additive vs subtractive processes printing motivations complexity access waste constraints failure resolution time cost Materials PLA, PETG, PMMA, ABS, HIPS, ... ventilation design rules supports overhang FCStd jpg stl clearance FCStd jpg stl unsupported angle FCStd jpg stl overhang FCStd jpg stl bridging FCStd jpg stl wall thickness FCStd jpg stl dimensions FCStd jpg stl anisotropy FCStd jpg stl surface finish FCStd jpg stl infill FCStd jpg stl post-processing processes stereolithography fused-deposition molding extrusion DED, WAAM ink-jet binder PolyJet cut sheets selective laser sintering two photon >machines RepRap Ultimaker Z-Unlimited MakerBot Prusa MMU parts Sindoh Formlabs Print the Legend Chase Me Stratasys J55 color Bot Factory Precious Plastic materials Proto-pasta MatterHackers NinjaTek software meshing MeshLab netfabb meshmixer Geomagic slicing ReplicatorG Skeinforge Slic3r Cura IceSL printing Printrun OctoPrint sharing Sketchfab Thingiverse