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Material identification during turning by neural network

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Denkena B. , Bergmann B. , Handrup M. , Witt M.

Journal of Machine Engineering

2020

tom Vol. 20, No. 2

65--76

A design concept for high-performance components involves the combination of different materials in hybrid workpieces. Different material properties and chemical compositions influence the machining quality of hybrid workpieces. To achieve a constant workpiece and process quality, it is necessary to adjust the process parameters to the individual material. Thus, it is mandatory to classify the material during machining for the relevant range of process parameters. This paper examines teaching strategies for neural networks to determine the machined material in process by a small amount of cross points. For this purpose, different training sets are compared. Process parameters with different cutting speeds, feeds and with constant and varying depth of cut are examined. In addition, the signal sources necessary for robust material classification are compared and investigated. The investigation is performed for the cylindrical turning of friction welded EN AW-6082/20MnCr5 shafts. The study shows that an F1 score of 0.99 is achieved at a constant cutting depth, provided that only the corner points of the process window and the machine control signals are used for training. With an additional variation of the cutting depth, the classification rate is significantly improved by the use of external sensors such as the acceleration sensor.

Energy-based characterization of precision hard machining using partially worn CBN cutting tools

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Grzesik W. , Denkena B. , Zak K.

Journal of Machine Engineering

2019

tom Vol. 19, No. 2

54--62

This paper highlights the performance of precision hard turning with CBN cutting tools from energy point-of-view with additional tool wear effect. For this purpose several wear tests were performed during which the tool nose wear VBC and the corresponding changes of component forces Fc, Ff and Fp were continuously measured. Based on the measured forces and geometrical characteristic of the uncut layer, specific cutting and ploughing energy were determined for several combinations of cutting parameters. Consequently, changes of energy consumption resulting from tool wear evolution for variable feed rate, depth of cut and tool nose radius were presented.

Autonomous machining – recent advances in process planning and control

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Dittrich M.-A. , Denkena B. , Boujnah H. , Uhlich F.

Journal of Machine Engineering

2019

tom Vol. 19, No. 1

28--37

While autonomous driving has come close to reality over the recent years, machining is still characterised by many manual tasks and prone to costly errors. In this article, an overview is given about the potential of autonomous machining and uprising technologies that support this vision. For that purpose, a definition of autonomous machine tools and the required elements is presented. Next, selected elements of an autonomous machine tool, e.g. sensory machine components and control loops, are discussed. Finally, some insights into ongoing research projects regarding the use of machine learning for process planning and control are given.

Controlled turning process for the production of friction-reduced cylinder liners with a defined free-form geometry

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Denkena B. , Bergmann B. , Handrup M. , Schmidt C.

Journal of Machine Engineering

2021

tom Vol. 21, No. 3

47--59

Friction in the piston-cylinder system of combustion engines has a great influence on fuel consumption. To reduce the friction of combustion engines, free-form cylinder liners and microstructured cylinder liners have proven to be advantageous. However, the combination of both processes is not industrially realized today because of an increased manufacturing effort due to a higher number of process steps. To save resources in form of honing oil in the production, the free-form can be machined by a dry turning process instead of form honing. A combination with the microstructuring process in a single manufacturing step would furthermore reduce non-productive time. This paper presents a piezo-actuated hybrid tool that can carry out both processes. The tool wear and the behavior during free-form fine machining of cylinder liners are investigated. A process control system is introduced that controls the cylinder liner geometry by adapting the process parameters during free-form turning.