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PublicationHybrid Thermal Error Compensation Combining Integrated Deformation Sensor and Regression Analysis Based Models for Complex Machine Tool Designs( 2023-06)Thermal errors remain the dominant sources of positioning inaccuracies in machine tools. Various methods of reducing them have already been developed, ranging from cooling and air conditioning strategies, thermally optimized machine tool designs and component optimization to accurate model based thermal error estimation methods used for control-integrated compensation. Some reasons for the limited success of these strategies are the general complexity of the thermo-elastic and thermodynamic processes involved and the fact that many models’ effectiveness is dependent on the machine tool type, workpiece, climatic conditions, tool, CAM strategy, condition of the machine tool and other factors. Depending on these circumstances, all model-based estimation and compensation methods have specific strengths and weaknesses, which make them more suitable in some aspects and less suitable in others. A possible way of circumventing this is via the combination of several methods to hybrid compensation. The goal of this investigation is to develop an effective hybrid compensation strategy for the 5-axis machine tool DMU 80 eVo by combining measurement-based compensation using integrated deformation sensors (IDS) with characteristic diagram based compensation. The former is used for the compensation of thermal errors in the vertical column containing the larger assemblies of the x, y, and z-axis and the latter is used for the table, which contains two rotational axes. The IDS placement has been determined through expert knowledge and compared to placement, which minimizes the variance of the TCP displacement. The hybrid compensation is tested on the DMU 80 eVo.
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PublicationScalable Production of Energy Storage Systems( 2023-05-05)
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PublicationSkalierbare Produktion von Energiespeichern( 2023-05-05)
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PublicationSelbstlernende Produktionsmaschinen für die automatisierte Fertigung von Lichtsystemen( 2022)Core elements of modern production machines for the automated manufacture of lighting systems are complex algorithms that analyses light distributions inline and actively correct them. This enables products of the highest quality to be manufactured with minimal waste. The Fraunhofer IPT is researching the use of artificial intelligence for industry-ready solutions that are capable of learning complex beam analyses and alignment processes automatically. This reduces the development effort and thus paves the way for innovative products and assembly processes.
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PublicationDecision Support by Interpretable Machine Learning in Acoustic Emission Based Cutting Tool Wear Prediction( 2021)Predictive maintenance is a prominent and active field for applications of machine learning in industry in recent years. The health and wear of equipment directly influences the productivity and quality of the production process. Especially in ultra-precision manufacturing, tool wear has a major impact on the achievable quality while the wear itself cannot be measured directly in-process. In this paper we present a machine learning-based classification of the tool wear in-process using acoustic emission sensors. To increase the interpretability of the process – to open the black box model – we apply a feature importance analysis and use the obtained feature importances to provide augmented data representations to the users. These representations increase the transparency of the model's decision process and assist the users in validating the model's decisions and gain new insight into the phenomenon of tool wear itself.
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PublicationOCT measurement of aspheric polymer lenses for adaptive assembly of micro optical imaging objectives( 2020)
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PublicationHigh precision automated tab assembly with micro optics for optimized high-power diode laser collimation( 2020)The industrial assembly processes for fast axis collimation (FAC) lenses with high power laser diodes are continuously being improved and automated. The system requirements allow for various solutions for the attachment process of the micro-optic component, the standard being active assembly relative to the light emitting laser-diode facet with joining by a UV-curable glue at attachment positions outside of the laser beam-path. To facilitate higher degrees of freedom and to optimize the results in the joining process with tighter tolerances in some critical functions, the FAC mounted on tab is one of the possible solutions and a viable process option. We report the results of high accuracy preassembly of FAC on tab with respect to the specific requirement of a target assembly back focal length within tight tolerance values.
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PublicationAutomated sensor-guided packaging of diamond tools( 2020)Automated, ultra-precise packaging strategies reduce production time and costs while increasing yield, quantity, and precision, making them one of the main research and development questions in the field of production technology. Fraunhofer IPT develops sensor-guided assembly solutions for packaging and testing of optical and non-optical components to meet the demand. In this paper, we present a prototypical process for the automated, ultra-precise passive alignment using the assembly of a diamond engraving tool as an example. The challenge is to place a diamond measuring three millimetres in its largest dimension into a groove of similar size and to position the tip of the diamond within tolerances of a few micrometres and arcminutes. This six dimensional assembly problem is tackled by feeding live camera data to an image processing algorithm and by aligning the diamond using Fraunhofer IPT's ultra-precise micromanipulator, collectively forming an automated, closed-loop assembly process. Thus, a fully automated packaging process with very high accuracy and reliability is proven to be technically possible.
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PublicationAutomated PM-fiber array assembly with high-precision four DOF alignment( 2020)Polarization maintaining fibers arrays are key enablers to process high bandwidth data, representing a powerful part within the photonic integrated chip technology. The different channels increase the information density and allow to multiple singles through one fiber bulk at the same time. Due to fiber's small dimensions (ø125 mm) they can be integrated in existing infrastructure easily and are very flexible at the same time. However, the compact design together with the flexible material properties demands for new precise tools and technologies to reach the necessary precision during packing. The Fraunhofer-Institute for Production Technology IPT develops, together with their partners Phix and Aixemtec, new handling and assembly tools, as well as processes as one of the leading companies in this field. In the self-developed assembly cell, the fiber handling tool-head operations automatically to pick up, manipulate and tack single fibers to a glass plate or fiber to chip. Each fiber is moved by a portal robot within the assembly cell with micrometer accuracy but also can be rotated with a repetition accuracy less than 0.01°. Advanced illumination units observation techniques allow to package fibers arrays much quicker and more robust than before. Therefore, additional camera systems and material characteristics are used to develop smart alignment routines. As a result, the observation of the orientation of the PM-fiber core as well as the fiber layout during the assembly process leads to high quality products within fast production cycles. Due to the flexible construction of the assembly call also PIC packaging and fiber-to-chip coupling is possible.
