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    Additive manufacturing

    Learn about the different kinds of additive manufacturing

    Stereolithography

    Stereolithography is a 3d printing method that can be used to implement your projects that involve 3D printing of objects. This is the oldest method in history of 3D printing.

    Whether you are a mechanical engineer, or a creative person who wants to make a prototype of a personal project, Stereolithography can help you to turn your models into a real 3D printed object.

    Charles Hull, co-founder of 3D Systems, Inc patented this method in 1986. The process of printing involves a stereolithograph apparatus (SLA) which is a 3D printing machine that converts liquid plastic into solid 3D objects.

    Generally, most printing techniques require computer aid design (CAD) file to process the object. This file contains information about dimensional representation of an object. CAD file must be converted into a format that a printing machine can understand.

    SLA 3D printers work with excess of liquid plastic that hardens and forms into solid object. Parts built with 3D printers type like this usually have smooth surfaces but its quality very depends on the quality of SLA machine used.

    The process starts from the creation of 3D model with a CAD program, which processes the CAD model and generates STL file that contains information for each layer. The SLA machine exposes the liquid plastic and laser starts to form the layer of the item.

    Once the plastic has hardened a platform of the printer drops down in the tank a fraction of a millimeter and laser forms the next layer until printing is completed. Once all layers are printed the object needs to be rinsed with a solvent and then placed in an ultraviolet oven to finish processing.

    The time required to print an object depends on size of SLA 3d printers used. Small items can be printed within 6-8 hours with small printing machine, big items can be several meters in three dimensions and printing time can be up to several days long.

    Stereolithography is widely used in prototyping as it doesn’t require too much time to produce an object and cost is relatively cheap comparing to other means of prototyping. Although this 3d printing method is rarely used for printing of the final product.

    Although Stereolithography is considered to be the oldest 3D printing technology many companies still use it to create prototypes of their projects.

    Digital Light Processing (DLP)

    Digital Light Processing is another 3D Printing process very similar to stereolithography.

    DLP technology was created in 1987 by Larry Hornbeck of Texas Instruments. It uses digital micro mirrors laid out on a semiconductor chip. This technology is applicable for movie projectors, cell phones and 3D printing.

    Like SLA, DLP also works with photopolymers however it works with a different source of light. For DLP, 3D amateurs generally use more conventional sources of lights such as arc lamps.

    The material used for printing is liquid plastic resin that is placed in the transparent resin container. The resin hardens quickly when affected by a large amount of light. Printing speed is pretty impressive. The layer of hardened material can be created in a few seconds.

    The results of such printing are robust and have an excellent resolution. The biggest advantage of DLP over SLA is that it requires much less materials to be used for detail production, that results in lower cost and it creates less waste.

    Fused Deposition Modeling (FDM)

    Fused deposition modeling (FDM) technology was developed and implemented by Scott Crump, founder, of Stratasys Ltd in 1980s.

    With FDM you can print not only functional prototypes, but also concept models and final end-use products. A positive aspect of this technology is that all parts printed with FDM can go in high-performance and engineering-grade thermoplastic, which is very beneficial for mechanic engineers and manufactures. FDM is the only 3D printing technology that builds parts with production-grade thermoplastics, so things printed are of excellent mechanical, thermal and chemical qualities.

    3D printing machines that use FDM Technology build objects layer by layer from the very bottom to the top by heating and extruding thermoplastic filament. When the thin layer of plastic binds to the layer beneath it, it cools down and hardens. Once the layer is finished, the base is lowered to start building of the next layer. Printing time depends on size and complexity of an object printed.Then objects can also be milled, painted or plated afterwards.

    FDM technology is widely spread nowadays in variety of industries such as automobile companies like Hyundai and BMW or food companies like Nestle. It is used for new product development, model concept and prototyping and even in manufacturing development. This technology is considered to be simple-to-use and environment-friendly.

    Different kind of thermoplastic can be used to print parts. The most common of those are ABS (acrylonitrile butadiene styrene) and PC (polycarbonate) filaments. There are also several types of support materials including water-soluble wax or PPSF (polyphenylsulfone).

