What is 3D Printing ?
3D printing also referred to as Digital fabrication technology or additive manufacturing, creates physical objects from a geometrical representation by successive addition of materials. Each of these layers can be seen as a thinly sliced cross-section of the object.
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3D printing technology is a fast-emerging technology. Nowadays, 3D Printing is at a tipping point and about to go mainstream in a big way. This technology is increasingly used for the mass customization, production of any types of open source designs in the field of agriculture, in healthcare, automotive industry, locomotive industry and aviation industries.
3D printing technology enables customized fabrication of 3D constructs based on computer aided design (CAD) software or images obtained from computed tomography (CT) and magnetic resonance imaging (MRI).
This technology was first developed in the 1980s and was called rapid prototype technology. With the rapid development of 3D printer, the overall 3D printing market grew to $9.9 billion in 2018 and is expected to reach $34.8 billion in 2024.
Types of 3D Printing
Varieties of 3D printing technologies have been developed with the different function. According to ASTM
Standard, 3D printing technologies divided into seven groups, such as :
- Binder jetting
- Directed energy deposition
- Material extrusion
- Material jetting
- Powder bed fusion
- Sheet lamination
- Vat photopolymerization.
There are no debates about which machine or technology function better because each of them has its targeted applications. Nowadays, 3D printing technologies are no longer limited to prototyping usage but are
increasingly also being used for making variety of products.
1. Binder jetting
Binder jetting is a rapid prototyping and 3D printing process in which a liquid binding agent is selectively
deposited to join powder particles. This technology uses jet chemical binder onto the spread powder to
form the layer.
This technology is used to produce the casting patterns, raw sintered products or similar large-volume products from sand. It can print a variety of materials including metals, sands, polymers, hybrid and ceramics. Some materials like sand not required additional processing.
The process of binder jetting is simple, fast and cheap as powder particles are glued together and it can also print very large products.
2. Directed energy deposition
Directed energy deposition is a more complex printing process commonly used to repair or add additional
material to existing components . It has the high degree control of grain structure and hence can produce the good quality of the object.
The process of directed energy deposition is similar in principle to material extrusion, but the nozzle not fixed to a specific axis and can move in multiple directions. Furthermore, the process can be used with ceramics, polymers but is typically used with metals and metal-based hybrids, in the form of either wire or powder. The example of this technology is laser deposition and laser engineered net shaping (LENS).
Laser deposition is the emerging technology and can be used to produce or repair parts measured in millimeter to meters.
Laser deposition technology is gaining attraction in the tooling, transportation, aerospace, and oil and gas sectors because it can provide scalability and the diverse capabilities in the single system.
At the same time, laser LENS can exploit thermal energy for melting during the casting and parts are accomplished
3. Materials extrusion
Material extrusion-based 3D printing technology can be used to print multi-materials and multi-colour printing
of plastics, food or living cells . This process has been widely used and the costs are very low. This process can build fully functional parts of product.
Fused deposition modelling (FDM) is the first example of a material extrusion system. FDM was developed in early 1990 and this method uses polymer as the main material. FDM builds parts layer-by-layer from the bottom to the top by heating and extruding thermoplastic filament.
The operations of FDM are as follows:
- Thermoplastic heated to a semi-liquid state and deposits it in ultra-fine beads along the extrusion path.
- Where support or buffering needed, the 3D printer deposits a removable material that acts as
For example, FDM uses hard plastic material during the process to produce 3D bone model.
4. Materials jetting
According to ASTM Standards, material jetting is a 3D printing process in which drop by drop of build material
are selectively deposited. In this technology, a printhead dispenses droplets of a photosensitive material that
solidifies, building a part layer-by-layer under ultraviolet (UV) light.
This technology creates parts with a very smooth surface finish and high dimensional accuracy. Multi-material printing and a wide range of materials such as polymers, ceramics, composite, biologicals and hybrid are available in material jetting.
5. Powder bed fusion
The powder bed fusion process includes the electron beam melting (EBM), selective laser sintering (SLS) and
selective heat sintering (SHS) printing technique.
This method uses either an electron beam or laser to melt or fuse the material powder together.
The example of the materials used in this process are metals, ceramics, polymers, composite and hybrid.
Selective laser sintering (SLS) are the main example of powder based 3D printing technology. It was developed by Carl Deckard in 1987. SLS is a 3D printing technology that functions in fast speed, has high accuracy, and varies surface finish. Selective laser sintering can used to create metal, plastic, and ceramic objects. SLS used a high power laser to sinter polymer powders to generate a 3D product.
Meanwhile, SHS technology uses a head thermal print in the process to melt the thermoplastic powder to create 3D printed object.
Lastly electron beam melting enhances an energy source to heat up the material.
6. Sheet lamination
According to ASTM definition, sheet lamination is the 3D printing process in which sheet of materials are bond
together to produce a part of object. The example of 3D printing technology that uses this process are laminated
object manufacturing (LOM) and ultrasound additive manufacturing (UAM).
The advantages of this process are :
- Sheet lamination can do full-colour prints
- It is relatively inexpensive
- Easy of material handling and excess material can be recycled.
Laminated object manufacturing (LOM) is capable to manufacture complicated geometrical parts with lower cost of fabrication and less operational time.
Ultrasound additive manufacturing (UAM) is an innovative process technology that uses sound to merge layers of metal drawn from featureless foil stock.
7. Vat Photopolymerization
The main 3D printing technique that frequently used is photopolymerization, which in general refers to the
curing of photo-reactive polymers by using a laser, light or ultraviolet (UV).
The example of 3D printing technologies by using photopolymerization is stereolithography (SLA) and digital light processing (DLP).
In the SLA, it was influenced by the photo initiator and the irradiate exposure particular conditions as well as any dyes, pigments, or other added UV absorbers.
Meanwhile, digital light processing is a similar process to Stereolithography that works with photopolymers. Light source is the major difference. Digital Light Process uses a more conventional light source, such as an arc lamp with a liquid crystal display panel. It can apply to the whole surface of the vat of photopolymer resin in a single pass, generally making it faster than Stereolithography.
The important parameters of Vat Photopolymerization are the time of exposure, wavelength, and the amount of power supply.
The materials used initially are liquid and it will harden when the liquid exposed to ultraviolet light.
Photopolymerization is suitable for making a premium product with the good details and a high quality of surface.