The Smart Factory needs a powerful PROFINET cabling system

  • December 04, 2014
  • HARTING Inc. of North America
  • Harting Inc. Of North America
  • Feature

By Rainer Schmidt, Harting What exactly does the protocol for process automation have to do with intelligent production? Is there really something new here, or is it just a battle between marketing strategists? Clear answer: The Smart Factory needs PROFINET. And PROFINET helps to control processes more intelligently, to organize production more flexibly and at the same time more efficiently. But that doesn’t happen by itself. PROFINET has to move – and that is what it is doing! The Smart Factory, or Industry 4.0 as it is also known, is the talk of the town. That is a good thing, because these expressions help to make it easy to talk about a very complex topic. But still it would be advisable to pay good attention to what the particular correspondent means by these expressions in the following discussion. By Smart Factory HARTING understands – besides all the structural and technical details – above all, the chance to innovate. As one who has for decades successfully developed, produced and marketed connection technology for industrial and associated applications, the Smart Factory opens up new applications which require new solutions. Intelligent production needs a uniform and intelligent net with participants/components which can communicate with each other simply and yet in real time and absolutely reliably – i.e., securely. And that is the challenge. There are networks for industrial communication with properties like fast, safe and reliable – e.g. PROFINET.But PROFINET is an independent, proprietary system, which is primarily used for communication between PROFINET components.In order to fulfill the Smart Factory requirement for open, barrier free communication, PROFINET has to open itself. It must become compatible with other network philosophies. And at the same time it must not lose its specific properties such as real time communication in Conformance Class C. How can that work? PROFINET has already completed a decisive step. PROFINET uses IEEE 802.3 Ethernet as its communication platform. In contrast to the PROFIBUS philosophy, PROFINET fundamentally has all the necessities for working in an open network architecture as well.So now PROFINET is able to support a range of functions for the Smart Factory already today, while further functions are on their way. That is primarily a topic for the system designers (hardware and software development), who find a continually widening framework for the PROFINET specification. These specifications are developed and documented in the PROFINET guidelines and the PROFINET user organization (PNO). Is everything shipshape then? No! A very important component is missing. The passive infrastructure, or simply – the cabling. Without cabling, no network infrastructure. PROFINET has always regarded itself as a solution package for its users. Thinking in system terms does not finish with the SPS. Like no other, PROFINET has understood the need to consider all the necessary components of the system comprehensively and to keep them under control – including the cabling. Strict specifications for cable, connector and installation lead to a reliable network infrastructure with high availability, which users can rely on at all times. That certainly sounds good. Where is the problem? PROFINET has set very narrow limits to ensure the quality of the net. These limits were largely set by the automation protocol PROFINET itself. For the cabling this means: PROFINET = Fast Ethernet with 100MBit/s + special stipulations for cable and connector e.g. star quad construction in Category 5- and 4-pole RJ45 (IP20) or M12 D-coded (IP65/67) plug components – field assembly. But if PROFINET should seamlessly communicate in future right into the SAP level of an industrial company, it runs into the structured cabling which the IT infrastructure of the company uses. Structured cabling has long represented a different philosophy than PROFINET cabling. It is not connected with ONE application, but is application-independent and thereby provides transmission paths for a large number of different services (telephony, data, video, controls, etc.). But even that is not an insoluble contradiction. PROFINET with Fast Ethernet also runs on structured cabling thanks to the downwards compatibility which is laid down in the cabling standards (ISO/IEC 11801, EN 50173-1 and 3). Most IT systems today, however, work with GigaBit Ethernet. Many devices, cameras for production monitoring or controllers, still only possess interfaces with Gigabit or higher functionality. Even smaller net nodes or sensor/actuator units already work with Gigabit Ethernet and POE or POE+ with power supplied via the same cable. So the real challenge for PROFINET is GigaBit Ethernet. And what that means for