Many people equate 3D printing with 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 injection moulding, providing a regrind
mix falls within an acceptable range and the
molecular weight of the polymer hasn’t been
compromised and meets the specifications,
the mix, typically no more than 10% to virgin
polymer, can be run through a machine.
However, moulders still remain cautious using
reground plastics, especially for precision
parts. The reason being even subtle changes
to the original material could affect the
shrinkage, cause flash or change the cosmetic
appearance.
One sustainability area that additive
manufacturing can assist with is extending the
life of products, printing obsolete moulded
parts if they are no longer in production.
Where there are complex geometries and
features, 3D printing can help manufacture
parts that may previously have been
considered impossible.
MYTH THREE: REAL TIME
MANUFACTURING
Printing on demand is one thing. Take for
example a medical situation where surgeons
pop next door to print a heart valve. Although
data is involved in the process, given the time
it takes to print one item, can this really be
defined as real-time manufacturing?
Instead, smart factories with fleets of injection
moulding machines, connected and capturing
data to achieve speed and scale is probably
the most revolutionary example of real time
manufacturing, especially when production
schedules can be automatically adjusted
based on stock levels. UK in-house moulders
are especially adept at managing production
volumes and contract moulders use Kanban
systems to ensure stock levels don’t run dry
and that there are no bottlenecks in the supply
chain.
switched to local moulding providers. The
key driver has been faster turnaround of
components with, Tier 1-4 suppliers eager
to protect their business from volatile trade
policies. This is certainly the case in the UK,
where Brexit, the weak pound, the potential
for increased red tape and disruptions to
supply chains has been the trigger to reassess
operations and productivity bottlenecks.
Obviously the import of raw materials
needs to be factored in. It’s here where both
technologies can benefit from having some
stock in reserve. Not only does it give some
extra business security, it reassures customers
who are reliant on components that their
orders can be fulfilled.
MYTH FOUR: REPEATABILITY
For mass volume production runs,
repeatability is non-negotiable. Today’s
injection moulding machines are designed to
deliver quality parts, consistently, with tight
tolerances and a high cosmetic finish, often in
just a few seconds.
Moulded parts can be created thousands to
millions of times in succession. For component
reliability, such as an automotive part, this
repeatability is critical.
If decorative features are required, In Mould
Labelling, where the polymer fuses with the
label inside the mould, can produce a good,
repeatable finish. In many instances, this
technology is used in combination with stack
moulds to increase output while maintaining
repeatability and quality. As well as packaging,
this technique is widely used when moulding
computer and mobile phone devices, as well
as door panels and trims.
Similarly, the use of digital files means that
3D printing can deliver repeatability, albeit in
smaller quantities.
MYTH FIVE: QUALITY
Of course, being able to produce components
closer to home rather than relying on imports
makes good business sense, especially during
times of geopolitical tension. For short run commodity parts that don’t have
critical dimensions or demanding mechanical-
performance requirements, additive
manufacturing can deliver functional parts.
However, finish remains a key sticking point
right now. Because the parts are printed in
layers, the surface finish can be a bit rough and
ready. Currently, most 3D components need
some post -processing work to smooth the
edges, adding to the overall processing time.
Many domestic manufacturers have pulled
forward their reshoring plans and have In plastic injection moulding, the finish
and surface texture can be created by the
mould tools itself. However, once moulded
the part may need to undergo additional
post production finishes, such as degating,
removing excess material if the resin bleeds
out, and potentially stamping and decorating.
Most of this process can be automated within
the moulding cell.
MYTH SIX: TRACEABILITY
Traceability of 3D printed parts has been a
key concern, particularly for industries like
aerospace and medical. Counterfeiting has
also been raised as a key issue, which can
significantly impact brand value. Additionally,
ensuring protection of intellectual property
(IP) is another challenge.
To address this, software and hardware needs
to be fully connected and the 3D print supply
chain completely transparent. Developments
include printing QR codes and embedding
digital files into the component as it’s printed.
Although in fledgling stages, this can help
with the checking of part authenticity, as well
as maintaining a secure and compliant supply
chain.
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 Identifier
(UDI), with all processing data held securely
by a manufacturing executive system (MES). It
represents a colossal change in how multiple
components are individually issued with a
UDI.
MYTH 7: STRENGTH
Variations in strength and durability will
depend on the materials used. However,
taking PET as an example, a 3D printer will
create a part in layers. Therefore, the 2D
contour might be strong, but the bonding
between the layers will not be comparable to
a solid mass that has been moulded.
The key test of strength is dependent on the
tensile properties. Before embarking on any
moulding or printing project, organisations
need to understand fully how the material
will perform long-term within the application
itself. How it might react to heat. How the
molecular structure will perform. This takes
skill and a good understanding of chemical
engineering.
A TIME AND A PLACE
To summarise, Nigel 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.”
uk.sumitomo-shi-demag.eu/
Issue 42 PECM
121