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Über dieses Buch

This contributed volume collects the scientific results of the DFG Priority Program 1180 Prediction and Manipulation of the Interactions between Structures and Processes. The research program has been conducted during the years 2005 and 2011, whereas the primary goal was the analysis of the interactions between processes and structures in modern production facilities. This book presents the findings of the 20 interdisciplinary subprojects, focusing on different manufacturing processes such as high performance milling, tool grinding or metal forming. It contains experimental investigations as well as mathematical modeling of production processes and machine interactions. New experimental advancements and novel simulation approaches are also included.





Measurement and Test Techniques

Nowadays, different measurement and test techniques are used to investigate the interaction between processes and machine tool structures. Machine and workpiece properties are determined after analyzing the individual factors of process metrology, which have an effect on the process. This chapter explains the measurement methods for the structural analysis of the machine tool as well as for manufacturing processes and for the workpiece analysis. In addition, an overview of different measurement and test techniques based on selected examples related to the priority program 1180 is given.
E. Abele, J. C. Aurich, B. -A. Behrens, D. Biermann, C. Brecher, E. Brinksmeier, M. Czora, B. Denkena, U. Engel, K. Großmann, U. Heisel, D. Heinisch, R. Hermes, B. Kirsch, F. Klocke, A. Krause, T. Kroiß, R. Laurischkat, M. Löser, F. Mahr, H. Meier, M. Pischan, P. Rasper, A. V. Scheidler, M. Storchak, E. Uhlmann, M. Weiß

Modeling and Simulation

One focus of the Priority Program 1180 is the prediction of process machine interactions. The investigated manufacturing processes as well as the machine tool behavior and the physical phenomena vary within the projects of this program. So depending on the issues that were investigated, the modeling approach that is best suitable for the specific problem has to be applied. To predict the interactions these models have to be coupled and simulated. Besides the modeling approaches different simulation techniques have also been applied. This chapter gives an overview of the applied models of the structural machine behavior and the manufacturing processes, the coupling of these models as well as the simulation techniques that were used.
C. Brecher, A. Bouabid, M. Deichmueller, B. Denkena, K. Großmann, A. Hardtmann, D. Hömberg, R. Hermes, F. Klocke, M. Löser, O. Rott, P. Steinmann, M. Weiß

Adaptive Finite Elements and Mathematical Optimization Methods

This chapter focuses on the topics of mathematical research in the priority program and on the application of the results to engineering problems. First, a posteriori estimates and adaptive methods based on them are presented for contact problems. In detail, frictional contact problems using a linear elastic material law, which are discretized by a dual-dual method, are considered. Using a different approach, adaptive methods are derived for elasto-plasticity with contact and friction. Then results for contact problems involving inertial effects are introduced. Second, parameter identification and inverse problems are considered. After an introduction into the general problem of setting and solution techniques, the balancing of a rotating system is discussed as a prototypical industrial application.
M. Andres, H. Blum, C. Brandt, C. Carstensen, P. Maaß, J. Niebsch, A. Rademacher, R. Ramlau, A. Schröder, E. -P. Stephan, S. Wiedemann



High-Performance Surface Grinding

This chapter presents experimental as well as modelling and simulation approaches to investigate a high-performance surface grinding process. The complex material removal mechanisms generate transient cutting forces that cover a wide range of excitation frequencies. The generated cutting forces impact the grinding machine and lead to deformations, which depend on the machine’s mechanical properties. In general, these deformations have an influence on the cutting forces. Deformations lead to a change of the depth of cut and, therefore, the cutting forces change. Thus, there are three aspects of great importance: the process, the machine and the process machine interaction. Advances in investigating the process are covered first. Afterwards, a new approach to model the machine, its deformation behavior and the way the machine interacts with the process will be described.
J. C. Aurich, A. Bouabid, P. Steinmann, B. Kirsch

