Jürgen Fleischer

INVESTIGATION OF SIZE-EFFECTS IN MACHINING WITH GEOMETRICALLY DEFINED CUTTING EDGES

The miniaturization of cutting processes shows process specific size-effects like the exponential increase of the specific cutting force k c with decreasing depth of cut h. Experiments were carried out in an orthogonal turning process. The influence of different process parameters on the results was investigated separately to identify process specific size-effects. Two materials were studied: a normalized steel AISI 1045 and an annealed AISI O2. To complement the experiments, parameter variations were performed in two-dimensional, thermo-mechanically coupled finite element simulations using a rate-dependent material model and analyzed by similarity mechanics. The influence of rounded cutting-edges on the chip formation process and the plastic deformation of the generated surface were determined numerically. The complex physical effects in micro-cutting were analyzed successfully by finite element simulations and compared to experiments.

Wertschöpfung in Netzwerken

Kurzfassung Zur Verteilung von Wertschöpfungsanteilen in globalen Netzwerken wird in diesem Artikel eine integrierte Planungsmethodik vorgestellt, die sowohl für intra- als auch für interorganisationale Wertschöpfungsnetzwerke anwendbar ist. Dabei werden sowohl hierarchische als auch heterarchische Formen der Koordination in Wertschöpfungsnetzwerken unterstützt. Zur Verteilung der Wertschöpfung findet der Begriff des Wertschöpfungsmoduls Verwendung. Wertschöpfungsmodule werden den jeweiligen, in einem Netzwerk verfügbaren Standorten zugeordnet. Diese Zuordnung basiert auf Fähigkeits-Matrizen, welche die Anforderungen von Wertschöpfungsmodulen sowie die vorhandenen Kompetenzen an den jeweiligen Standorten beschreiben. Ein Abgleich dieser beiden Matrizen führt zu einer Menge möglicher Zuordnungen von Wertschöpfungsmodulen zu Standorten. Zur Bestimmung der optimalen Lösung des resultierenden Zuordnungsproblems ergibt sich ein lineares Optimierungsproblem. Abschließend werden die einzelnen Wertschöpfungsmodule zu standortübergreifenden Geschäftsprozessen gekoppelt.

Mechanical module interfaces for reconfigurable machine tools

Reconfigurable manufacturing systems (RMS) enable industrial companies to adapt to frequent and unpredictable changes of production requirements in a cost-efficient way. RMS are constituted by modular machine tools that provide variable overall functions with the ability to add, remove, rearrange and replace functional sub-units. The performance of these machine tools as regards the quick and flexible arrangement of modules and high work piece quality strongly depends on the properties of the mechanical module interfaces. In this paper, performance parameters for mechanical module interfaces were defined and their influence on the machine tool’s performance discussed. Then flexibly arrange-able quick-coupling interfaces as a promising solution for module assembly were analyzed. Finally, tools for the determination for those interface performance parameters are presented, which require technical testing.

INFLUENCE OF FRICTION AND PROCESS PARAMETERS ON THE SPECIFIC CUTTING FORCE AND SURFACE CHARACTERISTICS IN MICRO CUTTING

For the production of small quantities of micro devices, machining is a low cost alternative to lithographic processing techniques. However, machining shows process specific size-effects upon miniaturization to the micrometer regime. Hence, the orthogonal turning process is chosen to study the influence of process parameters like uncut chip thickness h, cutting velocity vc and cutting edge radius rβ on the cutting force and the surface plastification by two-dimensional, thermo-mechanically coupled finite element simulations. A rate-dependent plasticity law is used for investigation of a normalized medium carbon steel (AISI 1045). Furthermore, the characteristics of the influences of the different parameters are analyzed mathematically by similarity mechanics. In particular, the frictional effects on the cutting process are studied in detail using a friction coefficient μ based on experimental results, and the influences of the process parameters on the cutting force and the plastic deformation of the surface layer are determined numerically. These results are compared with experimental measurements. The specific cutting forces are analyzed and discussed in detail. Size-effects observed experimentally are also found by numerical simulations.

