Manufacturers typically use one of two major cutting processes when cutting material for a project. These are known as laser cutting and water jet cutting. The choice of one or the other may be better depending on the type of material used and the desired end result. This article explains some of the basic differences between these fabrication processes and the materials and types of projects that they work well with.
A laser cutter relies on gas, typically CO2, for energy. The CO2 is transmitted through a beam, guided by mirrors, and directed at the material that will be cut. With CO2 lasers, the laser source is located inside the machine, and the beam can output between 1500 and 2600 Watts, which makes safety a primary concern and can occasionally increase the price point on a laser cutting job. Materials and applications, as well as precision and safety, are important factors to think about when considering laser cutting.
Materials and Applications
Laser cutters work well with a wide variety of materials, making them an easy choice for plastic, glass, wood, and most metals. It is important to note that laser cutters cannot be used on reflective metals. It can also work on material combinations as long as that combination consists of materials with similar melting points. If the materials have different melting points, it can be rather difficult to cut. Sandwich structures with cavities cannot be cut at all using a laser, and materials with limited access prove difficult as well. 3D material cutting is also hard to manage because of the rigid beam guidance with the mirrors.
Laser cutters do well with materials that range between 0.12 in and 0.4 in thickness and are commonly used to cut flat sheets of medium thickness steel. Typically, a laser cutter performs cutting, welding, drilling, engraving, ablation, and structuring.
Precision and Safety
Lasers are great when you want precision. The minimum size of a laser cutting slit can reach 0.006 in, depending on the speed of the laser. It is good to note that thinner workpieces may suffer from gas pressure if the proper distance cannot be maintained, and partial burring does occur frequently. Deformation and minor structural changes can occur as a result of thermal stress, and the cut material will appear striated.
Laser cutting produces smoke and dust, and some plastics and metals may produce toxic fumes, so being aware that those could impact time and cost is important. The overall risk involved in working with laser cutting machines is very low, however, and your time and budget can benefit from the minimal amount of waste produced and subsequent ease of cleanup.
Waterjet cutters use pressurized water to cut materials. There are often abrasives such as garnets and aluminum oxide added to increase cutting ability. The overall process mimics erosion in nature, just at a much higher speed and concentration: a high-pressure pump drives the water through rigid hoses, resulting in a forceful water jet—a typical water jet can output between 4 to 7 kilowatts. Unlike a laser cutter, where the laser source is located inside the machine, the work area and pump are often separate.
Material and Applications
Water jets can cut virtually any material including combination materials—with combination materials. However, water jets pose the threat of delamination. They can sometimes handle 3D material cutting, and exhibit limited ability with sandwich structures and cavities. Cutting materials with limited access is possible but difficult.
Water jets usually perform cutting, ablation, and structuring, specifically with materials like stone, ceramics, and thick metals. Materials that range in thickness from 0.4 to 2 inch benefit from water jet cutting.
Precision and Safety
Waterjet cutting is not quite as precise as laser cutting, with a minimum cut size slit of .02”. Because of the high level of force used, thin, small, parts do not fare well and must be handled carefully. Although thermal stress is not an issue and burring doesn’t occur in the cut, the surface of the material will appear sand-blasted as a result of the added abrasive to the waterjet. The waterjet cutting process is quite noisy, and requires a significant amount of clean up, which could mean a bit more labor cost. There is also a large amount of waste that occurs as a result of the mixed water and abrasive.