Kinematic and stochastic surface topography of machined tial6v4-parts by means of ball nose end milling

Ball nose end mills are usually applied during 5-axes machining of high functional parts especially in the aerospace industry. The systematical study of the relationship between process forces and kinematics, surface topography and subsurface properties is fundamental to ensure a high surface integrity. This paper deals with the topography of machined surfaces of TiAl6V4 parts by means of ball nose end milling. The machined surface has been analyzed and the kinematic topography, influenced by the process parameters and the geometry of the cutting tool, has been computed. By subtracting the surface measurements from the computed topography, the stochastic topography of the machined surface, e.g. roughness and cracks, can be determined. Furthermore, an approach is given for predicting the stochastic topography based on the process forces during machining of TiAl6V4. © 2011 Published by Elsevier Ltd.DFG/CRC/87

Mathematical description of aesthetic criteria for process planning and quality control of luxury yachts

In this paper, an innovative method for an automated process planning and quality control of the coating process of luxury yachts is presented. In order to show how aesthetic quality is achieved, the current manufacturing and quality control processes are demonstrated. Furthermore, general and yacht-specific meanings of the word "aesthetics" are introduced. The derived aesthetic criteria are used to create mathematical characterisations and limitations (e.g. maximum curvature) that need to be fulfilled by an acceptable outer surface of a yacht. Finally, it is described how these requirements can be used for an automated quality control. © 2019 The Author(s)

Prediction of the Principal Stress Direction for 5-axis Ball End Milling

While regenerating damaged components, e.g. compressor blades, the removal of excess weld material called re-contouring often determines the surface integrity including the residual stress state. A load-specific residual stress state is beneficial for lifetime. This leads to the necessity to predict the resulting residual stress state after machining. The paper describes two models, which predict the principal stress direction as a residual stress characteristic for 5-axis ball nose end milling of Ti-6Al-4 V. One model uses process force components, the other is based on the microtopography of the workpiece, which is influenced by the kinematics of the process.DFG/Collaborative Research Centre/87

Compensation of part distortion in process design for re-contouring processes

The repair of compressor blades requires a precise coordination of the material deposit and the subsequent re-contouring process. Since re-contouring is the last step in the process chain, it is a crucial stage for the final part quality and shape. Therefore, machining-induced part distortions must be considered in process design. This paper introduces a method for the simulation-based compensation of part distortions. The method combines process planning and evaluation by means of a geometric simulation. In order to validate the approach, milling experiments are carried out. A subsequent measurement of the part geometry shows that the part distortion can be reduced by up to 21% using the presented approach. © 2019 The Authors. Published by Elsevier Ltd

A novel process chain for the automated repair of leading edges in aircraft engines

Due to impacts and constant stress, the leading edges of aircraft engine blades often lose their shape, while the other parts of the blade are still functional. This results in unnecessary performance losses. Currently, there is no method for a fast and effective repair process as the initial shape of the blade cannot be restored. This paper presents an automated re-contouring process chain for leading edges without prior material application. Thus, it is a sustainable approach to extend the lifespan until an energy-consuming welding process can be performed. It consists of an in-machine scanning process to obtain information about the worn shape, a subsequent target model generation based on the worn shape, and an automated process planning. The process chain is evaluated using a universal, leading edge workpiece. The results show that the target requirements for shape and smoothness are fulfilled

Improving technological machining simulation by tailored workpiece models and kinematics

Geometric modelling is an established approach for gathering detailed knowledge about the chronological sequence of process conditions and for determining technological values of machining processes such as milling, turning, grinding or additive manufacturing. Performance and accuracy essentially depend on the chosen workpiece model and its parametrization. Furthermore, several influences on the investigated machine tool system lead to errors, which must be modeled separately. This paper shows approaches to increase performance and accuracy of the simulation by choosing an appropriate combination of different geometric representations of the workpiece and by considering possible errors within the kinematic model. Examples for different applications in metal cutting are given

Dexel-Based Simulation of Directed Energy Deposition Additive Manufacturing

Additive manufacturing is typically a flexible alternative to conventional manufacturing processes. However, manufacturing costs increase due to the effort required to experimentally determine optimum process parameters for customized products or small batches. Therefore, simulation models are needed in order to reduce the amount of effort necessary for experimental testing. For this purpose, a novel technological simulation method for directed energy deposition additive manufacturing is presented here. The Dexel-based simulation allows modeling of additive manufacturing of varying geometric shapes by considering multi-axis machine tool kinematics and local process conditions. The simulation approach can be combined with the simulation of subtractive processes, which enables integrated digital process chains

Prediction of the 3D surface topography after ball end milling and its influence on aerodynamics

The surface topography of milled workpieces often defines their performance. One example is blades in turbine engines, where the topography defines the flow losses. This type of complex goods is often machined by ball end mills, either for manufacture or repair. The literature offers various model types to predict the surface topography in order to design a machining process without prior experiment. The most accurate models use the real kinematics of the process and blend the tool with the workpiece. But this type of surface prediction ignores the differences between the reality and the simulation due to vibrations, tool chipping etc. This paper presents a combined approach using the kinematic topography from the machining simulation and adds a stochastic topography based on empirical data. It could be shown, that the usage of the stochastic topography greatly affects the flow losses and thus cannot be ignored.DFG/CRC/87

Analysis of dimensional accuracy for micro-milled areal material measures with kinematic simulation

The calibration of areal surface topography measuring instruments is of high relevance to estimate the measurement uncertainty and to guarantee the traceability of the measurement results. Calibration structures for optical measuring instruments must be sufficiently small to determine the limits of the instruments. Besides other methods, micro-milling is a suitable process for manufacturing areal material measures. For the manufacturing by micro-milling with ball end mills, the tool radius (effective cutter radius) is the corresponding limiting factor: if the tool radius is too large to penetrate the concave profile details without removing the surrounding material, deviations from the target geometry will occur. These deviations can be detected and excluded before experimental manufacturing with the aid of a kinematic simulation. In this study, a kinematic simulation model for the prediction of the dimensional accuracy of micro-milled areal material measures is developed and validated. Subsequently, a radius study is conducted to determine how the tool radius r of the tool influences the dimensional accuracy of an areal crossed sinusoidal (ACS) geometry according to ISO 25178-70 [1] with a defined amplitude d and period length p. The resulting theoretical surface texture parameters are evaluated and compared to the target values. It was shown that the surface texture parameters deviate from the nominal values depending on the effective cutter radius used. Based on the results of the study, it can be determined with which effective tool radius the measurands Sa and Sq of the material measures are best met. The ideal effective radius for the application considered is between 50 and 75 μm

Kinematic simulation to investigate the influence of the cutting edge topography when ball end micro milling

During the ball end micro milling of material measures, the cutting edge topography is imaged on the machined workpiece. The influence of the chipping on the resulting surface quality is much more dominant than other kinematic effects. In this simulative study, a model is built that is able to predict the correlation between the cutting edge topography and the resulting workpiece topography. Thus, the mentioned correlation can be investigated without overlaying effects of material separation or measurement uncertainties, which are unavoidable in an experimental study. The model has been validated based on four artificial chippings