Learning Objectives
By the end of this section, students will be able to:
- Define seven standard AM processes.
- Describe the similarities and differences between the seven processes.
Additive manufacturing has matured into a diverse set of technologies all of which share an adding, or layer by layer, approach. While AM can be segmented into seven broad categories, innovation is occurring so rapidly that hybrids and combinations of AM processes are frequently being brought to market.
Any AM process can be described with just three questions: How is the layer created? How is the energy applied? How is the material applied? If you can describe the process with this simplified view of AM, you can easily move to the next layer of detail.
With the simplified view in mind, the seven broad methods employed in AM are:
Binder Jetting – A manufacturing process in which a liquid bonding agent is selectively deposited to join powder materials.
Layer – The layer is made by spreading powder across a bed and stepwise lowering the bed defined by the slice thickness.
Energy – Two forms of energy are used: print ejectant which is deployed through a print head and contains a polymer adhesive to bind the particles together. Thermal energy is used to cure the adhesive in subsequent steps. In metals, a sintering or infiltration step is required.
Material – The materials used must be in powder form but may be metal, ceramic or polymer.
Directed Energy Deposition – A family of processes in which focused energy is used to fuse materials as they are being deposited.
Layer – The layer is made by depositing one or more beads onto a substrate, which could be an existing part, with new deposits building either beside or on top of the previous beads.
Energy – Two forms of energy are used: Thermal energy is used to melt the material in a fusion DED process akin to traditional welding. In a solid state DED process, kinetic energy accelerates powder particles to a high velocity splatting them into the previous layer, creating a solid state metallurgical bond.
Material – The materials used may be in powder or wire form and are predominantly metal.
Material Extrusion – A process in which material is heated and delivered precisely through a nozzle or an orifice.
Layer – The layer is made by layering new deposits over the previous.
Energy – Two forms of energy can be used: Heat is applied to cause the material to flow through the nozzle. This is true for all materials. For metals, a sintering step is required for bound particles but not for friction-based processes.
Material – The materials used can be polymer and/or metal where the polymer is a filament and the metal is a particulate bound in the filament. The metal may also be a wire or particulate in the friction-based version.
Material Jetting – A process that selectively deposits droplets of build material through a print head.
Layer – The layer is made by selectively and precisely depositing the material in a desired location in an X-Y manner and then stepping is defined by the slice thickness.
Energy – Two forms of energy are used. Print ejectant is deployed through a print head and contains a fluid to deliver the target material. Thermal energy is used to cure the deposit. In metals, a sintering step is also required.
Material – The materials used can be polymer, metal or ceramic in solution with a liquid delivery agent.
Powder Bed Fusion – A process in which thermal energy selectively fuses regions of a bed or build area made of powder particles.
Layer – The layer is made by spreading powder across a bed and stepwise lowering the bed as defined by the slice thickness.
Energy – A beam of energy is used to fuse the particles together which could be a laser or an electron beam.
Material – The materials used must be in powder form but may be metal, ceramic or polymer.
Sheet lamination - An additive manufacturing process in which sheets of material are bonded to form an object
Layer – The layer is created by joining sheets of a material.
Energy – Flexible: ranges from a bonding agent to welding techniques like ultrasonics.
Material – Sheets of polymer, metal, paper & fibers
Vat Photopolymerization - An additive manufacturing process in which liquid photopolymer in a vat is selectively cured by light-activated polymerization
Layer – The layer is created where the energy intersects the material to create the shape in a step wise fashion.
Energy – Focused energy in the form of a laser or focused light.
Material – Polymers, composites, and metals in photo curable polymers