The natural characteristics of the abrasive used in waterjet cutting and mineral processing have an effect on how the particular material will function as a waterjet cutting abrasive. As a fabricator, you should be aware of how these characteristics will impact the functioning of the abrasive.
There needs to be a balance between the cutting speed and consumable wear in case of waterjet cutters. If you make use of a soft abrasive, the nozzle life can be extended but the cutting speed becomes very slow. If the abrasive is very hard, the cutting speed is fast but the plasma torch nozzle will get eroded quickly. This will decrease the accuracy of the cutting process, result in frequent downtime and repeated nozzle replacement. Almandine garnet is a suitable abrasive that provides a reasonable tool life and satisfactory cutting speed.
An ideal waterjet cutting abrasive contains the heaviest particle that can be accelerated to the maximum velocity of the water stream. This produces the maximum cutting force. A heavy abrasive will not accelerate to the maximum velocity and the power of the waterjet stream will be weakened, whereas a very light abrasive will not be very effective. The key is to find an abrasive with the correct balance and almandine garnet is the best abrasive with the ideal range for acceleration and punch.
This plays a prime role in how the waterjet abrasive performs. Very friable material breaks up easily in the tube and becomes too fine to cut effectively, while an abrasive that is too tough becomes round and dull during the process of mixing and does not cut well. The ideal abrasive is one that produces angular and sharp cutting edges and also has a slow breakdown rate. Once again, almandine garnet is suitable because of its conchoidal fracture and semi-friable character.
You can get abrasives having different particle shapes from needle-like crystals of silicon carbide to perfect beads of steel shot. Waterjet experts have concluded that the most appropriate particle shape depends on the edge finish requisites and the material being cut. While rounded grains are used for standard and general-purpose cutting, angular, sharp grains are suited for quicker cuts and superior finish.
The other attributes that must be considered when choosing a waterjet cutting abrasive are the mineral processing attributes i.e. purity of the abrasive, cleanliness of the amount of superfines existing in the abrasive and the particle size distribution that is an important criterion that maximises the waterjet performance. When deciding on the type of the abrasive for waterjet cutting, you must consider the abrasive that offers the best balance between cutting, acceleration and wear.