- Rapid Prototyping Technologies:
All rapid prototyping uses some kind of method of additive fabrication, or additive manufacturing. This is a method of building a part by adding overlapping layers of material to a build area, which in-turn, will start to create a solid model of an object. The inputs for rapid prototyping are files created by 3-D CAD software, i.e. Inventor, Pro-E, Solidworks, Catia… etc. These files are then converted into one of two formats STL or SLC. These file formats convert the digital model into a series of surface triangles which the rapid prototyping device interprets and then converts into a solid model.
There are several different methods of additive fabrication, some of the most widely used include:
• Stereolithography (SLA)
• Selective Laser Sintering (SLS)
• Multijet Modeling (MJM)
• Poly-Jet Modeling (PJM)
• Fused Deposition Modeling (FDM)
• Liquid Binding Powder
• Film Transfer Imaging (FTI)
Stereolithography (SLA): The first Stereolithography Rapid Prototyping system was developed in 1986 by 3D Systems which has grown into a global company delivering advanced solid imaging solutions to every major market around the world. Stereolithography is an additive fabrication process utilizing a vat of liquid UV-curable photopolymer “resin” and a UV laser to build parts a layer at a time. On each layer, the laser beam traces a part cross-section pattern on the surface of the liquid resin. Exposure to the UV laser light cures, or, solidifies the pattern traced on the resin and adheres it to the layer below. After a pattern has been traced, the SLA’s elevator platform descends by a single layer thickness, typically 0.05 mm to 0.15 mm (0.002″ to 0.006″). A complete 3-D part is formed by this process. After building, parts are cleaned of excess resin by immersion in a chemical bath and then cured in a UV oven. Stereolithography requires the use of support structures to attach the part to the elevator platform and to prevent certain geometry from not only deflecting due to gravity, but to also accurately hold the 2-D cross sections in place such that they resist lateral pressure from the re-coater blade. Supports are generated automatically during the preparation of 3-D CAD models for use on the stereolithography machine. Supports must be removed from the finished product manually. The OEM of this technology is 3D Systems.
Selective Laser Sintering (SLS): Selective laser sintering is an additive rapid manufacturing technique that uses a high power laser to fuse small particles of plastic, metal, ceramic, or glass powders into a 3-dimensional object. The laser selectively fuses powdered material by scanning cross-sections generated from a .stl file onto 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. Parts must then be removed from the vat of resin and cleaned. The OEMs for this technology are 3D Systems, and EOS.
Models and jewelry (right) printed by the 3D Systems ProJet 3000 HD. – view product page
Multijet Modeling (MJM): Mulitjet modeling originated by 3D Systems, is part of a new generation of rapid prototyping technologies called 3D Printing. The term 3D printing is given to the additive fabrication technologies which are “office friendly” and in most cases under $100k price tag. MJM is one of the higher end versions of the 3D printing spectrum. This technology is unique because it uses a large print head which passes over the full width of the build area at once. The pros of this technology include build speed virtually independent of part size or quantity. This means that weather a person submits one part or 10, they will all print in almost the same time. MJM also uses phase change material; this provides very high surface finish, accuracy, and precision. As heated material jets onto the build plate it instantly freezes, and is then UV cured. Support structures are automatically generated. The support structure used with this technology is a wax which has a much lower melting temperature than the part printed and is easily melted out. This method of “hands free” support removal allows for highly complex, and delicate applications. Depending on material used, this technology has applications which include investment casting. The OEM of this Technology is 3D Systems.
Polyjet Modeling (PJM): Polyjet technology is very similar to MJM, and actually originated from patents originally developed for MJM. This family of technology is also thought of as one of the high end 3D printing technologies. Using the same principal as MJM, PJM has a smaller print head and requires more time to build bigger parts. Also due to the small print head, it is capable of using multiple print heads in the higher end models using this technology. Multiple print heads allows for printing in multiple materials simultaneously. The support material on for this technology is actually washed off with pressurized water. This method requires user interference, and increases the chance of human error. Furthermore, it is extremely difficult to remove support material from delicate and/or complex parts. The OEM of this Technology is Objet Geometries
Fused Deposition Modeling (FDM): Fused deposition modeling, which is often referred to by its initials FDM is marketed commercially by Stratasys, which also holds a trademark on the term. Like most other additive fabrication processes (such as 3D printing and stereolithography) FDM works on an “additive” principle by laying down material in layers. A plastic filament or metal wire is unwound from a coil and supplies material to an extrusion nozzle which can turn on and off the flow. The nozzle is heated to melt the material and can be moved in both horizontal and vertical directions by a numerically controlled mechanism, directly controlled by a computer-aided design software package. The model or part is produced by extruding small beads of thermoplastic material to form layers as the material hardens immediately after extrusion from the nozzle. The OEM of this Technology is Stratasys, and is subsidiary company Dimensions.
Liquid Binding Powder: As in many other rapid prototyping processes, the part to be printed is built up from many thin cross sections of the 3D model. In these printers, an inkjet-like printing head moves across a bed of powder, selectively depositing a liquid binding material in the shape of the section. A fresh layer of powder is spread across the top of the model, and the process is repeated. Printers can print parts in full color, by varying the color of the binding liquid applied by the printing head at any location. When the model is complete, unbound powder is removed with pressurized air. This process requires very delicate handling of the parts. These printers, though economical and fast, they have limited application in high accuracy, and precision applications. Furthermore, the parts are very fragile and brittle even after post processing. The OEM of this Technology is Z-Corporation.
Produce high-quality plastic models right at your desk with The V-Flash 3D Printer.
Film Transfer Imaging (FTI): This technology is very similar to that of SLA, in that it uses a resin and is then cured via a UV bulb. This resin is extracted from a reservoir onto a film, at that point a build platform is lowered into the film. Once the build platform is in contact with the film, an image is projected onto the film. This cross sectional image is then cured on to the build plate and hardened. This process is continued as the part begins growing layer by layer. The significance of this technology is that it is the first 3D printer on the market which is below the $10k mark. These parts have break away supports, and are targeted to general purpose prototyping, and not high precision, and high accuracy applications.
3D Rapid Prototyping from WB Engineering on Vimeo.
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