Digital twins are the virtual siblings of real prototypes - and they are increasingly conquering the machine tool industry as well. As an identical image of a machine with all its physical components, they enable the digital testing of system planning or production processes before the real processes begin. An element of Industrie 4.0, this process significantly increases productivity and is thus a way to save a lot of money and time. "When designing brand new machines, the lead times can be shortened by four to six weeks," explains Harald Preiml, Member of the Executive Board of Heitec AG in Erlangen.
This increase in efficiency is also urgently needed "since increasing complexity and smaller batch sizes mean that chipping production is reaching its limits," describes Eberhard Beck, Head of Control Technology at Index-Werke GmbH & Co. KG Hahn & Tessky in Esslingen. "Steadily growing technological requirements in combination with permanent cost and delivery pressure do the rest." The trend is to adapt machines quickly and flexibly to the most varied work piece requirements. A new challenge arises from applying this additional flexibility in a way that is technically reliable and brings economic benefits. This is where known planning methods and production processes are reaching their limits. In the context of Industrie 4.0, the merging of virtual and real production is also seen as the key to unlocking the great potential for increase in production at the Esslingen-based company.
Virtual commissioning of a machine
Anyone designing machinery and systems today should only do this digitally with modern engineering methods and tried and tested technological objects according to the engineers at Heitec. The company's technology objects describe all the physical components of a machine such as actuators, sensors, drives, robots, conveyor belts and so on. In a mechatronic approach, mechanics, electrics, pneumatics/hydraulics and software are considered as one unit. From these basic modules, a Heitec tool forms virtual models of automation components - the digital twins - which can be used for the planning, configuring and commissioning of a system.
A concrete example of a digital twin at Heitec: In the new generation of machines, a medium-sized provider wanted to convert the previously mechanically coupled parts of the drive technology to modular servo technology. The machines should execute product changes more easily and with more flexibility. With this new development, Heitec had the task of integrating the various units into the overall machine. To this end, the company developed a virtual model of the system. As only a short amount of time was scheduled for the commissioning, it was first performed on the virtual model.
In a pre-testing of the product run under maximum load, conceptual weak spots in the construction were discovered in the interaction of the many different digital components. For example, the access point between the infeed starwheel and the main drive had a mechanical misalignment of a of a few tenths of a millimeter. This misalignment then led to product feedback at very high system speeds and consequently to the shutdown of the system. However, since everything had previously been tested on the virtual model, there were no problems in making constructive changes to the CAD model, in creating new drawings and in reconciling them with the corresponding library elements. Today, the system in practice runs smoothly.
Simulation prior to processing
The Index-Werke in Esslingen, as a globally operative manufacturer of turn-mill centers and turning machines, already provides a standard in Industrie 4.0 building blocks such as digital twins. In principle, a virtual image is available for every real machine. Based on the real machinery software on a PC, each twin is configured with the original data of the machine control system as a one-to-one copy. Users can thus create and optimize new start-ups and machining processes in addition to automation in the machine room in a real-time relationship and with 100% transferability to the real machine.
At the start of the production, the twin shows its potential with its innovative functions: In coupled operation, the simulation checks each process in the machine in advance. If a collision is detected virtually, the machine stops before it is damaged. In addition, in synchronous operation, processing sequences which cannot be viewed in the machine can be monitored in real time on the control screen. "Virtual worlds of production are therefore already a reality today," emphasizes Eberhard Beck.