The term retrofit is made up of the Latin word 'retro' (backwards) and the English word 'fit'. A 'retrofit' is, for example, an existing machine that has been improved or retrofitted to meet current requirements. "Especially in the current age of Industry 4.0 and artificial intelligence, it is important to collect and transfer data from existing systems. Retrofitting in particular can provide support here," says Martin Folz from the Chemnitz SME 4.0 Competence Center, who works at the Chair of Factory Planning and Factory Operation at Chemnitz University of Technology. In contrast to the purchase of many new machines, the retrofit of an existing machine usually involves considerable savings on the investment, as the mechanics of a machine age much more slowly compared to the communication, control or automation technology. Retrofitting obsolete components can extend the service life of a machine enormously. In addition, the addition of modern sensor technology and communication capabilities increases the productivity of the machine.

In order to make the retrofit method better known in industry, the Chemnitz SME 4.0 Competence Center has developed several demonstrators in the Chemnitz University of Technology's Experimental and Digital Factory and put them on display for visitors to see.

Band saw and steam engine 'spiced up'

This includes a band saw that has been retrofitted with sensors, a PLC and a single-board computer. Folz explains the procedure: "A newly added control cabinet contains a Siemens controller that processes the sensor signals and forwards them to a single-board computer. A server application runs on this Raspberry Pi computer. Among other things, it provides the visualization for the operating tablet. Various devices can thus access user-centered information via a web browser."

A steam engine has also been modernized. Its retrofit is based on the use cases 'condition monitoring' and 'needs-based maintenance'. As the bearings of the steam engine have to be oiled every ten minutes of operation, a key objective was to ensure safe maintenance at short intervals. The first step was to install a light barrier that records the speed of the flywheel and also allows conclusions to be drawn about the operating time when the flywheel is running. After eight minutes of operation, the control system automatically switches off the heating of the steam engine. In the following two minutes, the boiler cools down and after ten minutes, a message appears on the display reminding the user to perform maintenance. The display also shows the temperature and pressure of the boiler - as current values and as values over time. These recorded parameters make it possible to draw conclusions about the various operating states the system may be in. A signal light visualizes these operating states. They are also shown in text form on the display and can be called up via the network into which the steam engine is integrated.