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The difference between 2D and 3D waterjet cutting

Making the correct choice based on your application

In the early days of waterjet cutting, applications were sparse. Initial waterjet systems were used to cut very thin materials such as paper and, aside from extremely niche applications, did not have a place in the mainstream manufacturing industry.

The continuous development of this innovative technology was the catalyst for the surge in adoption rates of waterjet cutting systems across the globe. Today waterjets are commonplace in manufacturing, seen in facilities ranging from small fabrication shops completing one-off jobs to expansive mass-production facilities. The evolution of waterjet cutting systems includes major developments in multihead functionality and the ability to cut 3D parts.

Contrasting 2D and 3D Cutting

The introduction of 5- and even 6-axis waterjet systems has facilitated the ability to perform complex cutting operations. Bevels, chamfers, weld preps, and angled holes are all made possible with 3D cutting. No longer is waterjet cutting limited to flat workpieces. With a 5-axis cutting head, precise cuts can be made in intricate, nonuniform, and asymmetrical materials as well.

While extremely beneficial for a variety of applications, the transition from 2D to 3D cutting does not come without its fair share of nuances that must be considered before jumping into a cut.

Fixturing. This is a crucial first step when preparing to cut a part on a waterjet. A proper fixture ensures that the material does not move throughout the cutting process, which is essential to maintaining part accuracy.

Affixing flat materials to a waterjet cutting table is a relatively simple process. The cutting table comprises multiple slats or grates that span the length of the tank, serving as the foundation of the cut. (While slats are commonly found on many waterjet systems, grates provide a sturdier foundation for the workpiece and double the number of fixture points.) Clamps are used to fixture the material to this foundation, preventing movement caused by the force of the jet stream and the agitation of the water below the workpiece.

The process of fixturing parts for 5-axis cutting on a waterjet is a bit trickier. Many 3D parts require custom fixtures to securely hold them on the cutting table without interfering with the path of the cutting head or the jet stream. These types of fixtures take time to create. Even with the help of CAM software to design the fixture, it will still need to be cut out, built, installed, and tested before use.

Cutting Heads and Accessories. Various waterjet cutting heads are available for 2D and 3D cutting. Each is tailored to a specific manufacturing function.

Here are the different 2D cutting head types:

  • The 2D abrasive cutting head comes standard on most waterjet systems. It cuts perpendicular to the workpiece; is capable of motion in the X, Y, and Z axes; and uses an abrasive medium to cut through hard, thick materials.

    Fixturing parts on a 2D waterjet is made easier when grates are used instead of slats in the cutting bed.

  • The 2D water-only head has the same motion capabilities as the 2D abrasive head, but no abrasive is used. Developed for cutting thin, flexible materials, these water-only heads deliver an extremely fine jet of water that can slice through materials such as foam, rubber, fabric, and plastic.

    For 5-axis cutting heads, the capabilities are more advanced:

  • Taper compensation is very important when operating a 5-axis cutting head. When cutting thicker materials, the cutting stream might begin to fan out, leaving a taper in the shape of a V. While this taper is a nonissue for the majority of applications, some fabricators are faced with instances when this must be eliminated to achieve the desired accuracy. In these cases, a taper-compensation cutting head can be used. These cutting heads tilt a number of degrees to adjust the angle of the cutting stream. With the angle of the cut adjusted, the taper is placed on the scrap side of the part, leaving a perfect 90-degree (or desired angle) edge on the final product.

  • A full five-axis cutting head delivers a full range of cutting capabilities. It can angle the cutting stream up to 90 degrees, spin around the workpiece indefinitely, and create multidimensional cuts in complex workpieces. These cutting heads are commonly used to make bevels, weld preps, and separation cuts on intricate 3D material, and are capable of both abrasive and water-only cutting.

  • A rotary axis spins the workpiece a full 360 degrees, giving the cutting head access to the entire surface of the material without having to manually adjust and reposition the workpiece. A rotary axis can be used in conjunction with a 5-axis cutting head, effectively turning the waterjet into a 6-axis cutting system.

  • Safety. 2D cutting on a waterjet is generally a very safe process, and injuries associated with it are rare. While the cutting head expels a water and abrasive mixture at almost three times the speed of sound, the cutting head is always directed downward, so the jet stream is safely dissipated in the machine’s tank.

    In 3D cutting, the cutting head may be angled upwards of 90 degrees, creating a situation that may require the implementation of additional safety features. Examples of available safety features are:

  • Steel guards around the perimeter of the cutting table.

  • Advanced technology that detects a stray waterjet stream and shuts the machine off before it leaves the boundary of the tank.

  • Perimeter mats that prevent the machine from running without an operator or that shut off the machine when a person steps on the mat.

    Both 2D abrasive and water-only cutting heads are found on this spreader bar.

  • Light curtains that detect when an object enters the cutting area and triggers the machine to shut down.

Collisions. Operators cutting in both 2D and 3D must be vigilant in preventing the cutting head from colliding with the workpiece. Cutting head collisions are extremely detrimental to profit margins as they likely will call for expensive repairs and lead to costly downtime.

Collisions are relatively easy to avoid when cutting in 2D, but the complexity of 3D cutting increases these risks. Five-axis cutting mechanisms have a much wider range of motion, equating to a higher potential for crashing. To prevent these incidents, intuitive software with simulation capabilities can be used to predict collisions and change the program accordingly. Alternatively, 5-axis crash sensors can be affixed to the cutting head that will cut power to the machine before a collision occurs.

Other Considerations

Currently there is no practical method of controlling the depth of a waterjet cut. The cutting stream does not stop once it breaches the opposite side of the workpiece. It continues to cut whatever lies in its path until the waterjet stream is diverted or stopped. In 2D cutting this is generally not an issue, as the cutting head is always pointed down into the tank where the stream is dissipated by the water. (It is possible, however, for the cutting stream to make a hole in the bottom of the tank if left on and in the same position for a long period of time.)

When working with a 5-axis cutting head, fabricators should take extra precautions to protect the material from accidental contact with the cutting stream. Examples include:

  • For cylindrical workpieces, such as steel tubing or PVC pipes, a sacrificial material should be placed inside the cylinder to prevent the cutting stream from damaging the opposite side of the material. This also applies to any 3D workpiece that contains bends or curves where the cutting stream could contact the material’s opposing face once the stream breaks through the original face.

  • For countersinks, both the angle of the cut and depth of the material must be considered. An angle that is too extreme or a hole that is too narrow results in the waterjet stream inadvertently cutting through the opposite side of the material, ruining the workpiece.

While the vast majority of waterjet applications can be accomplished with 2D cutting, businesses that regularly process 3D workpieces and require bevel cuts on flat stock have the option of investing in 5-axis technology. If a fabricator is thinking about purchasing a waterjet cutting system and would like to know if 3D cutting is necessary for an application, it should give a waterjet manufacturer a call to determine what approach makes sense. With years of experience in the industry, waterjet manufacturers are the best resource to determine whether 5-axis cutting or standard 2D cutting is right for the application.

Alex Ruegg is content marketing specialist; Benjie Massara is waterjet product manager; and Dennis Toering is technical service manager, WARDJet, 180 South Ave., Tallmadge, OH 44278, 330-677-9100, info@wardjet.com, www.wardjet.com. WARDJet is part of the AXYZ Automation Group, www.axyzautomation group.com.

About the Authors

Alex Ruegg

Content Marketing Specialist

330-677-9100

Benjie Massara

Waterjet Product Manager

330-677-9100

Dennis Toering

Technical Service Manager

330-677-9100