Is 3D printing the future of fluid power?

Moog's Additive Manufacturing Centers have been in operation for more than a decade, featuring 12 laser powder bed fusion (LPBF) metal machines and 10 machines for a range of plastic materials.

BY: Ken Korane, Contributing Editor and Mary C. Gannon, Editor

Three years ago, the big buzz heading into IFPE 2017 was the 3D printedexcavator — dubbed Project AME — which was a joint project between Oak Ridge National Laboratory (ORNL), in collaboration with CCEFP university student designers from the University of Illinois, the University of Minnesota, and Georgia Tech, as well as AEM and the NFPA. They worked to create novel designs for the cab, stick and heat exchanger that were all printed at the Department of Energy’s Manufacturing Demonstration Facility located at Oak Ridge National Laboratory.

Fast forward three years, and many fluid power manufacturers are dabbling in additive manufacturing, some more than others. Key components designed with additive manufacturing include valves, manifolds, heat exchangers, and more.

ITALIAN MANUFACTURER AIDRO AT THE FOREFRONT

Component manufacturer Aidro Hydraulics is pioneering a new approach to production, based on additive manufacturing, that will revolutionize fluid power markets, according to company CEO Valeria Tirelli. While the industry is still in its infancy, the potential benefits are obvious and the limitations are quickly being overcome, she said.

Aidro, based in Taino, Italy, makes high-pressure manifolds, valve blocks and other hydraulic components. 3D printing permits size and weight reduction and parts consolidation.

3D printing offers the possibility to create a new generation of hydraulic systems that surpass the limits of conventional hydraulic components. This technology lets Aidro produce fast prototypes, spare parts, and functional products that can routinely reduce size and weight by 75% versus conventional hydraulic components. It is being used to make products like high-pressure (10,000 psi) manifolds, valve blocks, heat exchangers, hydraulic spools and other components.

The process can consolidate multiple parts and functions into one, reconfigure ports to simplify connections and piping, and permit previously impossible complex geometries that improve performance, thanks to the optimization of internal channels, she explained. For instance, machining a traditional manifold often requires cross-drilled passages that must be plugged, creating potential leak paths. And pressure drop at the 90-degree intersection can be excessive. 3D printing permits smooth, curved flow paths that tests have shown improve flow efficiency by 30 to 70%. “So we can have smaller parts but with the same or better functions as a larger hydraulics manifold,” said Tirelli.

While 3D printing isn’t suited for every application, as of yet, interest and acceptance is growing rapidly, she continued. “It’s practical for special applications, because nowadays we have some limitations for additive manufacturing in the number of parts that we can produce. For a typical manifold, we can produce parts for prototyping and for small series in special machinery, but we cannot produce 10,000 pieces. But the 3D printer producers are working on larger machines that run ever faster and have higher productivity, so capabilities are constantly improving.”

“I think today we can say additive manufacturing is perfect for prototypes and special small series, so low-volumes, but in a few years, because machines are getting bigger and faster, I think that this will be a good alternative to traditional manufacturing,” she said. Automobile manufacturer BMW, she noted, is now producing some parts by the thousands with additive manufacturing.

Aidro uses laser power bed fusion technology (LPBF, DMLS or SLM), which ensures a high quality of metal materials and good mechanical properties of the printed parts. Materials are mainly aluminum for lightweight, stainless steel for food-industry machines, and Inconel for special application like oil and gas, and offshore. It takes a few hours to print a small manifold, she said.

Other fluid power companies are dabbling in the technology or relying on contract manufacturers. But she cautions potential users to do their homework. There are service providers with multiple machines that can make parts on contract, but they serve all markets, such as automotive and aerospace, and are not specifically expert on hydraulics.

“It seems simple: make a design, send a file to an external company, and they print it. But in the case of printing a hydraulic manifold with additive manufacturing is not easy. Because we have to take into account the complexity: the flow, pressure, how to orientate the manifold inside the machine, where to position internal supports, and many other issues that really requires expertise about the 3D printing process. So it is not easy to design a good 3D-printed manifold and to produce it, because we need more and more knowledge about what is inside,” she said.

“We have special software, of course. But the people are the main point. There is typical topology optimization software for 3D printing which is very good for mechanical parts. But for hydraulics, is not easy because we have pressure and fluid inside, so there are more aspects to consider in the design.“

“This technology, for the moment, is as I said, mainly for prototypes or special series. But what is important is to have the idea. And in the hydraulics and fluid power world, people are very conservative. So we have started to also promote the technology to allow designers and engineers to think in a different way. It’s definitely the future, and I prefer to be optimistic that they will fall in love with this technology,” said Tirelli.

