A variety of processes, equipment, and materials are used in the production of a three-dimensional object via additive manufacturing.
Techniques include jetting, extrusion, additive friction stir deposition, powder bed fusion, binder jetting, stereolithography, computed axial lithography, liquid alternative, lamination, directed energy deposition, selective powder deposition, and cryogenic manufacturing.
Types 3D printing processes, are grouped into seven categories by ASTM International in the ISO/ASTM52900-15:
Binder jetting Directed energy deposition Material extrusion Material jetting Powder bed fusion Sheet lamination Vat photopolymerization
Each process and piece of equipment has advantages and disadvantages associated with it. These usually involve aspects such as speed, costs, versatility with respect to feedstock, geometrical limitations and tolerances, as well as a mechanical and appearance properties of the products such as strength, texture, and color.
The variety of processes and equipment allows for numerous uses by amateurs and professionals alike. Some lend themselves better toward industry use (in this case the term additive manufacturing is preferred) whereas others make 3D printing accessible to the average consumer. Some printers are large enough to fabricate buildings whilst others tend to micro and nanoscale sized objects and in general many different technologies can be exploited to physically produce the designed objects.
History
Inkjet printing was pioneered by Teletype which introduced the electrostatic pull Inktronic teleprinter in 1966. The printer had 40 jets that offered a break-through speed of 120 characters per second.
Continuous inkjets were popular in the 1950–1960's before Drop-On-Demand inkjets were invented in 1972. Continuous three-dimensional inks were wax based and low temperature metal alloys. Printing with these hot-melt inks produced alpha-numeric characters that were solid and raised, but no one recognized them as 3D printing. In 1971, a young engineer, Johannes Gottwald patented a liquid metal recorder that printed large characters in metal for signage, but Teletype Corp ignored the discovery. Braille was printed with wax inks but never commercialized in the 1960s.
R.H. Research researched printing from 1982 -1983 and decided that single-nozzle inkjet was a possible fit. He recruited engineers Al Hock, Tom Peer, Dave Lutz, Jim and Kathy McMahon to join the company, which became Howtek, Inc. The company's Pixelmaster device used Tefzel nozzles, which allowed the inkjet to work at high temperature and support thermoplastic hot-melt inks. The device could handle a frequency range of 1–16,000 drops per second. It featured 32 inkjet single nozzles per printhead, printing 4 colors (8 jets per color) CMYK. The printhead rotated at 121 rpm and placed uniform drops precisely as subtractive printing. This technology of hot-melt inks printing layers of CMYK was a precursor to a 3D patent by Richard Helinski.
Chuck Hull patented stereolithography (SLA) in 1986.
In 1993, Helinski's patent was licensed first by Sanders Prototype, Inc.,(later Solidscape, Inc) manufacturer of the first desktop rapid prototype printer, the Modelmaker 6 Pro. It used Howtek style inkjets and thermoplastic inks. Models printed with thermoplastic were perfect for investment casting with no ash during burnout. Thermoplastic ink drop printing is accurate and precise enough for jewelers and detail sensitive CAD designers. The Howtek inkjets that were designed to print a page in 4 minutes were employed to print for as long as 4 days straight.
Processes Several 3D printing processes have been invented since the late 1970s. The printers were originally large, expensive, and highly limited in what they could produce.
A large number of additive processes are now available. The main differences between processes are in the way layers are deposited to create parts and in the materials that are used. Some methods melt or soften the material to produce the layers, for example. selective laser melting (SLM) or direct metal laser sintering (DMLS), selective laser sintering (SLS), fused deposition modeling (FDM), or fused filament fabrication (FFF), while others cure liquid materials using different sophisticated technologies, such as stereolithography (SLA). With laminated object manufacturing (LOM), thin layers are cut to shape and joined (e.g., paper, polymer, metal). Particle deposition using inkjet technology prints layers of material in the form of individual drops. Each drop of solid ink from hot-melt material actually prints one particle or one object. Color hot-melt inks print individual drops of CMYK on top of each other to produce a single color object with 1–3 layers melted together. Complex 3D models are printed with many overlapping drops fused together into layers as defined by the sliced CAD file. Inkjet technology allows 3D models to be solid or open cell structures as defined by the 3D printer inkjet print configuration. Each method has its own advantages and drawbacks, which is why some companies offer a choice of powder and polymer for the material used to build the object. Others sometimes use standard, off-the-shelf business paper as the build material to produce a durable prototype. The main considerations in choosing a machine are generally speed, costs of the 3D printer, of the printed prototype, choice and cost of the materials, and color capabilities.
