Showing papers by "Konrad Wegener published in 2012"

Microstructure, residual stresses and shear strength of diamond–steel-joints brazed with a Cu–Sn-based active filler alloy

Abstract: Brazing of diamonds is important in grinding technology. The brazing parameters can strongly influence the grinding tool's performance. In this work a Cu–Sn-based active filler alloy (73.9 Cu–14.4 Sn–10.2 Ti–1.5 Zr, wt.%) was applied to join monocrystalline block-shaped diamonds onto a stainless steel substrate using three different brazing temperatures (880, 930 and 980 °C) and two different dwell times (10 and 30 min), respectively. The characteristics of the joints were investigated by means of scanning electron microscopy and energy dispersive X-ray spectroscopy (microstructure and phase composition), by Raman-spectroscopy (residual stress) as well as by shear testing (bond strength). The microstructural investigations revealed an intermetallic interlayer of type Fe2Ti at the steel-filler alloy interface, which grew with increasing brazing temperatures and longer dwell durations. The brazing parameters strongly affected the residual stresses in the diamond. Compressive residual stresses with a maximum value of − 350 MPa were found in the samples brazed at 880 and 930 °C, whereas tensile stresses of maximum + 150 MPa were determined in samples joined at 980 °C. The effect of the brazing parameters on the shear strength is very pronounced. The shear strength decreased from (321 ± 107) MPa at 880 °C, 10 min to (78 ± 30) MPa at 980 °C, 30 min.

A new method for the characterisation of rounded cutting edges.

Abstract: The influence of the cutting edge micro geometry on cutting process and on tool performance is subject of several research projects. Recently published papers focus on optimising the cutting edge rounding. The results are partly inconsistent. Unfortunately, no international standard yet exists to properly describe the cutting edge micro geometry. This is seen as the root cause for detected discrepancies. To develop a common understanding for the influence of rounded cutting edges, it is indispensable to use the same basis to characterise the edge profile. This paper gives a review on existing characterisation methods, analyses the difficulties in their application and discusses different modelling ideas to describe the cutting edge profile. Based hereon, a new algorithm and geometrical parameterisation of the cutting edge is proposed, which reduces uncertainties and difficulties in the application of currently available methods. The proposed method considers measurement uncertainties and is robust against form errors and creates thus the basis required for the study of the influence of rounded cutting edges.

Dressing of Hybrid Bond CBN Wheels Using Short-Pulse Fiber Laser

Abstract: A systematic research analysis has been applied to study the effect of dressing parameters on grinding forces, work piece roughness and wheel wear of a hybrid bond CBN grinding wheel. This paper presents some of the results achieved by the comparison between a conventional SiC dressed wheel and a grinding wheel dressed by means of a short-pulse fiber laser. The results show high technological potential for the laser dressing method compared to conventional dressing. Lower grinding forces and specific energy, with relatively the same surface roughness and lower total grinding wear (wear by dressing plus wear by grinding) are the biggest advantages of the laser dressing method over the conventional method. However, the economic aspects of laser dressing (investment on laser source and associated add-ons) at the moment, cannot justify the integration of such systems on the grinding machine for all types of applications. The next challenge is optimization of the laser dressing process to increase the efficiency of the process and expand the possible applications both from a technical and commercial point of view.

Abrasive waterjet machining of three-dimensional structures from bulk metallic glasses and comparison with other techniques

Abstract: Bulk metallic glasses (BMGs) are a promising class of engineering materials, but they can be difficult to machine due to high hardness and a metastable structure. Crystallization due to machining can have negative effects, such as a decreased load-bearing capacity of fabricated parts, and thus should be avoided. Here, a Zr-based BMG was machined using abrasive waterjet (AWJ), electrical discharge, ns-pulsed laser engraving, and conventional dry-milling techniques. Characterization of the processed material indicated that AWJ preserves the amorphous phase and provides the combination of speed and flexibility required to rapidly fabricate small three-dimensional parts, while the other techniques did not achieve these goals. As proof-of-principle, a screw, similar to an orthopedic implant, was rapidly machined from the BMG using AWJ.

Machine Tool Optimization Strategies: Evaluation of Actual Machine Tool Usage and Modes

Abstract: The research activities of today not only strive to cope with the legislative pressure given by the Directive of the European Parliament on Energy Using Products but also aim for economic advantages for the machine tool user by investigating and applying suitable procedures and methods that help to model, forecast, and reduce the overall energy and resource consumption. The common goal is to reduce the amount of resources consumed and increase machine tool efficiency with the help of selective methods and a minimum investment. An approach to identify the above mentioned advantages is given on the presented research work and paper. This paper introduces a methodology for detecting and defining reasonable investments for retrofit solutions and optimization strategies depending on the actual circumstances, an approach for the effective acquisition of the required data, and the strategy used to detect optimization potentials based on these findings.

