Team's Steve Augustyn on applying the DfX principles from teh outset of a project.

1. design
The Magazine for Medical Product Design & Manufacturing
Image:Yevgen_Lyashko/iStockphoto.com
Steve Augustyn, Team Consulting Ltd, Ickleton, Cambridge, UK
To effectively manage the entire lifecycle of a medical product, from creation to end-of-life processing, whilst
achieving cost efficiencies, apply DFX principles from the outset.
D
esign for X (DFX)
reduces the opportunity
for error and improves
the quality and cost efficiency
of the final product. DFX is a
catch-all term for establishing
the performance of your design
solution against different
criteria.1 The term can be
used to describe design for
excellence, but whilst this term
is good for adopting a general
mindset, it does little to help
with focussing on the key areas
of design performance. In this
context the X in DFX is an
interchangeable characteristic
that the design performance can
be measured against.1 X has
seemingly countless variants,
including:
00 Design for manufacturing
and assembly (DFMA)
related to managing production costs.
00 Design for production, which matches
the design against production costs
and time-scales while maintaining the
required quality.2
00 Design for aesthetics governing the
visual aspects of the design; design for
ergonomics examining the performance
of the interaction between the user and
the product.
00 Design for maintenance to review how
the product will be maintained across its
functional life.
00 Design for inspection, design for
calibration, design for disassembly,
design for end-of-life processing, design
for strength . . . the list literally goes on
and on.
Objectives and design for
lifecycle
The typical cost of change
curve3 shown in Figure 1
maps the increase in cost to
correct a problem as the design
and implementation cost
progresses. It isn’t possible to
give precise figures, as design
programmes vary dramatically
(fitting steam catapults to your
aircraft carriers late in the
day costs a staggering amount
of money whereas making a
plastic spoon handle slightly
thicker so it doesn’t break is a
lot more manageable). A good
rule of thumb is that at each
stage of a development process,
the cost of correcting an error
increases tenfold. Therefore a
£10 error in the concept stage
(for example, correcting a
point on a specification) costs £10,000 to
correct by the time you’re in production
(spec rewrites, tooling corrections, repeated
tests, product recalls, process validation
reruns and so forth). This financial impact
provides a compelling argument for
applying DFX principles from the outset.
The cumulative approach of DFX can be
identified as design for lifecycle. 1 Figure 2
Design for X, and
Be Prepared for Anything

2. design
(adapted from BS 8887) shows how some
of the different DFX approaches map onto
the life of a product. This issue is too wide
ranging to give definitive answers for any
of the significant areas of impact in the
space of a magazine article, but some of
the references at the foot of this article
should prove useful. If we consider the
three main phases of a product’s life—
creation, use and end-of-life processing—
the implications of DFX become clearer.
Creation and realisation
DFMA is one of the better understood and
applied aspects of DFX. Whilst the origins
of design for manufacture, particularly
from the context of standardised designs,
can be traced back to Eli Whitney4 at the
end of the 18th century, it is Hitachi’s
Assembly Evaluation Method from the
1970s and the work of Peter Dewhurst and
Geoffrey Boothroyd at the University of
Massachusetts that really defined DFMA
with a deep, analytical methodology.
Originally based on a series of charts
and lookup tables, the Boothroyd and
Dewhurst DFMA approach is now
available as a software package that can
be used to analyse designs at any stage
of development to obtain an estimated
cost. This methodology will give you a
predicted cost of different approaches,
allowing the designer to choose the most
cost-effective option. However, this process
is limited by the knowledge built into the
system and it will only report one piece of
the puzzle. More specifically, it will allow
the designer to compare two puzzle pieces
that he is holding.
A component assembly variability risk
analysis review (CAVRA) can provide a
numerical score to compare the relative
assembly risks in different designs.5
Running a detailed analysis on a large
piece of equipment would dramatically
eat into the time and budget available,
but by using the guidelines as a
checklist as the design progresses, a
lot of the benefit can be achieved for a
fraction of the cost. For high-volume
mass-produced parts, spending more
time on the DFMA
process can be
easily justified,
but sometimes a
thorough review
of the design
with experienced
production
engineers can
generate a lot
of value (see the
section titled
Caveats and good
practices).
