Knowing when the cable breaks

Replacing parts before they fail, avoid unplanned downtime - that's what predictive maintenance promises. But how to determine the aging of a cable and predict when it will fail? LAPP has developed a solution for Ethernet cables that doesn’t require any changes to the cable.

LAPP predictive maintenance test
Guido Ege

Predictive maintenance is one of the foremost and most promising benefits of digitalisation in factories. Instead of replacing parts only when they have already failed and the machine has stopped working, as in reactive maintenance, or replacing still functional parts as in preventive maintenance, predictive maintenance is based on sensor data that is supposed to allow conclusions to be drawn about the actual aging of the part. The question of how to implement predictive maintenance also concerns connection systems. Even if cables usually last for many years, failure cannot be completely ruled out, especially in demanding applications. The importance of cabling should not be underestimated: a part that only costs a few euros can paralyze an entire production and cause high costs. "That's why we want to offer a solution that will sound the alarm before a cable fails," says Guido Ege, Head of Product Development and Management at LAPP.

 

 

Focus on Ethernet cables

Ethernet cables, especially when laid in energy chains, are more prone to failure than current-carrying cables due to their complex structure and the necessary high-frequency characteristics. For instance, broken shielding leads to increased EMC interference. If strands of wire break, the attenuation increases and the data rate drops. If a strand breaks, communication fails completely. Guido Ege's team has therefore concentrated on Ethernet cables and developed a predictive maintenance solution for them. The aim was to be able to predict the remaining lifetime of a cable and plan replacement in a way that would guarantee minimum disruption of machine operation. For this purpose, the transmission characteristics of data cables are monitored and changes in those characteristics are used to calculate the expected service life. "We want to help make factories smart, and predictive maintenance is a key issue here," says Ege.

Solution without “sacrificial wires”

It was one requirement to develop a measuring principle that works without changing the cable, i.e. without additional so-called “sacrificial wires” in the cable. Users do not want that because such additional wires require additional installation work. The solution should be only based on a protocol and a special algorithm. This means that standard Ethernet cables and standard connectors such as RJ45 or M12 can be used. The installer connects the cables as usual and does not have to connect any additional sacrificial wires. This approach has the advantage that existing systems can be retrofitted.

 

The measurement takes place in the so-called PMBX (Predictive Monitoring Box). The PMBX has two Ethernet ports and is simply inserted at the beginning of the Ethernet cable that is to be monitored. The data packets are transmitted transparently from one Ethernet port to the other, almost without delay. For a connected PLC, the PMBX is not visible, it has no influence on the data transmission. It is therefore also suitable for existing systems without having to make any changes to the PLC software.

LAPP Predictive Indicator

The failure prognosis is based on up to four transmission-relevant parameters. Based on these, the LAPP Predictive Indicator is calculated. Plausibility checks are also possible by measuring several variables. This minimizes misinterpretations of measured values. The predictive maintenance system uses a deep learning approach. For LAPP drag chain cables, millions of measured values have been collected in the in-house test centre and then analysed using mathematical algorithms. During the development process, LAPP analyses the data locally on a PC but this can also be done later in the cloud, depending on customer requirements. The more data is available, the more accurate the prediction. The system is self-learning. After just a few weeks of data collection at LAPP's own test centre, cable failure was predicted between a few hours’ notice and several days. If the cable failure is predictable, replacement can be planned: the maintenance technician is available as is the spare part and it is scheduled during a period when the machine is not running anyway, for example due to machine re-tooling or other maintenance processes.

 

At Hannover Messe 2019, LAPP presented the new predictive maintenance system in its futureLab. "We are in discussions with a number of interested parties and pilot customers with whom we want to integrate our solution into the specific applications and tailor it to the customer," says Guido Ege, "in the next step we want to develop a suitable business model.”

 

LAPP owes its success not least to a new innovation process: Innovation for Future. In this way, the company also wants to realize radical and disruptive innovations for which, for example, a classic stage-gate process is unsuitable. Innovation for Future has three prerequisites: There must be a technical solution, you must talk to at least one potential customer and a business model canvas must be filled in. Guido Ege is optimistic that LAPP will change profoundly with Innovation for Future and that it will continue to evolve from a provider of physical products to a provider of system solutions. "Innovation for Future creates the space for this.”

 

The team responsible for developing the PMBx won the LAPP internal innovation award, the Eddie Lapp award. “This is really innovation and industry 4.0”, said Ralf Moebus, Head of Product Management Industrial Data Communication about the project.

Prozess PM en

Function of the Predictive Maintenance System for data cables from LAPP

Lapp Predictive Maintenance Box

The Predictive Monitoring Maintenance System Box from LAPP is simply inserted into the cable to be monitored and is not visible to a connected PLC.