| contents | news | events | advertisers | website | e-newsletter |
Reducing residual stress in PBF-LB
Reducing residual stress with 500°C build chamber preheating for ‘first time right’ PBF-LB According to Germany's Trumpf GmbH + Co. KG, preheating the substrate plate in Laser Beam Powder Bed Fusion (PBF-LB) to 500°C brings significant advantages in serial production: complex parts are more likely to be built successfully on the first try, design freedom increases, there is little residual stress and no cracks – and, for the first time, high-carbon alloy parts can be built reliably, without cracks, to a density comparable with their conventionally produced counterparts. Here, the company shares the results of tests demonstrating the advantages of 500°C preheating, and introduces the technology making it possible for manufacturers to integrate this step into their PBF workflow, and reap the benefits.
Laser Beam Powder Bed Fusion has become the most successful industrial AM process for metals over the last fifteen years. However, with the rapid success and gradual establishment in series production, the demands placed on the process by industrial companies are also increasing. In addition to the general desire for shorter production times, there is, in particular, a demand for higher part quality and more reliable initial production – even complex parts should succeed right from the start without any approximation tests. These requirements can be met – by heating the substrate plate up to 500°C. Currently, preheating to 200°C is the industrial standard. This is a compromise between the advantage of inducing less residual stress by preheating on the one hand, and the disadvantages of a longer cooling time and possible problems with powder recycling on the other. In this article, we will demonstrate that this compromise is no longer necessary, and that a significantly higher preheating temperature is both reasonable and possible.
Vol. 7 No. 3 © 2021 Inovar Communications Ltd
Trumpf has been able to show in tests that, by preheating to 500°C, higher quality titanium alloy parts (especially Ti64Al4V) can be achieved, by reducing residual stress. Highcarbon-containing alloys such as H11 and H13 can also be processed using PBF-LB for the first time. This is of particular interest to the tool and die industry, which prefers H11 and H13, and can benefit significantly from PBF-LB due to its special production
processes. The results of these tests will be discussed in this article (Fig. 1). Further, we will discuss how to integrate the preheating technology into the manufacturing process such that the utilisation of the PBF-LB machine is maximised and – despite the high temperatures involved – any residual metal powder can be recycled without problems.
Fig. 1 Applications such as this inlet manifold from Laupp GmbH for the tool and die industry, with a rendering of internal cooling channels shown on the right, benefit from the ability to produce H11/H13 parts by PBF-LB
Metal Additive Manufacturing | Autumn 2021
189