Engineering design is the discipline of design applied to engineering.There are many kinds of design - graphic design, industrial design, software design, architecture,… - and each is a variation on the theme of design in general. In each design discipline, the basics of design are applied to a particular body of knowledge (in our case, engineering).This application creates differences in how different kinds of design are practised.
The practise of design is the practise of an activity - designing.We will keep these two terms separate: design (the noun) refers to a particular design, or the discipline of design, or the body of knowledge of design; and designing will refer to the activity of doing design. Our main concern here is with designing.
There is no standard, universally accepted definition of engineering design. What follows is Fil Salustri's attempt to combine a variety of definitions into a cogent single definition.
The engineering designing process is one of working with others to solve complex, open-ended, and often ill-structured problems, and to synthesize a specification of the function, form, behaviour, performance, manufacture, operation, maintenance, and disposal of a technological artifact (an element, system, or process), such that the artifact's use promotes a preferred situation addressing identifiable objectives and constraints in a given technological, environmental, health and safety, economic, ergonomic, corporate, societal, political, and cultural context.
Designing is the development of balanced, implementable solutions to poorly specified problems that promote preferred situations over a known time period.
What do you think was poorly designed here?
Designing is any process that leads to a design.
The first time I heard this definition was as uttered by Dr. Terence Love, at a conference. I don't know if he invented this definition, but I think it's very important, because it separates the activity from the outcome.
First we have to define a design. That will change from one discipline to another; the outcome of design in graphic design, for instance is different than that in engineering design. By crisply identifying what constitutes a design, we can distinguish expectations in different disciplines. Also, once we have the definition of what constitutes “a design” in a discipline, we can develop ways to assess which of many possible designs is best, by considering each element of the definition.
Second, given what “a design” is, we can start studying different ways of generating them, and assess which ways are best to create designs that are better than other designs. Note that a good design process doesn't only produce good designs, but is also “better” than other design processes.
Exercise for the Reader:
What constitutes “a design” in engineering? How many elements can you identify of such a definition? How would you measure them (to identify “good” designs)? Can all the elements be measured? Can they all be measured practically?
There are many different definitions of design in the sense of designing. Some of them are:
“Those who do not remember the past are condemned to repeat it.”George Santayana, 1863-1952.
Around the year 1400, Filippo Brunelleschi (1377-1446), the Italian architect and engineer, won a prestigious opportunity to design and build the cupola (dome) of the “new” cathedral for the city of Florence. Brunelleschi knew this was the chance to make a name for himself that would him famous. He was especially worried, however, that his contemporaries would try to steal his ideas, so he devised a way of designing the cathedral that would ensure the exact nature of the structure would remain hidden until it was too late. Of course, once the cathedral was completed, he even hoped it would be copied.
Until that time, however, buildings were not really engineered at all. The craft was then known as artisanship, and basically involved using well-understood principles and trial and error methods of building. This was not good enough for Brunelleschi. In the environment of artisanship, the artisan simply starts building or manufacturing the product. When insurmountable problems are encountered, the entire project is junked and started over again. This contributed to making engineers extremely conservative; innovation was rarely encouraged and often discouraged because of its implied risks.
Brunelleschi began by keeping a journal in which he sketched and described individual ideas for features and components of the cathedral from both architectural and civil engineering perspectives. He kept this one journal carefully locked away from prying eyes. Once he has developed what he believed were a wide enough assortment of different ideas and concepts for the cathedral, he started looking at the ideas with a more critical eye to how the different concepts would work together. Not all of them made sense if used together. Slowly he pieced together an overall concept for the cathedral, which he described in a single master plan, of which there was only one copy, and that he guarded carefully.
Then, Brunelleschi did something new. He knew he would have to “subcontract” the construction of the building materials to other people, but he did not want to show them the master plan – for fear of having his idea copied (and poorly at that) before he could finish the project. So he created a large collection of individual drawings. Each drawing specified only a few components of the cathedral's structure – few enough that anyone getting one or two of the drawings would be unable to intuit the nature of the building as a whole. He then distributed the drawings to the various manufacturers. Though they were curious, Brunelleschi did not tell them what the parts were for. He only wanted them made and delivered to a certain off-site location.
