Abstract: Within the framework of the Renewable Energies Act, besides biomass power stations wind turbine systems enact a significant role since they produce power by using a primary source of renewable energies. As widespread and technical advanced wind turbines are, they still exhibit shortcomings when operating in cold temperatures. Therefore, especially in frigid regions, there is a high risk regarding icing and forming of hoarfrost. Iced rotor blades lead to considerable disadvantages during operation, like ice shedding, unbalanced or off-centered loads, and downtimes.Different heating systems that are already available show some disadvantages, such as the difficulties in integrating the installation of those systems directly in the production process. Thus, a new technology is presented which eliminates existing challenges and can be integrated into current production lines. Furthermore, the results of the investigations for the applicability of this new system for de-icing wind turbines is pictured. Due to an innovative plasma technology, the surfaces of rotor blades can be coated with a heating structure layer. The new technology is presented and the influence of different machine parameters of the coating process are shown based on several experimental results. In further tests, the metal structured rotor blades are examined under real conditions and the suitability of this technology for a series launch is rated.
Abstract: A planning method is presented which allows to systematically building process chains based on a preliminary design of composite structures. The method utilises the specific sequences of procedural steps that occur in the production of carbon fibre reinforced plastic (CFRP) structures, to build sub process chains for each component of the structure. Process restrictions are considered to evaluate the suitability of different production processes. To obtain the whole process chain of the structure, different joining methods are applied in addition to combine the components and its sub process chains. The results of the presented method are used in an overarching development procedure to investigate resulting impacts on the solution. Possible impacts could be the production costs or the material characteristics.
Abstract: To realise the high cutting speeds required in wood machining for a productive cutting process, high-speed spindles are used especially in CNC machining centres. The high rotational speed during operation, however, results in great centrifugal forces at the tool. Particularly unbalance here leads to a great loading of the spindle bearing as well as to reduced occupational safety. Unlike metal removal, the machining of wood and engineered wood products is subject to other requirements regarding the process parameters, such as e.g. higher cutting speeds or material removal rates. For that reason, economical sensible balance qualities for tools in wood machining are analysed within the IGF project 18381 N „Establishing the necessary balance quality of tools in wood machining“, which is carried out in cooperation with a working group from industry and funded by the Federal Ministry for Economic Affairs and Energy (BMWi). In order to analyse how unbalances in tools influences the loads of the spindle bearing, a simulation model of a spindle will be developed and constructed for wood machining. Serving as a basis of the model, the frequency responses of the static spindle will be established by experiment. Based on this, the natural vibration behaviour of the spindle will be simulated in a finite element model. Finally, it will be presented how test tools with different balance conditions influence the bearing load of the spindle.
Abstract: This paper deals with a natural frequency distribution of a six-axis industrial robot in order to analyze chatter vibrations in upcoming milling processes. Since the dynamic vibration behavior of the robotic system can be manipulated by changing the robot’s joint configuration, experimental modal analysis is performed to determine the natural frequencies in the entire workspace. In this study, methods of design of experiments are used to derivate a mathematical model that predicts the natural frequencies of the robotic structure for any joint configuration within the considered workspace.
Abstract: In sheet metal forming, the fixation of tools in presses has not been considered to be variable for process optimization yet. Every clamping point fixes the tool. Tool areas without a fixation point have a vertical degree of freedom, respectively. Against this background, it seems to be evident that the kind of tool fixation can influence its static and dynamic beahviour. In shear cutting processes, tool vibration is an important phenomenon, as it affects tool wear on the one hand and influences part quality on the other hand. In this paper, a methodology for influencing the tool vibration by specific setups of the clamping situation is introduced.
Abstract: Presses with mechanical linkages based on levers between motor and ram (path-linked presses) tend to oscillate due to inertial forces as a consequence of the drive parts motion.In this publication a new approach for a mass-balancing system is presented. This system allows to generate the optimal compensation forces needed to counteract the inertial forces by means of four linear motors. The control signals for the linear motors are specified by an evolutionary optimization algorithm, which operates on the base of measured accelerations of the press frame. The control signals of the linear motors are created in a way that the machines oscillations are reduced to a minimum. This way the presented mass-balancing system adapts itself automatically to varying conditions during the operation of the machine, such as a tool change or a varying stroke rate.In particular, the present publication provides the results of the conceptual design and the virtual testing of this approach, which has been mainly carried out with the help of multiple-body simulations.
Abstract: Forming asymmetric parts leads to horizontal process forces applied to the ram of a form-ing machine. These forces entail horizontal ram displacement and influence the quality of the pro-duced parts negatively. By application of horizontal counterforces to the ram, the displacement can be avoided and the process stability be improved. For the purpose of applying horizontal counter-forces, an electromagnetic system, which will be integrated in a forming machine, is currently under development. The requirements to the system are presented as well as the design optimised in vali-dated electromagnetic simulations and the approach for the mechanical integration into a forming machine.
Abstract: Guiding systems for precision manufacturing machines have to fulfil high demands. Low compliance and the absence of friction is required to achieve a high production accuracy. This article presents a novel active guiding system based on the combination of ultrasonic levitation and magnetic actuators. Firstly, the combined actuator and its working principles are described. Subsequently, the concept for an active, frictionless and medium-free guiding system is outlined. In addition to the free degree of freedom (DOF) in guiding direction, the other 5 DOF are adjustable in order to improve the guides positioning accuracy. The experimental validation of the concept is conducted with a simplified prototype, acting as a 3 DOF adjustable planar guide. Finally, measured compliance frequency responses demonstrate the performance of this novel active guiding concept.
Abstract: Electromagnetic actuators are used in a variety of technical applications especially in the automotive industry. In-line process control methods are an essential component of the Lean and Six Sigma methodology to ensure process quality. However, the current state of the art in process and quality control is largely limited to end-of-line measurements of the force output. Analysing the magnetic stray field is a promising method that can be used to draw conclusions on the properties and defects of the flux-conducting magnetic materials. This phenomenon can potentially be used to identify defects in magnetic actuators thus allowing inline quality-monitoring. In order to realize this feature, patterns in the magnetic stray field of an actuator have to be identified and linked to a specific defect. The resulting challenge is the analysis of large datasets in order to characterize the stray field anomalies. This paper summarizes the results of a study on linear magnetic actuators trying to prove a relationship between parasitic magnetic stray field and the overall force output of an actuator by analysing the data with statistical methods. The findings of this study suggest that certain statistical methods, like regression, are not well suited to build a prediction model for defects in actuators using a similar approach of measuring stray field outside the actuator. This is mainly due to the fact that prerequisites for model building are difficult to full fill within the context of stray field analysis. Nevertheless, the findings also suggest that methods of exploratory data analysis can be used to derive quality relevant information from data of stray field measurements. The paper elaborates on the problem of defining a population, choosing variables for model building, as well as model error.
Abstract: In this research a confocal chromatic point sensor was implemented in a desktop sized machine tool. The sensor was used to detect the surface in z-direction. Data from the machine control of the x- and y-axes is extracted and combined with the z- information of the sensor to directly scan surfaces. With the presented sensor, micro structures as small as 5 μm can be characterized. Based on the possibilities of this measuring system, face milling before the actual micro machining can be avoided by determining tilts and waviness of the workpiece. Also the effective tool diameter can be determined and compensated. After machining, the structure can be measured for quality control. Based on this measurement system, a micro machining process was developed broadening the potential for the use of desktop sized machine tools.