Just a few days ago, Aidro presented its first serially manufactured AMES valves for improved flow, now GKN Additive is highlighting ongoing work on 3D printed hydraulic block subassemblies. Additive manufacturing of hydraulic applications, like hydraulic blocks (adapter blocks), is a powerful alternative to traditional manufacturing methods such as subtractive machining and casting. Because adapting the component geometry to AM allows a much higher level of design freedom, to reduce weight and improve the shape of internal channels for ideal flow.

GKN’s Business Development Director Ümit Aydin reported that, by using design for additive manufacturing (DfAM) practices, GKN was able to reduce by as much as 80% the weight of a 3D printed hydraulic adapter block. Hydraulic blocks usually have a compact, square design with multiple internal channels that enables them to control to the oil distribution of large machines or systems in automotive or industrial environments. Heavy-duty agricultural or construction vehicles, like excavators or lift tables and engines require hydraulic blocks as control units.

The traditional production of hydraulic blocks causes very high machining costs: Everything starts with a large steel block that is machined with milling and drilling operations to create the internal oil channels. Therefore, first a hole is drilled from above, then one from below. Finally, the two holes are horizontally joined together. Then threads must be cut. To prevent the oil from escaping on the side, a thread with a grub screw is used to close the horizontal connections.

However, the flow in traditional hydraulic blocks is highly inefficient. Sharp CNC’d edges create burrs that can’t be removed. Often they are not loosened and thus can’t be eliminated until the block is in operation. In addition, the oil flows with a channel pressure that can be easily above of 300 bar, which means that when it hits the connection areas between channels – resulting from assemblies of multiple parts – turbulences will cause large losses and inefficiencies. Dirt reservoirs and leakages in adjacent channels all contribute to further reduce flow efficiency.

The additive manufacturing process and GKN’s technology allow a totally free geometry design without the risk of bore overlap. Hydraulic blocks produced by AM are considerably lighter and can adapt to the requirements. Using DfAM ad AM as a production method resulted in a significant weight reduction of up to 80%, which i turn led to lower material costs. Redesigning the block caused weight savings from 30 kg down to 5.5 kg, which makes the lightweight part also easier to handle by an operator.

DfAM enables designs that have no dead corner areas where dirt is collected: no sharp corners and no areas where dirt is collected and can cause problems in operation. In addition, horizontal holes are no longer needed, which means that the oil can now flow around the corner and is not disturbed by corners and edges.

With more complex hydraulic blocks, it is possible to adjust the oil channel lengths to each other. The longer an oil channel is, the more wall friction and losses occur. Shorter channels mean less friction, less risk of leakage. Depending on how complex the system is, the hydraulic block should also react faster and run more stable due to less friction. Shorter channels and no sharp corners at which turbulence occurs mean higher energy efficiency.

Wall thicknesses can be adjusted as required, especially in parts that do not undergo particular stresses, while rapid design iterations and no tooling costs all contribute to reducing overall production costs. Additive manufacturing allows users more time for last-minute design decisions and total flexibility to respond to everything. With AM you can make adjustments to the design at any time. With conventional manufacturing processes, such as investment casting, you have to produce a new tool if you want to change the position of boreholes in order to optimize the oil flow.

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