Design for Product Build

Unit 12: Case studies

This unit is significantly different from others, in that it is intentionally a work-in-progress, the plan being to increase the number of case studies as suitable material becomes available. If you have chosen a suitable topic for Assignment 3, don’t be too surprised if we get in touch with you asking if we can post a bowdlerised version as part of this Unit, drawing out learning points that are different from those in existing case studies.

The unit is also different in that the length of the main unit text is deliberately quite short. It consists some specific case studies preceded by a review of the product design process, aimed to show the context in which we make judgements about a design whilst trying to make a product that can be built at a profit.

Study note

Many of the points made in this Unit will inevitably reflect the ideas that you yourself bring to Assignment 3, so don’t worry too much if you aren’t able to go through this Unit in detail before submitting your assignment. However, when you get to the end of the module, you might like to compare the general learning points that we make with the conclusions that you draw from your own study.

 

Acknowledgement

We are most grateful to those companies who have assisted us by providing detailed information about their products and the thought processes that accompanied their development. Links to their web sites are given on our Module contributors page.

 

Unit contents

Introduction

As well as taking into account the market, the application, the product specification and the planned volume of manufacture, the top-level design of a completed product has three interacting variables to consider:

Decisions that are made about these will affect the choice of technologies, how the equipment is built, how it is repaired or serviced, and how it is eventually disassembled for disposal. In consequence, the performance, installed cost and running costs of the product are determined relatively early in the product development process.

Figure 1: Flowchart of a typical product development process

A typical product development process

Whilst the primary direction of influence is between product design and manufacture, we should not forget that there are opportunities for manufacturing issues to influence design, so that the process flow is perhaps not as one-way as Figure 1 suggests. For example, designs benefit from manufacturing review carried out very early in the process, and preferably considered during the concept generation stage. More about this in our Final comments section.

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The product design process

Designing for product build is a process that is mainly carried out at a product’s inception, but which has implications throughout life, as parts of the process may be repeated both during volume manufacture and to meet service requirements at the end of life.

Figure 2: The product design process

This is a Flash object:
right-click the image to display a menu and then left-click the Zoom In option –
you will be able to steer the mind map with the hand cursor to look at it in detail;
restore the view by right-clicking for the menu and then left-clicking the Show All option

The product life cycle

The product life cycle has a number of stages which merge into each other, and sometimes overlap:

These last two stages may involve a number of iterations, until a satisfactory prototype has been produced.

The product design function is involved in the development/prototyping activity, in setting the scene for successful acceptance testing and volume manufacture, and ensuring that service, maintenance and eventual removal from the field are accomplished.

The length of the product life cycle from concept to end-of-life varies widely, depending on the industry and nature of the product. However, whether the product is a car or a mobile phone, market pressures are forcing the life cycle to contract, with designs needing to be developed very fast, and perhaps made in volume for only a relatively few weeks before the design is superseded by an apparently improved version.

This shortening of the life cycle has implications for the whole design group, in forcing:

Although computer aids are available, the actual work involved in design is if anything greater, with the result that, for example, board layout designs are rarely the work of individuals, but involve professionals working together, sometimes even “hot desking” where designs are worked on round the clock, passing designs and software licences from country to country as the earth turns.

Types of design job

Whilst some jobs are totally new designs, in fact quite a lot of work of any design department involves more fragmented and in some ways less satisfying work:

These last two involve similar challenges in issue control and documentation, but the drivers are different. For this reason, designs produced internally are normally better controlled than those driven by customer needs, where major changes to the requirement may result in what are almost “botches” in order to convert a perfectly designed but non-working product into one that will meet end user needs, albeit at some risk to long term reliability.

Totally new designs, as distinct from incremental improvements, fall into two categories:

Any new design involves some element of risk, but the use of emerging technology needs very careful management control at all stages during the process.

Design tasks in a real product

Designing a real product is generally more complicated and all-embracing than any one member of the product design team bargains for – depending on their speciality, engineers will tend to focus on board layout or equipment practice, and fail to take the broader overall view. To illustrate this, the next exercise uses the example of a personal computer. This is deliberately not a current generation type, to give you the opportunity of reflecting the changes made in current practice. However, there is sufficient detail for you to be able to consider the different aspects of design.

