Optimized Support Structures for Postprocessing of Additively Manufactured Parts

Abstract

Additive manufacturing (AM) changes the classical possibilities of production and the way in which products are designed. Due to its excellent creative freedom, AM leads to profound and sometimes novel changes in the design of future components, especially to achieve function integration and lightweight structures.

With the laser powder bed fusion (LPBF) technology metal components can be manufactured in small quantities with high productivity and material efficiency. With this process, materials like titanium and maraging steel M300 can be used for lightweight components in the aerospace industry, with a wide variety of applications including landing gears, helicopter undercarriages and rocket motor cases. Both materials offer a combination of high tensile strength and high fracture toughness. This combination is well suited for safety-critical aircraft structures that require strength and damage tolerance.

However, to achieve the required surface quality, post-processing following the additive process is usually unavoidable. But due to the material characteristics of both materials, machining poses a challenge. In order to obtain an optimum final product, knowledge of the additive manufactured raw part and the machining mechanisms are required.

In this article the influence and the possibilities of the LPBF process parameters on the subtractive post-processing are shown based on the example process of drilling. The chip formation, the cutting forces and the dynamic behavior during drilling are examined. Since the additive process offers great freedom in design, the material to be removed during cutting can be adapted for the cutting process. This work presents a novel support structure, which is optimized for the subtractive process. In addition, a comparison of the machinability between bulk material, standard support structures and the novel support structures is carried out.

The goal was to reduce process forces and to improve process stability by means of chip formation and surface quality. This contribution transparently illustrates the complex interrelationships between the different technologies within the additive-subtractive process chain using drilling as an example. At the same time, the article presents methods and approaches that can be used to meet the challenges of implementing additive-subtractive process chains.

Keywords: Additive Manufacturing; LPBF Process; Post-Processing; Support Structures; Drilling