Above: An ultra-high pressure waterjet system cuts through metal.

Researchers create a waterjet orifice that lasts longer, costs less

November 2014 - Metal fabricators and machine shops using ultra high-pressure waterjet cutting technology are concerned with the lifespan of the waterjet orifice. While diamonds are the elite standard and can last for over 1,000 hours, they also come at a higher upfront price point. A new synthetic option named tetraCORE offers a high quality, more affordable option.

“Diamond is absolutely the crème de la crème,” says Ted Jernigan, president of Olympia, Washington-based Diamond Technology Innovations (DTI), which designs and produces a variety of orifices, nozzles and assemblies for waterjet cutting applications. “But for many, their upfront cost appears to be a great deal more than lesser quality options.

“Metal fabricators spend hundreds of thousands of dollars on ultra high-pressure waterjet cutting systems, yet the whole system is often subject to the unpredictability and unreliability of a ruby or sapphire orifice,” Jernigan continues. “They have a quarter of a million dollars tied up in the system, and yet it’s relying on a $15 ruby to support it.”

Between industrial diamonds costing upwards of $425 and rubies and sapphires starting at $15, the market lacked an effective waterjet orifice offered at a price point within that wide chasm. This large price gap has been evident in the industry for many years. Lower cost alternatives have attractive upfront costs, but the trade-off is a lower lifespan.

“If operators have to perpetually shut the system down to change the orifice, it affects productivity and other machine components,” says Jernigan. “Rubies and sapphires sometimes blow out immediately, and a really good one may only last 30 to 40 hours. When companies are trying to be productive, the cost per hour for operation is crucial.” Frequent orifice assembly replacement can cause unplanned machine downtime, premature failure to surrounding equipment and even damaged or scrapped parts.

With tetraCORE, DTI created an effective and affordable waterjet orifice. Under harsh, abrasive environments, tetraCORE can maintain performance, its structural integrity and jet stream coherency for hundreds of hours. As a new orifice option, it has been tested to above 500 hours of performance, and is both impact- and erosion-resistant.

“We wanted to develop a significantly more robust material that would consistently outlast sapphires and rubies,” says Adam Miranda, head of orifice production. “That’s what we created with the lab-grown orifice (made with a binderless material that is more wear resistant than corundum, but less robust than diamond). It will stand up to poor water quality and impacts from debris within the system, and keep functioning at a high level,” he says. 

High wear, longer life

The orifice is a small but significant part of a waterjet cutting system. It alone harnesses and directs all the energy generated by the ultra high-pressure pump. By restricting the volume of water from the pump, the orifice is designed to transition this extreme pressure into a very high velocity, columnar jet of water. When particles of debris in the water system impact the inlet edge of a waterjet orifice—whether metal, silica, calcium or abrasive media—the accelerated particles can chip or fracture a less hardy orifice. As a result, the jet stream loses coherency, reduces edge cut quality, requires slower cut speeds and becomes more difficult to hold cutting tolerances, requiring frequent shutdowns for orifice change outs.  

A failed orifice can cause excessive wear on the pump by causing the intensifier to overstroke as it struggles to maintain constant pressure. High-pressure cylinders, check valves and internal seal components are subject to much shorter lifetimes in these conditions. At the cutting end of the waterjet system, a worsened jet stream results in early wear of the cutting head internals and abrasive focusing nozzles.  

“Mixing tubes in particular can cost upwards of $100 to replace,” Jernigan says. “Every time the orifice fails, it causes extreme wear on the mixing tube, causing the part to erode much faster than if a more efficient orifice were used.”

There’s a mindset that rubies and sapphires are better because they are less expensive, “but that’s only looking at the cost per part,” he continues. “The fact is, they aren’t inexpensive at all when you look at how failures affect labor and other costs.” The initial cost of a ruby or sapphire is affordable, but “when it comes to the frequency of orifice failure, system shutdowns and component repairs, the overall costs far outweigh the less expensive orifice.”

Controlled accuracy

Besides saving manufacturers valuable time and labor, tetraCORE promotes tight tolerances and higher quality cutting, whether an operator is cutting carbon steel, aluminum or any other metal.

“With the lab-grown orifice, manufacturers get a better edge quality, better speed and less wear on components,” Miranda claims. 

Jet streams are also more controlled and more accurate when using higher quality orifices. The tetraCORE orifice can efficiently control 60,000 psi of water pressure while maintaining accuracy. 

“It’s important for the jet stream to shoot right through the center of the mixing tube,” Miranda explains. “If it’s off a little bit, it’s going to impact the water and the abrasion and can cause premature wear and erosion to system components. The tetraCORE jet streams and tolerances are very tight. That means manufacturers can count on having the jet stream shoot directly to the target material.”

TetraCORE cannot match the 1,000-plus operating hours of a diamond orifice, but its 500-plus hour lifespan far surpasses the 30 to 40 hours that rubies and sapphires provide.

“All of our extensive in-house and field testing concludes that the lab-grown orifice is a very solid 500-hour material,” Miranda says. “So not only will the orifice give you those predictable hours, it will also give you peace of mind that you won’t have to scrap an expensive or even inexpensive piece of metal if the system fails during the middle of a cut.”

Creating choices

Most manufacturers that use waterjet cutting technology aren’t aware that they don’t have to put up with the challenges caused by rubies and sapphires just because a diamond orifice isn’t in the budget, Jernigan says. “We need to make sure the reliability of waterjet cutting systems are up to par and competing well at the prevailing cost-per-hour rate. The lab-grown orifice will help take our industry to that next level.

“It all comes down to options,” he continues. “Metal fabricators using waterjet cutting technology don’t have to make the big price jump to a premium diamond orifice, but they don’t have to suffer the challenges faced with sapphires and rubies either.” MM

With over 20 years experience in the manufacturing industry, Perry Hanchey is general manager of Diamond Technology Innovations, overseeing both the Diamond Division and DTI Exact Machining Division.