Manual prototyping by a skilled craftsman has been used for centuries,
but has now been largely supplanted by
Rapid Prototyping (RP) technology, also
known as Additive Manufacturing (AM).
RP produces three-dimensional objects
by a process of layer-by-layer material deposition; the
technique had its origin in the 1980s with the growth
in Computer Aided Design and Manufacturing (CAD/
CAM) technologies. The machines that generate these
prototypes one layer at a time are known as
In recent years, RP technology has expanded far
beyond its original applications to include electronic
circuits, software networks, even human organs. In
addition, the expanding technical capabilities and
declining equipment and material costs mean that RP
can now be used for low-volume production runs.
As a result, market research firm Canalys forecasts
that the 3D printing will be a $16.2 billion market by
2018, up from around $2.5 billion in 2013, representing
a CAGR of 45.7 percent.
The RP Process
The procedure for producing a 3D printable object
begins with a 3D model – a mathematical representation
of the object to be manufactured. A 3D model can be
created with a computer aided design (CAD) package,
by means of a 3D laser scanner, or via a digital camera
and photogrammetry software.
The manual modeling process of preparing geometric
data for 3D computer graphics is similar to plastic arts
such as sculpting. 3D scanning is a process of analyzing
and collecting digital data on the shape and appearance
of a real object. Based on this data, three-dimensional
models of the scanned object can then be produced.
There are many CAD packages available for generating
3D models, ranging from open-source offerings such
as Blender or BRL-CAD to high-end packages such as
Fusion 360, AutoCAD and Solidworks.
Regardless of the software used, the 3D model
(often in .SKP, .DAE, .3DS or another graphics
format) must then be converted to a format such as
.STL (stereolithography) or .OBJ to be readable by the
software which drives the printer.
3D Printing For Electronics
RP technology is no longer confined to purely
mechanical components: multi-material 3D printers
can now build up circuit boards and other electronic
assemblies. The primary applications are flat panel
display backplanes, EMI shielding, RFID tags, PCBs,
electroluminescent lighting, and touch screens.
The materials needed to produce an electronic
assembly are a thermoplastic for the base material
and a conductive ink for the electrical connnections.
Acrylonitrile Butadiene Styrene (ABS) was the
most popular base material for 3D printing several
years ago, but it required higher temperatures than
biodegradable thermoplastics such as Polyactic
Acid (PLA) a biodegradable polyester derived from
renewable resources such as corn starch, tapioca roots,
or sugarcane; other options include nylon and PET
(PolyEthylene Terephthalate), which is widely used to
make plastic bottles.
Given the fact that 90 per cent of plastic waste is
not recovered, one hot trend is the use of recycled
materials for the base material. Thermoplastics can
potentially be obtained from many different places
including milk bottles, plastic cups and even the insides
Printable conductors - for traces, vias and pads
- are made from a variety of exotic materials with
resistivities ranging from 10 to < 10-6 Ω-cm. Options
include conductive polymers, carbon nanotubes,
and silver micro-powder pastes, but metal nano-particle inks are most widely used. The ink contains
nanoparticles (typically silver) of 5 - 6nm in size; the
small particle size significantly reduces the melting
temperature of the silver below the bulk melting
point, allowing for very low processing temperatures
for sintering the nanoparticles into conducting films.
Technology Expands Into
By Paul Pickering, Technical Contributor