high pressure water. Fortunately, there are now systems on the market that are capable of extending component life. Waterjet system manufacturers do this by using fewer parts, constructing their systems of materials better able to withstand the high pressure environment, and precisely aligning all of the components to avoid excess wear. Seal life in high pressure pumps has also doubled with these technology advances.

Another trend is an advance in cutting head technology combined with a migration in orifice technology, from rubies and sapphires to diamonds. Diamond orifices, while initially more expensive than rubies and sapphires, result in a significantly lower long-term operating cost, as the life of a diamond is typically 30 times longer than the life of a ruby or sapphire. Diamond life is also much more consistent than the variability often found with rubies and sapphires.

The ability to better control the volume of abrasive being delivered to the cutting head is also becoming increasingly important. This is because the cost of abrasive—the highest expense when operating an abrasive waterjet—continues to rise. As a result, more and more abrasive delivery systems are able to accurately deliver the desired amount of abrasive at the desired moment to eliminate abrasive waste. Some waterjet manufacturers also use sophisticated methods to detect potential leak points. This ensures an operator is aware of an issue well in advance of failure and can plan for needed maintenance.

Overlap region

As stated earlier there are certain clear divisions for process capabilities. Thin material and oxygen cutting of mild steel up to ¾-in. thick is efficiently handled by many laser systems, while most non-metals and very thick materials can be cut cost effectively with abrasive waterjet. However, there are certain materials and thicknesses where the processes overlap. Many advertisements for fiber laser tout its ability to cut brass, copper, and aluminum. Because these materials are quite soft, they are also good candidates for an abrasive waterjet. Generally, though, laser will cut faster on aluminum less than 0.20-in. thick, and brass less than 0.16 in. As soon as the brass or aluminum gets thicker than that, the processes even out, as the speed of the fiber laser slows considerably. Besides material overlap, processing speeds are quite similar for the two methods (shown in charts) as are operating costs. A 3 kW fiber laser system will typically cost between $13 and $20 an hour to operate. This covers electricity usage, lenses, nozzles, and a high pressure nitrogen assist gas. The operating cost for a 75 horsepower abrasive waterjet can range from $15 to $23 an hour. This covers the cost of electricity, water, maintenance, and abrasive material. One difference: the abrasive waterjet does have the added advantage of being able to adjust the speed to achieve varying levels of quality, depending on the part requirements.

Conclusion

In summary, advances made in recent years have led to more overlap between the two cutting processes. Similar materials can be cut and operating costs are similar. Both systems are also more efficient, whether through the use of less electricity or a more efficient abrasive delivery system. However, the processes remain largely complimentary to one another. Laser excels at cutting thin metal very precisely and extremely quickly, while waterjet excels at cutting a wide range of materials, also very precisely, and with no heat affected zone.