“How can they possibly be making money on this job?” It’s a question people across metal fabrication continue to ask, usually after learning about a seemingly below-cost bid from a competitor. Many assume it’s just a low-ball offer to get the customer in the door; the competitor won’t be able to deliver at that price for long, and within a few weeks or months the prospect will be back requesting another quote.
This happens, of course. That said, big economic downturns—be it the dot-com bust, the Great Recession, or the great economic paralysis of 2020—tend to weed out those shops that don’t have a good handle on their costs. That leaves high-performing operations that manage costs very well, and when they do underbid the competition to win work, they tend to keep it and, even better, maintain or increase their profitability.
How exactly do they do this? They focus on operational excellence and scrutinize the entire quote-to-cash cycle. As part of this, they focus on their cost per part. As they continue to make strategic technology investments, their per-part cost continues to drop. This happens, however, only if a fabricator considers the big picture and weighs all the costs associated with buying and operating a certain technology.
Abrasive waterjet cutting is a prime example. Understanding all the costs associated with the abrasive waterjet process—and especially how these costs apply to the intended application—isn’t as straightforward as it might seem.
Abrasive Waterjet Basics
The abrasive is waterjet’s cutting edge. A science unto itself, selecting the right garnet abrasive hinges on your waterjet system setup, what you’re cutting, and the edge quality you need. But the abrasive is only half the equation; the other half involves how those sharp-edged abrasive particles propel through the kerf.
It starts at either a direct-drive or intensifier pump that generates high-pressure water, which flows through a jewel orifice and becomes high-velocity water. The water and abrasive mix in the mixing chamber where the abrasive particles accelerate to speeds close to that of the water stream. They are then refocused into a cohesive cutting stream through the mixing, or focusing, tube. The focusing tube’s inside diameter is usually recommended to be three times the diameter of the jewel orifice. For example, a 0.010-in.-ID orifice would be coupled with a 0.030-in.-ID mixing tube.
The idea is to optimize an abrasive waterjet stream’s velocity and power density for the application. Give the right velocity and power to the abrasive particles cutting through the workpiece, and you make the cutting action more effective.
Since 1971 waterjet cutting systems have been in operation around the world at fabrication shops. There have been many technology advances in the last 49 years. In 2008 waterjet manufacturers introduced 90,000-PSI waterjet pumps to improve production capabilities.
Over the years many have dissected the waterjet cutting process, describing the merits of different pumps, pressures, cutting head setups, and tables. These are all just pieces of the puzzle, though. What really matters are the results. The business owner needs to put together the pieces in the right way to meet or exceed quality requirements while providing the lowest cost per part for the majority of the job mix.
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