One equally
crucial piece of the
puzzle is design for
production. This is
distinct from DFMA, as it deals more with
the logistics of manufacturing; in the area
of medical device development, this can
have an even bigger impact. For example,
you run your DFMA analysis to compare
a steel spring against an elastomeric one.
With the number of features required,
the elastomer comes out as the clear
winner so you merrily proceed with the
information neatly tucked away. Now you
hit production planning and you find out
that the minimum order quantity for your
medical-grade elastomer is three metric
tons (enough for five years’ production
at full capacity) and the material is on a
12-week lead time, three weeks after the
product is supposed to be in clinical trial.
Use and implementation
The use and implementation of the
product crosses many boundaries and
expertise including mechanical design,
industrial design and ergonomics. The
effects of mechanical design can be felt
most keenly in areas such as design for
reliability, design for service and design
for wear. For example, when I worked on
the design of photocopiers at Xerox, a lot
of work was done to prevent paper jams
in the machines. Jams are inevitable—you
never know what sort of rubbish someone
will feed into the machine. However,
designing a paper path in the machine that
is easily accessible to the user allows these
failures to be recovered simply and quickly.
By reducing the importance of design for
service you can end up in the nightmare
position known to many car owners,
where replacing something as simple as a
headlight bulb can necessitate a trip to the
car dealership. Whether the decisions that
led to this state of affairs were motivated
by aesthetic or pecuniary concerns, I’ll
leave to the reader to decide.
Determining and measuring the benefits
of industrial design and ergonomics
can be more difficult. Poor design on a
Figure 1: The cost of correcting a problem increases considerably at each stage of the
product development process, as shown by the cost of change curve.
Costofchange
Specify Implement Verification Production
By reducing the
importance of design
for service you can end
up in the nightmare
position known to
many car owners,
where replacing a
headlight bulb can
necessitate a trip to
the car dealership.

3. design
consumer product or a fatal flaw in the
interaction could lead to an unappealing
product or something that is inherently
dangerous. An appealing or easy-to-
use product may compensate for some
lacklustre engineering, but a poorly
conceived product will present a barrier
that no amount of clever engineering will
be able to balance out. What constitutes
good industrial design is beyond the
scope of this article, but good guidance is
available for the definition of interaction
design. Two resources I have found useful
are the Principles of Universal Design6
and ISO/IEC Guide 71.7 Both of these
guides are based on an inclusive design
approach, but the principles hold up
well for all types of product interaction.
Design reviews, state space analysis
and user trials all work well to match
the performance of the product against
identified performance characteristics.
End-of-life processing
Design for end-of-life processing is often
low on a list of objectives for a designer.
Working in the medical device space does
come with its own requirements related to
product safety, and it can be necessary to
consider how to safely disable a single-use
product. With issues of cross-contamination
or dangerous, poorly controlled
reprocessing, finding ways to permanently
disable products after they have been
used once can become very important.
Single-use, auto-disable syringes such as
the BD SoloShot8 show how such features
can be easily engineered into products. It
may be enough to ensure that products
can be incinerated without producing
harmful toxins or optimised to use the
minimum amount of material. Beyond basic
safety issues and avoiding toxic materials
wherever possible, manufacturers and
importers are coming under increasing
pressure to consider the processing of their
products at the end of life.
With rapidly rising demand in developing
countries, the pressure on limited resources
such as rare earth metals is going to
become ever more acute, and recycling
and reprocessing will become ever more
important as European guidelines such
as WEEE and RoHS place responsibility
on the postprocessing and construction
of electronic products to minimise
environmental impact. This is an area
where car companies are leading the way,
with BMW (among others) adopting
thorough end-of-life strategies to recover
and reprocess as much material as possible.9
Design Engineering magazine has an article
that provides a very useful overview to
the whole issue of sustainable product
development and manufacturing.10
Caveats and good practices
It costs time and money to analyse
different designs against the various X
criteria and to implement the resulting
changes. These development costs will
have to be annotated over the entire
production run (or the projected payback
period). Unfortunately, numerous papers
and academic guides to DFX act as if the
engineers’ time costs nothing and that all
activity directly benefits the product.
