ADDITIVE MANUFACTURING | PROTOTYPING
PRIORITISING PRODUCTION In this article Alan Francis examines the pitfalls of
traditional prototype manufacture, and discusses why
a new method, based on prioritising final production
can both speed up time to market and reduce costs.
The importance of accurate
prototype manufacture
cannot be overstated.
The subject of detailed
testing and performance validation,
a prototype part reveals whether
any further design modification
is needed, as well as providing
vital data on the part’s published
performance attributes, warranties
and service intervals. For these
reasons, it needs to be the best part
you ever make.
Unfortunately, production
prototypes are often expensive, and
approaches to their development
have not always kept pace with other
areas of design, engineering and
manufacture.
The accurate manufacture of
prototype parts and assemblies is
vital for almost every engineering
sector. In most instances, the
prototype will be the only component
subjected to every testing and
performance validation procedure,
which ultimately influences key
decisions on design modifications,
published performance attributes,
warranties and service intervals.
At this stage, consistency and
accurate process documentation are
key. In the testing stage, for example,
it’s important for prototypes to remain
as faithful to the original design as
possible. Any deviations – whether
in shape, thickness or material – can
render test results unreliable, or even
invalid.
These results are vital to the
progression of a design, which is
why they need to be as accurate as
possible. If not, individual parts, or
even the whole assemblies, must
be examined, remanufactured and
reconfigured, all of which can lead
to substantial delays and additional
costs. Worse still, if inaccurate data
is carried forward into the next stage
of production, the ramifications can
be severe: from a shortened service
life or a failure to meet warranted
standards, to a catastrophic failure
while in service. For these reasons,
a prototype must be the best and
most accurate part a company ever
produces.
THE PROBLEM WITH
PROTOTYPING
Unfortunately, this field has not always
received the attention it deserves.
This could be for a variety of reasons.
For one, production prototypes are
often expensive, particularly when
you compare it to the cost-per-unit
of the component in its final form.
There has also, arguably, been an
inconsistent approach to prototype
development, which has meant that
it has not kept pace with its design,
engineering and manufacturing
counterparts.
Unlike the mass-production
of finished parts - which involves
detailed operations sheets, photos,
precise written instructions and
guidance on correct handling and
fixing – prototype assembly often
works based on a CAD representation
at best. As a result, quality and
repeatability can suffer. With most
projects working to strict deadlines,
re-engineering a component at a
later stage incurs project delays and
budget overruns
Why, then, has the manufacture
of prototypes been so neglected?
TAHBOE UT AUTHOR
Alan Francis, head
of supply chain
and operations at
Productiv
Traditionally, prototypes have been
prioritised and progressed according
to timeframe. Product development
and project managers tend to focus
on ensuring that all the required
components are available by a
certain date. In the worst cases, only
once the components have arrived
do engineers start worrying about
how, and indeed whether, these
components will fit together.
The number of tolerance and
assembly issues identified at this
stage is higher than many would care
to admit. Fixturing can also cause
problems, because investment in
adequate workholding equipment
16 WWW.EUREKAMAGAZINE.CO.UK | NOVEMBER 2019
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