3D printing, also known as additive manufacturing, is a general term that encompasses various distinct 3D printing processes. The implementation methods of these technologies for products are completely different, but some key processes are the same. For example, all 3D printing starts with digital models, and this technology is essentially digital. Parts or products were originally electronic files obtained from a digital parts library using computer-aided design software. Then, the design file is decomposed into slices or layers through special construction preparation software for 3D printing, generating path instructions for the 3D printer to follow.
The types of additive manufacturing can be classified based on the products they produce or the types of materials used. The International Organization for Standardization (ISO) categorizes them into seven general types (but these seven 3D printing categories are also difficult to cover an increasing number of technology subtypes and hybrid technologies).
① Material extrusion
Material extrusion, as the name suggests: The material is extruded through a nozzle. Typically, this material is a plastic filament that is melted and extruded through a heated nozzle. The printer places materials on the construction platform along the process path obtained through software. Then the filament cools and solidifies to form a solid object. This is the most common form of 3D printing. At first glance, this sounds simple, but considering the extruded materials, including plastic, metal, concrete, biological gel and various foods, this is actually a very broad category. The prices of this type of 3D printer range from $100 to seven digits.
② Reductive aggregation
It uses a light source to selectively cure (or harden) photosensitive polymer resin in a barrel. In other words, light accurately points to specific points or areas of liquid plastic to harden it. After the first layer is solidified, the construction platform will move up or down (depending on the printer) in a small amount (usually between 0.01 and 0.05 millimeters), and the next layer will be solidified and connected to the previous layer. Repeat this process layer by layer until a 3D component is formed. After the 3D printing process is completed, clean the object to remove any remaining liquid resin and perform post curing (in sunlight or ultraviolet chamber) to enhance the mechanical properties of the component. The three most common forms of barrel aggregation are Stereolithography (SLA), Digital Light Processing (DLP), and Liquid Crystal Display (LCD), also known as Mask Stereolithography (MSLA). The fundamental difference between these types of 3D printing technologies lies in the light source and its way of curing resin.
③ Powder bed fusion
Powder Bed Fusion (PBF) is a 3D printing process in which thermal energy selectively melts powder particles (plastic, metal, or ceramic) within the construction area to create solid objects layer by layer. Powder bed fusion 3D printers scatter a thin layer of powder material on the printing bed, typically using a blade, drum, or eraser. The energy from the laser is fused to specific points on the powder layer, and then another powder layer is deposited and fused to the previous layer. Repeat the process until the entire object is manufactured, and the final product is wrapped and supported by unmixed powder.
④ Material spraying
Material spraying is a 3D printing process in which tiny material droplets are deposited and then cured or solidified on the construction board. Build objects layer by layer using photosensitive polymers or wax droplets that solidify when exposed to light. The nature of the material spraying process allows different materials to be printed on the same object. One application of this technology is to manufacture parts with multiple colors and textures.
⑤ Adhesive spraying
Adhesive spraying is a 3D printing process in which a liquid adhesive selectively adheres to an area of a layer of powder. This type of technology combines the characteristics of powder bed fusion and material spraying. Similar to PBF, adhesive spraying uses powder materials (metal, plastic, ceramics, wood, sugar, etc.), and like material spraying, liquid adhesive polymers deposit from the inkjet. Whether it is metal, plastic, sand, or other powder materials, the adhesive spraying process is the same.
⑥ Directed energy deposition
Directional Energy Deposition (DED) is a 3D printing process where metal materials are supplied and melted with powerful energy during deposition. This is one of the most extensive 3D printing categories, including many subcategories, depending on the form of the material (wire or powder) and the type of energy (laser, electron beam, arc, supersonic, heat, etc.). Essentially, there are many similarities with welding.
⑦ Sheet lamination
Sheet lamination is a form of 3D printing technology that differs greatly from the aforementioned techniques. Its function is to stack and press very thin material sheets together to generate 3D objects or stacks, and then cut them mechanically or laser to form the final shape. The material layer can be fused together using various methods, including heating and sound, depending on the material, ranging from paper, polymers to metals. When parts are laminated and then laser cut or processed into the desired shape, there is more waste than other 3D printing technologies. Manufacturers use thin sheet lamination to produce cost-effective non functional prototypes at a relatively high speed, which can be used for battery technology and the production of composite materials, as the materials used can be interchanged during the printing process.
Note: There are many types of 3D printing technologies, and the above are the seven most common types of additive manufacturing technologies in 3D printing, which do not cover all 3D printing technologies in the market. With the continuous development and evolution of these 3D printing technologies, they have enormous potential in various industries, providing unlimited possibilities for innovation, customization, and sustainable manufacturing. In the future, we can expect to see more 3D printing technologies emerge, driving the progress of the manufacturing industry.
