Browsing by Author "Möhring, Hans-Christian"

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Open Access
Active runout compensation using the guide elements on metal band saws for a longer tool life and reduced material loss
(2024) Tandler, Tobias; Möhring, Hans-Christian
At a time of rising energy and material costs, manufacturing process efficiency is becoming increasingly important. This is one reason why cutting and especially sawing processes, usually the first step in most manufacturing chains in discrete part production, have to be investigated more intensively. Due to problems with runout and poor surface finishes, raw material is conventionally cut to oversize by either circular sawing or band sawing. This oversize has to be removed by following processes, costing extra energy and wasting material. Since the problem of runout increases with increasing tool wear due to higher deflections of the thin and compliant tools, an even larger oversize is required. This paper describes an approach to reduce the need of oversize even with increasing tool wear in band sawing by tilting the saw band in order to compensate for tool deflections during cutting. To achieve this, it is necessary to measure and understand the saw band runout. The next step is to present a system design and controller for tilting the saw band. Finally, tests are carried out to analyse the effectiveness of the system. In addition, the approach allows the use of increased process parameters to the end of the tool life without losing more material. The tool can therefore be used productively for a longer time period.
Open Access
Approach to developing low-noise circular saw blades by determining actual required chip space volumes
(2025) Güzel, Kamil; Möhring, Hans-Christian
Noise emissions are one of the most common health hazards in the workplace, especially in the manufacturing industries. In wood machining, for instance, circular sawing processes in particular cause extremely high noise emissions that often exceed the permissible limits. The main source of noise is the rotating tool, whose aeroacoustic behavior is influenced by air turbulence. Previous studies have shown the significant influence of the chip space dimensions on the flow-induced noise emissions. At the same time, the chip space filling during the circular sawing process in wood machining has not yet been scientifically investigated. This paper deals with this deficit and presents a method that makes it possible to estimate the volume of chip space actually required. As part of the approach, the modified chip loosening factor was first defined, which approximately reflects the expansion of the separated wood chips after the machining process. Empirical coefficients were determined for different materials and varying process parameters as part of experimental investigations. The findings indicated that the chip size distribution and the proportion of specific particle sizes have an influence on the settling behavior and compression of the chip material. The data obtained was used to derive characteristic maps for the chip space volumes actually required. Based on this, prototype tools with different chip space modifications were derived and examined regarding chip space filling and noise emissions. Based on the reference geometry, a significant reduction in the sound pressure level of approximately 11 dB was achieved by modifying the chip space volume to an empirical-analytical minimum value without exceeding the chip space filling limit.
Open Access
Assessment of the heat transfer conditions in the cavity of a rotating circular saw
(2024) Stegmann, Jan; Baumert, Moritz; Kabelac, Stephan; Menze, Christian; Ramme, Johannes; Möhring, Hans-Christian
To improve machining processes concerning the usage of lubricants, knowledge of the thermo-mechanical and thermo-fluid interactions at the cutting zone is of great importance. This study focuses on the description of the convective heat transfer which occurs during circular sawing when the lubricant is provided via an internal coolant supply. The highly complex flow field inside the cavity of the sawing process is separated into two distinct flow forms, an impingement and a channel flow. With the aid of experimental and numerical studies, the heat transfer characteristics of these two flow forms have been examined for water and a lubricant used in the circular sawing process. Studies have been conducted over a wide range of Reynolds numbers (impingement flow: 2×103
Open Access
Augmented reality to visualize a finite element analysis for assessing clamping concepts
(2024) Maier, Walther; Möhring, Hans-Christian; Feng, Qi; Wunderle, Richard
This paper presents the development of an innovative augmented reality application for evaluating clamping concepts through visualizing the finite element analysis. The focus is on transforming the traditional simulation results into immersive, holographic displays, enabling users to experience and assess finite element analysis in three dimensions. The application development process involves data processing by MATLAB, visualization in the software Unity, and displaying holograms through Microsoft’s Hololens2. The most significant advancement introduces a new algorithm for rendering different finite elements in Unity. The application targets not only university engineering students but also vocational students with limited background in finite element analysis and machining, aiming to make the learning process more interactive and engaging. It was tested in a real machining environment, demonstrating its technical feasibility and potential in engineering education.
