Making mechatronics child’s play

Ray Barnes of Hoerbiger-Origa tells Design Engineering of the latest plug and play developments in pneumatic control systems

Pneumatics systems might appear to be straightforward when compared to other more esoteric technologies, but often they are more complex than need be and carry with them unforeseen costs. Fortunately, new developments in the pneumatics business are coming to the rescue, and simpler systems and lower costs will be the result.

One such development is the deployment of fieldbus communications. This can contribute considerable savings in respect of system wiring, reduced electrical system design and installation time. Further savings accrue due to faster troubleshooting and maintenance procedures.

Another trend is the move towards mechatronics – which, as the word suggests, is a fusion of mechanical and electronic technologies. The idea is to develop a range of sophisticated machine elements that each satisfy a function, and which can be simply bolted together to create a machine.

One illustration of a mechatronic component that can be deployed in such a plug-and play fashion is a a completely interactive electro-pneumatic actuator.

With conventional pneumatics, creating a motion axis requires the combination of the basic pneumatic cylinder, several different types of valve, sensors, controls, tubing, silencers, end of stroke cushions and safety elements. The selection and design of the system and it’s integration with electronic controls, demands a high level of expertise in pneumatic, electrical and electronic disciplines.

By comparison, a mechatronic drive unit integrates all these parts into a single ready-to-run machine module, in which the individual elements are optimised for size and performance.

A significant advantage of the mechatronic approach is that while all pneumatic and electronic controls are integrated into the actuator element, the mounting dimensions remain exactly the same as the standard actuator unit.

In order to address the complex wiring and control problems associated with dedicated PLC controlled systems, such integrated mechatronic solutions must adopts a fieldbus interface: in the case of the Interact range of mechatronic solutions from Hoerbiger-Origa, the Asi bus has been chosen for two-wire control and communication.

For many pneumatic machine design applications, especially those in Germany, ASi is the clear favourite among end users, machine builders and PLC manufacturers alike. For systems demanding greater control complexities or using other fieldbus protocols, a range of gateways and masters, which interface with ASi, are available.

The mechatronic concept can of course, be extended to other pneumatic systems elements, such as a compact pneumatic module that similarly integrates all pneumatic controls and ASi Interface into a single unit.

A CASE IN HAND

The benefits of this approach are best illustrated by considering a typical application, such as the modular assembly line used for the manufacture of notebook computers.

The system itself comprises a series of assembly stations, each having a main feed conveyor; pallet-stop cylinder, station-loading cross transfer, station-unloading transfer, lowerator and out-feed transfer to a return conveyor.

While the initial installation features three duplicated assembly stations, it may easily be expanded to meet production requirements, in which case the benefits of using mechatronic technology become increasingly attractive.

When analysing total machine costs for the system manufacturer, a cost breakdown was first established. This is fairly typical for manufacturers of standard or modular machinery:

Of all the costs, 35% of the total was attributed to the pneumatic system and controls.

While the original design used a bank of conventional pneumatic valves and a standard PLC controller to minimise component costs, the machine builder had recognised the benefits of adopting ASI fieldbus technology. These included significantly reduced costs of wiring installations, improved system control, especially from a diagnostics perspective, and the flexibility to easily expand installations with additional assembly modules.

In comparison to the conventional pneumatic solution, the adoption of integrated pneumatic drives has a marked effect on the associated manufacturing costs.

Design time has now been reduced by 66%, logistics and administration by 50%, assembly by 82% and commissioning by 50%. In practice, the overall manufacturing costs are reduced by 18% for an increase in hardware costs of just 6%.

For the machine builder, the commercial benefits of such an integrated solution extend still further. The reduced time-to-market for a complete system provides a competitive advantage and also improves cash flow and profitability.

From the end users perspective, the system guarantees optimum performance, as the pneumatic control system is matched perfectly to each actuator size and type, ensuring peak performance and reliability. Maintenance and service functions are similarly reduced as faulty components are automatically identified. These may be quickly and cost effectively replaced without incurring expensive downtime. Furthermore, the modular construction subsequently ensures easy maintenance of valve, actuator, sensor and ASi elements.

{{TABLE

System cost % of Total Pneumatic & control element

Design 7% 2%Hardware 20% 5%Logistics and administration 8% 3%Commissioning 25% 15%Assembly 40% 10%Total 100% 35%}}

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