Additive Manufacturing (AM) is a new 3D printing technology utilized in creating and shaping functional, industrial components such as prototypes, toolings, and end-use products. AM’s advantages include the geometrical freedom in design, cost efficiency in production, and ability to use wide range of materials that otherwise would be impractical to apply. .
The 7 Categories of Additive Manufacturing 
In Vat polymerisation technique a chamber of liquid photopolymer resin exists that is used to construct the model in a layer by layer format. Then, the ultraviolet (UV) light is used to cure or harden the resin. In those spots that resin comes in contact with the light, it is cured or hardened. Objects are moved downwards after each hardening cycle. Unlike powder based methods in which the unbound material acts as a support for model, in this process, no structural support is available during the build phase, because the material used is in liquid form. In this case, support structures can be added.
Material jetting technique acts like a two-dimensional ink jet printer. In this method material is deposited through a nozzle which moves horizontally across the platform and places the material with a continuous or Drop on Demand (DOD) approach. In this method ultraviolet (UV) light is applied for solidification of deposited material and the model is built layer by layer. Those materials that are viscous in nature and can be deposited in drops are appropriate for this technique, so polymers and waxes are two materials commonly used with this technique.
In binder jetting technique two type of materials are used: the first one is a powder based material acting as the build material and the second one is the binder material which attaches powder layers together as a glue and usually exists in a liquid form. Build material and the binding material are deposited in alternating layers through horizontal movement of print head across the x and y axes. As new layers are added, the printed object goes lower in the platform. This technology is often referred to as 3DP technology. All materials are not compatible with this method and although the printing process is relatively fast, additional post processing is the time consuming part. Unlike this method, in other powder based manufacturing methods, the printed object is supported within the powder bed and is easily removable from unbound powder, after completion.
Fuse deposition modelling (FDM) is a material extrusion process which is commonly used and is commercialized by the company Stratasys. It is the main technique used in domestic and hobby 3D printers. Material is heated in a nozzle which moves horizontally and deposits layer by layer. After addition of each new layer the platform moves up and down. Multiple factors in this process determine the quality of final model and this process has great potential as long as these factors are controlled successfully. FDM process likewise all other 3D printing processes uses a similar layer by layer approach, but in this process the material is deposited through a nozzle in a continuous stream with a constant pressure and speed which is necessary to get the accurate results (Gibson et al., 2010). As shown in the diagram material is often added to the machine in spool form.
Powder Bed Fusion
The Powder Bed Fusion (PBF) process recruits the following techniques Direct Metal Laser Sintering (DMLS), Electron Beam Melting (EBM), Selective Heat Sintering (SHS), Selective Laser Melting (SLM) and Selective Laser Sintering (SLS). In powder bed fusion (PBF) methods, melting and fusion of material powder is done by laser or electron beam. For using Electron beam melting (EBM), a vacuum is required but it is applicable on metals and alloys. In all PBF processes, either a roller or a blade is recruited to spread the powder material over previous layers. In direct metal laser sintering (DMLS) unlike SLS which uses plastics as raw material, metals are used. The main difference of Selective Heat Sintering with other processes is utilizing the heated thermal print head for fusion of powder material together.
Sheet lamination processes is composed of ultrasonic additive manufacturing (UAM) and laminated object manufacturing (LOM). In Ultrasonic Additive Manufacturing process, ultrasonic welding is utilized for binding of sheets or ribbons of metal together, however, it is not the end-use product and additional machining is often required after the welding process. Laminated object manufacturing (LOM) constructs models layer by layer, but the difference is in eliminating the welding process and using paper as material and adhesive instead. In LOM process, cross hatching method is utilized, so the printed object once completed is easily removable. Laminated objects are often used as visual models and are not suitable for structural use. Copper, stainless steel and Titanium are the most commonly used metals in UAM (Ultrasonic Additive Manufacturing Overview, 2014). The temperature is kept low during the process, so internal geometries can be created. This process requires relatively little energy, since it attaches different materials while they are not melted.
Directed Energy Deposition
Directed Energy Deposition (DED) comes with a range of terminology: ‘Laser engineered net shaping, directed light fabrication, direct metal deposition, 3D laser cladding’. It is a more complicated printing process and its function is in repairing existing components or adding additional material to them (Gibson et al., 2010). DED process is similar to material extrusion, but in this process nozzle can move in multiple directions. The material can be deposited from any angle and laser or electron beam is used to melt materials in situ upon deposition. The most common materials used in this process are metals powder or wires, however, polymers or ceramics can also be used with this technique.
Materials Used In 3D Printing and Additive Manufacturing
The Vat polymerisation process uses Plastics and Polymers.
Polymers: UV-curable Photopolymer resin
Resins: Visijet range (3D systems)
The material jetting process uses polymers and plastics.
Polymers: Polypropylene, HDPE, PS, PMMA, PC, ABS, HIPS, EDP
Polymers: ABS, PA, PC
All three types of materials can be used with the binder jetting process.
The Material Extrusion process uses polyers and plastics.
Polymers: ABS, Nylon, PC, PC, AB
Powder Bed Fusion
The Powder bed fusion process is compatible with any powder-based materials, but according to the papers, common metals and polymers used include: SHS: Nylon DMLS, SLS, SLM: Stainless Steel, Titainium, Aluminum, Cobalt Chrome, Steel EBM: titanium, Cobalt Chrome, ss, al and Copper (Materials Arcam, 2014). More information on powder-bed systems can be found here
Effectively any sheet material capable of being rolled. Paper, plastic and some sheet metals.
The most commonly used material is A4 paper.
Directed Energy Deposition
The Electron Beam Melting process uses metals and not polymers or ceramics.
Available at CAVS
OPTOMEC Laser Engineered Net Shaping (LENS): a Direct Laser Deposition (DLD) additive manufacturing process for metals utilizing blown powder and in situ laser. The LENS has application in cladding and repairing valuable components.
• Dual-Camera Monitoring and Control System • 500W, 1kW laser power (Nd:YAG)
• Stratonics ThermaViz® melt pool pyrometer and in-chamber infrared camera
• Stratonics ThermaViz® process control capabilities
• 12in x 12in x 12in build envelope (300mm x 300mm x 300mm)
The AM250 contains an external powder reservoir with valve interlocks, so during the process run additional material can be added or multiple material types can be interchanged easily. This removable reservoir makes the cleaning process and materials exchange convenient, utilizing universal silo lift. The placement of powder overflow reservoirs outside the chamber and putting isolation valves on it is beneficial for saving the unused materials. The system has a build volume of 250 mm × 250 mm × 300 mm .