PROFINET cabling is eight cores in copper cables and eight contacts in connectors. And therefore structured cabling for PROFINET? Not quite. PI (PROFINET International) has already certified PROFINET in today’s form and in conformance class A for structured cabling, i.e. connecting 4-core PROFINET cabling with 8-core structured cabling is possible today. At least with the use of RJ45 technology (IP20) there is no problem at all as far as connectors are concerned. Investigations have shown that here the unused 4/5 and 7/8 pairs of the structured cabling do not need to be terminated with 100‚Ѷ resistors for reasons of impedance. Consequently the migration from PROFINET cabling to structured cabling is in full swing. But how does it look in the other direction? What do devices and equipment do which want to make a connection to PROFINET from their GigaBit Ethernet? This problem has also been recognized by PI – or rather their members – besides manufacturing firms, especially the PROFINET users. These are more and more often confronted with the need to integrate Gigabit devices in a PROFINET landscape. That is why the signs of the future with PROFINET quite clearly indicate the direction of GigaBit Ethernet and compatible cabling infrastructures. It is interesting to note that it is once again the cable experts who are getting to grips with this topic and who advancing solutions for the issues of Fast Ethernet vs. Gigabit Ethernet, or 4-core vs. 8-core. But what does that mean in concrete terms for the PROFINET cabling? The PROFINET cabling as we know it today will not be thrown overboard just because we are contemplating the Smart Factory. But it will be developed further in this direction. For this purpose, PI is extending its cabling guidelines with 8-core solutions. Always under the stipulation of keeping the installation simple, robust and secure. This therefore builds on industrial grade cabling components – just with the capability of supporting Gigabit Ethernet, i.e. 8-core and at least Category 5 (100MHz) or, preferably, Category 6 (250MHz) or 6A (500MHz). Note: Category 6A is required for 10Gigabit Ethernet transmission What do the cabling products for this look like? PROFINET has defined a new 8-core cable with PVC or PUR sheath. As before, these cables are classified into types A, B or C for fixed and flexible installation as well as for special applications e.g. cable carrier applications or hybrid cables (with additional power conductors in the same cable). However the star quad has been phased out. Shielded cables are offered with AWG24 cores (solid or stranded) in a construction with separation stars or as PIMF (Pair In Metal Foil). The separation star variant is better for production since the single foils are not needed.  This construction, however, leads to a larger external diameter that is not compatible with the cable entries and threaded unions of most connectors, so that many users prefer the PIMF variant. In the connector area, the trend is towards an upwards migration, i.e. the PROFINET RJ45 connectors will have 8 poles in future and all eight contacts will conform to structured cabling with ½, 3/6, 4/5 and 7/8 (see also connector standard IEC 60603-7-x). Here, particular properties such as insertion depth, vibration safety and contact quality (gold plated, freedom from porosity in accordance with DMG, increased corrosion resistance, etc.) are adopted from the four-core variants. For the IP65/67 qualified connectors, the RJ45 is integrated in PROFINET housing types such as the Han 3A or Han PushPull (AIDA interface). The 4-pole M12 D coded is replaced by the new 8-pole M12 X coded in Cat. 6A (see also connector standard IEC 61076-2-109). In addition PROFINET has defined new cabling components such as the cabinet cord. This IP 20 component is offered ready wired-up and tested (so no longer wired up on site) and takes account of the requirements for space saving and easy handling especially in the switching cabinet. Because of the high quality requirements for the connectors and cables used and the workmanship, the cabinet cord guarantees the operational safety demanded by PROFINET for the full life of the equipment. Here, HARTING uses its DualBoot overmold technology, which permits a tight bending radius with easy operation of the locking tab (limited space in the cabinet or in the distributor is no problem). Smart Factory will increasingly break up proprietary solutions, as we know them today especially as islands of automation, and rejoin them together in a unitary infrastructure. The unitary communication infrastructure is an essential building block for this. Even if PROFINET cabling and structured cabling originally followed different approaches, the two philosophies can now be connected together cleanly. Smart Factories simply need smart network infrastructures.

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