The Engineering Design Process
Have you ever wondered how engineering projects get done in industry? There are no written rules on how to approach engineering projects, but a generally accepted conceptual design process involves defining customer needs and specifications, brainstorming, narrowing the brainstormed ideas down to a few preliminary designs, selecting a final design through a rigorous decision-making process, and planning the project timeline.
Example Project Timeline (GANTT chart)
Defining customer needs and specifications (commonly referred to as “specs”) helps ensure that the product design heads in the right direction. You do not want to spend valuable resources designing and manufacturing a product that your customer is not looking for, so this step should be thought out carefully. Needs are vague and qualitative, while specs are specific and quantitative. Needs define what a product should do or be, and specs should have ranges of acceptable values. An example of each:
- Need: A bicycle wheel needs to be easily replaced.
- Specification: The time required to replace the bicycle wheel. (Goal: Should be less than 1 minute.)
Needs and specs should be solution-neutral. In other words, you don’t want your needs and specs to lead you to a specific design without considering all the available options.
The brainstorming phase is where creativity and an open mind can go a long way. Team members throw out any and all ideas that they may have for the problem at hand. No idea gets rejected, even if some may seem ridiculous. Sometimes the most ridiculous ideas are actually the best and most practical – you never know. Often, one broad problem encompasses several subproblems that need to be addressed. A tool known as a “morphological chart” can help people visualize solutions to the subproblems at hand. In a morphological chart, each subproblem is listed with pictorial icons that represent possible solutions. These icons can later be associated with design concepts to better visualize how the designs work and what the advantages are.
The selected preliminary design concepts from the large pool of brainstormed design concepts should be rational and have justification for why these designs were chosen over other ones. The selection process for preliminary designs does not need to be rigorous, but some form of justification is still necessary. This step is a good time for a presentation known as a “preliminary design review,” in which the selected preliminary design concepts are described, and feedback is given for them.
Selecting one final design from the preliminary designs should follow a more rigorous path. Building prototypes of the preliminary designs and testing them can show the pros and cons of each design. A tool called a “weighted design matrix” can also help with deciding the final design concept. In a weighted design matrix, design factors and associated weights for the preliminary designs are listed with a score for each design. Total scores for each preliminary design are then calculated, taking into account the weight of each factor and the given scores. This method provides a quantitative comparison between the preliminary designs, which could be more helpful than just qualitative comparison. After the final design has been selected, it can be presented in what is known as a “final design review.”
After the final design concept is selected, the next step is to manufacture and test the product. Project planning tools such as a PERT chart and Gantt chart help with scheduling and avoiding task dependency issues. A PERT chart shows task dependencies (which tasks must be completed before other tasks can be tackled), while a Gantt chart is similar to a timeline showing the planned duration of every task.
As stated at the beginning of this post, this is only one approach to tackling engineering projects. As with many tasks in life, there are many different ways to approach a problem at hand, and each may have its own merits and shortcomings. This particular approach aims at keeping all possible options available to the engineer, while keeping the project focused.
(Project Timeline image from personal collection.)
your blog is good