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Know Where to Work on ... For the First Time, it is Known in Advance Where a 3D Printed Part Needs Post-Processing

Source: Fraunhofer IWM | Translated by AI 3 min Reading Time

A model-based optimization strategy by Fraunhofer IWM allows for the targeted design of mechanical surface post-processing for additively manufactured metal parts for the first time...

Here at Fraunhofer IWM, an additively manufactured metal part is cyclically loaded in a test fixture after its highly stressed surface zones have been mechanically post-processed. Now, it is also known how to identify these areas before production.(Image: Fraunhofer IWM)
Here at Fraunhofer IWM, an additively manufactured metal part is cyclically loaded in a test fixture after its highly stressed surface zones have been mechanically post-processed. Now, it is also known how to identify these areas before production.
(Image: Fraunhofer IWM)

Additive manufacturing enables design freedoms that would otherwise be difficult to achieve. This applies to 3D printing in both plastic and metal. However, in safety-critical applications—such as in aerospace, automotive, or energy technology—the use of metal 3D-printed parts often fails due to insufficient fatigue strength, as researchers from the Fraunhofer Institute for Mechanics of Materials (IWM) point out. Surface roughness, tensile residual stresses, and structural defects (gas pores or lack of fusion, LOF) effectively act as starting points for cracks that can lead to premature component failure. Mechanical surface treatment methods such as shot peening, deep rolling, and smoothing could target these risks or at least reduce them. These techniques densify the surface layer, thereby reducing defect density and introducing compressive residual stresses into the printed structure. However, until now, a practical computational model for the targeted use of these post-treatment methods had been missing. According to the researchers, the IWM has now definitively closed this gap.

Calculate from Analysis to Lifetime Prediction

As part of a project funded by the Federal Ministry for Economic Affairs and Energy (BMWi), a model-based calculation chain was developed and validated using the metal alloys AlSi10Mg, 316L, and Ti6Al4V, which are designed for 3D printing. (The additive manufacturing processes used were LPBF = Laser Powder Bed Fusion and CMF = Cold Metal Fusion). The calculation chain links three steps:

  • 1. Component evaluation and process selection: Depending on the component geometry and location of the most highly stressed points, the appropriate post-processing method is determined;
  • 2. Process simulation: Surface layer properties such as residual stresses, roughness, and hardening are predicted and optimized based on process parameters (e.g., blasting pressure, contact pressure, path overlap);
  • 3. FKM-based lifetime evaluation: The lifetime prediction is based on the FKM guidelines established among designers and SMEs. It can be directly integrated into existing development processes. The FKM fatigue strength verification has been adapted for the printed and post-processed materials AlSi10Mg, 316L, and Ti6Al4V.

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