Additive Manufacturing Processes
There are number of distinct AM processes with their own standards, which include:
This technique uses a 3d printing style head moving on x, y and z axes to deposit alternating layers of powdered material and a liquid binder as an adhesive.
Directed Energy Deposition
Direct energy deposition additive manufacturing can be used with a wide variety of materials including ceramics, metals and polymers. A laser or an electron beam gun mounted on an arm moves horizontally melting wire, filament feedstock or powder to build up material as a bed moves vertically.
This common AM process uses spooled polymers which are either extruded or drawn through a heated nozzle which is mounted on a movable arm. This builds melted material layer by layer as the nozzle moves horizontally and the bed moves vertically. The layers adhere through temperature control or chemical bonding agents.
Powder Bed Fusion
Powder bed fusion encompasses a variety of AM techniques including direct metal laser melting (DMLM), direct metal laser sintering (DMLS), electron beam melting (EBM), selective laser sintering (SLS) and selective heat sintering (SHS). Electron beams, lasers or thermal print heads are used to melt or partially melt fine layers of material after which excess powder is blasted away.
Sheet lamination can be split into two technologies; laminated object manufacturing (LOM) and ultrasonic additive manufacturing (UAM). Laminated object manufacturing is suited to creating items with visual or aesthetic appeal and uses alternate layers of paper and adhesive. This technique uses ultrasonic welding to join thin metal sheets; a low energy, low temperature process UAM can be used with various metals such as aluminium, stainless steel and titanium.
This process uses a vat of liquid resin photopolymer to create an object layer by layer. Mirrors are used to direct ultraviolet light which cures each resin layer through photopolymerisation.
Additive Manufacturing Technologies
Additive manufacturing technologies can be broadly divided into three types.
The first of which is sintering whereby the material is heated without being liquified to create complex high resolution objects. Direct metal laser sintering uses metal powder whereas selective laser sintering uses a laser on thermoplastic powders so that the particles stick together.
The second AM technology fully melts the materials, this includes direct laser metal sintering which uses a laser to melt layers of metal powder and electron beam melting, which uses electron beams to melt the powders.
The third broad type of technology is stereolithography, which uses a process called photopolymerisation, whereby an ultraviolet laser is fired into a vat of photopolymer resin to create torque-resistant ceramic parts able to endure extreme temperatures.