The waterjet cutting industry depends on sources that can produce abrasives with high purity, tight particle size distributions, and a high degree of cleanliness, all of which are attributes that are controlled during mineral processing.
Purity. As a natural mineral, almandine garnet is mined, milled, and processed to meet the producer’s final specifications. High-purity materials typically involve added processing stages and call for greater attention to detail during the refining process when compared to low-purity products. As a result, high-purity materials cost more, but they also deliver superior cutting results. Low-purity products may contain materials other than garnet that rob a waterjet cutting machine of its ability to cut well. When produced for use as a waterjet abrasive, other minerals must be processed to meet the high-purity level required for waterjet cutting.
Particle Size Distribution. Tight, consistent control of the particle size distribution (PSD) is extremely important to maximize the performance of a waterjet. Coarse or oversized particles pose a real risk of clogging the nozzle, which can bring the machining process to a standstill and potentially damage the workpiece. Conversely, excessive fines can collect in the feed line or the cutting head, causing irregular feed or sputtering in the cutting stream. Inconsistent particle size distribution can create a nightmare for operators that have to adjust the abrasive feed rate to maintain cutting speeds.
Cleanliness. While similar to particle size distribution, abrasive cleanliness stands on its own as the final important attribute for a waterjet cutting abrasive. Cleanliness refers to the amount of super-fines present in the abrasive product. These fines are so small that they often adhere to larger particles. From a technical perspective, the producers of quality garnet abrasives use a measurement called “suspended solids” to quantify how clean the product is. Using a product that has not been properly processed generates nuisance dust while loading the abrasive hopper, which may cause poor feeding and cutting over time.