Table 3 DfAM strategies regarding geometry
Support structures, overhangs and cavities | Part size | Thin sections | Geometrical features | Build orientation | Path planning |
|---|---|---|---|---|---|
Orientate the part to provide enough support surfaces and reduce the use of support structures Reduce or avoid overhanging features Overhangs’ length should be short to ensure that the filaments do not fall off their nominal positions (lOh ≤ 1.8 mm) [21]. This is also applicable for support structures Reduce or avoid enclosed volumes or internal cavities Provide accessibility to all support structures. Provide holes or channels to allow the removal of support material from internal cavities Remove support structures in small sections to prevent the damage of the part Gap heights should be at least 0.4 mm to receive small dimensional deviations and to ensure the removal of support structures [21] If accessibility to the gap between elements is given along the complete width, the gap width can be chosen freely [21] Gaps’ lengths can be chosen freely because no disperse support structures are contained inside the gaps [21] | Consider the build volume constraint of the available AM system Decompose oversized parts into smaller sections suitable for AM fabrication [10] Consider design for assembly guidelines when decomposing a large part [3, 10] Consider the fastening method needed to assemble the part sections when decomposing a large part | Consider a minimum wall thickness no less than four times the layer thickness Element transitions’ thicknesses can be chosen freely as they do not influence element’s form accuracies [21] Orientate hole’s axes perpendicular to the build platform Consider a post-processing procedure to obtain extremely small features and tolerances | Avoid extremely small features and tolerances (beyond the system accuracy and resolution capabilities) Aim for small values of layer thicknesses Avoid sharp (outer and inner) edges or corners. Consider the nozzle radius as a limitation to any corner or edge radius Edges should be rounded. The rounding radii correlate with the outer radii of simple-curved elements [21] Edges that form vertical extreme points should be blunted parallel to the building plane. The dimensions of the blunted areas should be larger than non-curved elements’ thicknesses [21] Edges that form horizontal extreme points should be blunted orthogonal to the building plane. The dimensions of the blunted areas should be larger than non-curved elements’ thicknesses [21] Inner edges should be sharp in order to avoid surfaces that have to be underpinned with solid support structures [21] Locate small features no too closely spaced and far from support structures or part surfaces Aim for parts with small values of length/width ratios to reduce the distortion effect | Orientate the part to generate the minimum number of layers, i.e., with its minimum dimension matching the build orientation Orientate the part considering the staircase effect and the functionality of the part surfaces Orientate the part to avoid the staircase effect in curved and sloped surfaces Orientate axisymmetric parts with the axis aligned to the build direction Orientate the part to provide enough support surfaces and reduce the use of support structures Orientate the part with the build direction perpendicular to the principal load direction | Consider the effect of the filling pattern on the mechanical properties, material consumption, weight, inertia and cost of the part Aim for closed (high infill percentage values) and alternating filling patterns between layers for parts with high mechanical strength requirements (e.g., functional parts under mechanical loads) Aim for open (low infill percentage values) patterns for visual, light weight, low inertia, or low mechanical strength parts Consider orthotropic mechanical properties of the part according to the filling strategy, part orientation and layer orientation. The lowest structural performance is in the direction of the normal vector of the layer Consider fully dense parts, spiral and curved filling paths, and alternating filling patterns between layers, to reduce the orthotropic effect and improve the mechanical properties Align the filling pattern according to the principal direction of the mechanical loads in the part Reduce the number of contours to reduce the build time and material consumption Increase the number of contours to increase the structural strength |