One of my favourite engineering quotes
is attributed to Henry Ford: “An engineer
can do for a nickel what any damn fool
can do for a dollar.” Whilst this is a
pretty clear rallying call for the benefits
of applying DFX methodologies, it is
important to keep DFX in the context of
the whole development process. The crucial
point is to make these methodologies as
efficient as possible and understand that
the outcome of a review is limited by the
knowledge, experience and prejudices of
the review panel or process.
Going back to the cost of change graph
(Figure 1), applying these principles early
in the design process will reap the largest
rewards. Applying “three yards of DFMA”
once the prototype has been completed and
tested probably will lead to compromise
and frustration if the design is found to be
Design of parts and
manufacturing processes
Piece part
manufacture
Assembly
Design of parts and
manufacturing processes
Disassembly
Piece part
reprocessing
Material recovery or
disposal
Design for disassemblyDesign for service
Design for lifecycle
Design for manufacture
Design for manufacture and assembly Design for inspection Design for end-of-life
processing
Use
Figure 2: How various DFX approaches map onto the life of a product. Diagram adapted from BS 8887.
With rapidly rising demand in developing countries,
the pressure on limited resources such as rare
earth metals is going to become ever more acute,
and recycling and reprocessing will become ever
more important.

4. design
deficient. Getting a good brief and defining
a clear and considered specification to the
product will help ensure that these features
are built into the design from day one.
Delivering a better product
The job of the designer and engineer has
never been more difficult, with so many
competing demands and regulations to
balance in a rapidly evolving market.
However, taking responsibility for
the whole lifecycle of the product
and examining design decisions will
always lead to a better product and a
more considered execution. Catching
errors—or recognising opportunities for
optimisation—early in the design process
will help to produce a stronger product in
the most cost-efficient way possible. Some
excellent tools are available to help with
any of these analyses. They take time and
effort to implement, however, and even
then the results will only be as good as the
questions asked. Remember, it is entirely
possible to make five completely rational
design decisions and end up in some
completely irrational place. By applying
the principles of DFX, it’s possible to get
back to the right place and deliver a better,
more capable product.
References
1. ISO 8887-1:2006 Design for Manufacture,
Assembly, Disassembly and End of Life
Processing (DFMADE).
2. G. Pahl et al. as translated by Ken Wallace
and Lucienne Blessing, “7.5.8 Design for
Production,” in Engineering Design: A
Systematic Approach, Third Edition, Springer
Science and Business Media (2007).
3. M. Tarr, “The DFX Concept” (www.ami.ac.uk/
courses/topics/0248_dfx/index.html).
4. www.eliwhitney.org/new/museum/about-eli-
whitney/inventor.
5. J. D. Booker, M. Raines and K. G. Swift, “2.4
Component Assembly Variability Risks
Analysis” Designing Capable and Reliable
Products, 63-66, Butterworth-Heinemann,
Oxford, UK (2001).
6. The Principles of Universal Design, Version 2.0,
The Centre for Universal Design, Raleigh, NC,
USA (1997).
7. ISO IEC Guide 71 2001: Guidelines for
Standards Developers to Address the Needs of
Older Persons and Persons with Disabilities.
8. www.bd.com/immunization/products/
9. www.bmw.co.uk/bmwuk/about/corp/recycling
10. A. Plant, D. Harrison and B Griffiths, “Raising
the Standard: A review of standards and
legislation in sustainable product design,”
Journal of the Institution of Engineering
Designers, January/February (2011).
Guidelines for Running an Effective DFX Review
00 Gather at least three participants,
including a facilitator and device
expert.
00 Recruit at least one person who has
nothing to do with the project activities
other than to review.
00 Ensure that the reviewers have strong,
and complimentary, manufacturing
experience.
00 Keep the group small.
00 Limit sessions to no more than three
hours.
00 Leave egos outside the room.
00 Have review in hand in time to imple-
ment changes, not two hours before
design freeze.
Steve Augustyn
is Head of Mechanical
Engineering, Team Consulting
Ltd, Abbey Barns, Duxford Road,
Ickleton, Cambridge CB10 1SX, UK
tel. +44 1799 532 700
e-mail: sea@team-consulting.com
www.team-consulting.com
Reprinted with permission from EMDT, January/February 2013. On the web at emdt.co.uk.
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