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

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

Processing Parameter Effects on Residual Stress and Mechanical Properties of Selective Laser Melted Ti6Al4V

Selective laser melting (SLM) process is characterized by large temperature gradients resulting in high levels of residual stress within the additively manufactured metallic structure. SLM-processed Ti6Al4V yields a martensitic microstructure due to the rapid solidification and results in a ductility generally lower than a hot working equivalent. Post-process heat treatments can be applied to SLM components to remove in-built residual stress and improve ductility. Residual stress buildup and the mechanical properties of SLM parts can be controlled by varying the SLM process parameters. This investigation studies the effect of layer thickness on residual stress and mechanical properties of SLM Ti6Al4V parts. This is the first-of-its kind study on the effect of varying power and exposure in conjunction with keeping the energy density constant on residual stress and mechanical properties of SLM Ti6Al4V components. It was found that decreasing power and increasing exposure for the same energy density lowered the residual stress and improved the % elongation of SLM Ti6Al4V parts. Increasing layer thickness resulted in lowering the residual stress at the detriment of mechanical properties. The study is based on detailed experimental analysis along with finite element simulation of the process using ABAQUS to understand the underlying physics of the process

Rule-Based Free-Form Deformation for Additive Layer Manufacturing

Additive Layer Manufacturing (ALM) provides manufacturing of nearly arbitrary geometries flexibly and economically. The part properties, which are reachable by state-of-the-art systems, are able to fulfill the customer requirements in terms of series and spare part production. Nevertheless, there still arise problems prohibiting the prevalent application of those techniques. The presented approach focuses on a rule-based Free-Form Deformation (FFD) for ALM. The machine is characterized by a set of rules, which is identified through observable properties extracted from precedent building processes. Adapting and applying the FFD algorithm, a pre-deformation of desired geometries based on exclusively geometric rules is achieved. Using an exclusively geometric deformation technique, CAD data is deformed before manufacturing to provide higher part quality by considering the unique characteristic of a machine.Mechanical Engineerin

Examination of the Powder Spreading Effect in Electron Beam Melting (EBM)

In recent years, the scientific and industrial relevance of Electron Beam Melting (EBM) has grown. This is mainly due to the electron beam’s extensive power density and flexible positioning properties. Thus, considerable building rates as well as a favorable part quality can be realized. However, the appearance of transient physical effects constitutes a substantial drawback towards the broader use of the technology. Therefore, experimental examinations are being carried out in order to investigate the effect of sudden powder spreading during beam material interaction. Based on an existing mathematical model, an analytical approach is formulated in order to implement effective counter measures. Hence, a significant increase in process stability is being achieved as the undesirable powder spreading effect is being avoided securely.Mechanical Engineerin