What is the difference between pure and abrasive waterjet cutting?

Waterjet cutting is one of the fastest growing machining processes in the world today due to its incredible versatility and ease of use. While as a Mechanical or Design Engineer, you most probably know what waterjet profiling involves, you may not necessarily know about the finer details of the two different types of waterjet techniques available to you: pure and abrasive waterjet cutting.

Although the word ‘waterjet’ often refers to the more popular abrasive cutting, it actually defines a broader approach and both pure and abrasive techniques falls under it.

Understanding the difference between the two waterjet methods is essential towards choosing the right technique for your profile cutting needs. In this blog, we examine those differences and look at the capabilities and advantages of each technique.

Pure waterjet cutting:

A pure waterjet is the cleanest form of waterjet technology available on the market and it uses the pressure of water alone, forced through a tiny orifice, to cut through materials. Pure waterjets work by directing a stream of pressurised water onto a material. Unlike other machining solutions, the pure waterjet process is a form of cold-cutting, which removes the risk of heat-affected zones in the material, preventing it from hardening during the machining process. This, in result, eliminates or minimises the need for milling the parts following the cut to get rid of the hardened edges, thus, making the process faster and cheaper.

The only issue that can be encountered with pure waterjets is that their use if limited to thin materials only. A good rule of thumb is that if the material can be cut with scissors, it can be cut with a pure waterjet.

Some of the materials pure waterjets can cut through include:

  • Foil
  • Cardboard
  • Fabric
  • Wood
  • Rubber
  • Foam
  • Food
  • Thin plastic

There are several mechanisms a pure waterjet uses to cut, depending on the type of material that is being cut. Granular materials, such as sand stone are picked apart on a grain by grain basis, while fabrics and wood are cut by breaking fibres.

The advantage of pure waterjet cutting is its high precision. The width of the cutting gap can be reduced to just 0.08 mm, which allows for the production of complex geometries with fine contours, acute angles and tight radii.

Abrasive waterjet cutting:

The abrasive waterjet technology maximises the benefits of pure waterjet cutting for use on harder materials. It was in the 80s when manufacturers found that adding abrasive to the water stream generated a new process of cutting with far more extensive capabilities.

Though abrasive waterjets follow the same operating principles as pure waterjets, they introduce the use of abrasive particles, such as garnet, which mixed within the high-pressure stream, can erode virtually any material (of any thickness) with very high precision and speed. Which also makes the technique much more cost efficient. The opportunities offered by abrasive waterjets has made them an ideal choice for parts manufacturers and fabricators across a number of industries.

Abrasive waterjets can cut through:

  • Stone
  • Ceramic
  • Thick plastic
  • Steel
  • Aluminium

Click here to read our blog ‘Which materials are suitable for waterjet cutting?’

The abrasive waterjet cutting mechanism is quite similar to a grinding wheel. The abrasive particles are moved by the water jet rather than the wheel and chip out small pieces just like the abrasive particles in the wheel does. By using a hard abrasive such as garnet, an abrasive waterjet can cut a very wide range of materials and other hard materials and thus become a useful technology for machine and fabricating shops.

The cutting power of this method is based on the final speed of the abrasive particles. In more technical terms, the jet diameter and the width of the cutting gap are between 0.5 – 1.5 mm. The grain of the abrasive is approximately 0.05 – 3 mm.

If you’re still unsure whether waterjet cutting is the right method for you or simply want to find out more, download our free and comprehensive eBook ‘An engineer’s guide to waterjet cutting’ that will provide you with the finer knowledge necessary to determine whether this is the right technique for your needs.