What is a digital twin in mechanical engineering – and what isn't?
Im In the project meeting, the term digital twin comes up for the third time in ten minutes. The design engineer means the 3D CAD model, the automation engineer is thinking of the control simulation, and production refers to machine data from ongoing operations. Everyone nods – yet they’re talking about different things. This is precisely where the real problem often begins in mechanical engineering. Because if companies want to use virtual commissioning, simulation software, and end-to-end digital processes effectively, they first need a clear answer to the question: What exactly is a digital twin – and what isn’t it?
Not just a digital image
As we understand it, a digital twin is a virtual digital counterpart to a real machine or system that realistically depicts its structure and behavior and can be used in engineering. It represents multiple perspectives of a technical system.
This means that a digital twin not only shows how a machine is constructed, but also how it behaves. It models components, motion sequences, control logic, and processes in such a way that the machine can be realistically simulated and tested in the virtual space.
This is precisely where its value lies.
A digital twin is not created once for a presentation or as a static project model. It evolves in parallel with the real machine – from the initial planning stages through virtual commissioning to subsequent adjustments and optimizations during operation.
The digital twin is particularly important for virtual commissioning. Here, the model serves as a simulation environment for the real control system. All components are replicated in the digital twin. This allows the control programs to be tested in advance, long before the actual machine is built. This enables early detection and avoidance of planning errors. As a result, projects become more successful, commissioning times are reduced, and the coordination between mechanics, electrical systems, and software is improved.
What is often referred to as a digital twin
Nevertheless, the term is often used too imprecisely, especially in industrial settings. This applies, for example, to the 3D CAD model of a machine. CAD actually only describes the geometry and structure of a system. Information about dynamics, control logic, or process behavior is missing. While CAD is a central component of engineering, it does not automatically create a digital twin.
The same applies to isolated simulations such as kinematic studies or FEM analyses. Such models are suitable when specific questions need to be answered during the development process. However, these models are not continuously developed or even combined with other models. Some refer to 3D layouts or visualizations of systems as digital twins, even though these actually only serve planning or presentation purposes and do not simulate the machine’s behavior.
Sometimes, even purely data-driven systems are referred to as digital twins. Such platforms collect and analyze operational data from machines, providing valuable information about the system’s condition, but they do not offer a model-based representation of the machine. Without such a model, the data can be analyzed, but not sufficiently for testing and utilization.
The digital twin as a basis for simulation-based engineering
The digital twin is more than just a visualization or a collection of data; it’s a combination of system structure, physical behavior, and engineering integration. Only when all these aspects are present does the virtual counterpart emerge, realistically representing the machine. Only then can it be fully utilized in the development process.
In modern engineering environments, the digital twin evolves in parallel with the project. The initial models depict basic motion sequences or system logics. As the level of detail increases, mechanical properties, control programs, and sensor signals are integrated. The result is a digital twin of the machine that can be used for testing, optimization, and virtual commissioning.
Thus, the digital twin forms the basis of networked engineering, bringing together mechanics, automation, and simulation. Especially in complex machines and production facilities, this approach enables earlier validation of system behavior and creates the foundation for seamless digital development processes.
Additional FAQs about the article
1. How do you get started with a digital twin in practice?
In practice, companies usually do not start with a fully developed model, but take a step-by-step approach. First, basic motion sequences, logic, or selected parts of the machine or system are modeled. Then, additional details such as control programs, sensor signals, and physical behavior are gradually integrated. This creates a model that grows alongside the real project and delivers increasing value throughout the engineering process.
2. How can you tell whether a 3D model is already a digital twin?
A 3D model alone is not yet a digital twin. It may show the structure and geometry of a machine, but that does not automatically mean it reflects how the machine actually behaves. A true digital twin also includes motion, processes, signals, and control logic. Another key factor is the connection to the control system: only when the model is linked to the real or original PLC and can be used for simulation, testing, or virtual commissioning does it go beyond pure visualization.
3. What is the practical benefit of a digital twin in mechanical engineering?
A digital twin allows machines and systems to be tested virtually before they are built in the real world. This helps identify errors earlier, improves collaboration between mechanical engineering, electrical engineering, and software, and reduces commissioning time. As a result, projects become more reliable, risks are reduced, and engineering processes become more efficient and transparent.
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