3D Printing - Joe

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CHEM-ENG 535: Microfluidics and Microscale Analysis in Materials and Biology

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Terminology

Figure 1: CAD image of a teacup; additional rendering shows differences in final build due to differences in layer thicknesses[1]

3D printing is the colloquial term for the rapid prototyping process formally known as additive manufacturing or rapid prototyping[1]. Rapid prototyping (RP) is used generally across different industries to refer to a process in which different versions of a product are generated, evaluated, and improved upon in a relatively rapid, iterative manner until the final product is formed. However, the meaning of this term has also been extended to cover business development and software solutions (e.g. startup culture). It is thus beneficial to use the more specific terminology, additive manufacturing, or AM, which is the term that is generally agreed upon under ASTM standards. This terms covers iterative prototyping involving a manufacturing process that builds products or product parts designed using Computer-Aided Design (CAD) software by adding materials in layers[1]. This distinguishes AM from other rapid-prototyping processes such as injection molding or CNC machining, as well as from uses of the term RP in various other industries.

History

3D printing was first developed and described in 1986 when Charles W. Hull invented a stereolithography (SLA) 3D printing method where thin layers of material cured by ultra violet light were printed in layers to form a 3D structure[2]. This technology was commercialized by 3D Systems in 1989[3]. In the same year, S. Scott and Lisa Crump patented their invention of fused deposition modeling (FDM), which feeds a plastic filament into a heated extruder and precisely lays down the heated material, and co-founded Stratasys, Ltd[3]. In the early 1990s, a series of patents were filed for early versions of powder sintering printing technologies. These patents became the core technology of Z Corp, which later was acquired by 3D Systems[3].

Since then, development and innovation in the field has occurred at an increasingly rapid pace. Novel technologies include two-photon polymerization[4], which can print at the molecular level as well as contour crafting[5], which makes it possible to print large-scale concrete structures. Other technologies include food printing and bioprinting which could make it possible to print out human organs. Furthermore, the expiration of many early 3D printing patents has allowed the general public to co-opt additive manufacturing, which catalyzed the start of the RepRap movement, which is the open-source arm of the 3D printing movement[3].

General Workflow

Figure 2: General workflow from CAD to final part[1]

The specific of additive manufacturing varies across the different printing technologies, but the general process from design to final product remains similar. The general manufacturing stages are as follows[1].

  1. CAD: Any printed part needs to start as a fully-defined 3D solid and/or surface representation on a computer somewhere. This can be generated in a CAD/CAM software, or it can be reverse engineered from 3D scanning data.
  2. File Transfer to Printer: Nearly every 3D printer on the market accepts the STL file format, and most CAD software is able to output as an STL. Once this file conversion is done, the file is transferred to the machine, where further adjustments to size, position, and orientation of the part may be done before it is ready to build. Many printers also accept G-code, a programming language telling a printer the steps of printing decided by the user, to create objects.
  3. Build: Before building, the machine needs to be calibrated, connected to a power source, and loaded with materials. Once all of this is ready, building is simple as the process is usually fully automated.
  4. Post-Processing: Following the build, parts may need to undergo post processing and/or cleaning to improve mechanical properties and clear out support materials and/or structures. These processes vary between the different printing technologies. After this is done, the part is ready to test or use.

Types of Printing

There are many different technologies to do 3D printing. Since 2010, the American Society for Testing and Materials (ASTM) carried out the “ASTM F42 – Additive Manufacturing” standards[2]. Those standards are used to classify the additive manufacturing processes into 7 categories[2].

Those 7 categories are[2] [1]:

  1. Vat Photopolymerisation
    1. Stereolithography (SLA)
    2. Digital Light Processing (DLP)
    3. Continuous Liquid Interface Production (CLIP)
  2. Material Jetting
  3. Binder Jetting
  4. Material Extrusion
    1. Fused Deposition Modeling (FDM)
    2. Fused Filament Fabrication (FFF)
    3. Contour Crafting
  5. Powder Bed Fusion
    1. Selective Laser Sintering (SLS)
    2. Direct Metal Laser Sintering (DMLS)
  6. Sheet Lamination
  7. Directed Energy Deposition

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Gibson, I., Rosen, D. & Stucker, B. Additive Manufacturing Technology. in Additive Manufacturing Technologies 1–18 (Springer, 2015). doi:10.1007/978-1-4939-2113-3
  2. ↑ Lerner, K. L. 3D Printing. in The Gale Encyclopedia of Science 4383 (Gale, 2014).
  3. ↑ 3.0 3.1 3.2 3.3 Horvath, J. A Brief History of 3D Printing. in Mastering 3D Printing 3–10 (Apress, 2014). doi:10.1007
  4. ↑ Cumpston, B. H. et al. Two-photon polymerization initiators for three dimensional optical data storage and microfabrication. Nature 398, 51–54 (1999).
  5. ↑ Khoshnevis, B. & Epstein, D. J. Automated construction by contour crafting-related robotics and information technologies. doi:10.1016/j.autcon.2003.08.012
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