Excerpt from the Fabricator
The pressure behind abrasive waterjet cutting
Since the inception of waterjet technology nearly 50 years ago, there has been an ongoing argument concerning what combination of pressure and power results in optimal cutting performance. Do bigger numbers translate into better or faster cutting? What combination of pressure, horsepower, and nozzle assembly is best for a given application? What does all this really mean?
First, a Primer
To frame the discussion, let’s remove the intensifier versus direct-drive pumps argument. If you’ve ever investigated purchasing a waterjet system, you’ve probably been hit with an onslaught of marketing and sales data showing the benefits of each. Hydraulic intensifier pumps can deliver exceptionally high pressures at the cost of an energy-intensive hydraulic system. Others have advocated direct-drive systems that use a mechanical crankshaft pump.
In previous decades a trade-off between these technologies existed. Intensifier pumps were considered easier and cheaper to maintain, especially at high pressures, while direct-drive systems offered higher energy efficiency. The technology has evolved and the trade-offs have changed over the years.
Regardless, the basic principles behind waterjet cutting haven’t changed. The nozzle/orifice combination assists in pressurizing the water as it is squeezed from the high-pressure piping through an opening measured in hundredths of an inch. Passing through a small-diameter orifice, the water forms a coherent jet of water that then passes through a venturi nozzle, where a metered amount of granular abrasive is drawn into the water stream. The mixture of water and abrasive particles passes through a special ceramic mixing tube, and the resulting abrasive/water slurry exits the nozzle as a coherent cutting stream of abrasive particles traveling at very high speed.