Page 18 - Electric Drives and Electromechanical Systems

10 Electric Drives and Electromechanical Systems

for close nesting of parts and maximum material usage. In addition, the process does not
generate heat hence it is possible to machine without hardening the material, generating
poisonous fumes, recasting, or distortion.

1.2.3 Additive manufacturing processes
Additive manufacturing is defined as the process of joining material to make objects
from a 3D data model, usually layer upon layer. While the term 3D printing is widely
used, a range of Additive Manufacturing (AM) processes, the most familiar are sum-
marised in Table 1.1 and are formally defined in ISO/ASTM52900-15, Standard
Terminology for Additive Manufacturing e General Principles e Terminology (2015).In
all the processes detailed the underlying concept of the process is similar, a machining
head “prints” a single layer of the object on a pervious layer, after to which the object is
moved away from the machining heads by the thickness of the layer (Ford et al. 2019,
Frazer. 2014) . The printing operation can either be achieved by the addition of material
as found in material jetting or fused filament processing, Fig. 1.5A or the solidification of
a liquid polymer or metal powder by a laser, Fig. 1.5B.
In all cases, the manufacturing process is similar, and consists of three distinct steps.
The additive manufacturing process requires a series of closed 2D contours that are filled
with solidified material as the layers are fused together. To achieve this, a 3D model of
the object to be printed is created. This model can be generated using computer-aided
design (CAD) software or through reverse engineering techniques by for example by
scanning the object. It is widely recognized that the latter approach can have copyright
and other quality control implications (Fadhel et al., 2013). The CAD file is then

Table 1.1 Summary of available 3D printing processes, where the object is built up
from layers of raw material that are fused together.
Process Methodology
Polymerisation An ultraviolet laser is used to cure and harden a liquid photopolymer resin. The object being
printed is formed on the build platform, which is lowered by the thickness of the layer after
each layer is printed.
Material Jetting A polymer (e.g. polypropylene, PMMA, or ABS) is extruded onto a build platform using either
a continuous or Drop on Demand approach
Binder Jetting Uses a powder-based material including metals, polymers or ceramics and a liquid binder.
After the components has been printed it is subjected to additional curing in an oven.
Fused Filament A polymer (e.g. ABS or Nylon) is drawn through a nozzle, heated and extruded on to the
Fabrication build platform.
Powder Bed Fusion A laser or electron beam is used to melt and fuse a powder-based material together. The
processes involve the spreading of the powder material over previous layers prior to it being
fused.
Directed Energy Involves feeding powder or wire into an energy source (usually a laser or electron beam) to
Deposition form a melted or sintered layer on a substrate, widely used as a coating or repair process.