Once he'd received enough of the parts, he and a hand-picked construction crew, each member of which was sworn to secrecy (back when giving one's word was a very serious commitment of honour!), began to build the cathedral dome.
(Brunelleschi also encountered many problems in building the cathedral, in no small part due to the many different parts that had to be carefully assembled for the cathedral's dome. For this, he invented another method that is still in use today – surveying)
Brunelleschi completed the dome, and it was immediately recognized as one of the most impressive structures of its kind. Indeed, it still remains a masterpiece of engineering and architecture.
What does this have to with design?
Brunelleschi had unwittingly invented a design process. First he did some conceptual design, which included the sketches and ideas in his journal. He then examined and evaluated the concepts, blending some together and discarding others altogether, leading to a single overall concept of the cathedral; this is concept evaluation. Brunelleschi then detailed the idea to the level of a master plan – this is detailed design.
Then, Brunelleschi developed all the different parts drawings. In order to do this properly, he needed to keep in mind some sort of assembly process, and make sure that the parts were designed in a way that he could fit them all together on the building's site. This is process planning. The parts were then “outsourced” for manufacture, and assembled on-site.
Because of the immense success of the project, this basic process – conceptual design, concept evaluation, detailed design, process planning, manufacture, and assembly – became the standard way that buildings, and eventually everything else, was engineered. Indeed, one can look at virtually any engineering design textbook up to the 1970's and still find the basic design process described just as Brunelleschi developed it.
After Brunelleschi, design remained largely unchanged for hundreds of years. This was partly due to the spectacular success of the method and partly due to the highly qualitative nature of design. Science and technology began to take hold and lead to a variety of impressive discoveries that allowed all kinds of new products to be developed. No one noticed how poorly designed the products were because they were in whatever form they took far superior to their predecessors.
This unfortunate trend was only reinforced after the second world war. The United States attributed much of their victory to the ability of the American “scientists” to develop technologies that were superior to those of their enemies in that war. That most of those scientists were in fact engineers was a point lost on the politicians of the time. After the war, and flush with their newly-earned respect, engineers decided to focus their energies on teaching and researching in the “scientific”, quantifiable areas of engineering – analysis and manufacturing. They redesigned their university curricula to suit this goal. Canada did likewise. The result was that design was treated as a poor cousin and therefore neglected.
Even so, there were many acknowledged problems with the design process. Indeed, it should be quite obvious that a process that worked 500 years ago cannot possibly be expected to work well in modern times. Brunelleschi worked in a time without electricity, without running water, without mechanical pencils or ballpoint pens. Brunelleschi died when the Earth was still the centre of the universe (Copernicus would be born 25 years later), 200 years before Isaac Newton was even born, let alone discovered calculus and the classical laws of motion, and 400 years before Timoshenko figured out how to calculate the bending of beams (which is pretty important for civil engineers!). Brunelleschi didn't have concrete, reinforced or otherwise; there was no welding equipment, no structural steel; no telephones or telegraphs. Brunelleschi used only stone, wood, and ceramic/terracottas for his work. “Nails” were made of wood. Chemistry had not yet been invented. The world was still flat and would remain so for about 100 years. Germs would not be discovered for 500 years. There was no such thing as mass production.
It should be pretty clear that life was very different in Brunelleschi's day. How could anyone expect a method developed under those circumstances to work well in the “modern” world?
Brunelleschi was the only lead engineer on his project, and he controlled every decision that was made on the project. This means that (a) no allowance was made for so-called teamwork, and (b) there was virtually no documentation about the individual design decisions taken by Brunelleschi or the justifications for them.
The problem is that engineering has changed dramatically since Brunelleschi's time. By the late 1960's, it had become clear that designers were not able to take into account the requirements of mass production, that designers were not able to test the validity of their designs before prototyping, that design teams were usually highly dysfunctional, and that best practises were not being transfered between projects or maintained by corporations when employees left. Without appropriate documentation, errors in design that were not caught until manufacturing or later would require the entire process to be reverified in order to identify when the error occurred. This makes average lead-times extremely long, and usually pushes projects far over-budget.