    Pieces printed using this technology have very good quality of heat and mechanical resistance that allows to use printed pieces for testing of prototypes.

    The price for those 3D printers depends on size and model. Professional ones usually cost from $10,000 and more. 3D Printers designed for home use are not so expensive.

    Selective Laser Sintering (SLS)

    Selective Laser Sintering (SLS) is a technique that uses laser as a power source to form solid 3D objects. Carl Deckard, a student of Texas University, and his professor Joe Beaman developed this technique in the 1980s. Stereolithography is in some way very similar to Selective Laser Sintering. The main difference between SLS and SLA is that it uses powdered material in the vat instead of liquid resin as stereolithography does.

    Like all other methods listed above the process starts with creation of computer-aided design (CAD) file, which then needs to be converted to .stl format by special software. The material to print with might be anything from nylon, ceramics and glass to some metals like aluminum, steel or silver. Due to the wide variety of materials that can be used with this type of 3d printer the technology is very popular for 3D printing customized products.

    SLS is more used among manufactures than 3D amateurs at home as this technology requires the use of high-powered lasers, which makes the printer to be very expensive. Though there are several start-ups the work on development of low-cost SLS printing machines.

    Selective Laser Melting (SLM)

    Selective laser melting (SLM) is a technique that also uses 3D CAD data as a source and forms 3D objects by means of a high-power laser beam that fuses and melts metallic powders together.

    SLM process fully melts the metal material into solid 3D-dimentional part unlike selective laser sintering.
    Similarly to other 3d printing methods a CAD file needs to be processed by special software to slice the CAD file information into 2D layers. The file format used by printing machine is also a standard .stl file. Once the file is loaded the printing machine’s software assigns parameters and values for construction of the path.

    The fine metal powder is evenly distributed onto a plate, then each slice of 2D layer image is intensively fused by applying high laser energy that is directed to the powdered plate. The energy of laser is so intense that metal powder melts fully and forms a solid object. After the layer is completed the process starts over again for the next layer. Metals that can be used for SLM include stainless steel, titanium, cobalt chrome and aluminum.

    This method of printing is widely applied to parts with complex geometries and structures with thin walls and hidden voids or channels. Lots of pioneering SLM projects were dedicated to aerospace application for different lightweight parts. SLM is not widely spread among at-home users but mostly among manufactures of aerospace and medical orthopedics.

    Electron Beam Melting (EBM)

    EBM is a powder bed fusion technique. While SLM uses high-power laser beam as its power source, EBM uses an electron beam instead, which is the main difference between these two methods.

    The material used in EBM is metal powder that melts and forms a 3D part layer by layer by means of a computer, that controls the electron beam in high vacuum. Contrary to SLS, EBM goes for full melting of the metal powder. The process is usually conducted under high temperatures up to 1000 °C.

    The process of EBM is rather slow and expensive, and the availability of materials is limited, making the method not so popular though it is still used in some of manufacturing processes. The application of EBM is mainly focused on medical implants and aerospace area.

    Laminated Object Manufacturing (LOM)

    Laminated object manufacturing (LOM) is a rapid prototyping system that was developed by the California-based company Helisys Inc.

    Layers of adhesive-coated paper, plastic or metal laminates are fused together using heat and pressure and then cut to shape with a computer controlled laser or knife. Post-processing of 3D printed parts includes such steps as machining and drilling.

    LOM is one of the most affordable and fastest 3D printing methods. The cost of printing is low due to un-expensive raw materials. Objects printed with LOM can be relatively big, that means that no chemical reaction is needed to print large parts.

    Currently, Cubic Technologies, the successor to Helisys Inc., is the main manufacturer of LOM printers. There are not too many companies these days that work with LOM technology. But it’s worth mentioning the Irish company Mcor Technologies Ltd. that sells LOM 3D printers. Their devices are widely being used by artists, architects and product developers to create affordable projects from usual letter paper.

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