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.
2.
3.
4.
5.
•
Selecting criteria
Assigning weighting factors
Developing a rating scale
Constructing a decision making structure
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
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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