Rapid prototyping is the most convenient way to get a replica of a three-dimensional design CAD-generated 3D application way.
These physical models can be only aesthetic and useful for the study of the potential market of the product, or they may meet some or most of the mechanical requirements which would have the final piece, offering, in this case, the possibility to perform functional tests and approval before there even preliminary molds.
That man made his hands the means that would shape the objects that determine their evolution, devised object, the object designed: tools, utensils, art, and beauty, among others. Use of science was done to create the elements that should give matter and harmony with their creations.
Rapid prototyping is a process by which mathematical coordinates, created by Computer-Aided Design and Computer-Aided Manufacturing techniques, which are processed for scale models are introduced quickly .
Main technologies
The main technologies and techniques used in conducting rapid prototyping are into four major groups:
1. Stereolithography: Stereolithography (SLA) is a method in which a photocurable resin solidifies (epoxy resins and acrylic resins) liquid using the heat of an ultraviolet laser. This solidification is made in layers to complete the piece. The machine used for its realization is composed mainly by:
• An ultraviolet laser. The laser has the function to heat and melts the material according to the Computer-Aided Design.
• A container with liquid photocurable resin: The liquid is the raw material used to create the prototype .
• An elevator within the container. The elevator executes the movements in the three axes.
The procedure followed is as follows:
• When entering the model file on the computer, the machine divided into cross sections of 0.003". The cross section is a standard value for the industry.
• After processing the data, the elevator has a location of 0.003" below the surface of the liquid resin.
• The ultraviolet laser draws a cross section of the tank surface photocurable resin, thus solidifying the first layer. The cross section stays firm thanks to the reaction of the ultraviolet laser.
• Once the laser finishes solidifying the first layer, the elevator lowers the thickness indicated by the cross section and another new layer solidifies.
• This process is repeated layer by layer until the prototype is ready. The technique has the advantage that the client will not perceive the difference between two or more layers.
Cost and Safety:
The technique is secure for the user, because there is no radiation exposition. The cost of the technique starts since 500 USD for a 4” x 4 x 4”. The CAD software’s are almost compatible with all the Stereolithography machines.
2. Selective Laser Sintering: Selective laser sintering (SLS) is a procedure similar to Stereolithography, but with differences in the type of used material. In this case, a material powder is used, instead of liquid. The machine used in this case comprises:
• A CO2 laser: The CO2 has an inert quality that does not create oxidation to the material. New CO2 lasers have CO2 collectors with the goal to reduce CO2 emissions to the atmosphere.
• A roller: The roller rotates the piece in the three axes: X, Y, and Z.
• An elevator: The elevator translates the piece in the three axes: X, Y, and Z.
• Two tanks dust: The tank collects the resulting dust in the process. More than 80% of the collected dust may be recycled for future prototypes.
Regarding the procedure followed is as follows:
• STL file is part of the 3D data from CAD modeling.
• It is inserted into the computer, and it processes it.
• A layer of material was spread SLS powder by the surface construction.
• The machine sinters a section of the CAD file.
• Using the file information, a laser selectively O2 draws a cross section of the object on the layer of dust. As the laser drawing section, the material is sintered (heated and melted) creating a solid mass which represents a cross section of the object.
• The process repeats, i.e., it becomes to spread another layer of dust and the laser sinter it again, to finish the piece.
Cost and Safety:
The use must take previsions with this technique because there is exposition to CO2 gas. It is necessary a gas extractor in the work area. The cost of the technique starts since 1500 USD for a 4” x 4 x 4”.
3. Manufacturing is cutting and laminating: The manufacturing technique for cutting and laminating (LOM) is based on the rapid prototyping through overlapping and gluing of sheets-of-paper successive laser cut . The machine used for its realization is composed mainly by:
• A Laser: The laser has made plain cuts in a line or a plane, according to the relative movement of the laser according to the piece.
• Two rolls through which the paper is renewed.
• A roller is pressing each layer of paper before being cut by the laser.
• A mobile platform. The piece fixes to the mobile platform. The mobile platform can move the piece (translation) in the three axis X, Y and Z and two rotation movements.
Regarding the procedure followed is as follows:
• The laser cuts the outlines of the piece of paper on a 0.1 mm thick which corresponds to the layer height in the XY axis.
• The sectors of waste paper are cut into grids to facilitate their removal. The same square contour is always trimmed
• Then the rollers deposit a new layer of paper, and the process is repeated until all layers end.
Cost and Safety:
The use must take previsions with this technique because of the exposure of small particles in the air, similar risk than a metallic shop. It is necessary a gas extractor and basic protection in eyes and ears. The cost of the technique starts since 700 USD for a 4” x 4 x 4”.
4. Deposition molten thread: In the deposition method cast thread (DMCT) it is operated by extruding a small amount of a thermoplastic (polyester), through a tiny nozzle to form each section and in turn the three-dimensional object.
The machine used for its realization is composed mainly by:
• A tailstock, which pours polyester filament: The tailstock may have a wide range of angular speeds from 25 revolutions per minute to 1200 revolutions per minute. The tailstock uses the same principle of a lathe.
• A fixed platform.
• Roll polyester. The roll polyester is the filler material.
The procedure followed consists of the following steps:
• The material leaves the Extractor head in a semi-liquid state. Head movement in X and Y define each section or layer
• Subsequently, the platform descends Z-axis resulting in a new layer on the above.
Cost and Safety:
The techniques are one of the safest of the four techniques considered in this paper. The cost of the technique starts since 1200 USD for a 4” x 4 x 4”.
Advantages and uses
Stereolithography:
• Cheaper and faster method.
• Its purpose is to provide a physical and functional design vision.
• Possible applications: conceptual and aesthetic models, details and accuracy parts, teachers standards for secondary processes.
Selective Laser Sintering:
• Allows testing of resistance and durability.
• Ability to handle different materials
• Very resistant parts.
• Possible applications: prototypes and patterns of plastic and metal, machining complex, high-durability parts, parts with small features, small batches of metal or plastic parts.
Manufacturing cutting and rolling:
• The feedstock is an economical option for prototyping, especially when the pieces are large.
• The accuracy of 0.1 mm (height of the layer).
• The raw material is not transformed in the process, so we get a stable piece.
• There is no cure post-processing of the part.
Fused deposition thread:
• Greater speed (101 mm / sec).
• The size of the piece to create unlimited, only the machine (e.g. .: 304x203x203 mm).
• Resistant part obtained and need not be mechanized.
• Ductile material like any polymer.
Reference List
3D Systems. (2016). Stereolithography (SLA). Obtenido de 3D Systems: http://www.3dsystems.com/quickparts/prototyping-pre-production/stereolithography-sla
Cerejo, L. (16 de June de 2010). Design Better And Faster With Rapid Prototyping. Obtenido de Smashing Magazine: https://www.smashingmagazine.com/2010/06/design-better-faster-with-rapid-prototyping/
Palermo, E. (2016). What is Laminated Object Manufacturing? Obtenido de Live Science: http://www.livescience.com/40310-laminated-object-manufacturing.html