Printers that work directly with metals are generally expensive. However less expensive printers can be used to make a mold, which is then used to make metal parts. +3D Printing ProcessesTypeTechnologiesMaterialsMaterial jettingDrop-on-demand or continuous (single- or multi-nozzle) particle depositionHot-melt materials (wax, thermoplastic, metal alloy), dispersed materials (technical ceramics, metals, polymers)Material extrusionFused deposition modeling (FDM) or fused filament fabrication (FFF) and fused pellet fabrication or fused particle fabricationThermoplastics, eutectic metals, edible materials, rubbers, modeling clay, plasticineRobocasting or MIG welding 3D printing or direct ink writing (DIW) or extrusion based additive manufacturing of metals (EAM) and ceramics (EAC)Metal-binder mixtures such as metal clay, ceramic-binder mixtures (including ceramic clay and ceramic slurries), cermet, metal matrix composite, ceramic matrix composite, metal (MIG welding)Additive friction stir deposition (AFSD)Metal alloysComposite filament fabrication (CFF)Nylon or nylon reinforced with carbon, Kevlar or glass fibersLight polymerizedStereolithography (SLA)Photopolymer (including preceramic polymers)Digital light processing (DLP)PhotopolymerContinuous liquid interface production (CLIP)Photopolymer + thermally activated chemistryDynamic Interface Printing (DIP)PhotopolymerPowder bedPowder bed and inkjet head 3D printing (3DP)Almost any metal alloy, powdered polymers, PlasterElectron-beam melting (EBM)Almost any metal alloy including titanium alloysSelective laser melting (SLM)Titanium alloys, cobalt-chrome alloys, stainless steel, aluminiumSelective heat sintering (SHS)Thermoplastic powderSelective laser sintering (SLS)Thermoplastics, metal powders, ceramic powdersDirect metal laser sintering (DMLS)Metal alloysLaminatedLaminated object manufacturing (LOM)Paper, metal foil, plastic filmPowder fedLaser metal deposition (LMD) or Directed Energy Deposition (DED)Metal alloysExtreme high-speed laser cladding (EHLA)Metal alloysWireElectron beam freeform fabrication (EBF3)Metal alloysWire-arc additive manufacturing (WAAM)Metal alloys
Jetting
Material jetting In material jetting a nozzle is drawn across an absorbent surface. The material is either wicked, electrostatically pulled from a larger jet, pressurized to expel material either continuously, or in short bursts as spray or drops.
Nozzles can be single nozzle with one fluid chamber or multi-nozzle with single or multi-fluid chambers, or combinations of these.
The material needs to have low enough viscosity to pass through the nozzle opening. Hot-melt materials can be melted to become liquid. The inks must be thick enough to accumulate vertically.
Continuous inkjet technology (CIT) began by printing signs and documents on paper, later adapted to print metals. Wax and thermoplastics were the first 3D materials, printed by drop-on-demand (DOD) inkjets.
Binder jetting
Binder jetting deposits binding adhesive onto layers of powdered material. Also known as inkjet 3D printing, the process spreads powder (ceramic, metal, or plastic-based, including plaster and resins) across a platform. A print head deposits binder in the cross-section of each layer. Modern printers cure (solidify) the binder at each layer. The resulting part is further cured in an oven to remove most binder. Operators sinter it in a kiln following a material-specific time-temperature curve. Unbound powder supports overhangs during printing. The method enables full-color prototypes and elastomer parts. Strength improves by impregnating voids with wax, thermoset polymer, bronze, or other compatible materials. Extrusion
Fused filament fabrication (FFF), trademarked as fused deposition modeling (FDM), extrudes thermoplastic material to build objects layer by layer. As of 2023, FDM was the dominant 3D printing method.
A filament of thermoplastic feeds into an extrusion nozzle. The nozzle head heats the material to its melting point and extrudes it onto a build platform. Stepper or servomotors move the head and control flow along three axes. Computer-aided manufacturing software generates G-code. A microcontroller drives the motors.
Common materials include acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polylactic acid (PLA), high-density polyethylene (HDPE), PC/ABS, polyphenylsulfone (PPSU), and high impact polystyrene (HIPS). The filament forms from virgin resins.
Open-source projects recycle post-consumer plastic waste into filament using shredders and extruders like recyclebots.Mohammed, M., Mohan, M., Das, A., Johnson, M.D., Badwal, P.S., McLean, D. and Gibson, I., 2017, January. A low carbon footprint approach to the reconstitution of plastics into 3D-printer filament for enhanced waste reduction. In DesTech 2016: Proceedings of the International Conference on Design and Technology (pp. 234-241). Knowledge E.Baechler, C., DeVuono, M. and Pearce, J.M., 2013. Distributed recycling of waste polymer into RepRap feedstock. Rapid Prototyping Journal, 19(2), pp.118-125.Zhong, S. and Pearce, J.M., 2018. Tightening the loop on the circular economy: Coupled distributed recycling and manufacturing with recyclebot and RepRap 3-D printing. Resources, Conservation and Recycling, 128, pp.48-58.Despeisse, M., Baumers, M., Brown, P., Charnley, F., Ford, S.J., Garmulewicz, A., Knowles, S., Minshall, T.H.W., Mortara, L., Reed-Tsochas, F.P. and Rowley, J., 2017. Unlocking value for a circular economy through 3D printing: A research agenda. Technological Forecasting and Social Change, 115, pp.75-84. PTFE tubing transfers filament due to high-temperature resistance. Variants use pellets or particles instead of filament, known as fused pellet/particle/granular fabrication (FPF/FGF), aiding the use of recycled materials.Optimizing the Properties of Recycled 3D Printing Materials https://3dprint.com/223571/optimizing-recycled-materials/ Metal wire enables printing via wire arc additive manufacturing (WAAM), reducing costs. Molten glass deposition creates artistic works. Use of FDM limits complex geometries such as overhangs or stalactite structures. Slicer software adds removable support structures for such features.