Open Access
Cutting tool condition monitoring using eigenfaces : tool wear monitoring in milling
(2022) König, Wolfgang; Möhring, Hans-Christian
Effective monitoring of the tool wear condition within a machining process can be very challenging. Depending on the sensors used, often only a part of the relevant wear information can be detected. In the case of milling processes data acquisition is made even more difficult by the fact that the process working point is inaccessible for sensor applications due to the physical tool, the machining process itself, the chipping and used cooling-lubricants. By using a variety of sensors and different measuring principles, sensor data fusion strategies can counteract this problem. An approach to this is the eigenface algorithm. This approach, a face recognition technique, is tested for its suitability on tool condition monitoring in milling processes by using multi-sensor process data.
Open Access
A data-driven approach for cutting force prediction in FEM machining simulations using gradient boosted machines
(2024) Reeber, Tim; Wolf, Jan; Möhring, Hans-Christian
Cutting simulations via the Finite Element Method (FEM) have recently gained more significance due to ever increasing computational performance and thus better resulting accuracy. However, these simulations are still time consuming and therefore cannot be deployed for an in situ evaluation of the machining processes in an industrial environment. This is due to the high non-linear nature of FEM simulations of machining processes, which require considerable computational resources. On the other hand, machine learning methods are known to capture complex non-linear behaviors. One of the most widely applied material models in cutting simulations is the Johnson-Cook material model, which has a great influence on the output of the cutting simulations and contributes to the non-linear behavior of the models, but its influence on cutting forces is sometimes difficult to assess beforehand. Therefore, this research aims to capture the highly non-linear behavior of the material model by using a dataset of multiple short-duration cutting simulations from Abaqus to learn the relationship of the Johnson-Cook material model parameters and the resulting cutting forces for a constant set of cutting conditions. The goal is to shorten the time to simulate cutting forces by encapsulating complex cutting conditions in dependence of material parameters in a single model. A total of five different models are trained and the performance is evaluated. The results show that Gradient Boosted Machines capture the influence of varying material model parameters the best and enable good predictions of cutting forces as well as deliver insights into the relevance of the material parameters for the cutting and thrust forces in orthogonal cutting.
Open Access
Determination of the mechanical properties of prestressed fiber-reinforced polymer concrete
(2025) Wegner, Robert; Born, Larissa; Engert, Michelle; Werkle, Kim Torben; Möhring, Hans-Christian; Gresser, Götz T.
Polymer concrete is increasingly used in high-precision machine tools due to its excellent damping properties, thermal stability, and reduced environmental impact. However, its low tensile strength and stiffness limit its use in structural or dynamically loaded components. This study examines the mechanical enhancement of polymer concrete through the integration of prestressed continuous carbon fiber reinforcements. Specimens with embedded carbon fiber rovings prestressed up to 470 MPa were fabricated and tested under three-point bending and uniaxial compression loading. Bending strength increased by up to 35 % and bending stiffness by 16 %, with significant gains occurring beyond a prestress level of 70 - 110 MPa. CT imaging confirmed that prestressing delayed crack initiation and limited propagation. Under compressive loading parallel to the fiber direction, strength increased by up to 8 %, though the effect diminished at higher prestress levels. A reduction in compressive strength was observed for transverse loading, attributed to matrix discontinuities and stress redistribution. The results demonstrate that prestressed fiber integration significantly improves the structural performance of polymer concrete, offering enhanced load capacity and failure resistance. These findings lay the foundation for broader application of polymer concrete in load-bearing components and support the development of hybrid systems combining mechanical efficiency with design flexibility.
Open Access
Determination of the shear angle in the orthogonal cutting process
(2022) Storchak, Michael; Stehle, Thomas; Möhring, Hans-Christian
Determination of the shear angle by experimental and analytical methods, as well as by numerical simulation, is presented. Experimental determination of the shear angle was performed by analyzing the chip roots obtained by the method of cutting process quick stop through purposeful fracture of the workpiece in the area surrounding the primary cutting zone. The analytical determination of the shear angle was carried out using the chip compression ratio and was based on the principle of a potential energy minimum. Measurement of the shear angle in the numerical simulation of orthogonal cutting was performed using the strain rate pattern of the machined material at the selected simulation moment. It was analyzed how the parameters of the Johnson-Cook constitutive equation and the friction model affect the shear angle value. The parameters with a predominant effect on the shear angle were determined. Then the generalized values of these parameters were established with a software algorithm based on identifying the intersection of the constitutive equation parameter sets. The use of generalized parameters provided the largest deviation between experimental and simulated shear angle values from 9% to 18% and between simulated and analytically calculated shear angle values from 7% to 12%.
