At its spring meeting, the Industry Working Group Research & Technology of the VDMA Glass Technology Forum dealt with aspects of measurement and testing technology and future data protection requirements.
In their presentation, Dr.-Ing. Matthias Seel and Prof. Dr.-Ing. Michael Kraus dealt with the need-based use of the digital twin to increase quality in flat glass production. They emphasized the importance of measuring and testing technology. Quality assurance is often still based on subjective empirical values, which limit the internal resilience and the ability to innovate. The two experts drew a clear distinction between the digital twin and the digital shadow: While the digital twin enables bidirectional communication and control (interaction between digital model and physical production process for active control), the digital shadow is limited to data acquisition and diagnostics.
For applications in flat glass production for the digital twin, they highlighted several process steps. Monitoring and controlling temperature fields in the tempering process enables homogenization and need-based adjustment of glass and product properties. This leads to a reduction in distortions, anisotropies or roller waves. When cutting flat glass, the optimization and monitoring of cutting parameters (e.g. cutting force, cutting fluid) is crucial in order to ensure defined edge qualities. Early detection of nickel sulphide inclusions in combination with a digital twin can reduce the risk of nickel sulphide fractures in the future, even without a hot storage test. The implementation of the digital twin increases efficiency through predictive maintenance and process control and reduces costs through data-based decision-making. However, according to Seel and Kraus, the decisive factor for successful implementation is to develop a need-based and target-oriented design together with the users that is geared towards the specific requirements of the respective production.
Optical measurement technology in the glass industry
Modern optical measurement technology enables high-precision one- and multi-dimensional inspection processes that are used in various industries. Johannes Schuler from Keyence Germany presented exemplary applications of various measurement methods.
These technologies are used primarily in medical technology, for example in the measurement of contact lenses, which must be very precise. The precise determination of position data for downstream processes, such as robot handling, in which sensitive components must be gripped precisely, is also crucial.
Innovative measurement methods are also used in semiconductor technology. One example is the measurement of wafers with a special 2D transmitted light micrometer, in which the transmitter and receiver are calibrated and supplemented with additional optics. This allows not only the edge geometry of a wafer to be recorded, but also transparent wafers to be analyzed with high precision. Such methods are essential, as fragile and delicate components often have to be inspected in the micrometer range.
Schuler described 2D and 3D inspection using laser profile sensors as a further application. This technology can be used to generate and evaluate simple distances, individual profile sections of a component as well as entire 3D scans. A recently developed technology allows such 3D measurements to be carried out without external movement systems by swiveling the measuring head internally. According to Schuler, this combination of laser and snapshot technology offers advantages in many industrial applications.
Such methods are particularly challenging in the glass industry, as glass has both diffuse and specular reflections. The measurement of transparent objects can be problematic as reflections often occur in undesirable places. A special algorithm makes it possible to capture the actual transition of an object as a profile curve instead of measuring a diffuse reflection cloud within the material. In the case of reflective surfaces, the laser beam must also be aligned at a certain angle to avoid total reflection and enable precise measurement.
Using the automotive industry as an example, Johannes Schuler presented laser measurement systems for gap and height measurement in vehicle glazing. The edge position of glass components is recorded, which is essential for downstream processes such as robot handling. However, the use of optical measuring systems extends far beyond the glass industry. For example, the automation of food production is also a development focus for the industry.
Optical sensors in the flat glass industry
Precitec Optronik develops high-precision optical measurement methods for the flat glass industry. In particular, chromatic confocal and interferometric sensors are used. Chromatic confocal technology uses white light sources that are coupled into a measuring head. The light is split into a spectrum along the measuring range so that precise distance and thickness measurements can be carried out using the wavelengths. This method enables high-precision measurements in the micrometer range, whereby thickness fluctuations and deformations as well as inclusions and cracks in the glass can also be detected.
A currently new application is the detailed measurement of the scoring line including all breakouts and stresses. This is made possible by a confocal chromatic line sensor with 1200 points along a line length of a few millimeters. The result is a topography measurement of the entire scoring line.
Markus Rosskopf, representing Malte Hapich, from Precitec Optronik, named inline monitoring of production processes as another area of application, with sensors that can record up to 92 measuring points simultaneously. For special applications, such as the measurement of very dark glass with low transmission, the company has developed controllers with eight times the light intensity, which can reliably analyze coated or recycled glass.
