Simple digitisation with CPX-AP-I

Plastic sheet metal producer benefits from new remote I/O system

Making machines fit for the future means digitising them. With so many different communication protocols and control options, this is not always easy. How do you ensure that all components can (continue to) communicate with each other and the higher control system without having to redesign an entire topology? Festo offers a solution with the CPX-AP-I; a decentralised I/O platform.

With this solution, a machine builder can easily and modularly adapt or expand his future designs based on one automation platform without changing his original structure. The modularity also typically saves 5% on hardware.

CPX-AP-I was recently incorporated by a machine builder into his design for a machine that finishes plastic sheet parts. These are mostly pre-shaped, relatively long and narrow parts, into which cut-outs are made by means of punching. This is done pneumatically. Since not all sheet metal parts are the same thickness, sometimes also made of different plastics and furthermore shaped differently, the required pneumatic pressure must be set differently for each product and each cut-out. This was originally done using proportional pressure regulators that were controlled directly by the PLC.

From central to decentralised

The corresponding design of the machine had some disadvantages related to the central control of the pneumatic punching units. For this purpose, eight proportional controllers were integrated directly into a central valve island located in the control cabinet. Four punching movements were carried out at a relatively short distance from this valve island - 3 to 5 metres - but the other four were on the opposite side of the machine. For these four punching units, cables and air hoses with lengths of 10 to 12 metres had to be laid from the control cabinet. In addition to the high material and installation costs, this also meant less accurate control of the rear four punching units and a longer cycle time.

When the machine builder in question received an order for four identical machines, he consulted Festo - as his technical partner - about the possibilities that new technologies could offer. Faster, better, more durable, cheaper? The new CPX-AP-I emerged from these discussions as a possible solution for decentralised control of the punching units and also to make the machine 'future-proof'. But there turned out to be many more advantages.

Decentralised I/O system

To understand these advantages, here is an explanation of the CPX-AP-I. It is a new decentralised I/O system designed to directly connect a variety of I/O modules and valve islands in the field. The system can be easily integrated into the most important PLC systems via the most common field buses without the need to provide the individual components with a field bus node. It is also possible to integrate IO-Link, which makes it easy to connect any IO-Link component and provides all the associated benefits.

The structure of such a system is shown in the figure below.

This shows that valve islands and I/O link masters can be integrated directly into the master control system (PLC) regardless of the industrial automation network used. So both pneumatic and electrical modules and with support for all known field buses. In other words, it is no longer necessary to link/ integrate valve islands via an IO-link master; they can be controlled directly via the AP bus, which improves performance in terms of reliability and efficiency. In addition, this means a saving in the number of bus nodes or components.

Modular structure in a familiar environment

The CPX AP-I offers the possibility of a modular, and therefore easily scalable, design. Adding or removing functionalities, modules or otherwise is possible without the need to modify the existing topology. Changing the bus system is also possible by only modifying the bus node. The Bill of Materials (BOM) and control architecture are fully retained. Furthermore, the machine builder can continue to program in his familiar environment and is in no way affected by the fact that the I/O system works with a proprietary bus system. In terms of numbers, he is certainly not limited, since up to 500 modules can be linked in line, star and tree topology.

Ready for digitisation in the age of Industry 4.0

In addition to the fact that the CPX AP-I can easily integrate components, it also offers the possibility of sending data to the cloud. This is a typical feature that fits into Smart Industry and fully automated Smart Factories. It means that a wide range of data, for example short circuits, IO-link events, number of circuits, cable quality, temperature, voltage, operating hours, etc., can be collected centrally. This data can then be analysed and converted into valuable information in the context of optimisation, cost calculations or, for example, 'smart maintenance'. It makes it possible to monitor various modules and the channels and to give an alarm in time if things threaten to go wrong. Moreover, it enables efficient maintenance planning and steps towards predictive maintenance.

Applied in practice

The machine builder who started this story switched to the CPX AP-I on Festo's recommendation and has now literally seen the benefits with his own eyes. Due to the decentralised design, the group of eight proportional pressure regulators is now divided into two groups of four. The second group is placed on the other side of the machine and is therefore much closer to the punching units. This ultimately saved so much installation time and material that a cost saving of 5% was achieved when four machines were built. He was also able to offer his customer lightning-fast communication for all modules that do not use IO-Link. The figures of 200 MBaud and cycle times of up to 250 µs are impressive. Because two separate cables are used for communication and power supply, he also has the option of working with voltage zones if necessary. Finally, he was relieved that his existing topology could be fully retained. He can easily integrate valve islands without the need for additional bus nodes or IO-Link masters. The number of interface modules is also limited due to the large number of components that can be linked to a CPX AP-I bus module.

Ready for the future

The machines have now been delivered and are running satisfactorily. So well, in fact, that the machine builder has elevated the new remote I/O system to the standard for all new machines that will be developed and built in the future. Only when customers explicitly come up with different specs, will other systems be used. Whether these are for the automotive industry, packaging machines or otherwise. This is what we need" was the final verdict of the (happy) machine builder.

July 2022