MORE DESIGNS FOR BETTER FLOW CHARACTERISTICS

Many of the major players are using additive manufacturing to demonstrate flow-optimized designs in valve technologies.

Parker Hannifin demonstrated a further advancement in cartridge valve technology at the Hannover Fair with the introduction of its TFP series. The new 2-way servo proportional valve with VCD (Voice Coil Drive) technology is based on the current TDP and TEP families. The TFP series builds on the excellent flow characteristics, precision and dynamics of these existing products to deliver shorter cycle times, more stable processes and minimized scrap rates.

Parker Hannifin launched its TFP series 2-way servo proportional valve with VCD (Voice Coil Drive) technology at Hannover Fair earlier this year. The TFP Series is characterized by a completely new, flow-optimized design and, as a special highlight, Parker presented the new TFP series in both traditional and 3D-printed versions.

The TFP Series is characterized by a completely new, flowoptimized design and, as a special highlight, Parker presented the new TFP series in both traditional and 3D-printed versions.

This lets customers reduce their manifold size and yet maintain the same amount of flow. For example, users can downsize from a size 63 to size 50 valve with the same flow, explained Udo Heidrich, Parker’s sales manager for industrial motion systems. “Dynamics are better because there is less mass, and the next generation is the 3D-printed version of the same valve.” In-depth analysis using techniques such as CFD were used to optimize the cartridge profile. “The benefits include a smaller manifold, or higher flow from the same valve,” he said.

The fully functional valve clearly demonstrated the exciting possibilities of additive manufacturing, he continued. 3D printing is a technology many companies are considering. For hydraulics, properly made components are robust and have the necessary strength, sometimes better than die-cast parts. It permits flow paths that can be more efficient than those produced by machining or casting, and in the TFP they are well suited for applications like presses, die casting and other dynamic processes.

Currently, additive manufacturing technology is suited for lowvolume production, said Heidrich. “One day we may see factories full of 3D printers, but not tomorrow. It’s a long way off,” he said. “The problem is the time required to make a part. For this product we need about 24 hours. But every technology started slow, and then ramped up faster and faster.” The machines, software, materials and processes will all get increasingly better.

Bosch Rexroth tapped additive manufacturing for its new CytroBox hydraulic power unit, which features a sleek, intelligent and energy-efficient design, integrates IoT technologies and helps pave the way for implementing Industry 4.0 concepts.

Bosch Rexroth's CytroBox requires 50% less installation space than conventional units, runs much quieter, and integrates the latest IoT technologies. The unit features a 3D-printed manifold block which is 40% smaller than a comparable machined manifold.

“The intention was to move to the next step of innovation in the field of hydraulic power units,” said Steffen Haack, President Industrial Hydraulics at Bosch Rexroth, Lohr am Main, Germany. Compared to conventional power units, which haven’t markedly changed in decades, the company collaborated with its customers to integrate the latest technology offerings into a new type of power unit, he explained.

“And in the end, we wanted to change the perception of industrial hydraulics and power packs. When you look at the stamping lines of a Ford, GM or Chrysler, power units are mounted in the ground, they’re dirty, noisy and leaky, and no one wants to go near them. Our idea was to make a power unit that you can put in your living room, it looks like a refrigerator and runs silent. We believe this is a new approach for hydraulics, compared to what has been done for the last 30 years,” he said.

The unit has a number of key features that set it apart from a typical power pack, according to Haack, with a 3D-printed manifold block being one such design function that contributes to efficient operation. Additive manufacturing techniques let engineers create more-refined channels and make the manifold 40% smaller than a comparable machined manifold. This improves oil-flow characteristics, reduces pressure losses and minimizes potential leak points, as fewer plug screws are required.

Finally, Moog has its own additive manufacturing centers, with 12 LPB metal machines. The company also specializes in non-metal (AM) printing with close to 10 machines that are capable of a range of plastic materials. For the last 10 years, Moog has been designing, producing, inspecting and providing post processing through its R&D center, a metrology and material analysis lab and stress relief/ heat treat ovens.

“Many customers are looking for ways to use technology such as additive manufacturing (3D printing) to solve motion control challenges in a new way. Moog has leveraged the potential of metal additive manufacturing to produce hydraulic manifolds with flow paths that would not be possible with traditional manufacturing methods. Enabling these additively manufactured designs has resulted in hardware with significant weight reduction, smaller envelope size, and increased flow characteristics,” said Jay Sollecito, Additive Manufacturing Center Process Manager.

“Another attractive benefit of additively manufactured designs is the potential for parts consolidation, where multiple features and components of an existing assembly can be integrated into a one piece design. This not only allows manifolds to fit in design-constrained envelopes but also reduces the lead time and manufacturing costs associated with more complex assemblies,” Sollecito said.