Additive manufacturing is continually being adopted by industrial users across a range of industries, from aerospace, to medical, to manufacturing. In a recent case study, engineering company GKN demonstrated how additive manufacturing and design for AM could offer advantages for a hydraulic system over traditional manufacturing processes.
In the case study, GKN investigated how redesigning the interior of an existing hydraulic block for AM could offer benefits and enable manufacturers to overcome problems characteristic of traditional processes, including leakages of internal channels, efficiency loss and more.
Limits of tradition
Hydraulic blocks play an important role in hydraulic systems. The components themselves often resemble blocks from the exterior, though they incorporate complex internal channels that help control oil distribution in large machines such as agricultural or construction vehicles.
Traditionally, hydraulic blocks are made using subtractive machining process, meaning that they begin as solid steel blocks which are milled and drilled to create internal channels. As GKN explains on its blog: “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.”
Aside from incurring high costs, using subtractive processes also creates a series of problems in the final part causing inefficient oil flow. For one, the sharp edges in the channels created by the drilling can create burrs which cannot be removed. These connection areas can also cause “large losses and inefficiencies” when the oil flows through them at high pressures.
Other risks that GKN lists include the formation of dirt reservoirs which can cause failures, leakages in adjacent channels and a reduced OEE of the hydraulic system which occurs when the hydraulic block fails and must be replaced.
Redesigning a hydraulic system
In redesigning the hydraulic block for additive manufacturing, GKN ensured that the structure of the block’s channel holes, was consistent with the original design—enabling it to be fit into existing hydraulic systems.
The redesign process enabled the team to create a more lightweight part with more optimal oil flow. Post-printing the hydraulic block, GKN found a number of other notably benefits. Firstly, the 3D printed hydraulic block offered a weight reduction of up to 80% (from 30 kg down to 5.5 kg), which meant lower material costs and easier handling by the operator.
Second, the redesigned part did away with dead or sharp corner areas, reducing the risk of dirt collection. Similarly, by getting rid of sharp corners and creating smooth channels, the oil flow through the block was further optimized.
The 3D printed block could also be redesigned to include more complex channels. As GKN explains: “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.” It adds that in future the block could also be further adapted for even faster reactions, more stability and higher energy efficiency.
From a production perspective, additive manufacturing also provided GKN with more freedom to tweak and adjust the hydraulic block’s design, even at the last minute. Significantly, this freedom also entails that the company did not require tools for every design update, drastically reducing manufacturing costs.