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A review on basic 3D printing principles

3D printing, also known as additive manufacturing is a process of developing objects by adding layer upon layer of materials using a 3D printer. With the successive development of this technology over time, its application area is also expanding day by day. Its application is growing in industries like aerospace, automobiles, electronics, building construction, textiles, etc. rapidly with the pace of innovation in this industry.

Figure 1: 3D printer.

Efficient and cost-effective manufacturing is a big factor behind the development of various 3D printing technologies for these industries. Scientists, designers, and engineers are continuously working on various projects to develop 3D-printed textile products.

Even, it is predicted that the future of the textile and fashion industry will have an extensive change due to this technology. So, let’s have a look at the basic principles of 3D printing.

There are seven principal categories of 3D printing, according to the ASTM Standard F2792. These categories are based on the working principles of different 3D printing techniques. Binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination, and vat photopolymerization are these seven categories.

Figure 2: A 3D printed dress. Courtesy: Danit Peleg

These principal categories also have various derivatives like, digital light process (DLP), stereolithography (SL), selective laser sintering (SLS), direct laser sintering (DLS),  fused deposition modeling (FDM), multi-jet fusion, poly jet, electron beam melting which are very well known in the market.

Combinedly, these techniques are the principal mechanisms for more than 1500 industrial 3DP machines that are available in the current market across the world. Technologists have manifested different concepts of 3DP technologies for targeted application in various industries.

These categories help manufacturers to choose the best suitable technique according to their materials and objects.

Figure 3: The seven principal categories of 3D printing.
  1. Binder jetting: This printing system is based on powders, as the name suggests, a chemical binder is jetted onto the spread powder of the material to form a layer of the object. The object is created by making a layer on top of another layer by this process. Sintering is done to consolidate the structure after it is shaped. A broad range of polymer metals, composites, and ceramic materials can be printed by this method. Calcium sulfate hemihydrate, poly-methyl methacrylate (PMM), bronze, Inconel 625, alumina, silica, and titanium dioxide are some of the common materials, can be printed with this category. Available widest selection ranges of materials, shaping at room temperature, comparatively faster production than other 3D printing processes and the possibility of making slurries with higher solids loadings are some of the advantages of the binder-jetting. On the other hand, the requirement of multi-step processing, lower relative density, and higher surface roughness are some of the drawbacks of this process.

    Figure 4: Illustration of Binder Jetting.
  2. Direct energy deposition: In this category, the creation of objects is done by melting the material (most frequently used for metals such as titanium, aluminum, stainless steel, or copper) in powder or as a wire with a focused energy source as it is deposited by a nozzle on a surface. Though the process is preferred to use for metals and metal-based hybrids, it can also be used with ceramics, in the form of powder or wire by melting with a focused energy source, like, laser beams, electron beams, and arcs. Direct Metal Deposition (DMD), Wire and Arc Additive Manufacturing (WAAM), Laser Engineered Net Shaping (LENS) are various derivatives of this category.

    Figure 5: Illustration of Direct Energy Deposition.
  3. Metal extrusion: This is a form of additive manufacturing where a thermoplastic-filament /composite substrate is extruded through a printing nozzle and which is deposited layer-upon-layer on a surface to create a 3D structured object. Its ability to offer the potential to reduce cost and time and the possibility to create complex structures have made it widely used in a variety of industries like aerospace, architecture, automobiles, and medical devices. Fused deposition modeling (FDM), Robocasting, Multijet modeling (MJM) are some 3DP methods are the derivative of this category. Thermoplastic polymers, composites, highly filled polymers with metal/ ceramic, and highly filled inks with metal/ ceramic powder can be printed in this process.

    Figure 6: Illustration of Metal Extrusion.
  4. Material jetting: In this category, objects are made by depositing droplets of liquid photopolymers through printing heads and curing the deposited photopolymers with various energy sources, such as ultraviolet lamps. A 3D structure is developed by layer upon layer deposition and curing of liquid photopolymers. The photopolymers can be deposited on the surface following three different techniques, these are Continuous Inkjet, Drop-on-Demand (DOD) Inkjet, and Poly-Jet 3D printing. A large number of photocurable polymers and composites can be printed in this type of 3D printing.

    Figure 7: Illustration of Material Jetting.
  5. Powder bed fusion: An object is created by fusing or melting a layer of powder of the printing material together with either an electron beam or a laser. Then, another layer of powder is laid down upon that layer and the process of fusing or melting is repeated. In this way, the layers are built one upon another to make the ultimate structure of the object. These techniques can be used for polymers, ceramics, and metals. Direct Metal Laser Sintering (DMLS), Selective Laser Sintering/Melting (SLS/SLM), Electron beam melting (EBM), are the techniques included in this category.

    Figure 8: Illustration of Powder Bed Fusion.
  6. Sheet lamination: Processes of this category stack and then, bond the sheets of materials together to produce an object of the desired shape. Materials are fed in the form of continuous sheets which are generally wound around a spool. During printing, the sheets are pulled over a building platform and get attached to the previous sheets. Finally, a laser cutter or a knife is used to cut the contour lines at the cross-section of the printed object. Ultrasound additive manufacturing (UAM), and Laminated object manufacturing (LOM) are the derivatives of this category of 3D printing. Polymers, metals, ceramics, glass fibers, composites, etc. can be printed in this process.

    Figure 8: Illustration of Sheet Lamination.
  7. Vat photopolymerization: Layers of liquid photo-reactive polymer (known as photopolymer), placed in a vat are cured using laser, light/ ultraviolet (UV) rays as per the required shape of an object. Both photopolymers and ceramics can be used to make objects in this process. The ceramic is used in powder form mixed with photo-polymeric resin. Polymerization is stereolithography (SL), and digital light processing (DLP) 3D printing technologies are the derivatives of this category.

    Figure 10: Illustration of Vat Photopolymerization.

These are the basic principles of 3D printing technologies till now. A lot of research projects are ongoing to develop textile and apparel products by 3D printing. And textile engineers have the opportunity to play a significant role in the transformation of textile and apparel manufacturing.

If anyone has any feedback or input regarding the published news, please contact: info@textiletoday.com.bd

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