Additive manufacturing, commonly known as 3D printing, is a process of creating objects by layering material, usually plastic or metal, based on digital models.
There are 7 primary types of additive manufacturing techniques:
1. Binder Jetting (adhesives)
A variety of materials, in a powdered form, can be used such as metal, sand, and plastics. This powdered material is spread across a bed and a moving nozzle ejects adhesives onto the material to bind it. This process continues for each layer and does not require a heat source. This process is relatively inexpensive, but requires post processing to achieve additional strength and surface finishes.
2. Sheet Lamination (adhesive/heated)
Material, in the form of a roll, is laid out over a surface and cut to the desired cross-sectional shape. Then, another layer of material is jointed to the previous layer and cut into its desired cross-sectional shape. These layers will stack up to form the finished product. Jointing depends on the material type, but can consist of ultrasonic welding, brazing, and bonding. Although its an inexpensive process capable of creating complex prototypes, waste material is generated.
3. Directed Energy Deposition (heated)
Metal, in the form of powder or wire, is extruded out of a nozzle that also contains a heat source such as a laser or electrons. The nozzle moves and places this heated liquid material on the bed which eventually cools and solidifies to form a layer of the part. This process is repeated layer by layer until the part is complete. This process has the benefit of being able to add to or repair preexisting parts.
4. Material Extrusion (heated)
Thermoplastics (such as PLA and ABS) are heated through a nozzle and pushed of the extruder to build the part layer by layer over a bed. Support material may require removal and post processing may be necessary to smooth out the surface. It is used to produce durable prototypes and parts.
5. Powder Bed Fusion (heated)
Material, such as metal, ceramics, or plastics, are in a powdered form and spread out evenly over a bed. A laser moves and heats up small sections of this powder to fuse the material together. Once a layer is complete, the bed lowers and more powder is spread across the bed. The laser fuses the next layer together and repeats the process until complete. While this method produces stronger parts, special handling of the powdered material is required.
6. Vat Polymerization (UV)
A bed sits in a container of photopolymer resin and an ultraviolet laser is used to solidify a layer of resin on the bed. The bed is adjusted is that resin can cover the solid part and the ultraviolet laser creates another solid layer until the part is complete. This process can create parts with good surface finishes but requires cleaning of any liquid resin remaining on the part.
7. Material Jetting (UV)
A nozzle drops liquid photopolymer resin across a bed to form a layer of the part. An ultraviolet light source then goes over this layer to harden the material. The bed is then lowered and another layer of droplets is placed and cured until the part is complete. Although individual droplets causes this method to be slow, it is accurate and has good surface finishes.
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