Laser, Waterjet and Plasma Cutting Basics
In order to fabricate a variety of intricate part designs, appliance pieces and tools, manufacturers commonly use cutting technologies including waterjet, laser, and plasma processes. Each of these standard cutting methods employs different application tools; they are not always compatible with the same type of materials. Plasma cutting involves melting material surfaces via a high speed gas process. Another heat-centric process, laser cutting, involves using high temperature to melt materials while a gas jet propels excess materials out of the cuts. Waterjet cutting, which is used as an alternative to both aforementioned processes, does not involve heat treatment and employs jet streams to cut materials.
Here is an overview of the three cutting processes:
The Waterjet Cutting Process and Applications
Waterjet cutting—also known as pure waterjet cutting—was first available for commercial manufacturing use in the 1970s. The process, which is often used instead of plasma and laser technologies, incorporates a high-pressure stream of water that cuts a wide volume of materials. The process is commonly used for replacing milling operations. During the process, an orifice ejects a jet stream at speeds which exceed the speed of sound. This cutting technique is distinguishable for its ability to create precision cuts and is an efficient process for timely jobs that require intricate detail.
Another form of this process, abrasive waterjet cutting, involves incorporating an additional abrasive, such as garnet or aluminum oxide. Once these abrasive materials are added to a small chamber in the cutting tool, harder materials, such as concrete and steel, can be cut. Standard materials compatible with the water process include metal, foam, foods, rubber, plastics and glass, and flammable materials. Common applications associated with this process include parts for the automotive and shoe industry and standard products fabricated with this process include tissue paper and diapers. The process is also distinctive because it does not involve heat treatment and cause deformations as with other cutting technologies.
Some Advantages of Waterjet Cutting
- Detailed, precision cuts result in material savings;
- Minimal material loss in the pure cutting process;
- No thermal distortion;
- Short set-up time;
- Good to use in hazardous zones where heat is restricted;
- May be used for flammable materials;
- Cuts a wide variety of thick and thin materials
Waterjet Cutting Considerations
Although the waterjet cutting process is compatible with a vast amount of materials, there are limitations to consider. Experts note that the pure cutting process should not be applied to diamonds, which are too dense, or tempered glass, which will crack when under pressure. Additionally, the process is not efficient when it is used for fabric or material bundles, as the jet stream loses power after cutting through the first several layers of material. It is also helpful to note that water jet may be slower than the speed of a laser cut component.
Laser Cutting Process and Applications
The laser cutting process is a thermal method that employs energy to melt material. Typically, this process is used to melt material in a localized area, and lasers are able to achieve extremely thin cuts. An assist gas, typically CO2, is transmitted through a beam that treats the material. The gas jet is typically co-axial to the beam and works by blowing the excess metals out of a cut slit. As with flame cutting, laser treatment involves cutting work pieces along lines and curves. The process is sometimes used complementary to CNC/Turret cutting.
Overall, laser cutting is efficient for its precision and the ability to cut numerous materials such as precious and non-ferrous metals, (excluding reflective metals) wood, glass and plastics. The process is often used as an alternative to plasma and oxyfuel cutting, as it is distinctive for accuracy and heat input control and the ability to produce high-quality cuts without additional finishing.
Advantages of Laser Cutting
- Quick set up time;
- Ability to produce thin cut widths;
- Minimal waste clean-up;
- Low distortion rate;
- Applicable to small batches;
- Efficient alternative to mechanical processing
Laser Cutting Considerations
As with all cutting procedures, it is essential to consider safety precautions and wear appropriate gear when processing materials with laser tools. Although lasers work with a number of metals, they are not suitable for reflective materials, such as aluminum and copper alloys. In order to avoid partial burring on thin work pieces, a proper application distance must be applied when processing the material.
The Plasma-Arc Cutting Process
Materials processed with the plasma cutting process are treated with a high-temperature ionized gas arc. The gas content may be oxygen, nitrogen, argon. As the gas passes through nozzle, the restricted opening of the tool causes it to exit at a high speed, enabling it to cut through metals, and an electric arc ionizes the gas. Standard materials that can be treated using this process include aluminum, steel and stainless steel sheets. Typically, this process is used for heavier cuts, including processes such as welding and for cutting aluminum alloys and is commonly used as an alternative to mechanical saw cutting.
Advantages of Plasma-Arc Cutting
- Popular alternative to mechanical oxyfuel cutting;
- CNC is cost effective for thick metals;
- Ideal for cutting thin non-ferrous materials (up to 1 inch);
- Suitable for cutting various expanded materials;
- Efficient for producing non-linear cuts
Plasma Cutting Considerations
It is essential to consider plasma cutting limitations, specifically when compared to other processes. For example, plasma cutting machinery may cost more than other cutting methods such as oxyfuel cutting. In addition, keep in mind that the edges of the processed material may be rough, specifically with thicker materials. Professionals also note that warping may occur when processing intricate parts. Additionally, whereas laser and waterjet cutting may be used to achieve fine precision cuts, the CNC plasma cutting process is most effective for cutting 2D shapes that require less intricate details.