ASSIGNMENT – I
Rapid prototyping is the automatic construction of physical objects using additive manufacturing technology. The use of additive manufacturing for rapid prototyping takes virtual designs from computer aided design (CAD) or animation modeling software, transforms them into thin, virtual, horizontal cross-sections and then creates successive layers until the model is complete. It is a process where the virtual model and the physical model are almost identical.
With additive manufacturing, the machine reads in data from a CAD drawing and lays down successive layers of liquid, powder, or sheet material, and in this way builds up the model from a series of cross sections. These layers, which correspond to the virtual cross section from the CAD model, are joined together or fused automatically to create the final shape. The primary advantage to additive fabrication is its ability to create almost any shape or geometric feature.
The standard data interface between CAD software and the machines is the STL file format. An STL file approximates the shape of a part or assembly using triangular facets. Smaller facets produce a higher quality surface. VRML (or WRL) files are often used as input for 3D printing technologies that are able to print in full color.
Types of Rapid Prototyping:
Several rapid prototyping methods have been created to produce objects of complex geometries in a relatively short amount of time. These systems are beneficial to engineers by allowing them to better understand the products that they are designing and by providing them with a way to create a visual aid to communicate with others. Rapid prototyping allows design challenges to be determined earlier in the design process, saving time and money. The technology of rapid prototyping is easy to access and simple to understand.
A large number of competing technologies are available in the marketplace. As all are additive technologies, their main differences are found in the way layers are built to create parts. Some are melting or softening material to produce the layers (SLS, FDM) where others are laying liquid materials thermosets that are cured with different technologies. In the case of lamination systems, thin layers are cut to shape and joined together. Prototyping technologies| Base materials|
Selective laser sintering (SLS)| Thermoplastics, metals powders| Direct metal laser sintering (DMLS)| Almost any alloy metal| Fused deposition modeling (FDM)| Thermoplastics, eutectic metals| Stereolithography (SLA)| photopolymer|
Laminated object manufacturing (LOM)| Paper|
Electron beam melting (EBM)| Titanium alloys|
3D printing (3DP)| Various materials|
SELECTIVE LASER SINTERING
Selective laser sintering (SLS) is an additive manufacturing technique that uses a high power laser (for example, a carbon dioxide laser) to fuse small particles of plastic, metal (direct metal laser sintering), ceramic, or glass powders into a mass that has a desired 3-dimensional shape. The laser selectively fuses powdered material by scanning cross-sections generated from a 3-D digital description of the part (for example from a CAD file or scan data) on the surface of a powder bed. After each cross-section is scanned, the powder bed is lowered by one layer thickness, a new layer of material is applied on top, and the process is repeated until the part is completed.
Compared to other methods of additive manufacturing, SLS can produce parts from a relatively wide range of commercially available powder materials. These include polymers such as nylon, (neat, glass-filled or with other fillers) or polystyrene, metals including steel, titanium, alloy mixtures, and composites and green sand. The physical process can be full melting, partial melting, or liquid-phase sintering. And, depending on the material, up to 100%...