Orientation changes build-surface adhesion and support demand, so FFF candidates should compare both.[1] Service load relative to printed layers and surface condition also belong in the comparison.[2] EyeContact additionally proposes checking post-build tool access, cleaning, and measurement against the acceptance criteria.
FFF trades build adhesion against support demand
An ORNL-hosted FFF study frames orientation selection as a combined objective: maximize build-surface adhesion while minimizing support. Its method uses a configurable overhang angle.[1] It does not include every service load, surface, fixture, or inspection requirement.
Draw the service load relative to layer interfaces
An ORNL large-scale material-extrusion guide explains that inadequate interlaminar bonding can produce anisotropy and common failure modes. For mechanically loaded parts, the direction perpendicular to printed layers can have lower strength because of layer-to-layer interface properties.[2]
Mark whether the service load acts perpendicular to printed layers, where the guide reports lower strength because of layer-to-layer interface properties.[2] Final mechanical properties remain sensitive to process and material, so test the actual conditions rather than applying a universal percentage reduction.
A support is useful only if it can be removed
The same guide defines overhang angle as material- and process-sensitive because ME and DED have limited ability to deposit over thin air without support. A circular hole parallel to build layers can collapse near its top, while a self-supporting section or post-machined hole may be an alternative. Support removal can be economically prohibitive in large-scale material extrusion.[2]
That economic boundary is scale-specific. The report recommends designing for machining-tool access and high-tolerance mating surfaces.[2] EyeContact proposes also checking support removal and measurement access.
Internal metal surfaces connect orientation to function
FFF and L-PBF are separate processes; keep each result within its study conditions. An ORNL-hosted superalloy channel study varied orientation, contour settings, and upskin/downskin treatment across multiple L-PBF machines. In that experiment, CT showed significantly greater design deviation and roughness for horizontal coupons than for vertical coupons.[3]
Roughness correlated with pressure loss. In some cases, surface features increased pressure loss without a proportional increase in convective heat transfer.[3] This does not prescribe vertical orientation for every channel. Evaluate inaccessible surfaces with the part's flow and thermal criteria.
Compare candidate orientations against the acceptance criteria
For two or three orientations, document service-load direction, critical surfaces, support removal, build stability, machining and metrology access, and internal-feature cleaning and inspection. Test representative coupons or partial geometries; record build and post-processing time, dimensions, surface condition, and the relevant mechanical or flow result.
Orientation belongs near the start of process planning because it links design, printing, post-processing, inspection, and service function. Choose the candidate that repeatedly meets the acceptance criteria, not merely the one that leaves the printer first.
Sources:
- https://impact.ornl.gov/en/publications/determining-optimal-print-orientation-using-gpu-accelerated-conve/
- https://info.ornl.gov/sites/publications/Files/Pub154003.pdf
- https://impact.ornl.gov/en/publications/impacts-of-superalloys-on-the-surface-quality-of-additively-manuf/
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