Process Machine Interaction in Pendulum and Speed-Stroke Grinding

The complex interaction of process forces and machine structure affects the quality of ground workpieces, especially in highly-productive machining processes, if machines are operated at their limits. In speed-stroke grinding, the highly-dynamic process forces are caused by high workpiece velocities and high acceleration of the machine table. These forces are influenced by the process parameters, the material properties, the coolant application and the grinding tool specification. The paper describes the approach to simulate the process machine interaction in speed-stroke grinding by a coupled model. The machine is modeled by a multi-body simulation, which can depict the static and dynamic behavior of the machine for every working position. This machine model is coupled with an analytical-empirical force model, which predicts the process forces regarding the process parameters, the coolant application and the workpiece material. The machine control system is implemented in the model as well. The ability to model a speed stroke grinding process, including the machine, the control system and the process itself can be used to predict and improve the workpiece quality regarding the measurement accuracy minimizing time and cost intensive experiments.
M. Weiß, F. Klocke, H. Wegner

Simulation of Process Machine Interaction in NC-Shape Grinding

The study focuses on the NC-shape grinding process when using toroid grinding wheels and its simulation. First, the experimental investigation with respect to the machine structure and its dynamic behavior, the process forces as well as the temperature distribution in the workpiece and the grinding wheel are discussed. That forms the basis for the modeling and simulation of the NC-shape grinding process. The simulation consists of a geometric-kinematical simulation coupled with a finite element simulation. To validate the simulation, comparisons between the quantities measured and the corresponding calculated values are carried out. Subsequently to this validation the transferability of the simulation to other grinding processes is studied. Furthermore, the simulation is utilized to optimize grinding processes, especially with respect to the NC data.
D. Biermann, H. Blum, A. Rademacher, A. V. Scheidler, K. Weinert

Modeling of Process Machine Interactions in Tool Grinding

A systematic modeling approach to predict and manipulate the static and dynamic process machine interactions in tool grinding is described. The modeling approach is verified by experimental investigations gained by means of an industrial tool grinding machine and separate test stands. It combines models of the static and dynamic behavior of the grinding machine and its components with a microscopic grinding process model. Material removal algorithms are applied to cope with the changing shape and changing mechanical properties of the workpiece during grinding. The interaction model has been applied in the process planning phase to optimize tool paths and process parameters in order to reduce resulting shape errors in ground tools.
M. Deichmueller, B. Denkena, K. M. de Payrebrune, M. Kröger, S. Wiedemann, A. Schröder, C. Carstensen



HPC - Stability Simulation

The prediction of stable process parameters to maximize the productivity of milling machines has been an important field of research for a long time. In the past, simulation tools allowing an assessment of the process stability have been created. Nevertheless, the accuracy of predictions by simulation is not yet high enough to make efficient use of stability simulation in production planning. In this context, the article presents developments in the field of modeling the dynamic machine and process behavior for process machine interaction simulation in the field of high performance cutting processes (HPC). On the process side, a complex force model, which takes into account the effects of a phase shift between force generation and chip thickness variation, is introduced. Also, an analysis of fast-rotating main spindle systems has been carried out, which considers variations in the dynamic compliance behavior at the tool center point (TCP) due to rotor dynamic effects and variation of the bearing rigidity. With the Prime Cut software package, a calculation program is presented, which includes the state of the art and new developments in the field of stability simulation.
C. Brecher, R. Hermes, M. Esser

Development of a Stability Prediction Tool for the Identification of Stable Milling Processes

This chapter deals with a new mathematical model to characterize the interaction between machine and workpiece in amilling process. The model consists of a multi-body system representing the milling machine and a linear thermo-elastic workpiece model. An extensive experimental analysis supported the development of the governing model equations. A numerical solution strategy is outlined and complemented by simulations of stable and unstable milling processes including workpiece effects. The last part covers the development of a new algorithm for the stability analysis of large milling systems.
D. Hömberg, E. Uhlmann, O. Rott, P. Rasper

