Concept generation and Product specification

Concept generation is a creative process which is not easy but can fun although sometimes it can be frustrating. Other people lack imagination and others have a wild imagination that borders more on the line fantasy than reality, so it is important to have a starting base or model that will lead your creative process. If you tell someone to come up with a different concept of a car, you will most probably get a million different ideas most of which will not be fit for the ideal car you want to build. If instead, you limit the definition and say “concepts for small cars” you then narrow down the options, if you further say “concepts for small city use vehicle with two seats, driving a range of 100 km” then you further narrow down your options. Therefore to get more value from concept generation you need to understand the objective of your product and all the functions it must have. One of the best ways to go about it is to generate concepts for each function or sub-function of the product rather than generating concepts for the product as a whole.

Concept generation using the functional diagram

Using the illustration of the functional diagram of the scooter as an example we can generate the concepts now. While doing concept generation think about cost, manufacturing, and marketing implications. Often you will have to make trade-offs for quality, time and cost. You might decide you want to use aluminum because it is lighter than steel, but then you might discover that welding aluminum is not easy and you might have to use bolts and nuts which increases the complexity of your structure and thereby increases the time it takes to build your product.

  1. The top-level function of our product is: Convenient mode of transportation
    1. 1.1. Sublevel 1: Relatively inexpensive to maintain
      1. 1.1.1. Sublevel 2: Cheap replacement parts

Concept A: Cheap parts that can be found in local hardware stores (bolts, nuts)

Concept B: Parts are cheap, but are sold by us as an aftermarket business

      1. 1.1.2.Sublevel 2: Does not need to be serviced annually

Concept A: Supply the customer with a service kit so they can do it  themselves

Concept B: Make the parts durable to last for more than 5 years

Concept C: Reduce the amount of moving parts

      1. 1.1.3.Sublevel 2: Use durable materials

Concept A: Use aluminum

Concept B: High strength steel

Concept C: Use high-density polyethylene

    1. 1.2.Sublevel 1: Vehicle must be portable
      1. 1.2.1.Sublevel 2: Overall size must be adjustable
      2. 1.2.2.Sublevel 2: It must have a way of being carried by one person
      3. 1.2.3.Sublevel 3: It must have carry handles or hooks
      4. 1.2.4.Sublevel 3: It must be ergonomically possible to carry
      5. 1.2.5.Sublevel 2: It must be lightweight
      6. 1.2.6.Sublevel 2: Must be able to store it in an office
    2. 1.3.Sub level1: Reduce overcome delays caused by traffic
      1. 1.3.1. Sublevel 2: Can be driven between cars
      2. 1.3.2.Sublevel 2: Can be driven off-road and walkways
      3. 1.3.3.Sublevel 2: Must have a navigating tool to show possible roads
    3. 1.4. Sublevel 1: It must be able to power itself to drive
      1. 1.4.1.Sublevel 2: It must be rechargeable

Concept A: It must  use solar power

Concept B: It must use rechargeable batteries

Concept C: It must use solar power and rechargeable batteries

      1. 1.4.2.Sublevel 2: It must be environmentally friendly
      2. 1.4.3.Sublevel 2: Source of power must easily be available

To generate concepts using the functional diagram, you first need to list all the functions that the product must do. Then under those high-level functions, list sub-functions that the product needs to do in order to fulfill the high-level function. For example, (Function level 1)the scooter must be self-powered (meaning the user must not provide energy to move the scooter), the sub level function for this can be a different type of ways the scooter can be self-powered such as (sublevel 2) electricity or fuel. You can think of different ways, for example, there are different forms of electrical power it can be solar or batteries. Once you are at the lowest, you can then start generating concepts. The further down you go for each function, the more defined your product will be and you can generate more ideas.

Notice that this process leads to many different combinations and configurations that can be used to meet the same function of the product. This is different from creating different concepts at the top level, in which you can come up with many vague concepts. For example, if we use the top-level function of the product which is a “Convenient mode of transportation for city use”. This could mean a skateboard, human-powered jet, roller blades, bicycle, a scooter. Then questions would arise, should the scooter use two wheels or three, should it make of steel or aluminum? And most importantly how do you compare all these concepts? This process clearly is long, leads to more questions than answers and imagine in a team setting of 5 to 10 people all generating concepts that are vague and not related to the objectives of the product. Using the functional diagrams helps the designer generate objective concepts, function-based concepts, and comparable concepts.

Comparing different concepts

Once you have generated concepts it is time to evaluate them on the metrics that you care about, the most common metrics are the cost to produce, ease of manufacture, durability, ergonomics, and profitability. Then you need to create a selection matrix which you can use to rank all the concepts based on the metrics on a scale from 1-10. It is possible however that not all the metrics have the same weight, for example, the cost of manufacture may weigh more than ergonomics depending on the kind of product you are producing. A typical selection matrix will look something like this.

Selection criteria


Product concept generation selection matrix

Even though you can create a selection matrix for selection, all your rankings are somewhat biased and guesswork. To truly get the best concept you need to consult experts, get quotes, and do literature study before making the final decision.

Product specifications

Often times customers will use non-engineering terms to describe what they want, for example a user requirement from a customer might state that, “the phone camera must be able to take clear pictures at night” or “ The phone must not break easily when I drop it” these requirements are very vague and it is up to you as the engineer to decide what they mean in engineering terms so you can provide a good solution. The requirement must be converted to some metric that can be measured, for example for the phone not to break easily when dropped it needs to have a certain amount of toughness, and toughness is a mechanical property that can be measured and designed into the product. So the requirement to resist fracture when dropped can be converted to the specification such as the phone must have an impact resistant of 40 J when dropped from a height of 1.5 m. The reason for developing these specifications is to be able to test the product once it is has been manufactured and also to be able to compare it with other products currently available. Below is an example of user requirements that are converted to target specifications.

User requirements

  1. Convenient mode of transportation
  2. It’s not expensive to maintain
  3. Transport must portable
  4. Transport must have tracking installed in it
  5. Must reduce delays caused by traffic
  6. Must be stylish and fashionable
  7. Must be safe to use on the road and on walk ways-Meet safety standards of walkways as specified by government regulation
  8. Must be able to power itself for energy

Product specifications

  1. Convenient mode of transportation-Easy to use compared to cars, fewer requirements to get it to move, less time need to get it to work
  2. It’s not expensive to maintainCost less than $500 dollars a year to maintain
  3. Transport must portableMust have one-meter cubed volume and weigh less than 5kg
  4. Transport must have tracking installed in it-It must have a GPS installed that can be activated remotely away from the device
  5. Must reduce delays caused by trafficMust be small enough to be driven in pathways that ordinary cars will not be able to pass through
  6. Must be stylish and fashionableMust use materials and configuration that are considered attractive and appealing by most users
  7. Must be safe to use on the road and on walk waysMeet safety standards of walkways as specified by government regulation
  8. Must be able to power itself for energyMust have the power that can drive for at least 4 hours at a time before needing recharge or re-fuel
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