In addition to chromatic confocal sensors, white light interferometry is used for multilayer systems in particular. Here, broadband infrared light is used to determine the thickness of transparent materials with high accuracy by means of interference effects. For the interferometric measurement, there is a measuring head with a measuring distance of one meter for the measurement in the flat glass line at the hot end. The head can be positioned outside of the tin bath and provides responsive thickness values when adjusting the line.
Rosskopf cited laser radiometry, a technology for measuring the thickness of non-transparent materials, as another innovative process. The surface is minimally heated with a laser diode so that the heat spreads through the material. The reflection of the heat radiation from the substrate into the layer and back to the surface allows conclusions to be drawn about the layer thickness. This method is particularly useful for measuring paint layers on glass, for example for the enamel coating on windscreens.
According to Rosskopf, the various sensor technologies can be used both as offline solutions for laboratory analyses and for inline measurements in production lines. With special cooling systems, such as water cooling, measurements can also be carried out in demanding environments such as high-temperature processes. Overall, these highly developed measurement methods offer the flat glass industry precise, fast and flexible solutions for quality control and process optimization.
Quality measurement on toughened glasses
Kai Vogel from Viprotron GmbH, a specialist in glass inspection systems for architectural glass production, described various functions of scanners that are specially designed to detect specific defects. These check for inclusions and layer defects before cutting, detect soiling, scratches and other optical defects after the washing machine or record dimensional accuracy, drill holes and defects such as bubbles and inclusions. Over 600 inspection systems are in use worldwide.
A 5G temperature scanner is particularly relevant for measuring directly at the furnace outlet. This system analyzes the glass using five measurement methods: optical distortion (distortion and waviness), anisotropy, white haze, glass defects and layer defects. As optical distortion has a significant influence on the appearance of facades, special reflection methods can precisely determine the waviness of the glass. Anisotropy, which becomes visible through polarized light, causes disturbing stripe patterns under certain lighting conditions. White haze is caused by minimal surface roughness during the tempering process and is detected using dark field illumination. In addition, measuring systems enable the detection of bubbles, inclusions, scratches and coating defects.
The system works independently of the transport speed or unevenness and documents the measurement data for quality assurance. The results are displayed visually so that operators can quickly see whether a glass meets the requirements. The measured values are based on existing standards, in particular for anisotropy measurement, which the company developed in collaboration with Darmstadt University of Applied Sciences.
Scalability creates added value
Digitalized and automated processes must be scalable in order to create real added value, says Markus Kick from Phoenix Contact GmbH. This is the only way to integrate modern technologies such as artificial intelligence and machine learning in a meaningful way. Scalability also means involving all employees in the processes. To this end, the company is developing solutions that appeal to both existing and new generations of specialists.
One key aspect is the handling of data. It is not about collecting as much information as possible, but about collecting the right data and using it efficiently. There are numerous sensors and measuring points in many areas, but often over 90 percent of the data collected is not needed. The challenge is to use minimally invasive methods to extract only relevant information and process it bidirectionally.
Phoenix Contact relies on an open, interoperable system that works independently of the manufacturer. This enables the flexible integration of a wide variety of components and ensures efficient use of the collected information. Particularly in energy-intensive sectors such as the glass industry, it has been shown that targeted measurements and intelligent data processing enable considerable savings and minimize downtime. Practical and intuitive solutions make the digital transformation more tangible for all employees.
According to Kick, manufacturers, suppliers and users must work together on open, secure and scalable solutions. Modern processes are based on a sophisticated data architecture that can function both locally and in the cloud. The integration of machine learning makes it possible to derive well-founded decisions from a small number of specifically selected measured values.
The EU Data Act and Cyber Resilience Act
Companies must be aware that the collection and processing of data is subject to binding requirements. In her session, lawyer Salome Peters from VDMA explained that companies must comply with extensive provision and transparency obligations, including the disclosure of data and its provision in machine-readable form. The EU Data Act, which will be binding from December 9, 2025, affects networked products and associated services that collect and pass on data. This results in new compliance requirements.
The Cyber Resilience Act introduces mandatory cyber security requirements for digital products. Alexey Markert from VDMA explained that the CRA is closely linked to CE marking and affects products with digital elements. Companies should take immediate action to meet the new requirements. This includes, for example, adapting development and design processes.
