Characterization of a parallel kinematics actuated in situ reference measurement system for 5D-nano-measurement and nano-fabrication applications :
Charakterisierung eines parallelkinematisch aktuierten In-situ-Referenzmesssystems für 5D-Nanomess- und Fabrikationsanwendungen. - In: Technisches Messen, ISSN 2196-7113, Bd. 91 (2024), 2, S. 102-115
Die stetig voranschreitende Entwicklung im Bereich der Fertigung optischer und elektronischer Elemente auf Basis von Nanotechnologien führt seit Jahren zu einer steigenden Nachfrage nach hochpräzisen Nanomess- und Nanofabrikationsmaschinen (The International Roadmap For Devices And Systems, IEEE, 2020; C. Grant Willson and B. J. Roman, “The future of lithography: SEMATECH litho forum 2008,” ASC Nano , vol. 2, no. 7, pp. 1323-1328, 2008). Als technologisch besonders anspruchsvoll hat sich dabei die Fabrikation auf stark geneigten, gekrümmten, asphärischen und freigeformten Oberflächen herausgestellt (R. Schachtschneider, et al., “Interlaboratory comparison measurements of aspheres,” Meas. Sci. Technol. , vol. 29, no. 13pp, p. 055010, 2018). Aufbauend auf den zukunftsweisenden Entwicklungen der Nanopositionier- und Nanomessmaschine 1 (NMM-1) (G. Jäger, E. Manske, T. Hausotte, and J.-J. Büchner, “Nanomessmaschine zur abbefehlerfreien Koordinatenmessung,” tm - Tech. Mess. , vol. 67, nos. 7-8, pp. 319-323, 2000) und der Nanopositionier- und Nanomessmaschine 200 (NPMM-200) (E. Manske, G. Jäger, T. Hausotte, and F. Balzer, “Nanopositioning and Nanomeasuring Machine NPMM-200 - sub-nanometre resolution and highest accuracy in extended macroscopic working areas,” in Euspen’s 17th International Conference , 2017), wird an der Technischen Universität Ilmenau seit mehreren Jahren an Konzepten für NPMM mit erhöhtem Freiheitsgrad geforscht (F. Fern, “Metrologie in fünfachsigen Nanomess- und Nanopositioniermaschinen,” Ph.D. thesis, Technische Universität Ilmenau, 2020; R. Schienbein, “Grundlegende Untersuchungen zum konstruktiven Aufbau von Fünfachs-Nanopositionier- und Nanomessmaschinen,” Ph.D. thesis, Technische Universität Ilmenau, 2020). So besitzt der seit 2020 entwickelte Demonstrator NMM-5D (J. Leinweber, C. Meyer, R. Füßl, R. Theska, and E. Manske, “Ein neuartiges Konzept für 5D Nanopositionier-, Nanomess-, und Nanofabrikationsmaschinen,” tm - Tech. Mess. , vol. 37, nos. 1-10, 2022) neben dem kartesischen Verfahrbereich von 25mm × 25mm × 5mm zusätzlich ein Rotationsvermögen des Tools von 360˚ sowie ein Neigungsvermögen von 50˚. Imfolgenden Artikel wird davon ausgehend die mechanische und metrologische Charakterisierung der parallelkinematisch aktuierten Rotationserweiterung präsentiert. Hierbei konzentrieren sich durchgeführte Untersuchungen primär auf die kinematisch verursachten Abweichungen des Tool Center Point (TCP) sowie die Detektierung dieser Abweichungen mit einem interferometrischen In-situ -Referenzmesssystem. Darüber kann perspektivisch eine geregelte Kompensation der auftretenden TCP-Abweichungen erfolgen.
