Center for Mechatronics and Automation

Saarbrücken, Germany

Center for Mechatronics and Automation

Saarbrücken, Germany
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Steuer P.,Center for Mechatronics and Automation | Steuer P.,Saarland University | Weber O.,Center for Mechatronics and Automation | Weber O.,Saarland University | Bahre D.,Saarland University
International Journal of Refractory Metals and Hard Materials | Year: 2015

The wear in electrical discharge machining exerts a great influence on the result and quality of the workpiece being machined. Especially complex structures can lead to high costs for electrode preparation. In this investigation a process chain is set up using copper electrodes machined by Pulse Electrochemical Machining for structuring hard metal by die-sinking electrical discharge machining. After investigating the electrochemical machining behavior of copper, suitable parameters are defined for this wear-free working process. In the succeeding electrical discharge machining three consecutive structuring steps are performed using a new tool electrode each time. Reproducing four complex structures and estimating a validation factor for the reproducibility, it is shown that the introduced sequence can be used for machining complex shapes on hard metal. © 2015 Elsevier Ltd. All rights reserved.


Kuhn K.,Laboratory for Measurement Technology | Kuhn K.,FESTO | Pignanelli E.,Laboratory for Measurement Technology | Pignanelli E.,Center for Mechatronics and Automation | Schutze A.,Laboratory for Measurement Technology
IEEE Sensors Journal | Year: 2013

Based on a low-cost micro-machined infrared (IR) source with subsequent gas specific filter, photoacoustic absorption (PA) measurements were investigated in a nonresonant operating mode of a gas cell. In addition, nondispersive IR (NDIR) transmission measurements based on a thermopile detector were used to expand the measurement range, but also for an inherent self-monitoring scheme of the system. Compared to other systems using expensive laser sources for stimulation of acoustic pressure waves in a resonant mode of operation, the approach is based on low-cost components. The IR source was modulated in the frequency range between 1 and 10 Hz. To achieve enhanced resolution and a good signal to noise ratio the sensor raw data-both for transmission as well as absorption measurements-were evaluated using discrete Fourier transformation. By combining PA and NDIR transmission measurements a wide concentration range is achieved, e.g., 100-20 000 ppm of carbon dioxide for a measurement cell with a length of 9 cm. Whereas the NDIR transmission measurement is suitable for monitoring higher concentrations, the PA measurement offers better detectivity at lower gas concentrations. Furthermore, the modular system allows the realization of a self-monitoring scheme by comparing the signals measured with both approaches, thus omitting the need for a second filter at a reference wavelength. © 2012 IEEE.


Muller R.,Center for Mechatronics and Automation | Vette M.,Center for Mechatronics and Automation | Scholer M.,Center for Mechatronics and Automation
Assembly Automation | Year: 2014

Purpose - The paper aims to deliver an approach of how lightweight robot systems can be used to automate manual processes for higher efficiency, increased process capability and enhanced ergonomics. To show how these systems can be utilized in practice, a new collaborative testing system for an automated water leak test was designed using an image processing system utilized by the robot. Design/methodology/approach - The "water leak test" in an automotive final assembly line is often a significant cost factor due to its labour-intensive nature. This is particularly the case for premium car manufacturers as each vehicle is watered and manually inspected for leakage. This paper delivers an approach that optimizes the efficiency and capability of the test process by using a new automated in-line inspection system whereby thermographic images are taken by a lightweight robot system and then processed to locate the leak. Such optimization allows the collaboration of robots and manual labour which, in turn, enhances the capability of the process station. Findings - This paper examines the development of novel applications for lightweight robotic systems and provides a suitable process whereby the systems are optimized in technical, ergonomic and safety-related aspects. Research limitations/implications - A new automated testing process in combination with a processing algorithm was developed. Practical implications - To optimize and validate the system, it was set up in a true to reality model factory and brought to a prototypical status. Several original equipment manufacturers showed great interest in implementing the system in their assembly line. Social implications - The direct human-robot collaboration allows humans and robots to share the same workspace without strict separation measures which is a great advantage compared with traditional industrial robots. The workers benefit from a more ergonomic workflow and are relieved from unpleasant, repetitive and burdensome tasks. Originality/value - A lightweight robotic system was implemented in a continuous assembly line as a new area of application for these systems. The automated water leak test gives a practical example of how to enrich the assembly and commissioning lines, which are currently dominated by manual labour, with new technologies. This is necessary to reach a higher efficiency and process capability while maintaining a higher flexibility potential than fully automated systems. © 2014 Emerald Group Publishing Limited.