Synthesis of Stability Lobe Diagrams

Chatter vibrations during machining lead to poor workpiece surfaces and increased tool wear. In the worst case, the tools and even the main spindle can be damaged. Nowadays, the surface regeneration is considered to be the main effect causing chatter instabilities. Regenerative chatter is initiated by repetitive tooth engagement where the currently engaged tooth cuts the surface produced by the preceding tooth. In a stability lobe diagram (SLD), the stable and unstable areas are separated by the graph of a critical cutting parameter plotted against the spindle speed. Stability lobe diagrams can be used to optimize machining processes in terms of maximizing material removal rate under stable cutting conditions. These SLDs are computed by time domain simulations. However, this consumes a lot of computational time. Thus, several time efficient algorithms in discrete time as well as frequency domain have been developed in the last decades. This chapter scrutinizes under what conditions different algorithms in frequency domain can be applied. The processes are separated regarding cutting conditions and dynamic behavior so that the most time efficient algorithm can be chosen for each class.
K. Großmann, M. Löser

Analysis of Industrial Robot Structure and Milling Process Interaction for Path Manipulation

Industrial robots are used in a great variety of applications for handling, welding, assembling and milling operations. Especially for machining operations, industrial robots represent a cost-saving and flexible alternative compared to standard machine tools. Reduced pose and path accuracy, especially under process force load due to the high mechanical compliance, restrict the use of industrial robots for machining applications with high accuracy requirements. In this chapter, a method is presented to predict and compensate path deviation of robots resulting from process forces. A process force simulation based on a material removal calculation is presented. Furthermore, a rigid multi-body dynamic system’s model of the robot is extended by joint elasticities and tilting effects, which are modeled by spring-damper-models at actuated and additional virtual axes. By coupling the removal simulation with the robot model the interaction of the milling process with the robot structure can be analyzed by evaluating the path deviation and surface structure. With the knowledge of interaction along the milling path a general model-based path correction strategy is introduced to significantly improve accuracy in milling operations.
J. Bauer, M. Friedmann, T. Hemker, M. Pischan, C. Reinl, E. Abele, O. von Stryk

Process Machine Interactions in Micro Milling

In this chapter, both analytical and experimental studies on the process stability of micro milling are presented. The investigations are carried out in order to improve a comprehensive model, which describes interactions of the dynamic cutting forces and the dynamic machine tool behavior including the end mill. Dominant chatter frequencies at different operating points are determined by analyzing the process forces, acoustic signals as well as optical measurement signals. Results are documented and discussed by means of stability lobe diagrams. The findings are confirmed by analyses of the milled surfaces. Finally, some suggestions for improving the parameter identification are given.
E. Uhlmann, F. Mahr, Y. Shi, U. von Wagner

Numerical Computation Methods for Modeling the Phenomenon of Tool Extraction

Tool extraction is a phenomenon, where the end mill slips out of the shrink-fit chuck in axial direction during the cutting process. This leads to severe damage of the workpiece, the tool and in some cases even the machine spindle. So far, this is an unexplained problem with no repeatability. In this article, experimental investigations such as scanning electron microscopy (SEM) and residual stress measurements on the clamping surface of shrink-fit chucks affected by tool extraction are presented. Furthermore, results from experiments on a special testrig and a mathematical approach, which aims at the prediction of failures due to Process Machine Interaction, are described. Within the mathematical approach, a finite element model of the tool and the tool holder is linked with a cutting force simulation. The dynamic behavior of the spindle is determined by frequency response function measurements. From these measurements, a modal model is deduced and coupled with the finite element model of the tool holder. The presented mathematical model is used to compute the resulting stresses in the interface of those components due to process forces.
B. Denkena, E. P. Stephan, M. Maischak, D. Heinisch, M. Andres

