How metal Additive Manufacturing is transforming modern hydraulic systems

Hydraulic pumps, cylinders, and other actuators deliver greater power in smaller packages than engines, electric motors, and mechanical actuators. Hydraulic valves easily control direction, speed, torque, and force through controls that range from the fully manual to those managed by sophisticated electronics.

Historically, the production technologies that create these hydraulic components have not kept pace with their expanding range of applications. Enter metal Additive Manufacturing, a set of industrial processes offering new opportunities to capitalise on hydraulic technology’s high power density by improving the design and production of fluid power parts such as manifolds, valve blocks, and valve components.

As Additive Manufacturing continues to make headway across industry as a whole, a growing number of hydraulics and fluid power system users are already benefitting from the use of weight- and size-optimised hydraulic components with complex features that would be difficult or impossible to produce via conventional manufacturing. This is especially the case since AM overcame challenges linked to the very high pressures under which hydraulic components are used.

Why AM is different

Additive Manufacturing offers a different approach to the established methods of designing and manufacturing hydraulic parts. Instead of starting with a metal block, the Additive Manufacturing process allows engineers and technical designers to design hydraulic parts based on the specific needs of an application, rather than the constraints of past manufacturing processes.

Free from the limitations of conventional machining, parts can be designed for the most efficient combination of manufacturing and performance, including the optimisation of internal channels for higher flow and lower pressure drop. It is also possible to produce numerous different prototypes, within a matter of hours, to determine the best design before going on to mass production, whether that is via conventional or Additive Manufacturing methods. These components can be made from a variety of materials – including stainless steel, aluminium, and Inconel – the performance of which compares favourably to forged materials. Indeed, many AM-processed materials have better mechanical properties and densities than their cast equivalents.

Although hydraulic components can be produced either by conventional manufacturing or AM, conventional manufacturing necessarily has drawbacks. As a subtractive process, material is removed – generally via CNC machining – from a larger piece, usually a metal casting or bar, to leave the desired shape. Excess material is often left in place to save the expense of removing it, resulting in parts that weigh far more than necessary.

Machining is also limited in its ability to produce certain designs. Passageways in conventional manifolds often must be positioned to prevent cross-drilled channels from intersecting, and allow enough material between channels to provide adequate strength. Further, auxiliary holes drilled to connect internal passageways need to be plugged, creating the potential for a future leak.

Additive Manufacturing, on the other hand, ‘builds’ the desired part layer by layer. With this technology, flow channels can be placed exactly where they are needed – and be optimised for size and shape. Until now, flow channels, particularly in components such as valves, were usually circular because they were machined with rotating cutters. By building a component in layers, designers can specify configurations that would be difficult or impossible using subtractive manufacturing methods.

Manifold flow paths can now be made with cross-sections and in special shapes instead of a round hole, optimising flow capacity in a channel of the same (or smaller) width, sometimes in a smaller space. Because passageways connecting internal channels don’t have to be machined from outside a manifold, the need for hole plugs is eliminated.

Although there is a wide variety of Additive Manufacturing processes, this article focuses on Laser Beam Powder Bed Fusion (PBF-LB), in which metal powder is melted, layer-by-layer, using a laser. Other processes used for hydraulic components include Binder Jetting (BJT), in which the powder particles are held together by a binder before being sintered.

In both cases, material is added only where necessary. This enables manufacturers to create new, lightweight designs with varying geometries and reduced part counts. Instead of assembling three or four components (e.g. valves and manifolds), a single part incorporating these components can be designed. This delivers weight reduction, eliminates assembly operations, reduces the risk of leakage from joining multiple parts, and cuts down machining hours.

Delivering sustainability in both production and usage

In many instances, Additive Manufacturing delivers significant sustainability benefits. AM processes require substantially less material than subtractive processes such as CNC machining, which must necessarily start with more material than the final component requires. Reductions in energy consumption when comparing forging or casting to Additive Manufacturing have also been demonstrated.

