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Advancing the aerospace industry with automation

It only takes a thin stream of water to easily penetrate 8 inches of titanium. A six-axis robot drives the procedure, carefully moving the waterjet nozzle across the part to form the curvaceous shapes of jet engine airfoils. You won't believe it unless you see it.

Advances in robotic machining have allowed for some impressive innovations. Despite the tight tolerances necessary in the aerospace industry, robots have proven to be reliable and accurate enough to meet these challenges. This time around, they were able to accomplish their goal with the aid of a liquid product. An integrated bladed rotor (IBR) for a commercial jet engine is being rough cut by a robotic waterjet system in the first section of the video referenced above. This robotic waterjet system can cut through solid metal up to a foot thick using only tap water combined with abrasive material and sprayed out of a small aperture at ultra-high velocity. Waterjet 3D cutting is demonstrated here, explains Dylan Howes, VP of Business Development at Shape Technologies Group (SHAPE) in Kent, Washington. The Aquarese system (shown) is the world's only 3D robotic abrasive waterjet machine capable of 94,000 psi (6,500 bar).

As a member of the SHAPE family of companies, Aquarese works together with Flow International Corporation, the maker of the ultrahigh-pressure pumps and waterjet technology, to provide customers with cutting solutions and integrated systems. Turnkey solutions for the aerospace, energy, and automotive industries are made possible by Aquarese's integration of Flow's technology with cutting-edge robots. A robotic waterjet system can generate a stream of water flowing at supersonic speed, allowing it to cut through a wide range of materials, including the superalloy components used in the aerospace industry. The waterjet process is made more adaptable and fluid thanks to the robot. The articulated arm has six degrees of flexibility, allowing it to approach the workpiece from almost any angle and then follow a smooth, accurate, and highly repeatable toolpath to carve out intricate details. When used for metal cutting, waterjets typically do rough cuts before the components go through final milling. Howes cites the waterjet's adaptability as one of the technology's main advantages. Just about everything, including metal, plastic, stone, glass, paper, and even food, may be sliced with this. Cutting metal one day and foam the next on the same machine? That's possible with waterjet.

Titanium alloys, Inconel, Ni-based alloys, other superalloys, stainless steels, composites, and more can all be cut using an aquarese system. Metals can only be cut with an abrasive waterjet. In nearly all abrasive waterjet applications, garnet is used as the abrasive material. Its cutting power is multiplied by a factor of a thousand when water and garnet leave the waterjet cutting head at approximately four times the speed of sound. There is no heat-affected zone (HAZ) or thermal fatigue in robotic waterjet machining because it is a cold-cutting process, despite the high cutting speed and pressure. Compared to plasma and laser cutting, this is a significant improvement. Howes claims that, in contrast to milling or conventional machining, the part is not subjected to any mechanical stress, which means that the item's integrity is preserved while only minimal fixturing is needed.

Howes claims that waterjet is superior to rough milling and electrical discharge machining (EDM) using a wire. When compared to the chips you receive from a milling process, "it is significantly faster, has a lower operating cost, and creates huge offcuts which are easier to recycle." There are no harmful chemicals used in the waterjet procedure. Both the water and the abrasive garnet can be reused. Howes claims that there are no harmful vapors present. You can use water systems with a closed loop if you want to. In contrast to laser or plasma applications, there is no dross waste produced.

A commercial airplane titanium blisk is 3D-cut using a robotic abrasive waterjet technology

Precision, consistency, and firmness in robotic performance. The robot used in the highlighted waterjet application is made by Swiss company Stäubli Corporation. Specifically for this cutting application, we choose Stäubli because of its reliability and path precision, as Howes explains. Together with Stäubli, we were able to fine-tune this procedure to meet our demands. Robotic waterjet has often been used for softer materials and other industries. The aerospace sector has recently adopted it for use in metal and composites cutting.

"Now that we can reach higher performance, it's become a more prevalent application," says Sebastien Schmitt, North American Robotics Division Manager at Stäubli Corporation in Duncan, South Carolina.

The arm's stiffness and accuracy have both greatly improved thanks to our efforts. It paves the way for us to do research and development in that field today. Schmitt elaborates, "Our proprietary gear box, which we build and design ourselves, provides the accuracy, repeatability, and stiffness that our customers demand." That's because we're the only robot maker that also makes its own gear box from scratch. This results in improved trajectory performance. Schmitt recommends a 100-kilogram robot for its stiffness, and this model fits the bill. In addition, the counterforce from the supersonic waterjet makes this a crucial feature. Aquarese encountered almost no resistance from the Stäubli machines. Consider the possible repercussions of turning a fire hose on and off. None of these systems. Schmitt adds, "The fact that we are rigid, highly precise, and very repeatable gives you the capacity to push the edge of performance." This allows them to compete with more conventional milling techniques. "A 5-axis CNC machine will set you back three or four times as much as this setup here."

