Dr. Steffen Haack, Bosch Rexroth AG: Hydraulics of the future will be "invisible"

"Nowadays, machine manufacturers often plan hydraulic systems in detail, design power units, specify valves and plan piping in the machine. For many applications, this procedure will soon be a thing of the past. After all, developers and engineers are increasingly opting for ready-made automation functions. Practically “invisible” in the background, they take advantage of the well-known benefits of hydraulics.

With its first ready-to-install modules, Rexroth has already put into practice the idea of designing hydraulic systems as ready-made “building blocks” for entire systems, and OEMs are using them more and more often. The independent SHA axis is just one example. It is a completely pre-assembled module with a variable-speed drive, a valve block, a pump, a cylinder and its own decentralized fluid circuit. Assemblers install it as a ready-made module, connect it to the power supply and then to the control communication – job done. A central hydraulic power unit is no longer needed. Commissioning is possible with the same engineering tools used for electro-mechanical versions and the range of functions is at least as good. Neither assemblers nor commissioners require a knowledge of hydraulics because the hydraulic system is completely encapsulated – making it essentially “invisible”.

For engineers, the issue of drive technology in these independent axes is only of interest if they require a specific power profile that would not be available without hydraulics, namely a very high power density and, to a large extent, a maintenance-free design. The independent axis as a “building block” reduces the complexity of individual parts and simply provides the required function including the option of a continuous hydrostatic transmission function.

Converting a technology which was previously regarded as complicated into easy-to-handle “building blocks” requires a great deal of preliminary work – something that Rexroth is doing at the moment. A key point is the shift from valve based throttle control to a displace control system via a pump drive speed control. At the same time, a switchover from central hydraulic power units with large fluid quantities to decentralized circuits with very small amounts of hydraulic oil – in some cases less than ten liters – is taking place. The developers are also using software to provide all functions which in the past were achieved hydromechanically with valves. This means that they are replacing hydraulic power distribution with more straightforward electrical power distribution.

In terms of commissioning and operation, there are hardly any differences between independent hydraulic axes and electro-mechanical drives. They only are doing the jobs requiring more power and robustness.

Our vision for the Factory of the Future: all machine modules are equally intelligent. System engineers no longer need to know in detail which individual hydraulic components they need for their solution. They simply use the “building block” which matches their concept."

Dr. Steffen Haack, Head of the Industrial Hydraulics Business Unit of Bosch Rexroth AG