3D printing technologies and the 3D printing process
What is 3D printing? What can be done with the 3D printing technology?
3D printing is a production technique for building structures and objects. It can also be called additive manufacturing. To create the object, the 3D printer deposits layers of printing material on top of one another, following the design of a 3D file.
The layered building technique is similar to how an igloo is built: bricks of snow are stacked on top of one another until the snow house is built; similarly thin layers of material are built up one at a time to complete the designed object.
3D printing is also known as Additive Manufacturing (AM), additive layer manufacturing, freeform fabrication or fast prototyping.
There are a wide range of printing materials available for 3D printing applications:
- Plastic is the most common 3D printing material for consumers.
- Professionals can use powerful 3D printers, capable to 3D print with almost any material: metals, alloys, plastics, ceramics and paper.
Shedding many of the constraints of traditional production processes, 3D printers enable quick production of virtually any object. The time and money required to move from initial object design to prototype is drastically shortened.
The rise of 3D printing is already greatly impacting both manufacturing and design processes in many industries.
Infographic materials and 3D printing technologies mapping
3D printing technologies
3D printing is similar to additive manufacturing and used to be called rapid prototyping. Several technologies belong to the 3D printing manufacturing methods. Those 3D printing technologies can be classified in 7 categories.
Extrusion uses plastic filament as the printing material. The filament is heated, melting in the printing head of the 3D printer. The printer then deposits the melted filament in precise detail, layer by layer. Driven by small motors, the printing head moves on two horizontal axes while the tray supporting the developing object moves vertically.
When one layer is complete, the tray holding the object lowers very slightly and the layering process resumes, depositing a new layer on melted filament on top of the previous one.
Deposited layers are fused together as the melted plastic quickly solidifies to form a solid three-dimensional object.
The 3D printing extrusion process. Image credit: KUL3D.com.
Stacked layers of plastic create the object, similar to the building of a brick wall. The precision and quality of the final result depends mostly on the diameter of the printing head and the mechanics of the 3D printer.
Extrusion is also known as: Fused Filament Fabrication (FFF), Fused Deposition Modeling (FDM), Plastic Jet Printing (PJP).
The compatible 3D printing materials with this technology are different categories of plastics. Extrusion is compatible with popular thermoplastics such as thermoplastic Aliphatic Polyester (PLA), Acrylonitrile Butadiene Styrene (ABS), Polyvinyl Alcool (PVA) or Nylons.
Material jetting machines utilize inkjet print heads to jet melted materials or binder material, which then cool and solidify. By adding layer on layer, the part is built. When the print head jets directly the building material, the technology is called Photopolymer Jetting (PJ). The photopolymer is then cured by a light/heat source.
Another option is to jet a binder material onto a powder material to construct the 3D object. This technology is called Binder Jetting (BJ). Both the Photopolymer Jetting (PJ) and Binder Jetting (BJ) can be classified in the Material jetting category. Photopolymer Jetting (PJ) is a 3D printing technology that can combine different plastic print materials within the same 3D printed model in the same print job.
The material jetting is also known as: Multijet modeling, DOD, drop on demand, Thermojet, Inkjet printing, Binder Jetting (BJ), Photopolymer Jetting (PJ).
The material jetting is compatible with those 3D printing materials: Ceramic, Metal, Plastic, Wax.
Binder jetting 3D printing technology. Image credit: 3Dprintingindustry.com.
The lamination 3D printing technique can produce high detailed colored objects. The building material is a thin layered material such as paper or aluminum foil cut into appropriately shaped layers, often by lasers or a very sharp blade.
Layers are coated with adhesive and successively glued together layer by layer, similar to other 3D printing techniques. The precision of the result then depends mostly of the thickness of layered materials used. Paper is the most popular based material. 3D printed objects in paper are resistant and can be fully colored.
The 3D printing lamination process. Image credit: 3DPrintingIndustry.com
The compatible 3D printing materials with the lamination technology are paper, metal foils and plastic film. However the only commercial 3D printers available on the market use paper.
Thanks to a good price to performance ratio, the photopolymerisation printing technique has enjoyed a wide adoption.
Photopolymerisation is based on the use of specific plastics, which have the property of solidifying when exposed to certain light beams. A tray is immersed inside a liquid plastic solution, close to the surface. A projector or laser emits a beam of light, tracing the shape of the object. The traced shape solidifies on the surface after a quick resting period and the tray is then immersed deeper into the liquid plastic solution. The process is repeated to create additional layers fused to the previous ones.
The photopolymerisation technique is also known as: Stereolithography (SLA) aka optical fabrication, photo-solidification, solid free-form fabrication or solid imaging or Digital Light Processing (DLP)
The compatible 3D printing materials with the photopolymerisation technology is Photopolymer (photo resin).
To get a better understanding of differences between FFF and SLA, please read this comparison article between these two 3D printing technologies.
Digital Light Processing (DLP) technology. Image credit: 3DPrintingIndustry.com.
Powder bed fusion
Powder bed fusion is a very powerful industrial technique requiring a controlled printing environment.
Powder, made out of plastics or various types of metals and alloys, is the building material. Laser (Laser Sintering (LS) or Laser Melting (LM)) or electron beams (Electron Beam Melting (EBM)) are used to heat the construction material, which fuses and solidified to constitute a layer.
Similar to other 3D printing techniques, the heating device is held by a tray driven by motors. When a layer is built, the tray underneath the object being manufacturing lowers, sinking into the powder pool. The fabrication of the next layer of the object begins, fused to the previous layer by heat. The precision of the result then depends mostly on the precision of the heating device.
The powder bed fusion 3D printing technology is also known as: Laser Sintering (LS), Laser Melting (LM), Electron Beam Melting (EBM), Selective Heat Sintering (SHS), Selective Laser Sintering (SLS), Direct Metal Laser Sintering (DMLS), Selective Laser Melting (SLM) or Plaster-based 3D Printing (PP).
The main difference between these advanced manufacturing technologies are at which point the materials are melted. EBM, EBAM and SLM entirely melt the material while SLS and LS rather fuse it together.
Selective Laser Sintering (SLS) 3D printing technology. Image credit: sculpteo.com.
3D bioprinting is the process of generating spatially-controlled cell patterns using 3D printing technologies, where cell function and viability are preserved within the printed construct. With this technique it is possible to manufacture living tissue.
3D bioprinting technology infographic. Image credit: Broadsheet.ie.
The first 3D tissue printer is called “Regenovo“ and was designed by researchers from Hangzhou Dianzi University in China. This printer have already been used it to successfully print multiple tissue samples, including liver units and human ear cartilage.
The fabrication of a 3D functional tissue made of several cell types is a 3 steps process:
- Cells are sorted, multiplied and differentiated. They make what is called a bioInk.
- Cells or cell aggregates are embedded in 3D to enable subsequent hierarchical tissue building.
- The obtained 3D structures are matured in a perfusion reactor to create a vasculature system. This is called the maturation phase.
- The 3D printed tissue can be used in medical research.
3D printing of cell aggregates thus allows bio engineers to assemble complex tissues. Proof-of-principles include pieces of both blood vessels and liver tissues.