The robot used by Aquarese is a Stäubli TX200 HE (pictured). Humidity index, or HE, indicates a damp setting. This is a robot that was made for use in damp places. Arm suppression further improves the waterproofing of the fully encased arm structure (rated IP65). The wrist has an IP67 rating, which means it is protected against dust and water at low pressure. The stainless steel construction of the tool flange and other vital components ensures they will not corrode. The six-axis robot, ultrahigh-pressure waterjet pump, cutting head, control system, and programming software make up a robotic waterjet system. (Reprinted with permission from the Shape Technologies Group) The longevity of your robot is crucial, especially if it is used in demanding situations like abrasive waterjet applications. According to Schmitt, "you're making an investment for years to come." Stäubli takes pride in its ability to maintain quality over time. We have systems that are twenty years old and still functioning as well as they did when they were first installed. Stäubli's VAL 3 robot programming language was developed with CAD-to-path compatibility in mind. Howes from SHAPE claims that importing a CAD model and getting an optimized toolpath is a breeze. FlowXpert, SHAPE's in-house software suite, is used to program the waterjet systems and is included in the package. The AquaCAM3D module is included for 3D robotic waterjet cutting, and it has pre-installed modules and functionalities for various uses, such as roughing of blisks and trimming of fan blades. The resulting toolpath from AquaCAM3D can be easily exported for use with Stäubli robots.

Quantitative Gains

Robotic waterjet has many benefits, one of which is the reduction of material waste. Let's take a look at the movie again; the 3D nesting with the robotic waterjet begins at 0:35. The method is used to rough out two turbine blades from a single bar of lightweight metal.

According to Howes, "for one slug, you get two pieces that are near net shape before final machining and grinding."

With waterjet, you can leverage 3D nesting, which is a major benefit over milling. Wire EDM is the only alternative option, and it's incredibly pricey. When cutting sheet metal, standard cut lines can also be used. Intricate detail is possible because the waterjet has a narrow cutting width (between 0.003 and 0.015 inches for a clean waterjet stream and 0.015 and 0.070 inches for abrasive waterjet). Howes claims that traditional machining methods are inefficient for this because the kerf, or width of the cut, is too great. Utilizing standard cutting paths, 3D nesting, and larger offcuts all result in considerable material savings. As part of the MRO industry, Aquarese also incorporates robotic waterjet stripping solutions for the removal of coatings on aircraft engine components like boosters and combustors. Investment casting foundries, such as those catering to the aerospace or industrial gas turbine industries, can also take advantage of their ceramic shell and core removal methods. System that uses a robotic waterjet to remove coatings off turbine parts during MRO. (Reprinted with permission from the Shape Technologies Group) "We can also link the core removal technologies with cutting solutions for de-gating and flashing from forged materials," explains Howes. Each of these "robotic applications"

Studying Facilitative Technologies

However, there is a limit to how stiff and accurate robotic machining can be, whether it is done using waterjet or more traditional methods. Scientists are looking into new approaches to overcome these constraints. Newly opened on the campus of Georgia Institute of Technology in Atlanta is the Boeing Manufacturing Development Center (BMDC), where studies are now under progress. Shimless machining is just one example of the non-conventional approaches to industrial automation that the BMDC is working on. Delta Advanced Manufacturing Pilot Facility, a 19,000-square-foot building, is home to the center (AMPF). According to Shreyes Melkote, Associate Director of the Georgia Tech Manufacturing Institute and Morris M. Bryan, Jr. Professor of Mechanical Engineering for Advanced Manufacturing Systems at Georgia Tech, the center was officially opened in June, but Georgia Tech's strategic partnership with Boeing is in its tenth year. Melkote, who is also an affiliated member of Georgia Tech's Institute for Robotics and Intelligent Machines, serves as a bridge between manufacturing and the robotics and automation fields by working at the Advanced Manufacturing Partnerships Facility (AMPF), a translational research facility focused on discrete parts manufacturing. Melkote is an expert in the field of robotic milling. His goal is to develop technologies that will make it possible for robots to accurately generate increasingly complex features and surfaces. Melkote notes that there is "still need to overcome" issues with "lack of stiffness" and "precision." Over the past four to five years, we have been developing technologies including sensing, compensation, and metrology to overcome the stiffness and constraints of articulated arm robots.

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