Open Access
Determination of the tool-chip contact length for the cutting processes
(2022) Storchak, Michael; Drewle, Konstantin; Menze, Christian; Stehle, Thomas; Möhring, Hans-Christian
The thermomechanical interaction of the tool with the chip in the most loaded secondary cutting zone depends on the contact length of the tool rake face with the chip. Experimental studies of the dependency of the contact length on the cutting speed, the undeformed chip thickness, and the tool rake angle, performed by the optical method, are used for comparison with the contact length obtained by the FE modeling of the orthogonal cutting process. To determine the parameters of the constitutive Johnson-Cook equation, which serves as a material model of the FE cutting model that has a predominant influence on the contact length, a software-implemented algorithm was developed. This algorithm is based on determining the generalized parameters of the constitutive equation through finding the intersection of these parameter sets. The plurality intersection of the parameter sets of the constitutive equation is determined by means of the design of experiments and refined by subsequent multiple iterations. The comparison of the contact length values, obtained by simulating the cutting process using the generalized parameters of the constitutive equation as a material model with their experimental values, does not exceed 12% for a wide range of cutting speeds and depths of cut, as well as for the tool rake angle.
Open Access
Development of a multi-sensor concept for real-time temperature measurement at the cutting insert of a single-lip deep hole drilling tool
(2022) Ramme, Johannes; Wegert, Robert; Guski, Vinzenz; Schmauder, Siegfried; Möhring, Hans-Christian
The mechanical energy resulting from cutting processes is turned almost completely in thermal energy, which encourages thermal procedures, such as diffusion, leading to higher wear in the cutting tool and thus to higher temperatures. Furthermore, high temperatures influence the properties of the marginal zones in the workpiece. In this presented work, the in-process temperature of a cutting insert during single-lip deep hole drilling (SLD) is investigated. Therefore, a sensor-integrated tool with resistance temperature detectors (RTD) placed beneath the cutting insert is developed. First, the thermal properties of the cutting insert are adjusted to fit the assembled tool. Afterwards, a CEL-Simulation is obtained to examine the temperature distribution at the cutting edge of the SLD-tool. The temperatures calculated by simulation can be compared to the in-process temperatures of the sensor integrated tool. Because of the usage of a cooling lubricant, simulated temperatures can be varied with a factor to fit the experimentally measured temperature curves. The highest temperature during the process appears at the outer edge of the cutting insert. By knowing the thermal properties, the maximum process temperatures for the deep hole drilling operation are to be calculated. The results represent a contribution to an interdisciplinary research project “Surface Conditioning in Machining Processes” (SPP 2086) of the German Research Foundation (DFG).
Open Access
Einsatz von KI bei der Prozessvorhersage für Bandsägen : Einsatz von künstlicher Intelligenz zur Vorhersage von Prozesskräften beim Bandsägen
(2023) Tandler, Tobias; Hirth, Thomas; Eisseler, Rocco; Stehle, Thomas; Möhring, Hans-Christian
Open Access
Evaluation of methods for measuring tool-chip contact length in wet machining using different approaches (microtextured tool, in-situ visualization and restricted contact tool)
(2022) Ellersiek, Lars; Menze, Christian; Sauer, Florian; Denkena, Berend; Möhring, Hans-Christian; Schulze, Volker
The contact length is one of the most important factors to evaluate the chip formation process and the mechanical loads in metal cutting. Over the years, several methods to identify the contact length were developed. However, especially for wet cutting processes the determination of the contact length is still challenging. In this paper, three methods to identify the contact length for dry and wet processes in cutting of Ti6Al4V and AISI4140 + QT are presented, discussed and analyzed. The first approach uses tools with a microtextured rake face. By evaluating the microstructures on the chip, a new method to identify the contact length is established. The second approach applies high speed recordings to identify the contact length. The challenge is thereby the application of high-speed recordings under wet conditions. In the third approach, tools with restricted contact length are used. It is shown that with all three methods the contact length is reduced using metal working fluid.