https://doi.org/10.1515/teme-2023-0109
Direkt abgeformte Betonbauteile für Präzisionsanwendungen im Maschinen- und Gerätebau. - Ilmenau : Universitätsverlag Ilmenau, 2023. - 1 Online-Ressource (XIII, 168 Seiten). - (Berichte aus dem Institut für Maschinen- und Gerätekonstruktion (IMGK) ; Band 40)
Technische Universität Ilmenau, Dissertation 2023
Präzisionssysteme können durch die Verwendung von Werkstoffen mit dem gleichen thermischen Ausdehnungskoeffizienten thermisch stabil realisiert werden. Häufig wird Naturstein für Präzisionsanwendungen verwendet, da dieser sehr fein bearbeitet werden kann, thermisch sowie mechanisch langzeitstabil und korrosionsbeständig ist. Die Gestaltungmöglichkeiten sind jedoch durch die kostspielige und zeitaufwendige Bearbeitung stark eingeschränkt. Ein vielversprechender Ansatz zur Herstellung von Präzisionsbauteilen für die gesamte Maschinenstruktur ist die Verwendung von speziellen selbstverdichtenden Betonen (SCC=Self Compacting Concrete). Mit Beton als Alternativmaterial können vergleichbare mechanische Eigenschaften erzielt und wesentliche Gestaltmerkmale urformend hergestellt werden. Durch die niedrigen Materialkosten amortisieren sich die Werkzeugkosten schon bei kleinen Losgrößen. Teile aus SCC weisen im Herstellungsprozess ein zeit- und klimaabhängiges Schrumpfen und Quellen auf, womit Änderungen in der Bauteilgestalt verbunden sind. Allerdings konnte die Stabilisierungszeit beim Aushärteprozess deutlich verkürzt werden. In einer Langzeitstudie über fast zehn Jahre wurde eine mit Naturstein vergleichbare Formstabilität belegt. Darüber hinaus wurde eine Simulationsmethode entwickelt, um die Formänderung komplexer Geometrien vorherzusagen. Mit diesem Werkzeug kann eine Schalungsgeometrie entwickelt werden, die zu einem Fertigteil führt, welches annähernd der idealen Geometrie entspricht. SCC kann auch als alternatives Material für Teile mit hoher spezifischer Steifigkeit in beweglichen Maschinenstrukturen eingesetzt werden. Um eine mit Stahl- oder Aluminiumleichtbauteilen vergleichbare Zuverlässigkeit zu gewährleisten, muss die Betriebsfestigkeit verbessert werden. Der Einsatz von Stahl– oder Kohlefasern als Bewehrung ist nicht sinnvoll, da diese zu inhomogenem thermischen Verhalten führen. Alternativ kann eine Armierung durch die Aufbringung von organo–funktionellen Beschichtungen mit erhöhter Zugfestigkeit erfolgen. Die Wirkungsmechanismen und Zusammenhänge mit der Dauerfestigkeit wurden analysiert, um eine experimentelle Methode zur Bestimmung des Beschichtungseinflusses zu entwickeln. Abschließend erfolgt die Übertragung der Ergebnisse auf ein Verfahren zur Vorhersage der Betriebsfestigkeitssteigerung von beschichteten Betonbauteilen mit beliebiger Geometrie.
https://doi.org/10.22032/dbt.59146
Calibration of positioning microsystems with subatomic accuracy. - In: Engineering for a changing world, (2023), 1.4.117, S. 1-6
Multidimensional positioning, measuring and manipulation with a spatial resolution in the subatomic range are an upcoming demand in the area of nanotechnology. Nanopositioning and measuring machines (NMM) enable to measure and manipulate objects within a large addressable 3D-range of up to a few hundred millimetre in each dimension with a specified spatial resolution of down to 0.1 nm [1]. New approaches are needed to extend the potential of NMM technology to even smaller scales. In previous work [2] a proof-of-concept positioning system has been designed to achieve reproducibility and resolution for precise motion on subatomic scale. In a first approach, a scanning probe microscope will be used to measure a nanosized periodic lattice that serves as a scale for the position according to [3]. Here, we present a microsystem design with an addressable positioning range of ±100 μm that will carry the lattice structure. In order to precisely control the motion, the electrostatic drive and position sensor characteristics of the demonstrator must be calibrated thoroughly by means of an optical measuring system. A focused, range-resolved fibre-optic laser interferometer is comprised as the calibration standard. An uncertainty estimation for the measurement setup is carried out. It is shown that the desired positioning accuracy for the first tip- and grating-based setup can be achieved with the presented microsystems.
