Industry 4.0 retrofitted
More efficient condition monitoring via IoT gateway
Many plant operators are asking themselves how they can upgrade their existing machines for Industry 4.0. When it comes to implementing a simple connection of solutions for condition monitoring, for example, the use of IoT gateways is a worthwhile approach.
When we think of Industry 4.0, we usually envision brand new production lines with state-of-the-art technology. However, the current innovation cycle is faster than the service life of machines and systems. This is why many companies are currently looking for ways to continue using their older but still functional machines while still being able to integrate them into the new environment. This is also the case at Bosch Rexroth's plant in Homburg, where, among other things, hydraulic valves are manufactured that are used in mobile machinery such as tractors.
The valves are used to control the working hydraulics. As part of the production process, machining centers mill and drill high-precision channels and holes into the cast blanks. Once the individual components have been cleaned and assembled, all valves are functionally tested on test benches to ensure that they match the electronics and are leak-tight. To do this, employees connect them to the hydraulic circuit of the test benches and test the valves with the specified working pressure.
Although the valves have been cleaned beforehand, it cannot be ruled out that there are still metal particles, chips and water residues in the valves." These can get into the hydraulic oil during the test cycle and cause damage to the test bench or the test specimens in subsequent cycles. Specifically, system downtimes at the Homburg Rexroth plant caused by contaminated hydraulic oil were responsible for around 25% of the downtime costs at the test benches on average over the long term. For this reason, the filter media were previously replaced at fixed intervals - regardless of the degree of contamination - and this process was documented manually. A procedure that was no longer up to date in view of Industry 4.0!
"We see Industry 4.0 as an opportunity to make our plant fit for the future, to manufacture more efficiently and to deliver customized products of high quality quickly. However, we must always keep an eye on profitability during the changeover," says Fabian Borowski, responsible for Industry 4.0 at Bosch Rexroth in Homburg, describing the challenges of networking.
Commissioning without PLC or IT knowledge
With this in mind, Borowski, together with a team of specialists from the entire Bosch Group, initially set about retrofitting a test bench built in 2007 with an IoT gateway developed by Rexroth and corresponding IT tools, and installing a comprehensive condition monitoring concept based on this. The ultimate goal: to implement continuous condition monitoring of the filters and automated commissioning of maintenance.
The IoT gateway in question evaluates the data from various sensors for this purpose. The sensors record the pressure difference before and after the oil filter as an indicator of the degree of contamination of the filter cartridge. Other sensors count the size and number of particles, monitor the temperature and record the content of dissolved water in the hydraulic medium.
With conventional PLC industrial control systems, which could in principle also be used for such purposes, commissioning requires complex programming. "Our specialists would have estimated at least one man-week for the modernization including the connection of the sensors and interfaces with a classic PLC," Borowski calculates and adds: "Thanks to the web-based configuration of the IoT gateway used, a master electrician without any PLC knowledge can complete commissioning within half a day. That corresponds to a 90% reduction in engineering work!"
The infrastructure of the gateway is a Rexroth controller of type XM21. The software is based on a Java virtual machine and an overlying OSGi framework. This offers the advantage that the typical PLC real-time world can run in parallel to an IoT runtime on a controller via Open Core Engineering. The sensors are connected in the gateway via analog interfaces and, in future, Bluetooth LowEnergy and I/O-Link, among others, and commissioned via a web-based software component. The user only needs to set a few parameters and tick a few boxes. The IoT gateway then translates all data internally, significantly reducing complexity. As an open system, the solution supports a large number of sensors from any manufacturer.
Installation of the IoT gateways: The 'Open Core Engineering' software technology enables access to core functions of the compact controller without PLC programming.
© Bosch RexrothAt the test bench in Homburg, the gateway then sends the sensor data to a server on which standard Bosch software modules are installed. For example, the Production Performance Manager (PPM), an information and evaluation system that records the production and machine data of the networked test bench almost in real time. The module brings the information together in a visualization within milliseconds and forwards specified events to defined persons. Communication can also take place via the machine language PPMP recently presented by Bosch.
The Production Performance Management Protocol (PPMP) is a simple format that uses existing technologies from IoT development, but also covers industrial needs. It is flexible enough to be transported via multiple protocols. Compared to the M2M communication protocol OPC UA, PPMP is intentionally designed to be much more lightweight, as existing hardware is often not designed for the continuous operation of an OPC UA stack. Last but not least, PPMP is free of license fees and the Eclipse Unide project provides the technical framework for development. Once installed, a theoretically unlimited number of gateways can be connected to the PPM.
Model rules graphically
The Production Rules Configurator (PRC) then monitors compliance with the defined parameters. This involves much more than the rigid definition of limit values. "We can now easily model any rule graphically, such as when a warning is generated or when a filter or oil change is necessary," explains Borowski. No IT or programming knowledge is required and the rules can be changed or new ones added at any time.
Finally, a maintenance support system simplifies the execution of maintenance work. This serves as a link between the software modules for the networked machine and the plant's ERP system. For example, it automates the processes for ordering filter media and stocking spare parts.
Test passed - concept rolled out
It took just five months from the initial idea to commissioning on the first test bench. The integration of further test benches only takes a few hours. The project already achieved significant improvements within the first few months.
In terms of process quality, the retrofitted test bench now provides documented data on oil purity at all times, which previously had to be analyzed in a time-consuming manual process.
At the same time, the rule-based condition monitoring with predictive maintenance significantly reduces downtimes. "The overall equipment efficiency of the modernized test bench has increased by 5 %. Downtime costs have been reduced by 25%," says Borowski, summarizing the most important key figures, adding: "The subsequent networking pays for itself within 18 months - without taking the process improvement into account." Specifically, the investment for an IoT gateway is in the four-digit euro range.
Bosch Rexroth in Homburg is therefore currently retrofitting 22 additional test benches with the IoT gateway and the corresponding sensors. Many more machines throughout the Bosch Group will gradually follow in subsequent steps.
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