Application Independent Cabling of Machine Networks

Application Independent Cabling of Machine Networks

Everything stays the same. If you know how to install a field bus, you can install Ethernet too! For HARTING, the first challenge Ethernet presents is providing an adequate solution to the connector problem. The RJ Industrial is setting the standards here as it not only represents an industry-ready housing, but also an industry-ready RJ 45 contact insert.

From HARTING‘s standpoint, the Ethernet connector, as part of comprehensive installation systems, is the key to making Ethernet manageable in industrial environments. As the existing field bus systems are the standard here, they also provide a solid foundation for Ethernet. On the other hand, DIN EN 50173 is the standard for office wiring. For a long time, one or the other of these competing approaches has been held up dogmatically as THE solution. Approaching the problem from a user point of view, HARTING has focussed on the requirements of the application. An analysis of key customers has shown that, in some areas, there is good reason for office and field wiring to live together. All you need is the right interface.

Application-independent cabling

Structured cabling systematics

When work groups on generic (structured) cabling talk about industrial applications, they are influenced by their office backgrounds. Machines are separate units that are integrated into the network of the building wiring. Because office and industry converge here, the higher levels of the hierarchy are influenced by the office, and the field level by the environmental conditions of the machine. The lacking compatibility between office and machine environments has already been described. In the future, not every installation will have to be designed based on machine requirements. There are clear transitions between the two worlds. The German Electrotechnical Commission (Deutsche Kommission Elektrotechnik, DKE) is taking a practical route as part of preparation for an industry DIN EN 50173. A machine outlet (MO) is defined below the machine distributor (MD). An industrial building network is located above this outlet and below is the machine network.

Application-independent cabling

This differentiation is important because it meets the various relevant requirements. All of the controversies of the past had focussed on this division. The machine network was given increased attention in the requirements of the Profibus Users‘ Organization (Profibus-Nutzerorganisation, PNO) and other field bus-oriented organizations.

In the office, application-independent cabling is thought of as the use of one system for different applications such as ISDN and Ethernet. This means that the transmitted data protocol was seen as the application. In the industrial environment, application-neutrality is seen as an easy transition from classic field bus systems to Ethernet. The change in communication protocols must not change the structure of communication in such a way that the entire design of a machine is influenced as a result.

Cabling for PROFInet

Cabling for PROFInet

The PROFInet connector serves to make connections between machines or entire network segments. For this connection to work reliably, it is necessary to design the interface to meet the requirements of industrial environments. Connectors that work reliably over a long life cycle, as in machine tools, for example, differ significantly from office solutions.

But even within industrial applications the most varied requirements are encountered. The differentiations within industrial applications pertain to the wiring inside and outside of the switch cabinet on the one hand, and in the integration of the 24 V voltage supply of the stations on the other. This integration of the 24 V voltage supply for PROFInet is referred to as hybrid wiring, analogously to Profibus.

The switch box interior differs from the floor distributors of the office world in key respects such as the levels of soiling and temperatures. Therefore the requirements for connectors within the switch cabinet are also more demanding than in office wiring.

Consequently there are two wiring classes for PROFInet applications: inside and outside of the switch box. These classes are specified in such a way as to cover the major share of industrial applications. The specification of these classes follows the experience gained with the Profibus recommendations.

Transmission physics

Transmission physics include both the electrical twisted pair wiring and the fiber-optic wiring. The transmission performance of the connectors is adapted to 100 Mbit Ethernet. Only RJ 45s and 4-pin M12s that comply with the specifications of Category 5 (DIN EN 50173) are permitted.

Connection cable

Connection cables

As opposed to Profibus, no passive T-pieces are used in PROFInet. All machines are connected via an active network component. To ensure the simpliest installation possible, the transmission cable was defined as identical at both ends. This connection line therefore fulfills the function of a patch line that is prepared in the same way on both ends. The contact assignment of the RJ 45 was selected to be compatible with IEEE 802.3. This provides compatibility to the structured building cabling.

Coupling connectors

Coupling connector

Extension cables or flying couplings can be implemented using coupling connectors. These couplings are available for all listed connectors (M12, RJ 45).^

The insertion of coupling connectors creates additional transition points that influence the maximum link length. Each additional plug-in point reduces the link length by 5 m. A coupling connector therefore reduces the length by 10 m.

Contact assignment

Contact assignment

The contact arrangement is specified as follows:

Shielded, B-coded models were used for M12 connectors. However contact position 5 is closed. The pin side of the connector is always on the cable side. Selecting this M12 type prevents mix-ups with Profibus lines and sensor/actuator lines.

Cabling types

Field cabling

Industrial wiring makes a connection between machines in an industrial environment. The cable used must be designed for this environment. Connectors must therefore be designed for connecting industrial cables, regardless of whether they are used in the IP 20 area of the switch cabinet or in the IP 67 field area.

In contrast to field cabling (analogous to link technology), a cable with reduced transmission performance (DIN EN 50173) can be used with pure switch cabinet cabling (patch technology). This exception is also permitted in the industrial environment. The reduction in transmission distances caused by this (maximum 10 m patch cable within one connection between components) leads to a restriction that does not exist when one cable type is used consistently.

Crossover

Cable termination

Because 100 Base T Ethernet in full duplex mode is always run via two separated core pairs, a crossover takes place. Because crossovers should be avoided at the installation stage, all network components must be designed so that they perform an automatic crossover. It must be ensured that all terminal devices are connected via network components with autocrossing.

Termination equipment and System cabling

Ethernet system cabling

An essential criterion for industrial usability is the manageability of the termination equipment on site. Appropriate connectors both for M12 and RJ 45 are available for this purpose. These connectors can be prepared easily on-site using standard tools. Connector solutions that offer this option should be used whenever possible. For the end user, the PROFInet system wiring is not any different than Profibus wiring.

Installation philosophies living in harmony

A machine is not a building. But a machine is often housed in a building. Therefore the integration of a machine into a company network nearly always represents an integration into a building network. By defining the MO, it has become possible to establish a clear, concise interface between different installation philosophies. By drawing this dividing line, users will benefit from the best of both worlds.

As a symbol the MO: Inside, a connection technology that has prov-en itself in the office. Outside, a genuine industrial connector.

So everything stays the same – after all.

Andreas Huhmann

Strategic Marketing ICPN



 

Global Business Unit Electric
HARTING Electric GmbH & Co. KG

HARTING Editorial Office