Dynamic and Thermal Interactions in Metal Cutting

This contribution presents a physical cutting process model based on the Discrete Element Method (DEM), which allows the simulation of dynamic and thermal interactions in metal cutting. Core component of the approach is the DEM model of a solid with elastic-plastic deformation modes, which is verified in standardized tensile and Charpy impact tests as well as other non-standardized tests. The model is enhanced such that the thermo-dynamics of a solid due to heat conduction can be included, which is also verified in different tests. The applicability to model-cutting processes is shown in the simulation of orthogonal cutting processes. The results of the simulation are compared to experimentally obtained results for both forces as well as temperatures. For verification purposes, an FEM model is made, which predicts both forces on the tool as well as temperatures
P. Eberhard, U. Heisel, M. Storchak, T. Gaugele

Surface Generation Process with Consideration of the Balancing State in Diamond Machining

In order to manufacture optical components or mechanical parts with high requirements regarding surface quality, diamond machining is frequently applied. Nevertheless, to achieve the desired surface quality, the understanding of the surface generation process and its influencing parameters is highly important. One crucial parameter is the residual unbalance of the main spindle. As the residual unbalance affects the process and vice versa, the investigation of the process-machine interaction is necessary. In this paper results of experimental work and mathematical modelling of diamond machining under varying balancing states are presented. The experiments show the connection between unbalances and resulting surface quality; the mathematical model provides the possibility to simulate the surface quality for given unbalances distributions. Furthermore, regularization techniques in order to solve the inverse problem of computing the optimal balancing state for a given or desired surface quality are presented.
C. Brandt, A. Krause, J. Niebsch, J. Vehmeyer, E. Brinksmeier, P. Maaß, R. Ramlau

Modeling and Simulation-Based Optimization of a Turning Process

Today, the productivity of machine tools is limited by the interactions between machine and process. A method to predict these limits is presented here using simulation model and an appropriate optimization algorithm. Therefore, a short overview of the used theories in multi-body dynamics, cutting processes and the mechanical model of the turning lathe is given. Furthermore, a modular cutting force model as well as the coupling between process and structure is introduced. For optimization, it is necessary to develop an objective function, where the quality and the productivity of the processes have to be represented. Finally, results of the optimization process are shown.
R. Britz, T. Maier, F. Schwarz, H. Ulbrich, M. F. Zaeh



Advanced Forming Process Model - AFPM

This chapter discusses methods of modeling and simulating metal forming processes and explains their application in product design, production and process planning. In today’s Finite Element (FE)-based forming analysis, major effects on the forming process are being neglected. Based on the analysis of the elastostatic press and tool properties, a conventional FE process model was extended with the most dominant elastostatic influences. It is shown that complex elastic systems, such as die cushions and tool guidance, are quite easily implemented in FE process simulations by using discrete elements and other reduction methods, recently introduced in commercial simulation software. The benefit of the Advanced Forming Process Model (AFPM) is demonstrated by an experimental verification. Servo mechanical presses enable the manufacturers to establish high-speed processes in sheet metal forming. There, the dynamic press behavior has a much larger influence on the forming process than it has in the relatively static conventional deep drawing. As an example, a highly dynamic forming process is simulated and explained in the following.
K. Großmann, A. Hardtmann, H. Wiemer, L. Penter, S. Kriechenbauer

Consideration of the Machine Influence on Multistage Sheet Metal Forming Processes

Metal forming processes are highly affected by the properties of the forming machine. In multistage processes, the force path curve of each stage is influenced by the surrounding stages. This research focuses on the interaction between the forming machine and multistage processes with respect to the quality of the workpiece. The accuracy of the numerical results could be increased by coupling the process simulation with the machine simulation. Further influencing factors, such as different friction conditions during forming and the elasticity of the tool, were considered in the simulation. In addition, the thermal properties of the press were investigated and considered in the machine simulation. Hence, a better correlation between the numerical results and the experiment could be achieved.
B. -A. Behrens, A. Bouguecha, R. Krimm, T. Matthias, M. Czora

Optimization of Tool and Process Design for the Cold Forging of Net-Shape Parts by Simulation

