87
Protection and Restoration
characteristics. Finally, AM processes reduce material waste by recycling or reusing
residual materials.
There are diverse individual processes that vary in their method of layer manufacturing depending on the material and machine technology. The range of additive
manufacturing processes can be classified into the following seven categories (Singh
et al., 2020):
• Vat photopolymerization
• Material jetting
• Binder jetting
• Material extrusion
• Powder bed fusion
• Sheet lamination
• Direct energy deposition
Vat photopolymerization (VPP) is a process in which a container or vat of liquid
photopolymer resin is used to form an object. A layer-by-layer model is constructed
with the help of ultraviolet light. This process has a high level of accuracy and gives
a good finish.
Material jetting creates objects by a similar method to an inkjet printer using
polymer, plastic, and a solution of sodium hydroxide. The material is jetted through
a nozzle onto a previous layer surface in the form of droplets.
The binder jetting process uses a powder-based material as a binder, i.e., an adhesive between powder layers. The binder is usually liquid, while the build material
is a powder. Metals like stainless steel as well as polymers and ceramics can be
processed with binder jetting in various combinations, e.g., parts of different colors
can be developed, but due to the binding characteristic this technology is not suitable
for structural parts.
Material extrusion takes place when a heated material is drawn through a nozzle
and then deposited layer by layer. One of the most common material extrusion processes is the fused deposition method (FDM), where a nozzle can move horizontally
and a platform can move vertically after each layer of deposition. The FDM working
principle is shown in Figure 2.4. The materials generally used in this process are
polymers and plastics.
Sheet lamination includes two types of processes, namely ultrasonic additive
manufacturing (UAM) and laminated object manufacturing (LOM). In LOM, any
rolled sheet material like paper or plastic can be used effectively.
Direct energy deposition (DED) is based on a nozzle mounted on a multi-axis arm
which deposits melted material on a surface where it solidifies. Generally, titanium,
chrome, and cobalt are used; this process, however, is not suitable for polymers or
ceramics. This technique has a great degree of control over grain structure. Zheng
et al. (2021) emphasize extensive use of DED methods for repairing.
Powder bed fusion (PBF) includes all processes where focused energy (electron
beam or laser beam) is used to selectively melt or sinter a powder bed layer (Neikov,
2019). Goodridge and Ziegelmeier (2017) emphasize that polymer PBF processes
Protection and Restoration
characteristics. Finally, AM processes reduce material waste by recycling or reusing
residual materials.
There are diverse individual processes that vary in their method of layer manufacturing depending on the material and machine technology. The range of additive
manufacturing processes can be classified into the following seven categories (Singh
et al., 2020):
• Vat photopolymerization
• Material jetting
• Binder jetting
• Material extrusion
• Powder bed fusion
• Sheet lamination
• Direct energy deposition
Vat photopolymerization (VPP) is a process in which a container or vat of liquid
photopolymer resin is used to form an object. A layer-by-layer model is constructed
with the help of ultraviolet light. This process has a high level of accuracy and gives
a good finish.
Material jetting creates objects by a similar method to an inkjet printer using
polymer, plastic, and a solution of sodium hydroxide. The material is jetted through
a nozzle onto a previous layer surface in the form of droplets.
The binder jetting process uses a powder-based material as a binder, i.e., an adhesive between powder layers. The binder is usually liquid, while the build material
is a powder. Metals like stainless steel as well as polymers and ceramics can be
processed with binder jetting in various combinations, e.g., parts of different colors
can be developed, but due to the binding characteristic this technology is not suitable
for structural parts.
Material extrusion takes place when a heated material is drawn through a nozzle
and then deposited layer by layer. One of the most common material extrusion processes is the fused deposition method (FDM), where a nozzle can move horizontally
and a platform can move vertically after each layer of deposition. The FDM working
principle is shown in Figure 2.4. The materials generally used in this process are
polymers and plastics.
Sheet lamination includes two types of processes, namely ultrasonic additive
manufacturing (UAM) and laminated object manufacturing (LOM). In LOM, any
rolled sheet material like paper or plastic can be used effectively.
Direct energy deposition (DED) is based on a nozzle mounted on a multi-axis arm
which deposits melted material on a surface where it solidifies. Generally, titanium,
chrome, and cobalt are used; this process, however, is not suitable for polymers or
ceramics. This technique has a great degree of control over grain structure. Zheng
et al. (2021) emphasize extensive use of DED methods for repairing.
Powder bed fusion (PBF) includes all processes where focused energy (electron
beam or laser beam) is used to selectively melt or sinter a powder bed layer (Neikov,
2019). Goodridge and Ziegelmeier (2017) emphasize that polymer PBF processes