CNC safety through Digital Twin

Two master's students from KU Leuven developed a real-time collision avoidance system for CNC machines as part of their thesis work. This promising solution uses a digital twin to predict and automatically prevent machine collisions during production, with direct impact on cost control, safety, and production continuity.

ASCO has been an established name in the international aerospace industry since 1954. The Belgian company has been part of the Montana Aerospace Group since 2022, which employs approximately 6,000 people worldwide. With around 1,100 employees in Belgium across four sites, including its headquarters in Zaventem, ASCO develops and manufactures complex mechanical components for aircraft wings and landing gear. These components are produced on state-of-the-art CNC machines controlled by Siemens technology, where precision and reliability are critical.

Collisions: An Industrial Reality

In aerospace production, NC programs are routinely simulated in a digital twin before being transferred from CAM to the machine. Yet the risk of collisions remains. Variations in tool length, deviations in workpiece zero points, or human errors during input can lead to crashes during machining. The consequences are significant, with potential damage to the machine, the workpiece, or production schedules that can result in costs reaching tens of thousands of euros.

"Human errors are inevitable in a complex production environment," says Mohamed El Hatri, Senior Lead Engineer at ASCO. "An incorrectly entered tool length or manual operation via jog mode can be enough to cause a serious crash. We therefore looked for a way to actively manage that risk, not only beforehand, but also during the machining process itself. In aerospace production, we work with extremely expensive and complex CNC machines. A spindle alone in such a CNC machine can cost more than 100,000 euros. Despite extensive simulations beforehand, collisions remain possible due to minor variations or human errors. We wanted to not only limit that risk, but actively control it during the machining process itself."

Two Seconds Ahead

This concrete challenge became the starting point for a collaboration between Siemens Industry Academy, Aerospace Machining Academy, and ASCO, with two KU Leuven master's students developing an innovative solution. The project, which ran from October 2023 through the end of the 2024-2025 academic year, focused on developing a system that simulates the machining process in real time two seconds in advance. First, a digital twin of the machine was created using Siemens NX CAM and NX MCD, which continuously communicates with the Siemens 840D sl machine controller. If the system detects a potential collision, it automatically sends a stop signal to the machine—faster than any operator could ever intervene. The process was also tested with SinuTrain, Siemens' software package for CNC programming, design, and simulation. This approach ultimately proved to be the most efficient.

The choice of the two-second rule is deliberate. It accounts for both the extremely fast reaction time of the Siemens controller and the human factor. If an operator is present, the simulated image closely aligns with the actual state of the machine at the moment they shift their attention from the screen to the physical installation. At the same time, the system provides a crucial safety layer for unmanned machines operating autonomously or overnight.

Although the collision avoidance system is not yet operational in production today, ASCO sees clear future opportunities. The solution addresses a widespread problem in the aerospace industry, where many machines are not of the latest generation and where collision damage has significant impact.

Combining Technologies

For the development, the students used a broad Siemens software stack, including NX CAM, NX MCD, NX Open, SinuTrain, and the Brown Field Connector gateway, which enables integration of older machines. "The strength—and also the challenge—of this project lay in the possible combination of these Siemens technologies," says Jan Vereecke, Service Operations Team Leader MC MTS at Siemens. "By directly connecting NX CAM/SinuTrain, the digital twin, and the 840D sl controller, we were able to simulate the machining process in real time. This means the digital twin functions not only as a design tool, but also as an active safety layer during production. It was precisely this innovative approach that made the project particularly challenging and, at the same time, highly relevant for the students: they worked with state-of-the-art technology and saw how its combination can solve a concrete industrial problem."

Co-Creation Within Siemens Industry Academy

The project aligns perfectly with the philosophy of the Siemens Industry Academy, which emphasizes co-creation around real industrial challenges. Students have the opportunity to work in a professional context, guided by both academic experts and engineers from industry. For ASCO, the added value extended beyond the purely technical result. The initiative provided space to explore and evaluate innovative technologies without impacting ongoing production, while simultaneously building valuable internal knowledge.

"This project perfectly demonstrates how our collaboration with Siemens and the academic world helps us look ahead," states Mohamed El Hatri. "Students bring a fresh perspective, we bring industrial experience, and within the Siemens Industry Academy, we can explore innovative ideas without impacting our ongoing production. By developing a first proof of concept together, we build knowledge, gain insight into new technologies, and can approach innovation in a phased and thoughtful manner. This collaboration confirms how industry, education, and technology partners strengthen each other—and together build safer, smarter production in the aerospace sector."

For the students themselves, the project was equally valuable. "We worked with the same software and conditions as in a real industrial environment. That made the project technically challenging, but also particularly educational. The guidance from ASCO and Siemens ensured that we constantly had to think about what is feasible and relevant in practice," concludes master's student Rohan Vits.