Adapting discrete-event simulation tools to support tactical forecasting in the automotive industry

Abstract: The automotive industry is an example of flow production and manufacturing efficiency. Its performance is based on taking the right decisions on strategic, tactical, and operational processes by the responsible engineers. Over the last decade, discreteevent simulation became the tool of choice to verify strategic decisions and tactical measures in the production process. However, the verification process itself is tedious and the usage of the tool is complex. Therefore, the task of verifying suitable solutions is accomplished by simulation experts and limited to high priority projects. For the optimization of operational processes, companies established lean manufacturing initiatives with real-time monitoring systems to measure production processes and to reveal bottlenecks. However, the improvement process is often based on trial-and-error and could be heavily supported by extending the current tool set with discrete-event simulation. Based on a use case of an assembly line in the automotive industry, we propose an approach in which running production environments benefit from simulation experiments without any intensive support by simulation experts. The goal is to extend the current tool set and to simplify the usage of discrete-event simulation tools, so they can be applied by production engineers on a

Measurement set-ups and -cycles for thermal characterization of axes of rotation of 5-axis machine tools

Abstract: Up to 80% of all deviations on machine tools are caused by thermal effects [1]. To investigate the influence of thermal caused location errors of rotating and swiveling axes, different measurement set-ups (e.g. R-test) are examined. Thermal errors caused by rotary axes are compared to thermal errors caused by the environment, linear axes and spindles. It is shown that rotary axes can have a significant share in the total thermal distortions of 5-axis machine tools.

Resource consumption measurement in manufacturing environments

Abstract: Efficient resource consumption and sustainable manufacturing reveal an extensive field of research and have become increasingly important in fulfilling multiple requirements in ecological, economic and legislative activities. The energy consumption in manufacturing and shop floor level is still not well understood or is based on assumptions. In order to support optimization activities, measurement and monitoring strategies have to be developed that deliver the desired accuracy within an acceptable cost-to-information ratio. This paper introduces a condign strategy for manufacturing monitoring which merges Environmental Value Stream Mapping (EVSM), a method which originates from lean manufacturing, with power consumption measurement techniques, required accuracy and measuring point definition, elements adapted from machine tool measurements. The applicability is verified in a use case and meets the industrial needs in line with current legislation and desired accuracy. From the combined productand manufacturing process viewpoint, this paper addresses the trade-off between strategic goals of an organization regarding required information and accuracy of information obtained from energy consumption measurements on the shop floor.

Relevance of laser touch-dressed diamond tools for the dressing performance of vitrified-bonded silicon carbide wheels

Abstract: Touch dressing of electroplated diamond grinding and dressing tools enable the generation of well-defined profile modifications and grain protrusions. This paper contributes to the utilisation of ultra-short pulse laser in touch dressing technology and outlines the cutting performance of laser touch-dressed diamond tools in dressing operations of vitrified-bonded silicon carbide. Surfaces of abrasive diamond tools are cut using a picoseconds laser beam to generate a well-defined grain protrusion without thermal damage of either the nickel matrix or the diamond structure. Irradiation parameters were systematically varied in order to determine a process window. Dressing operations were carried out using conventional and laser touch-dressed dressing tools. Lower dressing forces and higher dressing force ratios outline the advantage of the laser touch-dressed diamond tools in terms of material removal efficiency. Additionally, no remarkable differences in wear progression of conventional and laser touch-dressed diamond tools were observed. Furthermore, the laser touch-dressing model is presented using stochastically-distributed grain morphologies.

Toolbox for control system analysis of machine tools

Abstract: Machine tools have to reach high levels in accuracy and speed. For the detailed analysis of the machine dynamics with respect to these properties, a machine model has to include the main concepts of multibody dynamics and feedback control systems. With such a model available, dynamic investigations in frequency-and time-domain can efficiently be done. This work shows how to build a multibody system, and its integration in the feedback control loop. A control system model being coupled with high DOF structural model permits the simulation of interactions between machine tool manipulators and its spatial effects at the TCP (Tool Centre Point) including the position dependency of the properties. The available results and analysis functionalities of a proprietary implementation in a simulation environment are explained and illustrated.

Function module drivers for assessing the similarity between product functions

Abstract: Today a description of product functions and how they are realized becomes widely accepted in order to support future development with high quality product functions as an outcome Generally, this function-oriented product description becomes very extensive for complex mechatronic products Therefore modularization has to be applied which makes it easier for subsequent development steps Because modularization is bound to a specific viewpoint the extent of each resulting module has to be defined according to some kind of similarity that reflects this point of view Unfortunately, specific aspects for assessing the similarity between product functions from a function-oriented viewpoint are unknown and not clearly defined Therefore a series of expert interviews has been conducted in the automotive industry in order to identify these specific aspects This article presents the results of this interview series and also proposes an approach how similarity between product functions may be assessed and quantified

Dynamic loads and thermal errors on machine tools

Abstract: Thermal effects on machine tools are one of the major influences on machine tool accuracy. In order to analyze the effects of thermal deformation, numerical analysis using FEM is a common procedure. The quality of the FE analysis largely depends on the accuracy of the boundary conditions. A common heat source is the friction in machine elements as guide ways, ball screws and bearings. The friction losses in these components generally depend on the loading. In this paper multibody dynamics is coupled with FEM to compute the dynamic loads and thermal errors on machine tools. Multibody dynamics system (MBS) is used to compute the loads which are used to derive the friction losses. These friction losses are then transferred to a thermomechanical FE model of the machine tool in order to calculate the thermal errors at the TCP (Tool Center Point).

Improvement of the dynamic behavior of machine tools by geometrical optimization of the machine tool axes movement

Abstract: A new approach for the geometrical optimization of five-axis-movement is presented in this paper. Rega rding a fiveaxis-movement with large tolerances for lead and ti l -angle for example in the case of laser-cutting there are endl ess ways of generating motions without violating the orientation-tolerances. By regarding the movement of the involved axes it i s shown that for a given 5-axis trajectory and given tolerances there exists an optimal motion with a minimal amount of mechanical excitation of the machine-tool within the tolerances. The traj ectory is described by quintic non uniform rational B-splines (NURBS). The decrease of mechanical excitation is exemplifie d by the use of a simplified machine-model.