Additive Manufacturing - Exam with Questions and correct Answers

Additive Manufacturing - Exam A material sample with the cross-sectional area of 1 square-cm peaks at a stress of about 41 MPa. What's the maximum force it could withstand? - Answer-The maximum force is 4.1 kN. Sigma = F/A (Stress mutiplied by the area) Describe the "Meshing" step of the 3D-printing process. - Answer-(, or conversion to an STL file) - the CAD package must be able to export the object in a manner that the subsequent steps can handle. The "mathematical" CAD model is discretized into a collection of triangles that represent the outer surface of the desired object. At this point, comprimises in terms of accuracy (resolution) and file size are made. Describe the "Planning" step of the 3D-printing process. - Answer-The tool path (route) required to generate each slice must be planned. (This does not occur in image-based photopolymerization methods.) Describe the "Post-processing" step of the 3D-printing process. - Answer-Many printing methods require some sort of post-processing such as removal of support material or completion of curing. (Since one could argue that this is not part of the printing process, I will not deduct points if you have not listed it.) Describe the "Slicing" step of the 3D-printing process. - Answer-Most (all?) printers can handle a single 2-dimensions at a time. The slicing process breaks the model into, usually horizontal, slices so that each one can be handled independently. This height should be matched to the physical height of each layer the printer creates. Describe the phase change(s) involved (e.g. from what to what) in the Melting technique and name the printing method(s) that uses it. - Answer-Melted, as in SLM (Selective Laser Melting), which is similar to SLS except that the particles are fully melted (instead of sintered) and then solidified, or as in FDM (Filament Deposition Modeling), in which the plastic is melted in an extruder and deposited as a filament of liquid, which in turn solidifies to a solid, glass, or gel. (SLS and FDM are clearly two different printing methods.) Describe the phase change(s) involved (e.g. from what to what) in the Photopolymerization technique and name the printing method(s) that uses it. - Answer-Photopolymerized, where light initiates a polymerization and/or cross-linking reaction that turns a liquid resin into a solid, glass or gel. This is the basis for SLA (Stereolithography). Describe the phase change(s) involved (e.g. from what to what) in the Sintering technique and name the printing method(s) that uses it. - Answer-Sintered, where the edges of small particles of plastic are softened or melted so that the particles stick together. This is the basis for SLS (Selective Laser Sintering). Describe the phase change(s) involved (e.g. from what to what) in the Solution-processing technique and name the printing method(s) that uses it. - Answer-Solution-processed, in which they are deposited in liquid solution (e.g., in a syringe printer like Katla). The s