Exercise

Examine the computer product that is described at this link. To make it easier to see the structure of our argument, we have:

You will realise of course that a personal computer, though it has much of the complexity of typical designs for other markets, certain elements are missing from this application. As you consider our deconstruction of the design, make a list of additional elements that the designer would have to consider were the design to be for another type of equipment.

Whilst we don’t claim completeness, we have provided our own comments.

 

Figure 3: A design deconstructed

This is a Flash object:
right-click the image to display a menu and then left-click the Zoom In option –
you will be able to steer the mind map with the hand cursor to look at it in detail;
restore the view by right-clicking for the menu and then left-clicking the Show All option

The nature of the design task

Having looked at this typical product, you will have some flavour of the design task in a real product, embracing enclosure, electronics and interconnections, with more than a passing glance at software development and test design. Many of these tasks are inter-related, and the task of the product design professional is to take a holistic view of the situation – don’t get bogged down in the detail of the trees and forget the wood. Typically the product designer has to make decisions, each of which will have some implication for cost or performance. The process is a series of questions:

Then comes the crunch, verifying that what appears to be the best option that is compatible with the constraints of timescale, costs and technology.

The decision process is characterised by its iterative nature – you go round the loop more than once – and frequently you need to compromise, there being no perfect solution which exceeds everyone’s requirements. In some cases, one even ends up with “least worst”. Of course the decision has to be made now, if not yesterday, responding to the fact that most product design professionals are working in an increasingly pressured environment.

People in the design process

The design task is also characterised by the need to involve other people in the decision-making process. Figure 4 illustrates some of the influences in product design, which come from many sources other than the direct players in marketing, as well as the different disciplines within product design.

Figure 4: People in the product design process

 

This is a Flash object:
right-click the image to display a menu and then left-click the Zoom In option –
you will be able to steer the mind map with the hand cursor to look at it in detail;
restore the view by right-clicking for the menu and then left-clicking the Show All option

Note that the links between product design and electronic design and test are particularly strong, but good two-way communication is also needed to the board fabricators and those carrying out assembly. This can be a challenge, now that fabrication is almost always carried out by independent houses, and assembly is increasingly sub-contracted to specialists.

From the diagram, you will notice a number of implied comments on, perhaps even criticisms of, the way in which information flows to product design within many companies:

There is always good useful information to be had as feedback from the field, whether this is the customer, the serviceman, or the installation engineer. Unfortunately, much feedback is of poor quality and may not even arrive at the person who could influence the outcome. Product design professionals need to build relationships with a wide variety of support personnel.

Aids to the product design process

We have seen how much of the design task is “front-loaded”, that is the early parts are most significant in determining the eventual outcome. For this reason, industry generally organises separate groups who are responsible for the so-called “New Product Introduction” process. Making the right part, at the right time, at the right cost, all within an increasingly competitive environment, is the subject of our topic paper Requirements for an efficient NPI process.

Much of the focus for New Product introDuction is on communication, ensuring that the information flow is both sufficient and timely. But there is also a requirement throughout the process to evaluate the results of each process step, answering questions such as: Are we making the right thing? Can what we have defined be made at an acceptable price? Are we building in cost elements that are not needed? Have we designed the product in the best possible way for manufacture?

Answering questions of this type is mostly a matter of pulling together information from all those involved, demanding only a structured approach to the challenge and the will to reach compromises. However, there are also some useful techniques for design review, as indicated in Figure 5 and considered in our paper Some New Product Introduction tools.

Figure 5: The product development process with some suggested tools for each phase

The product development process with some suggested tools for each phase

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Case studies

Apart from emphasising the need for effective communication between all parties, it is difficult to give generic guidance about what constitutes good practice, since every application is subtly different. Whilst the reasons for many important differences will lie in the market being served and in the customer requirement, another key factor is the culture, history and structure of the company responsible for the design. This is because, inevitably, some features of any design will have resulted from a compromise between competing views; different departments are subject to different influences, have different objectives, and may have more or less ‘clout’ within the organisation. For example:

Marketing will focus on functionality, price, aesthetic appeal and short development time.

Design may be motivated by the technical challenge to employ new solutions, or pressured by lack of time into reusing elements of existing designs.

Manufacturing will be cost-driven, seeking to eliminate design features that they believe will increase cost, reduce first-pass yield, or cause procurement problems.

