Additive Manufacturing Questions and Answers

Answer: A

The match is P-3, Q-4, R-2.

• Fused deposition modelling melts a filament of polymer (such as ABS or PLA) in a heated nozzle and lays it down bead by bead (3).
• Laminated object manufacturing cuts and bonds sheets, paper, thermoplastic or green compacted metal sheet, one layer at a time (4).
• Selective laser sintering uses a laser to fuse a bed of heat fusible powder, layer by layer (2).

The unused material, photo sensitive liquid resin (1), belongs to stereolithography, which cures resin with ultraviolet light; it is not the input for any of the three techniques listed, so every option using 1 is wrong. 'P-4, Q-1, R-4' also uses item 4 twice.

Answer: B

The correct matching is P-3-II, Q-2-IV, R-4-I, S-1-III.

Stereolithography cures a liquid photopolymer layer by layer (3), typically an epoxy or acrylate resin (II). Fused deposition modeling extrudes melted thermoplastic (2), commonly ABS (IV). Laminated object manufacturing bonds and cuts sheets (4), traditionally paper (I). Laser-engineered net shaping injects a powder stream into a laser melt pool (1), used for metals such as titanium (III).

The other options give SLA titanium, LOM powder injection, or LENS sheet deposition, each of which contradicts how the process works.

Answer: A

The one that is not an STL file error is the staircase effect.

The staircase effect is a build error: slicing a part into layers of finite thickness leaves stepped surfaces on slopes and curves. It arises in fabrication whatever the quality of the STL file.

Missing facets (gaps in the triangle mesh), non-manifold topology (edges shared by more than two triangles, for example) and degenerate facets (triangles with collinear vertices or zero area) are all defects of the STL tessellation itself.