Influence of Flank Face Structuring on Cooling, Tool Lifetime and Borehole Quality When Drilling Inconel 718: Physical Simulations and Experimental Validation

When drilling difficult-to-cut materials such as Inconel 718, the drills are exposed to high thermomechanical loads. Due to the low thermal conductivity of the workpiece material, a large amount of the generated heat has to be dissipated by the metal working fluid (MWF). However, the cutting zone is located inside the workpiece, which makes it challenging to provide sufficient MWF to the cutting zone. To solve this, drills with internal cooling channels are commonly used. In this work, the influence of differently structured flank faces on cooling efficiency, tool life, process forces and borehole quality is investigated. The influence of the structures on the cooling was investigated by Computational-Fluid-Dynamics (CFD) simulations. These simulations allow a detailed analysis of the flow conditions inside the borehole and showed that the structuring improved flow conditions, especially near the thermally highly loaded main cutting edge. The improved flow conditions resulted in an extension of the tool life by up to 22 % compared to unstructured drills in experimental investigations

Development and Validation of Energy Simulation for Additive Manufacturing

Additive manufacturing (AM) is a promising manufacturing technology towards cleaner production systems. Nevertheless, recent studies state that environmental benefits of AM are case-specific and need to be evaluated and confirmed in the design phase. To enable the energy performance evaluation in the design phase, developing convenient tools for energy prediction of AM has been an important research task. Aiming at this problem, this paper presents the research for energy modeling, simulation implementation, and experimental validation of an energy simulation tool of two AM processes: Selective laser melting (SLM) and Fused deposition modeling (FDM). The developed simulation tool can be conveniently used for energy consumption quantification and evaluation during the product and process design for AM

Visualization in Human-Centered Virtual Factories

In a manufacturing system (MS), a wide range of human activities are applied in production processes. The human factor plays a core role and should be incorporated into the design, planning and decision making processes. In this work we describe different definitions, developments and existing concepts of a Virtual Factory (VF) and discuss VFs from the human oriented point of view. Furthermore, we analyze the potential need and use of visualization methods in VF study and propose a human-centered VF concept. Following this concept we introduce an example implementation and describe how our model facilitates the decision making and design process in MS. In addition, we show an example of a noise analysis of working environment, which is based on our virtual factory model

Physics Simulation of Material Flows: Effects on the Performance of a Production System

In cyber-physical production systems, material flows show complexity due to varying physical aspects of transported work pieces and autonomously selected transport routes. As a result, physically induced disturbances that may lead to delays or damages are hard to predict. The on-line usage of a physics engine offers potential to derive material flow parameters that enable safe transports with optimized accelerations. Previous work showed the feasibility of this approach and potential operational benefits through faster material flows. In consequence, the scope of this paper is to apply discrete-event simulation to investigate whether physics simulation of material flows leads to positive impacts on production system performance indicators such as throughput times and capacity utilization. The results indicate that increased velocity and acceleration of material flows can positively influence these indicators. In consequence, applying physics simulation to ensure safe transports with such high velocities and accelerations can improve the overall performance of a production system

Physical Modeling of Process-Machine-Interactions in Micro Machining

Increasing demands for smaller and smarter devices in a variety of applications requires the investigation of process-machine-interactions in micro manufacturing to ensure process results that guarantee part functionality. One approach is the use of simulation-based physical models. In this contribution, methods for the physical modeling of high-precision air bearing and magnetic bearing spindles are presented in addition to a kinematic model of the micro milling process. Both models are superimposed in order to carry out investigations of the slot bottom surface roughness in micro end milling. The results show that process-machine-interactions in micro manufacturing can be modeled by the superposition of a physical model of the machine tool spindle taking cutting forces into consideration and a purely kinematic model of the machining process, providing the necessary tools for a variety of further investigations into process-machine-interactions in micro manufacturing

Quality of Drilled and Milled Rivet Holes in Carbon Fiber Reinforced Plastics

AbstractIn this paper, a conventional drilling process and a circular milling process are compared with respect to delamination and fiber protrusion when machining carbon fiber reinforced plastics (CFRP). The tool design (tool orthogonal clearance, drill-point angle) and the parameters (feed rate, cutting speed) are varied when drilling. The axial feed force and the spiral angles of the cutting edges can cause damages to the CFRP when circular milling. In this study, the possibilities to reduce those errors by the application of end mills with no spiral angle at the circumference cutter and no feed in axial direction are investigated. This milling process requires pre-drilled holes, and the final rivet hole dimension is then machined by circled movements without any motion in axial direction. For this special circular milling process, the tool design (rake angle of the circumference cutters) as well as the setting parameters (depth of cut, feed rate, cutting speed, up and down milling) are varied. The machining quality of both processes is compared. This is done by measuring the delaminations using an optical microscope. The fiber protrusion are visually identified with the help of an adapted imageprocessing algorithm. The diameters of the rivet holes are measured on two planes of the hole by a coordinate measuring machine. The cylindricity of the holes is determined using an instrument for roundness measurement

Simulation and Application of a Piezo-Driven System Enabling Vibration-Assisted Micro Milling

The ongoing miniaturization of components and the functionalization of surfaces necessitates the improvement of micro machining processes and to increase their efficiency. One method to increase the machining efficiency is reducing the process forces and tool wear, which is achieved by the implementation of vibration-assisted cutting in conventional machining processes. In vibration-assisted cutting, the conventional cutting movement is superimposed by a vibration with defined frequency. By using vibration-assisted cutting technologies, besides increased efficiency, a wider range of materials can be machined. In this paper, vibration-assisted cutting is transferred to micro machining. For this purpose, the design, simulation and application of an easy to integrate system that enables vibration-assisted cutting for micro machining processes is described. The setup was tested using a micro milling process. Two orientations between feed direction and vibration direction were investigated. Frequencies up to 15 kHz were examined, the machined material was brass (CuZn39Pb2). The effect of the superimposed vibration was analysed on the basis of process force, surface roughness, burr formation and slot bottom and was compared with the process results of micro milling without vibration-assistance. A decrease in process forces of up to 63 % was observed during vibration-assisted micro milling

Compensation of thermo-mechanically induced workpiece and tool deformations during dry turning

Dry turning is accompanied by considerable process-induced deformations of the workpiece and the tool. Such deformations decrease the accuracy of machining. In this paper, finite element models are used in order to calculate the deformations of the workpiece and the tool regarding the cutting condition used. The correction of the depth of cut according to the calculated deformations allows for the compensation of the workpiece and tool deformations. The compensation is carried out by a computer-aided-design / computer-aided-manufacturing (CAD-CAM) approach. The results reveal a significant increase of the machining accuracy in dry turning when compensating the workpiece and tool deformations

Infobrief FBK 68/22

Informationen aus dem Lehrstuhl für Fertigungstechnik und Betriebsorganisatio

Manufacturing of new roughness standards for the linearity of the vertical axis – Feasibility study and optimization

AbstractIn order to provide an alternative for the vertical axis calibration of stylus instruments which is usually performed based on step height standards, a new measurement standard geometry for the calibration of the linearity and research on its manufacturing is needed. For the manufacturing of these geometric measurement standards there is, according to the type of the measurement standard, a broad range of manufacturing processes that can be applied. New measurement standards for the roughness calibration were developed at the University of Kaiserslautern and an ultra-precision turning process was chosen for its manufacturing. The paper presents a feasibility study of the chosen manufacturing process. The aim of the investigations is to present the development of the standard and the qualification of the ultra-precision turning process for the manufacturing of calibration standards. An examination was performed in order to characterize the influences of different process parameters on the quality of the manufactured roughness standard