https://doi.org/10.22032/dbt.58741
Monolithic compliant mechanism for an EMFC mass comparator weighing cell. - In: Engineering for a changing world, (2023), 1.4.112, S. 1-14
Mass comparator weighing cells based on electromagnetic force compensation (EMFC) find application in the most demanding force and mass measurement applications. The centerpiece of these devices is a highly sensitive compliant mechanism with thin flexure hinges. The compliant mechanism forms the mechanical part of the mechatronic overall system. A novel mechanism based on an advanced adjustment concept has been developed, manufactured, and experimentally investigated. The adjustment is designed to further reduce the measurement uncertainty for mass comparisons by canceling out first-order error components. The focus is on the mechanical properties: stiffness, tilt sensitivity, and off-center load sensitivity. The elastic stiffness of the compliant mechanism is compensated by introducing a negative gravitational stiffness to enable the compensation of manufacturing deviations and to increase mass resolution.
https://doi.org/10.22032/dbt.58738
Preliminary characterization of anelastic effects in the flexure mechanism for a new Kibble balance at NIST. - In: Engineering for a changing world, (2023), 1.4.101, S. 1-13
A new Kibble balance is being built at the National Institute of Standards and Technology (NIST). For the first time in one of the highly accurate versions of this type of balance, a single flexure mechanism is used for both modes of operation: the weighing mode and the velocity mode. The mechanism is at the core of the new balance design as it represents a paradigm shift for NIST away from using knife edge-based balance mechanisms, which exhibit hysteresis in the measurement procedure of the weighing mode. Mechanical hysteresis may be a limiting factor in the performance of highly accurate Kibble balances approaching single digit nanonewton repeatability on a nominal 100 g mass, as targeted in this work. Flexure-based mechanisms are known to have very good static hysteresis when used as a null detector. However, for larger and especially longer lasting deformations, flexures are known to exhibit anelastic drift. We seek to characterize, and ideally compensate for, this anelastic behavior after deflections during the velocity mode to enable a 10 accurate Kibble balancemeasurement on a nominal 100 g mass artifact with a single flexure-based balance mechanism.
https://doi.org/10.22032/dbt.58743
A laser beam deflection system for heat treatments in large scale additive manufacturing. - In: Engineering for a changing world, (2023), 1.4.082, S. 1-15
Large Scale Additive Manufacturing (LSAM) based on plastic raw material is known for high material output and thus, increased productivity. For an improvement of part properties LSAM is combined with a laser process. Depending on the deposition direction, the laser beam needs to be repositioned to reach the space between two adjacent and consecutively printed strands. Therefore, an optomechanical design is required that allows variable orientation of the laser beam. It consists of a combination of an elliptical, tube-like mirror with an additional, rotatable flat mirror in one of its focal axes. The deflected laser beam hits the second focal axis where the extruder nozzle is located. Thus, > 75% of the nozzle circumference is covered during a laser beam treatment. Both mirrors are individually designed custom-made parts. Its functional verification lays the foundation for an improved additive manufacturing process, which aims to homogenize the component structures to improve the mechanical properties of 3D-printed components.
https://doi.org/10.22032/dbt.58739
Validation of experimental setup for aerostatic bearing simulation. - In: Engineering for a changing world, (2023), 1.4.079, S. 1-10
Aerostatic bearings are extensively used in precision engineering applications that require high positional accuracy and low friction motion. In these bearings, externally pressurized gas is fed through a restrictor into the bearing gap. The viscous shear in the gap restricts the flow, thus forming a pressurized film between the bearing and the guide surface. In the development of models and in investigations of, for example, effects of manufacturing errors and porous material permeability properties, characterization of bearing performance is required. The performance is commonly characterized with a measurement setup, either under static or dynamic conditions. In the present study, an experimental setup for the measurement performance of aerostatic bearings is presented. The investigated measurement setup is validated with a comparison to a literature model. The results of the present study include the load capacity, stiffness, air consumption, and pressure distribution of a commercially available axisymmetric graphite thrust bearing. The results show good agreement between the measurements and the model. Thus, the results show corroborative evidence on the usability of the measurement setup in future aerostatic bearing research.
