Investigation of the Oven Process in Indirect Metal Laser Sintering

This paper deals with the optimization of Indirect Metal Laser Sintering. Different experimental analyses have proven that the oven process is highly responsible for the part distortion. By means of polished micrograph sections and thermogravimetric and dilatometric investigations, the oven process has been divided into four main steps: polymer removal, solid-state sintering, infiltration and liquid-phase sintering. Further experiments were carried out at higher temperature phases of the oven process, using modified process parameters. The aim of this research is to improve the knowledge about the oven process. In another step, this process will be simulated by means of finite element analysis in order to minimize the part distortion.Mechanical Engineerin

Simulation of the Process Step Polymer Removal in Indirect Metal Laser Sintering

With the Indirect Metal Laser Sintering and by means of a heat treatment in an oven process metal components can be produced. In the first step the polymer is transformed from the solid state into the gas phase. This takes place all over the component at different velocities depending on the local temperatures and temperature gradients. The creation of the gas phase develops a pressure inside of the component because the diffusion of the polymer within the part has a finite velocity. The pressure may contribute to a damage of the component. This essay deals with the procedure to simulate the gas pressure on the basis of the implementation of kinetic models in the Finite-Element-Analysis.Mechanical Engineerin

Layer Formations in Electron Beam Sintering

Among direct metal processing manufacturing technologies (Rapid Manufacturing), Electron Beam Sintering (EBS) exhibits a high application potential. Especially, the fast beam deflection provided by electromagnetic lenses allows the realization of considerable building speeds and minor residual stresses. Therefore, this paper aims to examine and utilize the given potential for additive layer manufacturing. In this context, the deployed scanning strategy is a very important aspect. By means of an increasing computer power, innovative and flexible patterns for the solidification of the powder can be implemented. Thus, different patterns are being examined and evaluated. Finally, occurring effects in the exposed zone are introduced.Mechanical Engineerin

Transient Physical Effects in Electron Beam Sintering

The extensive use of the electron beam in manufacturing processes like welding or perforating revealed the high potentials for also using it for solid freeform fabrication. First approaches like feeding wire into a melt pool have successfully shown the technical feasibility. Among other features, the electron beam exhibits high scanning speed, high power output, and beam density. While in laser-based machines the fabrication is working in a stable way, transient physical effects in the electron beam process can be observed, which still restrict process stability. For instance, a high power input of the electron beam can result in sudden scattering of the metal powder. The authors have developed an electron beam freeform fabrication system and examined the above mentioned effects. Thus, the paper provides methods in order to identify, isolate and avoid these effects, and to finally realize a reproducible process.Mechanical Engineerin

Process Chain for Numerical Simulation of IMLS

Additive layer manufacturing methods imply, among other advantages, extensive flexibility concerning their ability to realize mass customization. Despite various efforts towards process enhancement, numerous deficiencies concerning part distortion or residual stresses are still observable. The present work deals with the definition of an efficient process chain for numerical simulation of indirect metal laser sintering (IMLS), in order to improve dimensional accuracy. The underlying method is based on investigations of dilatometric behavior of iron based powder, which is integrated into reaction kinetic models and coupled with a finite element analysis (FEA). Thus, singular process steps, e. g. solid phase sintering, phase transformations or infiltration, are numerically modelled with adequate accuracy. Referring to thermomechanical simulation, possibilities for pre-scaling of part geometries are presented.Mechanical Engineerin

Modeling of the Thermomechanical Process Effects on Machine Tool Structures

AbstractThermally induced deviations are a key issue in the development of machine tools, especially when considering the actual trends of high performance and dry cutting. The interactions between the cutting process and the machine tool structure are significant boundary conditions for the numerical prediction of the thermomechanical machine behavior. Within this paper an approach for the holistic modeling of process effects is presented, including process heat, cutting forces and increased load on feed and main drives. The modeling approach is supported by experimental investigations on a lathe to provide empiric data for the link between cutting forces and active drive power

An Analytical Approach of Modelling Friction Stir Welding

AbstractA simple model for torque in friction stir welding is developed, based on a sliding/sticking condition in the contact interface, correlating the fundamental response variables temperature and axial force to torque. The model is validated by experiments using a special test rig enabling the precise measurement of the response variables. From the measured torque and axial force the friction coefficient μf is calculated and analyzed. It is observed that μf increases with decreasing rotation speed and drops with abrupt step-ups of the plunge depth. μf is found to mainly vary in the range of 0.3-0.4

In-Process Deformation Measurement of Thin-walled Workpieces

AbstractDuring the finish milling process of thin-walled workpieces, deformations occur due to the mechanical and thermal influences. The measuring method outlined in this publication allows an accurate assignment of these deformations to their respective cause in size and form, due to the high temporal and spatial resolution of the used optical measurement system. Furthermore, dividing the dis-placement into its mechanical and thermal proportion allows a fully decoupled validation of process models. Especially the simula-tion results of thermal models, which are mainly validated by measured temperature fields, can be further ensured

A Method for the Prediction of Process Parameters for Minimal Distortion in Welded Frame Structures Using a FE-simulation

AbstractWelded frame structures are often subject to unintended distortions due to the thermal joining process. In order to precisely quantify and reduce the distortion of welded frame structures using Finite Element (FE) simulation, a fast and reliable method is required, especially for industrial applications. This paper presents a methodical, simulation based and time optimised framework for the prediction of appropriate process parameters for minimal component distortion of complex welded frame structures by means of e.g. a variation of the process parameters or the weld seam sequences. To achieve a minimal distortion of the final structure, different optimisation algorithms will be used in combination with a database

Laser Intensity as a Basis for the Design of Passive Laser Safety Barriers – A Dangerous Approach

AbstractModern laser beam sources provide radiation with high output power and brilliance. Additionally, innovative laser system technology enables the deflection of the laser into every direction. These developments depict new aspects in laser safety. On the one hand, there is no standard design approach for laser safety barriers and, on the other hand, no practical database of resulting protection times is available. A prototype test rig was built up, which allows the determinationof the protection time of different passive safety barriers. By experimental investigations, a process model for single steel sheets was established, which provides a relation between the applied process parameters and the protection time of the safety barrier. Within the conducted investigations, the laser power and the spot diameter were varied, whereas former investigations only considered the total laser intensity. The presented results show the influence of the varied parameters on the protection time and provide a first database, which will be extended within further investigations