As this is a complex area, we have chosen to present a number of case studies to illustrate the influences of design on manufacture and other downstream activities, and, conversely, to show how practical manufacturing considerations can influence design.

Each of these case studies illustrates some generic learning points on good practice for Design for eXcellence in the widest sense, and not just from the point of view of manufacturability. Although there is some commonality, the considerations are often different for products intended for volume manufacture and those made in only small quantities. There are also differences in emphasis according to whether the product is purely electronic (in the sense that it is the electronic function that “sells” the product), or whether electronics merely enable the overall function, as in the case of a piece of capital equipment.

Electronics for capital equipment

Our first two examples are taken from suppliers to the electronics assembly industry, but are broadly representative of equipment that is mainly mechanical, where the electronics are used for actuation, control, and safety, as well as feedback on correct operation.

Exercise

The first of these is a reflow oven made by BTU International. Read the short description of the application at this link, and consider the consequences of the design decisions on other members of the BTU team, concentrating on reliability and servicing aspects.

Now read our comments.

 

Exercise

Our second case study concerns a recent enhancement made to the well-established printer range produced by DEK. Read this more extended case study carefully, and generate a list of generic pointers to good practice that can be observed in this application.

Now read our comments.

 

Electronics on a smaller scale

Our next two case studies are physically very much smaller! The first concerns an extreme high-tech application – a state-of-the-art hybrid module that incorporates several different technologies; the second refers more generally to the issues and the decision-making process that lie behind typical portable electronic devices of the type that are fuelling much of the progress of electronics as seen by the man or woman in the street.

Exercise

Read at this link about a challenging hybrid made by Technograph Microsystems. Then, bearing in mind that this is a highly-specialist communications product, reflect on what general learning points might be drawn that are relevant to more mundane applications.

Now read our comments.

 

Exercise

What we would like you to think about now are the requirements that are specific to hand-portable equipment but apply generally to that class of product. What aspects are crucially important, and how might you best tackle a design? Formulate your own ideas before reading our paper.

 

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Final comments

Good design is making the right choices in the first instance, and reviewing the design as it progresses against a wide set of criteria, representing both the requirements of the application (Figure 6) and the interests of the different interested parties.

Figure 6: Just some of the factors that influence the enclosure selection

Just some of the factors that influence the enclosure selection

 

Whilst in many cases the key factor will be either the cost of components or the practicality of the enclosure design, we should not forget the part played by “partitioning”, the dividing of the overall circuit function into discrete elements. In the case of the personal computer we discussed, typically the power supply will be a separately-procured module, the bulk of the processing capability will be provided on a mother-board, and optional functions, such as drivers and memory, added either as plug-in modules or as separate daughter-boards. The partitioning here is driven partly by technology (splitting the heavy-duty components in the power supply from the rest of the system) and partly by the need for modularity, to allow both versatility of initial configuration and upgrading.

In other cases, partitioning might be for ease of testing, for performance improvement, for thermal management reasons, or to allow other technologies to be integrated within the system. So every application will present different challenges, and it is prudent not just to approach each design as a modification of its predecessor. There will be occasions when a fresh look will give fresh opportunities either for product enhancement or cost reduction.

At the same time, we have to remember that new technologies are always becoming available, and these may demand the re-thinking of our product. We strongly urge all engineers involved in product design to examine closely each new product they come across, in order to establish why it has been built in a particular way, and thus be able to evaluate critically the success, or otherwise, of the design approach. It is always interesting to see how things are made, and we would encourage you to look at the Tear Down project archive at the Binghampton Integrated Electronics Engineering Center, for a view of how a number of challenging products have been assembled.

Make regular visits to sites like these part of your continuing professional development. Try hard not just to view the information, but to process it actively and critically, remembering that you should always ask questions like How? Why? What? When? and How much?

Quote

“Curiosity killed the cat” – a favourite expression of Maureen’s. Especially where Lucy was concerned. It may well have done – some cats, under particular circumstances. It does not so often kill human beings; Maureen was quite wrong there. An expedient spirit of enquiry is more likely to be a salvation, to lead to survival and prosperity, let alone a more interesting life. It is the prime indication of mental health, which is why it should never be discouraged, even in cats.

Cleopatra’s Sister by Penelope Lively

 

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