Why is Surface Finish Important in Additive Manufacturing?

Why is Surface Finish Important in Additive Manufacturing?

Laura Davis, Manufacturing Technology Insights | Thursday, July 09, 2020

Additive manufacturing (AM) is attaining ground rapidly and is now leveraged to produce numerous certified aerospace components.

FREMONT, CA: The beginning concerns with density, porosity, and grain structure have been overcome. AM components have microstructures equivalent to forged parts, suitable for most demanding structural applications subjected to high cyclic loadings. A significant factor for aerospace components is weight reduction, with the operators who are willing to pay for the reduced operating costs that is derived from a higher fuel economy. AM components have a more refined grain structure than cast components, comparable with wrought components. Another substantial performance benefit of AM components is the ability to control the internal geometry to formulate cooling channels and heat exchangers with features such as turbulators, which increase heat transfer.

Top 10 Surface Technology Services - 2020Surface finish is an unresolved challenge for AM. The components subjected to fatigue must be completely machined or undergo some other surface modification, like shot peening, to allow inspection. The new processes add cost, but significantly prevents the benefits of AM from being realized. Theoretically, AM gives complete freedom to create complex shapes, like those generated by topology optimization. If surface machining is needed, then the same limitations on form apply as for any other machined component. If shot peening is used, then restrictions are placed on thin and slender structures that may be vulnerable to this process.

PBF components have as-deposited surfaces made up of partially fused powder. The deposition layers might be visible, although surface roughness measurements are no higher when profiles are taken throughout the layers than when taken along a single layer. The surface texture is dependent on powder particle size, melt parameters, layer thickness, and the orientation of surfaces relative to the build plate. Surface roughness makes the inspection difficult and may also reduce performance by providing crack initiation sites. This reduces fatigue resistance and fracture toughness. Although the surface finish is continuing to improve, surface machining or shot peening is often needed to improve surface finish. However, internal surfaces and some small features may be challenging to finish in this way.

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