Unit 8- Design Decisions: How can I make better design decisions?

Unit 8- Design Decisions: How can I make better design decisions?

1. Factor of Safety
The principle of adding new elements into its construction to offset the effects of unknown variables and       prevent system failure.
Factor of safety is also known as factor of ignorance.
This principle is implemented to minimize the probability of failure in a design.
New design produced must has large factor of safety to overcome the large number of unknown variables.

Example:

Factor of safety design principle is implemented in blade utility knife, which the blade can be fixed in a certain length when using it to avoid any accident. The fixation of the blade is the new elements added to the blade utility knife to offset the effect of injuring users.

2. Redundancy
The use of more elements in a system to maintain its performance if one or more elements has failed to perform.
Redundancy is a method to prevent a 'whole' system failure.
There are four kinds of redundancy: diverse, homogenous, active and passive:
(i) Diverse redundancy is the use of multiple elements of different types, which can resist a single cause of failure.
(ii) Homogenous redundancy is the use of multiple elements of single type, which easily influences other failure of elements.
(iii) Active redundancy is the application of redundant elements, which allows for single element failure, repair, substitution, resulting in minimal disruption of system performance.
(iv) Passive redundancy is the application of redundant elements only if the active element fails.

Example:

Redundancy design principle is implemented when one of the brake malfunction, for example handbrake is malfunctioning, leg brake is used to stop the car. The hydrolic brake system and handbrake system is the diverse redundancy, which a car possess two different types of brake system that can resist single cause of failure.

3. Flexibility-Usability Tradeoff
It explains that a system with high flexibility will decrease its usability.
Flexible designs can perform more functions but the functions will be performed less effeciently as flexible designs are more difficult to use.

Example:

This Casio scientific calculator is a flexible design because it perform more functions but those functions are performed less efficiently. The flexibility of the scientific calculator is higher compared to the normal calculator, whereas the usability of the scientific calculator decreases with its numerous types of function.

5. Satisficing
Satisficing is also known as the enemy of good design.
Best design decision is not always the optimal design decision.
A success design, in certain circumstances, is served by design decision that is 'satisfy'.
There are three kinds of problems for which satisficing should be considered:
(i) Complex design problem- Characterized by large number of interacting variables and unknowns. Satisficer recognize that the complexity and unknowns makes an optimal solution unlikely. Satisficer seeks an alternative satisfactory solution.
(ii) Time-limited problem- Characterize by time frames that do not permit adequate analysis of optimal solution. Satisfacer selects the first solution that meets the design requirements satisfactorily.
(iii) Solutions beyond the satisfactory yield diminishing returns- Knowledge of design requirements is needed to know which satisfactory is best. Optimal specifications will not consume design resources unless they are critical to success and accorded value by users.

Example:

The design of a nail cutter is satisfied for user to use although it is not the optimal design decision as it could cause minor damage to the user's nail.

6. Ockham's Razor
It explains that the assets that simplicity is preferred to complexity in design.
Unnecessary weight (physical, visual or cognitive) degrades the performance because it has the potential to create problems.
It emphasizes in cleaner design to produce a purer result.

Example:

The watch on the right shows purer result because its design is cleaner than the watch on the left. Therefore, a good simpler design product is preferred.

7. Form Follows Function
The primary goal of a design is its intended function or purpose.
It can be interpreted into two ways: descriptive and prescriptive.
(i) Descriptive interpretation is based on the belief that form follows function in nature. Functional criteria presents a more clearer criteria for the judgement of quality.
(ii) Prescriptive interpretation is likely derived from descriptive interpretation. Functional considerations should be the primary consideration to aesthetic considerations in a design.

Example:

The form of the pencil case follow its function of storing stationary. The form of the pencil case is designed to store stationary and thus the form is suitable for its function.