Open Access
Flow visualisation and evaluation studies on metalworking fluid applications in manufacturing processes : methods and results
(2023) Fritsching, Udo; Buss, Lizoel; Tonn, Teresa; Schumski, Lukas; Gakovi, Jurgen; Hatscher, Johnson David; Sölter, Jens; Avila, Kerstin; Karpuschewski, Bernhard; Gerken, Julian Frederic; Wolf, Tobias; Biermann, Dirk; Menze, Christian; Möhring, Hans-Christian; Tchoupe, Elio; Heidemanns, Lukas; Herrig, Tim; Klink, Andreas; Nabbout, Kaissar; Sommerfeld, Martin; Luther, Fabian; Schaarschmidt, Ingo; Schubert, Andreas; Richter, Markus
Metalworking operations rely on the successful application of metalworking fluids (MWFs) for effective and efficient operation. Processes such as grinding or drilling often require the use of MWFs for cooling, lubrication, and chip removal. Electrochemical machining processes require electrolyte flow to operate. However, in those machining operations, a fundamental understanding of the mode of action of MWF is lacking due to the unknown flow dynamics and its interaction with the material removal during the process. Important information on the behaviour of MWFs during machining can be obtained from specific experimental flow visualisation studies. In this paper, promising flow visualisation analysis techniques applied to exemplary machining processes (grinding, sawing, drilling, and electrochemical machining) are presented and discussed. Shadowgraph imaging and flow measurements, e.g., particle image velocimetry, allow the identification of typical flow and MWF operating regimes in the different machining processes. Based on the identification of these regimes, efficient machining parameters and MWF applications can be derived. In addition, detailed experimental analyses of MWFs provide essential data for the input and validation of model development and numerical simulations within the Priority Programme SPP 2231 FluSimPro.
Open Access
Fundamental characterization of lubrication effects through various cooling lubricants in the chip formation zone
(2025) Biermann, Dirk; Saelzer, Jannis; Bergmann, Benjamin; Schenzel, J.; Menze, Christian; Gerken, Julian Frederic; Wolf, T.; Denkena, Berend; Möhring, Hans-Christian; Zabel, Andreas
Using cooling lubricants in metalworking requires a high consumption of energy and resources. However, cooling lubricants serve to increase the productivity and quality of these processes. Accordingly, it is necessary to expand the efficiency of their application. This requires fundamental understanding of the working mechanisms. Driven by this motivation, this publication compares six cooling lubricants regarding their lubrication effect in orthogonal cutting. Three types of fluid supply, each conducted on a specific special machine tool for chip formation analysis, and two cutting speeds have been used in the tests. In order to analyze the lubricating effect of these different scenarios, force measurements were carried out and the chip formation was recorded with high-speed recordings. It was found that the process improvements due to lubrication is determined by the interaction of fluid properties, supply strategy and cutting speed. Moreover, clear limitations of water-based cooling lubricants (especially oil-water-emulsions) in the ability to lubricate the chip formation zone have been determined and quantified.
Open Access
Generalizable process monitoring for FFF 3D printing with machine vision
(2023) Werkle, Kim Torben; Trage, Caroline; Wolf, Jan; Möhring, Hans-Christian
Additive manufacturing has experienced a surge in popularity in both commercial and private sectors over the past decade due to the growing demand for affordable and highly customized products, which are often in direct opposition to the requirements of traditional subtractive manufacturing. Fused Filament Fabrication (FFF) has emerged as the most widely-used additive manufacturing technology, despite challenges associated with achieving contour accuracy. To address this issue, the authors have developed a novel camera-based process monitoring method that enables the detection of errors in the printing process through a layer-by-layer comparison of the actual contour and the target contour obtained via G-Code processing. This method is generalizable and can be applied to different printer models with minimal hardware adjustments using off-the-shelf components. The authors have demonstrated the effectiveness of this method in automatically detecting both coarse and small contour deviations in 3D-printed parts.
Open Access
Geometry modifications of circular saw blades to reduce aeroacoustic noise emissions
(2025) Güzel, Kamil; Möhring, Hans-Christian
In the manufacturing industries, noise is one of the most common health hazards at workplaces. In wood machining, for instance, circular sawing processes in particular produce high noise emissions that often exceed the permitted limits. The main source of noise is the rotating circular saw blade, whose aeroacoustic behavior is influenced by air turbulence on the tool contour. So far, no numerical approach to study and optimize the aeroacoustic noise emissions from circular saw blades has been investigated. This paper addresses this deficit and presents a methodology for modeling the flow-induced sound generation on rotating circular saw blades based on computational fluid dynamics (CFD) simulations. With the implementation of the acoustic analogy according to Ffowcs-Williams/Hawkings, the sound pressure levels could be calculated with sufficient accuracy. With deviations between 7 and 10%, the influence of the rotational speeds could be plausibly modeled. Based on the validated numerical model, geometry variants with various modifications were investigated regarding their potential for reducing sound pressure levels. Based on a conventional reference geometry, different chip space volumes and various modifications to the tooth rim and tooth shape were investigated and evaluated as part of simulative parameter studies. Sound pressure level reductions in the range of 2.2-10.8 dB were achieved. The results obtained and the systematic approach investigated provide a suitable set of instruments for industrial practice. Digital prototypes can be designed at an early stage in the product development phase of circular saw blades regarding their aeroacoustic properties.
