Levels of Design Problems - From Application to Contradiction

I learnt that as Design engineers we broadly face three types of problems

1. Developing a new concept or design
2. Improving or refining or optimizing an existing design
3. Resolving issues in existing design.

Each of these engineering problems are solved by applying knowledge learnt earlier or by applying known principles of physics/ logic or by experimentation.

Problems solved by:

• Applying Engineering analysis
• Applying Known design principles
• Applying Best Practices
• Applying Manufacturing Limits
• Applying Material limits.

This, I inferred is Level 1 problem solving which is applying what is already known to new problems to derive solutions or applying analytical techniques to solve problems. While this approach solved 90 % of the problems there were a minority which required a higher-level thinking approach.

I observed that in such problems improving parameter of design degraded another parameter of design leading to a contradiction.  I understood that just application alone cannot solve these contradiction problems, it required a more holistic approach.

An example:

Level 1 : Application: Performing Stress calculations on a structure to improve load bearing

Level 2 : Solve Contradiction: Developing a mounting system which is very compact but can take high loads

While the first problem statement is straightforward and narrow focussed the second one is more holistic and requires a trade-off.

Another example:

Level 1 : Application: Analysing motion, velocity of a mechanism to optimize

Level 2: Solve Contradiction : Developing a battery pack that needs high energy density (for range) but low weight (for efficiency)

We as Design engineers regularly face situations in which improving one aspect of a design/system would degrade another performance metric of the system.

• Improving design for Durability increased its weight.
• Adding features to a design made it more complex increasing cost
• Adding weight would increase the system inertia  in turn affecting performance

Such Design problems are always about solving contradictions and making tradeoffs. Seldom would we be able to meet all requirements.

Here are some common contradictions which result in Tradeoffs.

• Cost vs Performance : Improve performance but don’t increase cost
• The Light weighting Paradox : removing material to save weight often reduces structural rigidity or safety margins.
• Function vs. Form : An engineer wants a large heat sink to ensure the processor doesn't melt; the designer wants a slim, seamless chassis that fits in a pocket.
• Sustainability vs. Durability  : We want products to last forever (to reduce waste), but we also want them to be biodegradable or easily recyclable.

Case study: Improving the Crash Safety of a Car :

Engineering parameter to improve:

• Engineers work on Increasing strength and load absorbing ability

Engineering parameter which degrades

• Due to addition of material the Vehicle becomes heavier in weight , but light weight design is required for better performance in dynamics, efficiency.

The solution when solving the contradiction :

Instead of making the entire car uniformly strong and rigid (which adds massive weight and transfers shock to the passengers), engineers invented crumple zones.