Steuer P.,Saarland University | Steuer P.,Center for Mechatronics and Automation | Rebschlager A.,Center for Mechatronics and Automation | Ernst A.,Saarland University | Bahre D.,Saarland University
Key Engineering Materials | Year: 2015

The Pulse Electrochemical Machining Process is an innovative, non-conventional process, based on the Electrochemical Machining process. Herein, pulsed current instead of constant current and a feed overlaid mechanical vibration of the tool electrode allows a higher precision and copying accuracy in contrast to the well-established ECM process. Yet, in this context the pulse-pause time and the length of the pulse on-time used in the process cause changes in the material removal while processing and therefore influences the processing result as well as cycle times and other industry relevant criteria. Understanding these pulse- and process specific changes is a key to the process design for industrial applications, since different sets and variations in parameters also change the final form and surface topography. This contribution shows, at the example of two materials 1.4301 and electrolytic copper, how a machining process can be designed and calculated based on material specific data. The way to acquire the necessary material data sets using industrial equipment, as well as the use and information which can be drawn from the data will be addressed. © (2015) Trans Tech Publications, Switzerland.


Izadi M.,Center for Mechatronics and Automation | Mahjoob M.J.,Center for Mechatronics and Automation | Soheilypour M.,Center for Mechatronics and Automation
ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010 | Year: 2010

A Tetrahedral Walker (TET Walker) is a robot made to extend space exploration into inaccessible regions. The motion of the tetrahedron is due to the changes in the struts length. This work presents the implementation and walking gait design of a tetrahedron walker robot. A model for walking gait of the robot is developed. A comparison is then made between different computer simulations of the gaits. A navigation algorithm for walking gait of this type of robots is also developed and discussed. © 2010 by ASME.


Swat M.,Saarland University | Rebschlager A.,Center for Mechatronics and Automation | Trapp K.,Saarland University | Stock T.,TU Berlin | And 2 more authors.
Procedia CIRP | Year: 2015

The initial planning of manufacturing process chains provides the opportunity to sustainably influence the energy requirement for the manufacturing of industrial products by selecting the process chain with the lowest energy consumption. However, the task is still challenging due to the need for energy consumption data of manufacturing equipment. In this paper, the analysis of the energy consumption of a manufacturing process is illustrated by the example of the Pulse Electrochemical Machining (PECM) process. A comparison of two machine tool generations of the same manufacturer shows the improvement in energy consumption. Based on the information gained from the analysis, an approach for the provision of energy consumption data is presented. © 2015 The Authors. Published by Elsevier B.V.


Weber O.,Saarland University | Weber O.,Center for Mechatronics and Automation | Natter H.,Saarland University | Bahre D.,Saarland University
Journal of Solid State Electrochemistry | Year: 2015

In this paper, a new layer-based simulation method for predicting the steady-state current of a pulse electrochemical machining (PECM) process is described. The basic concept of the method is a simple two-layer model consisting of a porous oxide and an adsorption layer. The oxide layer of PECM-machined samples, characterized by Raman spectroscopy and electron microscopy measurements, shows a similar structure as the oxide layer formed in electrochemical impedance spectroscopy (EIS) measurements. Therefore, the electronic equivalent circuit developed according to EIS results was used as analogy for the description of the overall impedance of the PECM model. The difference between the assumed layers of a PECM and EIS measurement is modeled with a material-dependent adjustment function. In this way, the calculated values of the equivalent circuit elements can be directly derived from experimental PECM data. It could be shown that the procedure allows the calculation of the steady-state current of PECM processes for different work conditions (e.g., pulse on-times, pulse frequencies). The procedure is applied to the electrochemical dissolution of three different types of cast iron in NaNO3 electrolyte on realistic machining conditions. All samples were characterized according to their chemical composition, graphite particle morphology/structure, and their anodic dissolution behavior. © 2015 Springer-Verlag Berlin Heidelberg