Open Access
Improving machinability of additively manufactured components with selectively weakened material
(2021) Maucher, Clemens; Teich, Heiko; Möhring, Hans-Christian
Part design and the possibilities of production are disrupted by the increased usage of additive manufacturing (AM). Featuring excellent creative freedom due to the layer-by-layer buildup of components, AM leads to profound changes in future part design and enables previously impossible geometries. Laser powder bed fusion (LPBF) technology already allows to manufacture small quantities of parts with high productivity and material efficiency. Due to the specific process characteristics, the resulting surface finish of these parts is insufficient for a wide range of applications, and post-processing is usually unavoidable. Specifically for functional surfaces, this post-processing is often done by machining processes, which can pose challenges for intricate and complex AM parts due to excessive machining forces. In the present paper, the influence and the possibilities of the LPBF process parameters on the subtractive post-processing are shown. A novel weakened structure is developed to selectively reduce the strength of the material and improve the cutting conditions. Chip formation, cutting forces and vibrations during drilling as well as cutting forces during an orthogonal cut are examined. To quantify the differences, a comparison of the machinability between bulk material, standard support structures and the weakened structure is carried out.
Open Access
In-process approach for editing the subsurface properties during single-lip deep hole drilling using a sensor-integrated tool
(2024) Wegert, Robert; Guski, Vinzenz; Schmauder, Siegfried; Möhring, Hans-Christian
Single-lip deep-hole drilling (SLD) is characterized by high surface quality and compressive residual stress in the subsurface of the drill hole. These properties depend significantly on the thermomechanical conditions in the machining process. The desired subsurface properties can be adjusted in-process via process monitoring near the cutting zone with a sensor-integrated tool and closed loop control when the thermomechanical conditions are maintained in the optimum range. In this paper, a method is presented to control the thermomechanical conditions to adjust the properties in the subsurface. The process model integrated in the controller is implemented as a soft sensor and takes into account the residual stresses, the roughness, the hardness and the grain size in the surface as well as in the subsurface depending on the process control variables, such as the feed rate and cutting speed. The correlation between the process variables, the thermomechanical conditions of the cutting process and the subsurface properties are investigated both experimentally and by finite element (FE) simulations. Within a justified process parameter range, characteristic fields for the soft sensor were established for each property. In addition, the procedure of controller design and the employed hardware and interfaces are presented.
Open Access
Influence of a closed-loop controlled laser metal wire deposition process of S Al 5356 on the quality of manufactured parts before and after subsequent machining
(2021) Becker, Dina; Boley, Steffen; Eisseler, Rocco; Stehle, Thomas; Möhring, Hans-Christian; Onuseit, Volkher; Hoßfeld, Max; Graf, Thomas
This paper describes the interdependence of additive and subtractive manufacturing processes using the production of test components made from S Al 5356. To achieve the best possible part accuracy and a preferably small wall thickness already within the additive process, a closed loop process control was developed and applied. Subsequent machining processes were nonetheless required to give the components their final shape, but the amount of material in need of removal was minimised. The effort of minimising material removal strongly depended on the initial state of the component (wall thickness, wall thickness constancy, microstructure of the material and others) which was determined by the additive process. For this reason, knowledge of the correlations between generative parameters and component properties, as well as of the interdependency between the additive process and the subsequent machining process to tune the former to the latter was essential. To ascertain this behaviour, a suitable test part was designed to perform both additive processes using laser metal wire deposition with a closed loop control of the track height and subtractive processes using external and internal longitudinal turning with varied parameters. The so manufactured test parts were then used to qualify the material deposition and turning process by criteria like shape accuracy and surface quality.
Open Access
Influence of the manufacturing parameters of an AlMg5 wire-based hybrid production process on quality and mechanical properties
(2021) Möhring, Hans-Christian; Becker, Dina; Eisseler, Rocco; Stehle, Thomas; Reeber, Tim
Hybrid manufacturing processes are known for combining the advantages of additive manufacturing and more traditional manufacturing processes such as machining to create components of complex geometry while minimising material waste. The trend towards lightweight design, especially in view of e-mobility, gives aluminium materials an important role to play. This study examines the use of aluminium alloys in laser metal wire deposition (LMWD) processes with subsequent subtractive machining, which is considerably more difficult due to the different process-related influences. The investigations are focussed on the influence of the differently controlled laser power on the shape accuracy, the microstructure, and the hardness of the AlMg5 test components after the LMWD process with subsequent subtractive machining by turning. The long-term goal of the investigations is to increase the stability of the hybrid production process of AlMg5 components with defined dimensional accuracy and mechanical properties.