Rocco Eisseler

Prediction of Parameters for the Burr Dimensions in Short-Hole Drilling

The following paper presents a method for the determination of the burr dimensions to be expected in short-hole drilling, simultaneously taking the parameters into consideration which influence the burr formation. These parameters are yield stress, forces and the geometry of the inserts. The method is based on empirical cutting examinations and takes account into the correlation between different burr parameters and the machining conditions such as cutting speed, feed and tool geometry. Using Schaefers burr value g, it is possible to make a quantitative evaluation of the burr dimensions. The method was verified for the materials 16 MnCr 5 and Ck 45 in case of dry machining.

Numerical modeling and optimization of machining duplex stainless steels

The shortcomings of the machining analytical and empirical models in combination with the industry demands have to be fulfilled. A three-dimensional finite element modeling (FEM) introduces an attractive alternative to bridge the gap between pure empirical and fundamental scientific quantities, and fulfill the industry needs. However, the challenging aspects which hinder the successful adoption of FEM in the machining sector of manufacturing industry have to be solved first. One of the greatest challenges is the identification of the correct set of machining simulation input parameters. This study presents a new methodology to inversely calculate the input parameters when simulating the machining of standard duplex EN 1.4462 and super duplex EN 1.4410 stainless steels. JMatPro software is first used to model elastic–viscoplastic and physical work material behavior. In order to effectively obtain an optimum set of inversely identified friction coefficients, thermal contact conductance, Cockcroft–Latham critical damage value, percentage reduction in flow stress, and Taylor–Quinney coefficient, Taguchi-VIKOR coupled with Firefly Algorithm Neural Network System is applied. The optimization procedure effectively minimizes the overall differences between the experimentally measured performances such as cutting forces, tool nose temperature and chip thickness, and the numerically obtained ones at any specified cutting condition. The optimum set of input parameter is verified and used for the next step of 3D-FEM application. In the next stage of the study, design of experiments, numerical simulations, and fuzzy rule modeling approaches are employed to optimize types of chip breaker, insert shapes, process conditions, cutting parameters, and tool orientation angles based on many important performances. Through this study, not only a new methodology in defining the optimal set of controllable parameters for turning simulations is introduced, but also the optimum set of process input variables for turning duplex stainless steels is defined.

Ultrasonic-assisted machining of stone

Hybrid machining processes represent a potential approach to meeting the constantly increasing demands on cutting. In ultrasonic-assisted cutting, as a part of hybrid machining, the machining process is superimposed with a high-frequency vibration of small amplitude. This paper presents investigations on the drilling of stone materials, i.e. different granites and marble, in which this process is applied. It could be observed that the resultant forces and torques were reduced, which had already been discovered in investigations of various other materials. The influence of different parameters on the force reduction is shown, which is basically similar to the theoretical reduction of friction by ultrasound for small speed ratios δ, but is considerably increased. This increase must be due to other effects. Besides the force reduction, a reduction of cratering at the drill exit can be observed. Based on the present results, definite conclusions on tool wear cannot be drawn yet.

Burr formation in short hole drilling by ultrasonic assistance

Both in the industry and the service sector, the three aspects of time, costs and quality are among the most important characteristics in the manufacturing. This implies time as well as the costs incurred should be minimalized while preserving the high quality of a product. On top of that, the quality should be high as well. Burr formation has a negative influence on all of these three aspects. In most cases, formed burrs require additional remachining in most cases, leading to higher costs as well. In addition, the quality of the component is also impaired by burr formation.This paper examines to what extent short hole drilling by ultrasonic assistance can reduce burr formation. In order to assess the influence of ultrasound, the vibration amplitude is measured with and without load, depending on the excitation power. Based on these findings, the tests are carried out measuring exit burrs and evaluating them. Results show that the smallest burr values were measured without excitation, yet burr formation tends to decrease again with growing power.

Experimental Investigation and Multiobjective Optimization of Turning Duplex Stainless Steels

This paper addresses experimental investigations of turning EN 1.4462 and EN 1.4410 duplex stainless steel grades with multilayer coated carbide inserts. Single-point wet and dry longitudinal turning tests of cylindrical bars are conducted; cutting forces, effective cutting powers, and tool wear are measured. The parametric influences of cutting speed, feed rate, and process conditions on the cutting performances such as resultant cutting force, specific effective cutting power, and flank wear are analyzed and proper conclusions are drawn. Nature-inspired metaheuristic bat algorithm is employed to handle the multiobjective optimization of the conflicting performances. Finally, the optimum cutting condition for each process condition can be selected from calculated Pareto optimal fronts by the user according to the planning requirements.

Spanformbeeinflussung durch Schwingungseinkopplung beim Einlippenbohren

Kurzfassung Bei der Fertigung von Bohrungen mit kleinem Durchmesser und großem l/D-Verhältnis in metallischen Werkstoffen, wird das Einlippenbohrverfahren eingesetzt. Einer Leistungssteigerung des Verfahrens durch erhöhte Vorschubwerte sind insbesondere bei der Bearbeitung schwerzerspanbarer Werkstoffe Grenzen gesetzt. Die hier vorliegenden Spanformen neigen zum Verklemmen in der Bohrung, was zu einer verminderten Bearbeitungsqualität oder sogar zum Bruch des Werkzeugs führen kann. Eine Möglichkeit zur Spanformbeeinflussung hinsichtlich kurzbrüchiger Späne ist die Überlagerung des Vorschubs durch Einkoppeln einer zusätzlichen, oszillierenden Axialbewegung. Dazu bieten sich piezoelektrische Translatoren an, deren Einsatz derzeit am Institut für Werkzeugmaschinen der Universität Stuttgart untersucht wird.