Design Specification sets out in detail the requirements to be met in
order to achieve a successful product."
That is it
in a nut-shell. Writing one that contains all the facts relating to the
product, which takes into account the manufacturer and the user, is more
complex. You should try to avoid "leading" the design and predicting
the outcome even if, at this stage, the end product is crystal clear in
your mind. In fact you are at a disadvantage if this is the case as it
will hamper your scope for initial ideas. Equally your specification should
contain realistic constraints based on things like the law, the facilities
available, time etc.
A good specification, one that you refer to throughout the whole design
process, is key to a successful outcome. It is the main control for the
whole of your design activity but that doesn't mean it can't be changed.
It should be seen as something that may have to evolve if the situation
changes. Your starting point must be research; analysing what is being
done at the moment or what has been tried in the past, looking at statutory
legal requirements, conducting market research through interviews or questionnaires
with the intended user.
are categories, with descriptions, for you to use to draw up your own
specification. They are in no particular order but it seems only right
that we begin with performance or function.
What do you want the object to do? How well do you want it to do it? How
often? How fast? Is the performance attainable in an economic manner?
Try to specify a level that is obtainable rather than the ultimate.
Consider all aspects of the product's environment (we're talking about
"surroundings" environment not "pollution" environment).
ie. temperature range, humidity, shock loading, dust, corrosion from fluids,
chemicals, noise, vibration, users.
Are you expecting the product to perform its task 24 hours a day, 52 week
a year for five years or once in a lifetime?
Is regular maintenance available or desirable? Will maintenance-free operation
prove too expensive to incorporate in the first place? If maintenance
is required occasionally will the user be able to gain access to the part
and will they need special tools and equipment?
Target costs should be established from the outset and checked against
existing or similar products. As one-off manufacturers your costs are
going to be very different to everyday manufacturers but that doesn't
mean that you're unable to see how costs in real-life might be reduced
by using different materials or processes.
A thorough analysis must be carried out of products that are in direct
and similar competitive markets. There is little to be gained from making
something which you can easily buy. If your specification shows serious
mismatches or deficiencies when compared with what already exists, it
might be wise to reconsider.
Clearly the scale of production has a massive influence upon the manufacturing
processes used. You are all making one-offs but you need to consider how
your idea might be adapted for mass-production.
Obvious really, but there are likely to be size constraints for your projects
which must be adhered to.
As above. Particularly important for anything portable.
Whatever the product, the customer sees it first, the performance comes
later. Aesthetics are difficult to specify in a meaningful way at this
stage. You want it to look good, of course, who doesn't? It might be important
that it stands out or is visually striking or perhaps discrete, so try
to specify colour(s), shape, form, texture of finish.
The choice of materials should be influenced by the design rather than
the other way round. It may be the case that certain properties particular
to certain materials are desirable. Conversely there may be strong reasons
for not using a material ie. toxicity.
Does the product need to meet British/International standards? If so copies
must be obtained from BSI or ISO to see what needs to be done in order
to meet them.
All products have, to some extent, a man/machine interface. It is therefore
important to take into account ergonomic considerations. What height,
reach, forces, postures, lighting levels should be considered?
It is essential to obtain first-hand information on client likes/dislikes,
preferences and prejudices. Their input will vary depending upon whether
there are already like products on the market or whether the product is
breaking new ground.
Both of these are difficult to obtain objective information for prior
to manufacture although statistical data for some components, particularly
electronic, is available. You can certainly draw attention to those aspects
of your project for which quality and reliability are important. A project
is only ever as reliable as its weakest component.
It is important to come up with some criteria that you will use to measure
the performance of the product. How can you judge whether your project
has met the quality and durability criteria that you have laid down?
Much of this links in with standards and regulations, but you should additionally
consider things like operating instructions and warning labels. You ought
to consider what the implications are if your product is misused either
inadvertently or deliberately.
just about all aspects of the specification that you will need to worry
about. Each point can be considered from the point of view of the user
and the manufacturer (you or a main-stream manufacturer if this is a prototype
which is worthy of mass production).
You should present the specification as a predominantly written document
but use illustrations and diagrams where appropriate.