The creation of lightweight parts through the use of AM also benefits the sustainability goals of end-user industries. Vehicles or mobile machinery into which the lightweight parts are installed can benefit from improved fuel efficiency, as the use of lightweight components reduces overall vehicle weight and, thus, fuel use. This is especially useful in aeronautics and space applications, where every gram shaved from components means not only a lower environmental impact but significant cost savings.

Case study: the UGO manifold

An interesting example from the agricultural machinery sector is the hydraulic manifold shown in Fig. 4. Designed by Aidro, the UGO is an excellent example of an additively manufactured manifold that showcases the advantages of the technology for fluid power systems.

The UGO manifold is the system through which combine harvesters are controlled. It operates on hydraulic cylinders and motors, traditionally consisting of:

• Six directional control valves
• Four pressure-reducing valves
• One pressure release valve
• One bypass
• Two pilot-operated check valves

The additively manufactured manifold performs exactly the same functions as the original unit it replaces, but it is half the size and weight (Fig. 5). While the conventional manifold is made from multiple materials (aluminium for the base, cast iron and steel for the valves), the new design is made entirely from 316L stainless steel. This material combines excellent strength, high ductility, and good thermal properties, which, along with its high resistance to corrosion and pitting (including from chemical corrosion), makes it particularly suited to machines used in agricultural applications. 316L is also able to better withstand the atmospheric agents and chemical products used in this sector.

Pressure testing of additively manufactured 316L has also shown that mechanical properties – such as tensile strength, elongation, impact toughness, and hardness – are as good if not better than conventional materials.

As previously highlighted, one advantage of adopting Additive Manufacturing is the ability to combine multiple parts into one, reducing assembly time and simplifying the supply chain. In the case of the UGO manifold, the original consisted of 194 parts; including thirteen main blocks, twelve valve body blocks, one base manifold, and numerous small components such as spools, o-rings, screws, gaskets, and caps. The AM version of the manifold consists of only forty-two parts, including one central block.

Performance

The operating performance of the UGO manifold exceeds that of the original part because the curved shapes of the internal channels mean that there are no 90° angles at intersections (Fig. 6). Further, as mentioned above, passageways connecting two or more internal channels don’t have to be machined from outside the manifold and subsequently plugged to prevent fluid from flowing out. Indeed, in the conventional manufacturing of hydraulics, manifold intersections are created by drilling a hole on one side and another on the other side of the block, a result of machine tools limitations. Free of these limitations, engineers can design components based on the principles of Computational Fluid Dynamics.

The ability to additively manufacture optimised curved channels enables better flow dynamics and reduces pressure drops. This, combined with removing the risk of leakage through the elimination of auxiliary caps and plugs, offers a two-fold advantage: performance is optimised and the risk of environmental damage is limited.

Moreover, the design freedoms enabled by Additive Manufacturing allow engineers to position flow channels precisely where they are needed in a variety of shapes and sizes. This means that flow channels can be spaced closer together than with conventional manifolds, which makes finished products more compact and lighter. In this example, the AM UGO manifold is 50% smaller than the original component.

The smaller sizes of components enabled by AM are especially valuable when parts are intended for mobile applications with comparatively little space for hydraulic systems. The shape of the UGO manifold has been adapted to the available space, with connections customised to exactly where the external piping arrives. This means the manifold needs no modifications after production, as it is designed precisely for its unique application.

Conclusion

Additive Manufacturing represents a transformative shift in the design and production of hydraulic components. By freeing engineers from the constraints of traditional manufacturing, AM enables the creation of lighter, more efficient parts with optimised flow dynamics and enhanced performance.

The case of the UGO manifold demonstrates how AM can drastically reduce component size and weight, simplify assembly, and improve reliability by eliminating features prone to failure, such as auxiliary plugs. Beyond performance, the sustainability benefits of AM, including reduced material use and energy consumption, align with the growing emphasis on environmentally responsible production. As the technology continues to evolve, it is set to play an increasingly critical role in the fluid power sector, driving innovation while meeting the diverse demands of modern applications.

Author

Valeria Tirelli
President & CEO, Aidro Srl – A Desktop Metal Company
Via Prati Bassi 36
21020 Taino VA
Italy
[email protected]
www.aidro.it