less material waste. Yet in rapid
prototyping where the development
cycle could involve printing
multiple versions, waste is still high.
Additionally, because of the mix of
different materials, grinding up and
recycling printed parts that have
been 3D printed can be challenging.
In plastic moulding, providing
a regrind mix that falls within an
acceptable range and the molecular
weight of the polymer, hasn’t
been compromised and meets
speci cations, the mix (typically 10%
regrind to virgin polymer) can be
run through a machine. Nevertheless,
moulders remain cautious of using
reground plastics, especially for
precision parts, arguing that even
subtle changes to the original material
could affect the shrinkage, cause ash
or change the cosmetic appearance.
Additive manufacturing can,
however, assist with extending the
life of products, printing obsolete
moulded parts no longer in
production. It can also manufacture
parts with complex geometries
and features previously considered
impossible.
REAL TIME
MANUFACTURING
Printing an individual part, for
example a surgical heart valve, takes
time so it’s questionable if this can be
de ned as real-time manufacturing.
Instead, smart factories with eets
of injection moulding machines,
connected and capturing data to
achieve speed and scale is probably
the most revolutionary example,
especially when production
schedules can be automatically
adjusted based on stock levels.
“During times of tension and
volatile trade policies, being able to
produce components locally rather
than relying on imports has driven
many manufacturers to pull forward
their reshoring plans and switch
to domestic moulding providers.
The key rationale has been faster
turnaround of components, ensuring
business security and reassuring
customers reliant on component
orders being ful lled,” says Flowers.
REPEATABILITY
For mass volume production runs,
repeatability is non-negotiable.
Today’s injection moulding machines
deliver
quality
parts,
consistently, with
tight tolerances and a high
cosmetic nish, thousands to
millions of times in succession.
QUALITY
For short run commodity parts that
don’t have critical dimensions or
demanding mechanical-performance
requirements, additive manufacturing
can deliver functional parts. However,
because parts are printed in layers,
most 3D components need some post
-processing work to create a smooth
surface nish. This adds to the overall
processing time and therefore cost.
In injection moulding, nish and
surface texture can be created by
mould tools. Once moulded the part
may need to undergo additional post
production nishes, such as degating,
removing excess material if the resin
bleeds out, and potentially stamping
and decorating. However, these
processes are often automated within
the moulding cell.
TRACEABILITY
For industries like aerospace and
medical, traceability of 3D printed
parts has been raised as a key
concern. Counterfeiting and IP
protection is another key issue.
To address this, software
and hardware needs to be fully
connected and the 3D print supply
chain completely transparent.
Developments are in the early
stages but include printing QR codes
and embedding digital les into
components.
Traceability in injection moulding is
more advanced, with most machinery
suppliers providing secure data
capture and documentation. Recently,
Sumitomo (SHI) Demag developed
an In Mould Decorating (IMD) cell,
whereby each moulded part can be
issued with a Unique Device Identi er
(UDI), with all processing data held
securely by a manufacturing executive
system (MES).
STRENGTH
Variations in strength and durability
will depend on materials used. A
3D printer creates a part in layers.
Although the 2D contour might be
strong, Flowers says the bonding
between PET layers will not be
comparable to a solid mass that has
been moulded.
A TIME AND A PLACE
To summarise, Flowers emphasises
that there’s room for both techniques
and technologies: “3D printing is
great for iterating designs and we are
increasingly seeing moulders using
them to test out new concepts and
create tooling prototypes. Rather that
pitching the two against each other,
recognise that they each have distinct
advantages and that the level of
innovation will continue to accelerate
for both.” !
JULY 2019 | WWW.EUREKAMAGAZINE.CO.UK 21
/WWW.EUREKAMAGAZINE.CO.UK