https://doi.org/10.22032/dbt.58841
Cement-bound mineral casted parts in precision engineering. - In: Engineering for a changing world, (2023), 1.4.077, S. 1-14
The design of a machine frame, supporting a plurality of components/modules, is a major challenge during the development of precision systems. The geometric stability of the supporting parts under thermal and mechanical loads has a decisive influence on the achievable accuracy. Common materials like cast iron or natural stone have preferable properties but often come with high costs and long lead times due to sourcing or manufacturing process and required geometric precision. Concrete is an interesting alternative. Polymer concrete and cement-based concrete such as self-compacting concrete have been considered as cost-effective alternatives for quite a while now. This paper summarizes recent research and findings on these alternative materials and reviews their applicability in machine frame design. Aspects of the cold primary shaping process will be covered with an emphasis on ready-to-use features with geometric tolerances in the order of magnitude of micrometers. The potential for integrating functional elements is discussed. The advantages of concrete as an alternative material are summarized with regard to the application of the design principle "functional material at the location where functionality is required".
https://doi.org/10.22032/dbt.58740
Synthesis of optimized compliant mechanisms for ultra-precision applications. - In: Engineering for a changing world, (2023), 1.4.071, S. 1-9
Compliant mechanisms for ultra-precision applications are often required to achieve highest accuracy over largest possible ranges of motion along multiple axes. The typical synthesis approach for such high demands is based on the substitution of the revolute joints of a suitable rigid-body model with optimized flexure hinges. However, during the transition from rigid-body model to compliant mechanism, the effects of multiple input parameters are still widely unknown. Among them are the degrees of freedom of the rigid-body model, the integration of the drive elements, as well as the coupling of mechanisms to achieve multiple motion axes. The following contribution expands the fundamentals of the synthesis of compliant mechanisms based on rigid-body models for their application in ultra-precision technologies. Based on the investigation of the aforementioned parameters as well as the knowledge gained from previous research work, a novel synthesis method has been developed.
https://doi.org/10.22032/dbt.58844
Development of a tool-changing system for nanofabrication machines. - In: Engineering for a changing world, (2023), 1.4.025, S. 1-6
The frequent use of a growing diversity of tools in nanofabrication machines raises the need for a highly reproducible tool-changing system that is capable of working with tools of different weights and moments of inertia. Since the tool-changing system is designed beneficially based on an open, force-paired kinematic coupling, means to apply a holding force are required. The holding force needed is about 40 N in total and has to be applied without heat dissipation or other disturbances. Since variations in the elastic deformation at the contact points of the coupling directly influence the reproducibility of the tool position, the force application needs to be highly reproducible. An analytical model is developed to determine the force application requirements, taking into consideration elastic deformation and friction. Based on this model, the allowable variation of the holding force in amount and direction, as well as the allowable deviation of the force application point, are determined. Thereby, the resulting influence of the force application on the reproducibility of the position of the tool-center point is intended to be 5 nm or less. Eleven solution principles for force application are developed based on the physical effects of magnetic force, spring force, and weight force. Based on a systematic evaluation, an arrangement of three permanent magnets with flux guide pieces at an angle of 120˚ to each other has been chosen at the fixed side. On the tool side, ferromagnetic plates are used to close the magnetic circuit. Thereby, the air gap and, thus, the holding force can be adjusted individually for each tool. During the tool change, the magnetic force is switched off by short-circuiting the magnetic flux with an additional rotatory-mounted flux piece, which is driven by a gear motor. The designed prototype will be tested and further optimized within a nanofabrication machine.
https://doi.org/10.22032/dbt.58846