Design for eXcellence
Unit 1: Introduction to DfX
Section 3: Other Design for Xs
Although Design for Manufacture and Design for Assembly are the most widely
used, there are other Design for Xs that designers frequently consider. The
use of these guidelines is the same – gather knowledge by consulting
experts in the field, and use this during the design phases. There are many
guidelines and which of those are appropriate will depend on the product and
its intended use, including its environment and eventual disposal. Presented
below are Design for Environment, Design for Maintainability and Serviceability,
and Design for Low Cost, together with sample guidelines for each.
Design for the Environment
This aspect of product design is becoming increasingly important with the
emergence of the European Union Directive on Waste from Electrical and Electronic
Environmental Management Systems (EMS) have been developed to address the
measurement and continuous improvement of processes in relation to emissions,
energy usage and the minimisation of waste and materials. This aspect of organisational
management is defined in standards documents such as ISO 14001. Certification
to this standard is becoming increasingly important to electronics companies.
There are also a number of software tools that can help analyse a product’s
impact on the environment throughout its life. Named Life Cycle Assessment
(LCA) systems, these tools will generate a score for each product analysed,
so that a company may assess the relative merits of each product and compare
them with previous versions.
When generating DfE guidelines, thought should be given to the processes used
for manufacture, any waste during its use and the final disposal of the product.
Sample guideline list:
- Use processes that minimise waste and energy
- Encourage a culture of process waste reduction
- Design and use processes that employ recyclable or environmentally friendly
waste material or consumables, for example, replacing solvents with water-based
- As much as possible use recyclable materials for a product’s components.
If not recyclable, then use biodegradable materials
- Ensure any materials used in the products manufacture adhere to any local
or global environmental standards
- If recycling is an aim, design the product so that unqualified personnel
can disassemble it.
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Design for Maintainability and Serviceability
Field service and logistics staff should be actively involved in the product
design process so that aspects of service and maintenance are addressed. A
product that is well designed for maintenance can save a great deal of money
in its later life.
In some products (for example, plant equipment essential to a manufacturing
line) maintainability may be one of the highest priorities, but it should be
considered for all products, even if the eventual decision is that a product
should not be repaired but simply scrapped if a failure occurs. Areas for consideration
- The use of quick fastening and unfastening mechanisms
- Highlighting the parts most likely to fail and ensuring that they are
easy to replace
- Using built-in self-test to indicate and isolate failures
- Eliminating the requirement for adjustment and set-up
- Using parts that are easy for service personnel to source
- Using ‘mistake-proof’ fasteners and connectors to avoid errors.
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Design for Procurement
In Design for Procurement, product designers work effectively with suppliers
and sourcing personnel to identify and incorporate technologies or designs
that can be used in multiple products, facilitating the use of standardised
components to achieve economies of scale and assure continuity of supply.
You won’t find too much of help from a web search, so the only way to
obtain Design for Procurement guidelines is to speak to component procurement
and sourcing staff, try to understand the issues they face and the problems
they encounter, and discuss how to prevent these. Some guidelines are:
- Ensure that the expected supply of the components exceeds the life of the
products. Cooperation with suppliers is the key to this information. Trust
may have to be built up between yourself and your suppliers. This may be
less of a problem for larger companies that can impose demands on smaller
suppliers. (See later under Design for Obsolescence)
- Keep records of components with a longer than standard lead-time, for
example, ASICs and other components that cannot be bought off-the-shelf.
This will prevent surprises for sourcing staff and production planners. Informing
sourcing staff of any new suppliers required will allow price negotiations
to take place earlier in the process.
- Work with sourcing staff to ensure that any Approved Supplier/Vendor Lists
are up to date, and that Bills of Materials (especially costed BoMs) are
accurate. For a steady supply, and to prevent or at least delay obsolescence,
try to give multiple sources for all components. Bear in mind, however, that
these must be genuine second sources in terms of form, fit and function.
- Cooperate with manufacturing staff by using the package types preferred
for their process. Then ensure that any components chosen for your design
are readily available in those package types.
- Keep in touch with your organisation’s component stock controllers.
It may be possible to make a slight alteration to your design and use up
unused stock. [For many companies stock control is now left to the vendors.
In these instances, the organisation has agreed a system where the ‘consignment
stock’ remains the property of the vendor until fitted to the board]
- For prototype quantities, think about the issues involved in procuring
just a small quantity of components, especially small components that are
packaged many-off on a reel. This is a very good reason for specifying parts
that are stocked for other items, wherever this is possible.
Finally, bear in mind that assemblers always prefer to start with a ‘clean
kit’, containing all the parts needed to complete a build. It is much
more expensive to add even one missing component at the end of the process,
and there may also be unreliability implications in doing so. ‘For the
want of a shoe . . .’!
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Design for Reliability
Using simulation tools at an early stage in the product design process can
model the performance of each component and module at the extremes of its environmental
and manufacturing specifications. This is something that cannot be done using
prototypes, so it provides a valuable insight into the reliability and repeatability
of a product once it has entered manufacturing.
Areas that should be considered under this topic include:
- Is the product design based on the expected range of operating environments?
- Is the product designed to minimise mechanical and thermal stresses?
- Have components been de-rated for added margin?
- Have proven components and materials been used where possible?
- Has the parts-count and interconnection-count been minimised?
- What tests will need to be performed on prototypes to ensure reliability
(for example, vibration, temperature cycling, drop test)?
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Design for Obsolescence
Rather than reinvent the wheel, we are encouraging you to obtain a superb
article on component obsolescence from the EDN Access website at www.edn.com:
- Go to the Archives and select the year 2002
- Under 4th Quarter click on November 14th 2002
- Choose the article Guarding against component obsolescence by
This gives a comprehensive description of obsolescence in the electronics
industry which you can use as a resource for the following activity.
Design for Obsolescence
For what reasons will a component manufacturer make a product
Traditionally, the military were the most concerned with
obsolescence, due to the extended duty lives of military products
(usually more than a decade). This has changed, and consumer
electronics manufacturers are now just as concerned. What are
the reasons for this?
What options do manufacturers have for replacing obsolete
What steps can an organisation take to prevent obsolescence?
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