Weber O.,Center for Mechatronics and Automation | Weber O.,Saarland University | Weinmann M.,Saarland University | Natter H.,Saarland University | Bahre D.,Saarland University
Journal of Applied Electrochemistry | Year: 2015

The electrochemical dissolution of three cast iron types in NaNO3 electrolyte was investigated by cyclic voltammetry, chronoamperometry, and numerical simulations. The measurements were performed with commercially available materials with different iron matrix compositions and graphite particle shapes: lamellar graphite particles in a ferritic/perlitic matrix, spheroidal graphite particles in a ferritic matrix, and spheroidal graphite particles in a ferritic/perlitic matrix. With regard to electrochemical machining (ECM) applications, the measurements were performed in different kinds of flow cells which realize the high electrolyte flow of an ECM experiment. It could be shown that the electrochemical dissolution was especially influenced by the microstructure of the cast iron and the pH of the electrolyte. Electrochemical measurements as well as numerical simulations show that the graphite geometry and the matrix structure are responsible for inhomogeneities of the electric field in the outer sample surface region which were formed during the dissolution process. The resulting shape of the electric field is responsible for different dissolution mechanisms. The kinetics of the dissolution reaction was influenced in the same manner. Finally, it was found that an alkaline electrolyte pH impedes the dissolution process, whereas no significant difference can be observed between acidic and neutral electrolytes. © 2015, Springer Science+Business Media Dordrecht.


Zapp N.,Saarland University | Weber O.,Center for Mechatronics and Automation | Weber O.,Saarland University | Natter H.,Saarland University
International Journal of Electrochemical Science | Year: 2015

The corrosion behavior and the electrochemical dissolution of three different cast iron types and one high purity iron sample in NaNO3 electrolyte (25°C, 1 M, pH: 7) were investigated by comparing three different cell setups: a relatively simple beaker-cell, a small-sized capillary flow-cell and a high-current gap-cell. The electrochemical cell types differ in electrolyte flow rate, size of the measured sample surface and applied current density. The work aims at investigating the electrochemical dissolution of inclusion containing materials (cast iron) and the evolution of a strategy that allows the determination of process parameters used for the design of electrochemical machining (ECM) processes. All samples were characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy and scanning electron microscopy. Electrochemical characterization was carried out by cyclic voltammetry and chronoamperometry experiments. It could be shown that the electrochemical dissolution behavior was dominated by the matrix structure and the geometry of the included graphite particles. The determination of corrosion potential and -current were mainly influenced by the electrolyte flow rate. Our new flow cell design (gap-cell) is suited for an easy and fast electrochemical characterization of materials under high current densities. © 2015 The Authors.


Baehre D.,Saarland University | Ernst A.,Saarland University | Ernst A.,Center for Mechatronics and Automation | Weisshaar K.,Saarland University | And 3 more authors.
Procedia CIRP | Year: 2016

Commercially pure titanium (titanium grade 2), Ti90Al6V4 (titanium grade 5) and intermetallic Ti60Al40 (γ-TiAl) were investigated concerning their electrochemical dissolution behavior in aqueous potassium bromide-, sodium chloride- and sodium nitrate electrolytes with different pH-values. Therefore, in a modified micro-flow cell different electrochemical experiments like cyclic voltammetry, linear sweep voltammetry and chronoamperometry were performed. The experimental results show that the dissolution behavior is influenced by the composition of the material and the electrolyte conditions. An increasing titanium content impedes the electrochemical dissolution of the material. Halide containing electrolytes are preferred for the machining of titanium alloys. © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.

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