Fundamentals of Additive Manufacturing Technologies

A: A would also show inconsistent bead width and mass loss across X-Y coupons which you don't see. B changes bulk stiffness but doesn't selectively kill Z-strength with a dry surface. C gives a glossy but brittle interface and is fan-speed dependent across the whole part. D creates micro-voids and poor polymer chain diffusion specifically between layers, matching the Z-only failure with otherwise stable process temps.

A: A mainly affects the green state surface and wouldn't propagate cracks hours later. B raises modulus but doesn't explain rapid crazing when solvents are present. C leads to delayed mass change and warpage rather than sharp cracks. D matches solvent-assisted crack initiation in highly crosslinked SLA resins exposed to acetone vapour.

A: A ignores that recoating sets the pace once layer count explodes. B drops the layer-by-layer overhead that dominates SLS builds. C underestimates because coupon intuition misses volumetric scaling. D follows first principles on layer count and cycle time, landing in the right decade even before heat soak penalties.

A: A would show field-wide distortion tied to galvo position, not just edges. B leaves a repeating pattern everywhere the hatch runs. C gives macroscopic curl and warpage rather than fine ripples. D explains localized density variation where the blade loses support at the perimeter.