3 D printing is often touted as a rival to
injection moulding. But rather than
competing, for the right application,
they complement each other. While we
cannot knock the level of innovation occurring
in the 3D-printing space, in reality, additive
manufacturing is not the universal panacea
it’s made out to be. Right now, it continues to
perform strongest for prototyping, rather than
mass manufacturing.
Looking to the future, there are exciting
developments in both markets. But the idea
that 3D printers are about to overthrow
traditional manufacturing techniques –
including moulding, forging, casting and even
subtractive CNC manufacturing – is simply
scaremongering. There is space for all these
technologies. The key for any manufacturer is
to make a well-informed decision, based on a
number of criteria. So let’s look at some
myths.
Economies of scale – Cost is obviously a big
factor when considering which technology to
opt for, especially in the production of plastic
parts. For manufacturing components in high
volumes, 3D printing today is currently not
fast or cost-effective enough to produce
precision parts in large quantities. Where 3D
printing is beneficial is for prototyping and for
generating customised parts in low volumes.
Functionality also plays a big part, too.
Just because you can print anything you want,
it doesn’t mean that the design or materials
will perform any better than injection
moulding.
For several years now the medical sector
has successfully used 3D printing to produce
bespoke components. Among them
prosthetics, implants, hip replacements,
Complementary
processes
Nigel Flowers, UK managing director of injection mould machine supplier
Sumitomo (SHI) Demag, considers the rivalries and tensions between
plastic parts produced by moulding and those via additive manufacturing.
He says both have their place, explaining their pros and cons
hearing aids and even dentures. For these
individual parts, injection moulding
would not be a financially viable
option, due to the cost of
creating a mould tool.
Similarly, aerospace
manufacturers are
embracing 3D
printing to upgrade
components and
create replacement
parts for maintenance,
repair and overhaul
Injection
(MRO), which is big
moulded
business. In a report
part with high
issued by Airbus, MRO
quality finish
spend will double to
over US$120bn/year in the next two
decades, which involves upgrading the
existing fleet of passenger aircraft. For those
parts that may have a long lead time,
a complicated supply chain or may no longer
be in production, 3D printing offers a viable
and agile alternative to the aerospace sector.
When designing a prototype using
injection moulding, the process can again be
quite lengthy. Whereas a 3D printer will let
you create the part using the end material,
injection moulders will typically use foam and
adapt the design until it’s approved, and the
tool can be designed and tested. Here, an
industrial 3D printer is often used to scope
out and fine-tune the part, which can then be
used as a blueprint to design the mould tool.
The tipping point for injection moulding will
come relatively quickly, once mass-production
ramps up. Typically, a contract mass moulder
producing electronic casings estimates a ROI
of 10,000 parts.
Environmental footprint – The
sustainability credentials of 3D
printing are often
inconclusive. While some
advocates say printing
locally saves on
transportation costs,
gauging the true
environmental
impact is
inherently more
complex.
Take for example
energy consumption.
While injection moulding
machines, particularly allelectric
systems, continue to cut
energy use – the latest Sumitomo (SHI)
Demag IntElect range for example uses the
same amount of energy as switching on a
household kettle – some 3D-printing
processes used 50-100 times more
electricity than injection moulding machines.
On the other hand, several years ago, a study
by Loughborough academics, dubbed the
Atkins Project, did find that the in-use phase
through lightweighting, particularly for
components used by the aerospace industry,
saved on fuel costs. These savings more
than compensated for the energy used during
production.
As to less material waste, 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.
For injection moulding, providing a regrind
36 February 2020 www.machinery.co.uk @MachineryTweets
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