ES305: Virtual Tools in Engineering Design:

The Eng. Design Process

James Carroll,Associate Professor

Electrical and Computer Engineering

Total Design

• Total Design is a systematic process– from Identification of market/user need– to selling of a product that meets the need

• The process is also referred to as the Product Delivery Process or Product Development Process (PDP)

• The process is centered on the Design Core– a set of activities central to all PDP

The Design Core

• Consists of:– a market (user need) – the starting point– product design specification (PDS)– conceptual design– detailed design– manufacturing– sales – the ending point

The Design Core• An iterative process with information

flowing in all directions

• Inputs include techniques for– analysis, synthesis, decision making,

modeling, etc.– some are discipline or

technology dependent, e.g.,

strength of materials,

some are not

The Design Core• Current trends in current design practices

– Life-cycle design: concept to final disposal– Design for manufacture and assembly– Design for quality– Faster design cycles (concurrent engineering)– Engineering without walls, e.g., virtual

corporations– Design for export using global standards, e.g.,

the EU RoHS Directive (calls for "the restriction of the use of certain hazardous substances in electrical and electronic equipment“)

Product Design Specification

• A statement of need that overviews the product to be designed– often called a brief– places boundaries on the subsequent design

activities which are carried out within the envelope of the PDS

Product Design Specification

• Elements of a PDS often address– desired performance & service life; operating

environment & maintenance; target cost; competition; size, weight & shipping; manufacturing & quantity; materials; aesthetics, appearance & finish; ergonomics; quality and reliability; shelf life & storage; testing & safety; market, legal, social and political constraints; installation; documentation; disposal, etc.

Product Design Specification

Conceptual Design (Synthesis)• Involves the generation of solutions to meet

the stated needs of the PDS (or partial PDS) and the evaluation of these solutions to select the optimum candidate

• Can be applied at the complete system, subsystem or component level of the design process

• Three primary components, referred to as controlled convergence– Concept generation (individuals)– Development of evaluation criteria (groups)– Evaluation/selection of concepts (groups)

Conceptual Design (Synthesis)• Common techniques used to generate

ideas in the context of controlled convergence– analogy– brainstorming/sketch-storming– attribute listing– checklists– inversion– combination

Conceptual Design (Synthesis)• Most techniques used to evaluate concepts

involve:1. Selecting criteria2. Assigning weighting factors3. Developing a rating scale4. Constructing a decision making structure5. Determining the best design alternative

• Common evaluation techniques include weighted objectives trees and evaluation matrices, morphological charts, and black boxes

Conceptual Design (Synthesis)• The outcome of this phase of the

design process should be– a complete concept engineered to an

acceptable level to establish its validity

– e.g., set of part layouts or schematic drawings using CAD/CAE tools: a focus of this course!

– e.g., hand or CAE-based calculations that estimate the system performance, etc.

Detailed (Technical) Design• In this stage of the process, the individual

subsystems and components are designed in detail

– this level of design relies heavily on the technical/engineering disciplines

• It is often helpful to come up with individual component design specifications (CDS)

– similar to a PDS w.r.t. elements addressed – includes issues such as component interfacing

and a component’s effect of the whole part, etc.

Detailed (Technical) Design• General pointers

– never carry out detailed design without reference to a specific concept or vice versa

– interactions between different subsystems must be considered within the overall constraints of those subsystems

– keep in mind that the very act of defining a component places constraints on the overall system

– keep in mind load lines, cost, size, simplicity, standardization of parts, ways of manufacturing, etc.

Manufacturing• The design of a product together with its

manufacturing process is called concurrent engineering

• The aims of design for manufacture (DFM)– minimize component and assembly cost– minimize development cycle time– produce higher-quality products

• Ideally the detailed design of the product is performed simultaneously with the manufacturing process

Sales (Marketing)• Two primary aspects

– Establishing the nature and characteristics of the product to be made by means of market research

– Marketing the final product, e.g., distribution, service, etc.

• Example questions for potential customers– desired product performance?– desired product cost?– time-scale: when do you want a product with

this performance? Will less faster be better?

Related Topics• Design management, e.g., design reviews• The computer/internet as a tool to drive total

design, e.g., CAD/CAE and visualization tools, web-based tools, etc.

• Quality Function Deployment (QFD)– developed to better assess customer

needs and drive the total design process• Functional cost analysis• Failure mode and effect analysis• Fault tree analysis

References

• S. Pugh, “Total Design,” Addison Wesley, 1991