What is Additive Manufacturing (AM)?
The basic principle of Additive Manufacturing technology is that a CAD generated 3D model is used directly to fabricate a three-dimensional object by adding layer-upon-layer of material and fuse them together. ( You can read how additive manufacturing works in 7 step here)
Although initially referred to as Rapid prototyping in a product development context, in recent years these technologies have made giant strides and moved from prototype to production-ready part manufacturing. Term 3D Printing is also widely used for these technologies, and it was coined by MIT for the ink jet printing based AM they invented in the 90s. Hence these terms do not effectively describe more recent technological advancement in the sector.
A technical committee under ASTM international finally defined these processes appropriately as Additive Manufacturing (AM), as the technology builds 3D parts by adding material, as compared subtractive manufacturing.
According to ISO/ASTM 52900-2015, Additive manufacturing is commonly given to the technologies that use successive layers of material to create a three-dimensional object. By using various techniques the printer builds the 3D geometry by constructing a thin 2D plane layer by layer.
There are seven main categories of AM technologies viz Vat photopolymerisation, Material Extrusion, Material Jetting, Binder Jetting, Powder bed fusion, Direct energy deposition and Sheet lamination.
Types of Additive manufacturing
Many companies have invented and introduced new techniques and Because the technology is fairly new, the companies who develop and introduce different techniques come up with their own marketing terms for the process, even though the core technique might be the same.
As per ISO/ASTM standards AM can be divided into the following seven process categories or types according to the techniques used to create those layers. Though companies who have developed some of the AM technologies have their own names.
You can partially view the standards here.
Vat Photo Polymerization
In this process, a liquid photopolymer is selectively cured by light-activated polymerization to create a 3D part. It is based on curing and hardening of photopolymers on exposure to the ultraviolet radiation. Main types of this technology are Stereolithography (SLA), Digital Light Processing (DLP) and Continuous Digital Light Processing. Only Plastic can be printed using these technologies. Read more….
Binder jetting process
As the name implies this technique selectively deposits bonding agent a binding liquid to join the powder material together to form a 3D part. This process is different to any other AM technologies as it does not employ heat during the process like others to fuse the material. Read more….
Directed energy deposition
Direct energy deposition uses focused thermal energy such as a laser, electron beam, or plasma arc to fuse materials by melting as they are being deposited. Types include LENS, EBAM. Read more….
Material Extrusion is an additive manufacturing technique which uses continuous filament of thermoplastic or composite material to construct 3D parts. Fused Deposition Modelling (FDM) only type in this category and both Plastic and composite can be printed using this technology. Read more….
In Material jetting, build material droplets are selectively deposited layer by layer into the build platform to form a 3D part. The Powder Material Jetting includes the following commonly used printing technologies: UV cured Material Jetting, Drop on demand (DOD), Nanoparticle jetting (NPJ). Read more….
Powder bed fusion
Powder bed fusion is an Additive Manufacturing technique which uses either laser or electron beam to melt and fuse the material together to form a 3D geometry part. The Powder Bed Fusion includes the following commonly used printing technologies: Multi Jet Fusion (MJF), Direct metal laser sintering (DMLS), Electron beam melting (EBM), Selective heat sintering (SHS), Selective laser melting (SLM) and Selective laser sintering (SLS). Read more….
Material sheets are stacked and laminated together using either adhesives, chemical, ultrasonic welding or brazing to form a 3D part. Once the object is built, unwanted sections are then cut layer by layer. The Sheet lamination includes the following commonly used printing technologies: Laminated Object Manufacturing (LOM), Selective Deposition Lamination (SDL) and Ultrasonic Additive manufacturing (UAM). Read more….
Advantages and disadvantages of additive manufacturing
Advantages of additive manufacturing
- Complex 3D geometries with internal features can be printed without any tooling
- Reduced waste compared to machining
- Part can be printed directly from the 3D model without the need for a drawing
- Prototypes can be made quicker allowing designers to check different iterations resulting in quicker design cycle phase
- Less tooling for smaller batches compared to traditional machining
- Production tooling can be printed
- Different materials can be mixed during the printing process to create a unique alloy
- Different sections of the part can be different variant of the same alloy
Disadvantages of additive manufacturing
- Because the technology still in its infancy the build process is slow and costly
- High production costs because of the equipment cost
- Various post-processing required depending on the type of additive manufacturing used
- Small build volume compared to other manufacturing part size such as sand casting
- Poor mechanical properties hence need post-processing
- Poor surface finish and texture