As a result of the research work in this project, a comprehensive approach is presented for the consideration of the interactions between process, tool and machine in the FE-based design of cold forging tools and processes: The approach comprises an efficient determination of the deflection characteristic of press and tooling system and its subsequent condensed modeling in combination with the FE simulation of a cold forging process. Then, based on a set of simulations, a parametric process model is developed. It permits an optimization of the values of influencing parameters to achieve high workpiece accuracy considering the interactions. By acquiring and, afterwards, applying knowledge on the process behavior, the required number of simulations for the parametric process model and the optimization can be reduced considerably. The approach can be completed by using the parametric process model for estimating scatter and uncertainties of target values depending on those of the influencing parameters.
T. Kroiß, U. Engel

Interaction Effects between Strip and Work Roll during Flat Rolling Process

During the flat rolling process (cold or hot), the strip flatness and thickness profile are highly influenced by the interaction effects between strip and work rolls. To understand and analyze these effects a new modeling concept was developed. Within this concept, the tool simulations are separated from the process simulation. With the help of an automatic coupling module, the influences of the tool effects are realized within the process simulation. With this modeling concept, three types of interaction phenomena are studied and validated using experiments: elastic roll effects during the cold rolling process, work roll thermal effects during the hot rolling process and tribological effects (abrasive wear) on the process simulation. It was also shown that, compared to the single FE model, this modeling concept is relatively faster and suitable for large 3D models without losing the quality of the predicted results.
S. Puchhala, M. Franzke, G. Hirt

Increase of the Dimensional Accuracy of Sheet Metal Parts Utilizing a Model-Based Path Planning for Robot-Based Incremental Forming

The principle of robot-based incremental sheet metal forming is based on flexible shaping by means of a freely programmable path-synchronous movement of two tools, which are operated by two industrial robots. The final shape is produced by the incremental infeed of the forming tool in depth direction and its movement along the geometry’s contour in lateral direction. The main problem during the forming process is the influence on the dimensional accuracy resulting from the compliance of the involved machine structures and the spring-back effects of the workpiece. The project aims to predict these deviations caused by compliances and carry out a compensative path planning based on this prediction. Finite element analysis using a material model developed at the Institute of Applied Mechanics (IFAM) [1] has been used for the simulation of the forming process.
H. Meier, S. Reese, Y. Kiliclar, R. Laurischkat

Gear Rolling Process

The rolling process is an efficient alternative to currently exclusively applied cut-ting processes for the production of high gears, particularly regarding economic and ecological aspects. The manufacturing of involute gear profiles by forming, specifically by rolling, has several advantages in comparison to cutting methods, e. g. significantly shorter process times, no material loss and subsequently no chip disposal, strength increase in the forming zone and a high surface quality. Due to these characteristics gear forming will continue to gain relevance in future gear manufacturing. The Chapter presents the efforts being made at the Fraunhofer IWU Chemnitz to reach an advancement of the high gear rolling process by improving the gearing qualities. It presents the investigation and analysis of the interaction between tools, machine and forming process in gear rolling. The results of measurements on the displacements of workpiece, tools and clamping device during the rolling process of a high gearing are displayed. The setup and results of accompanying simulation of the forming process are also given.
R. Neugebauer, U. Hellfritzsch, M. Lahl, M. Milbrandt, S. Schiller, T. Druwe

Investigation of the Complex Interactions during Impulse Forming of Tubular Parts

The expansion of tubes by direct application of gas detonation waves or electromagnetic forming (EMF) is an alternative forming method for hollow section workpieces. In particular, the process can be used for typical hydro-formed parts, car body or exhaust elements in the automotive industry, for example. The introduced processes belong to the category of high speed forming methods and provide typical advantages, such as higher achievable strains, compared to quasistatic methods using high water pressure. Another advantage of these processes is the avoidance of high contact forces by employing an “inertia-locked tool” system due to the extremely short process time. To develop a controllable process it is essential to gain a good knowledge of the interactions in the system. This can be achieved by using simulations in combination with experimental investigations; their results are the topic of this paper. Also included are special investigations of the material behavior at high strain rates.
Fr. -W. Bach, M. Kleiner, A. E. Tekkaya


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