The very few researchers in North America that worried about such matters began suggesting various modifications to the basic process in order to address those shortcomings, as early as the 1940's. However, the cultural inertia of the past centuries and the perceived successes of science after the second world war made it extremely difficult for their ideas to gain acceptance.
By the 1970's, one idea had emerged from all the theory and research in design that for some reason we shall probably never fully understand was accepted by industry: concurrent engineering. The idea came from the observation that people seemed to have always thought it necessary to associate expertise in a given stage of engineering only with the execution of that stage. So, for example, manufacturing expertise was only needed during manufacturing.
The fact is, however, that there is no reason for this to be so. Once this was realized, the next obvious question to ask was what benefits could be served by making expertise available during other stages of product development. This quickly developed into the notion of a Tiger Team (imported from Japan), a team that included expertise from every stage of the product development process who would coordinate and manage the entire process of developing a particular product. This means for example that during design, manufacturing engineers are available to comment on a design while it is being developed.
Within just a few years, concurrent engineering had turned the product development world – and design – upside down. By putting a team in charge of product development, instead of just one person, documentation was absolutely fundamental to ensure that the team was well coordinated. This same documentation became invaluable to track progress on the design and document decisions as they are made. This meant that errors could be much more quickly tracked by looking through the documentation. Also, having such broad expertise available at every stage of product development – and especially in the design stages, where the most important decisions are made anyways – caused radical improvements to product quality, scheduling, management, and cost. For example, in the 1980's, it was quite common for companies who switched from conventional to concurrent engineering practises to experience improvements of more than 100% in engineering costs, quality, and other key measures of engineering performance.
Since then, of course, there have been literally thousands of new design methods developed and proposed to industry. Most of them do not really work – because most of them have not been properly worked out – but quite a few new methods have been successful and have substantially improved how we engineer products.
And the changes continue. The interest in engineering design worldwide has been increasing over the last 10 years, and many new initiatives are on-going, some of which will further revolutionize engineering design in the years to come.
The basic premise of engineering design is based on four perspectives of objects, each of which builds on the last.The perspectives are structure, behaviour, function, and purpose.We call them perspectives because they are four different ways of looking at the same object.
To understand the four perspectives, we will consider a simple, existent product, and see how the four perspectives are built upon each other.
Consider a simple stapler for home or office use, such as that shown to the left.It is a system. As an object in the universe, it has structure, which we can measure and define to whatever level of accuracy and precision is needed.The stapler has specific dimensions, mass, strength.Its components are connected such that it exhibits certain dynamic aspects too - its parts move in particular ways.
Because of its structure, this stapler will exhibit certain behaviours, which we can also measure.Some of these behaviours include its reactions to externally applied forces (like a human hand pressing down on the handle). These reactions include more than just the pivoting motion of the upper part with respect to the lower part. (Think of what goes on inside the stapler.)
The stapler does not exist in a vacuum, however. It is surrounded by other systems, each of which has its own behaviours; this is the situation of the stapler. These behaviours are channels through which the stapler system interacts with other systems. The stapler's behaviours can combine with behaviours of other systems to provide functions. The stapler can serve the function of a paper-weight, or even a weapon, depending on the nature of the situation in which it exists.
Can you think of situations in which the stapler serve the function of being a paper-weight, or a weapon? How are these different from the more typical situations in which the stapler would be used?
Finally, one of the stapler's functions is essential to it - to bind papers together. If it couldn't perform this function, it wouldn't be a stapler (or at least, it would be a broken stapler). This is the stapler's purpose.
So to summarize:
Exercise for the reader: Enumerate all the purpose, function(s), and behaviours of a light bulb.
When we design, it is the structure that we want but don't yet have. That is, designing is about developing a structure out of essentially nothing.We do, however, know why we are designing a product; that is, we know - or we can develop - the purpose of the product we want to design. So to design, we run through the perspective in the reverse order of that we considered in the previous section. We start with purpose, then proceed through function, to behaviour, and finally to structure. Once we have the structure, we know the shape, material, etc. of the product, and we are ready to actually make it.
This basic process - from purpose to function to behaviour to structure - underlies every reasonable engineering design process, including the one described in this web site.