Spectral correlation of partially or fully developed speckle patterns generated by rough surfaces

The correlation between the intensities of partially or fully developed far-field speckle patterns of two different wavelengths is investigated, assuming Gaussian field amplitudes. The degree of spectral speckle correlation depends mainly on the standard deviation of the surface height distribution, the wavelength difference, the angle of incidence, and the number of independent scattering cells in the illuminated surface spot. It provides a simple way of performing noncontact surface-roughness measurements with a variable measuring range. The theory, which has so far been restricted to fully developed speckle patterns with circular field statistics, is extended to partially developed speckles. Assumptions about the circularity or noncircularity of the speckle patterns are not necessary. An experiment has been carried out to support the theoretical results.

Machine Life Cycle Cost Estimation via Monte-Carlo Simulation

Recently an increasing number of customers demands more extensive warranties from the machine building industry. In order to control and maintain the arising costs from the seller’s point of view, the paper in hand presents a generic and comprehensive approach to estimate the distribution function of machine warranty cost. Based on the estimation of the failure rate distribution certain life cycle cost elements are quantified either deterministically or stochastically depending on their characteristic. The Monte-Carlo simulation is used for the flexible consideration of the entire system and the estimation of risk figures such as the Value-at-Risk.

Innovative Machine Kinematics for Combined Handling and Machining of Three-Dimensional Curved Lightweight Extrusion Structures

Abstract The importance of rigid and self supporting space frame structures for the automotive and aerospace industry continually increases. To meet the market requirements for a flexible and competitive small batch production, innovative machine concepts must be investigated. By integrating handling and machining capabilities into one machine structure, redundant degrees of freedom can be reduced and a former idle economic potential can be made use of. This paper introduces a systematic approach to reveal synergetic potentials that emerge by integrating two different fields of function, the handling and the machining. Therewith a matrix with technical solutions for a combination of handling and machining is generated. These solutions are the base for new machine concepts that fulfill both tasks with a minimal number of machine axes. A detailed model of an innovative machine concept is presented that allows a flexible and cost-efficient production of three-dimensional curved extrusions.

Simulation and optimization of complete mechanical behaviour of machine tools

Up to now the consideration of forces between flexible, moved structures, e.g., linear guides on base frame components, depending on different workspace positions wasn’t possible in multi-body simulation. Thereby neither the representation of the complete mechanical behavior nor the optimization of the frame structure depending on different workspace positions is possible. In the context of the Priority Program 1099 of the German Research Foundation “Production Machines with Parallel Kinematics”, methods have been developed, which enable the transmission of forces between flexible bodies multi-body simulation. The existing, flexible MBS-model of the coupler kinematics “Genius 500” is extended by a flexible frame structure and the total deformation is analyzed. Furthermore the present frame structure is replaced by a design space for topology optimization in different workspace positions.

Business Capabilities as configuration elements of value added networks

The ubiquitous globalization, which opens up new markets, often with local content requirements and different labor cost levels, forces enterprises to organize their added value within global networks. The tendency to concentrate on the companies’ core competences challenges the companies further not only to organize their different sites but also to consider their partners and suppliers. The emerging value added networks have to be configured, operated, optimized and dynamically reconfigured. This article presents an approach for the configuration and evaluation of these value added networks based on Business Capabilities and Value Added Modules. Therefore the needed Business Capabilities to achieve the intended added value are matched with the Business Capabilities provided by the different nodes of the network and different network alternatives are developed and assessed to find efficient configurations.

Optimizing the Life-Cycle-Performance of Machine Tools by Reliability and Availability Prognosis

The Life-Cycle-Performance of machine tools is a key figure concerning aspects of cost and benefits such as a high reliability and availability [1]. The dependence of production facilities on a high and constant availability increases with the degree of utilization. Hence, the availability of machine tools is substantial for the economic success of a manufacturer. The configuration of equipment elements in line with adapted product-accompanying services decisively contributes to the availability assurance. Thus, the aim of the article is to present a comprehensive calculation model to optimize the Life-Cycle-Performance of machine tools by a suitable reliability and availability prognosis considering the availability contribution of alternative machine equipment options and product accompanying services.