**2.1 Design quality**


Quality is defined as the ability of the supplier/producer to meet the specified and measurable requirements of the customers. From this definition of quality,

#### **Table 1.**

*Summary of theoretical design framework.*

*Improving Product Quality through Functional Analysis Approach: Case of Dual Axis Solar… DOI: http://dx.doi.org/10.5772/intechopen.93951*

design quality is then defined as a practice of ensuring that products developed in a process of design meet the expectation of customer (without imposing any harm to the social and natural environment of society). It is important to control and monitor quality of products in order to minimise cost, resource, time and relative environmental impact of product development.

A five-level hierarchy of design quality was proposed by reference [6]. The attributes outlined in the reference are namely; functionality, reliability, usability, maintainability, and creativity. Functionality of products is considered paramount in controlling, managing, and ensuring that high quality designs are achieved [6].

Simplicity and complexity are also concepts used to define quality of design products. Simplicity is the exact converse of complexity. Simplicity of an artefact is defined as the use of the lowest possible number of lines, shapes, components, etc. without compromising its functional requirements.

#### *2.1.1 Functional analysis*

**2. Design process model**

**Figure 1.** *Product lifecycle [1].*

**2.1 Design quality**

**Design stage (descriptive)**

function deployment, and many others [5].

**Sub-stages (prescriptive)**

Setting design objectives

Setting technical specification

Generating design alternatives

validation of product

Product improvement

*Summary of theoretical design framework.*

Evaluation Testing and

**Table 1.**

**94**

Planning Deriving customer's needs

There are many design models. For instance, French's descriptive model has four stages, namely; a) analysis of problem, b) conceptual design, c) embodiment of schemes, and d) detailing [2]. Cross' model is four staged too. The four stages are; a) Exploration, b) generation, c) evaluation and d) communication [3]. So is Ullman's model consisting of; a) product planning, b) conceptual design, c) product development and d) product support [4]. The stages of all the three models above are nearly similar and apply the general framework given in **Table 1**. Other models comprise of Axiomatic design, the VDI model, quality loss function, and quality-

*Quality Control - Intelligent Manufacturing, Robust Design and Charts*

Quality is defined as the ability of the supplier/producer to meet the specified and measurable requirements of the customers. From this definition of quality,

**Relative techniques**

etc.

etc.

etc.

maps, etc. Generation Functional analysis Function-means tree, Becoming-the-flow, Converter-

matrix etc.

analogy, 6-3-5, etc.

miniaturised models etc.

Documentation Detailed design Technical drawings, designs portfolios, procurement plans etc.

Design documenting Design database, patents, product manuals, design report etc.

Questionnaires, usability lab studies, ethnographic field studies,

Checklists, objective and key results (OKR), Specific, measurable, actionable, realistic and time-based (SMART) framework, mind

Operator-Transmitter-Control model (COTC) Bond graph model,

Quality function deployment, design for assembly, design for manufacture, theory for inventive problem solving (TRIZ)

Morphological analysis, brainstorming, biomimetic, design by

Value engineering, Failure mode effect, Fault tree analysis, design

Simulations, mockup, prototyping, mathematical models,

for environment, design review, Strength, weakness, opportunities and threads (SWOT) analysis, Pros-cons analysis

Functional analysis transforms customer's requirements into functional means (physical components). In the approach, the designer surveys the prospective customer's market to develop a product that is suitable for their need. Often, simpler and competitive products than existing ones are realised by this approach [7].

#### *2.1.2 Design complexity*

Design complexity is a field in design engineering which focuses on analysing and managing uncertainties of designs (i.e. process and product) due to many interwoven elements and attributes which make an object difficult to understand. Managing complexity in design is important as it reduces effort and resources used when developing products. Design complexity metrics measure a number of design aspects such as; structural complexity: (i.e. physical arrangement and interactions of constituting components), functional complexity: (i.e. number, variety, and interactions of basic and support functions), behavioural complexity: (i.e. predictability and understand-ability of product's behavioural in the field) [8].

Three complexity metrices exist. Bashir and Thompson (1999) developed a design complexity metric system that uses a functional analysis approach [9]. The devices are broken down from basic to advanced functions. This approach considers a linear relationship of functions at each level, but the number of assemblies and components in a device are neglected. Roy et al. (2010)'s complexity metric method was formulated to address the demand of the device with regard to the commonality of components used to construct the device [10]. Whereby product commonality is the number of parts being used for more than one product and is measured for all product family. Keating (2000) developed a complexity metric system which is based on the number of components and their interaction in a device [11]. **Table 2** gives a summary of the metrics and reasons for disregarding some and choosing one.
