ADDITIVE MANUFACTURING WHERE DOES 3D PRINTING FIT INTO THE PLASTICS MANUFACTURING MIX?
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 on
reground plastics, especially for precision
parts. The reason being that 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.
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.
Of course, making parts closer to home,
rather than relying on imports, makes good
business sense, especially during times of
geopolitical tension. Many domestic
manufacturers have pulled forward their
reshoring plans and have 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 have
been triggers to
reassess operations
and productivity
bottlenecks.
Obviously, the import
of raw materials
needs to be factored in.
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 and to the same quality
into the millions. Decorative features can
also be included via in-mould labelling. Of
course, 3D printing can deliver repeatability,
albeit in smaller quantities.
Quality – 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.
In plastic injection moulding, the finish
and surface texture can be created by the
mould tools itself. That said, additional postproduction
operations, such as degating,
removing excess material if the resin bleeds
out, and potentially stamping and decorating,
may also be required. Most of this process
can be automated within the moulding cell,
however.
Traceability – This is a key concern for 3D
printed-parts, 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.
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, where each moulded part can be
issued with a Unique Device Identifier (UDI),
with all processing data held securely by a
manufacturing executive system (MES).
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. ■
Mould tools can create
special surface textures and
blend materials and colours
for numerous consumer
products
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