MOW 323
Simulation-based design
Mechanical Design Process
Introduction
Stephan Schmidt
1
Problem:
A low-cost product needs to be
developed that makes it easy to
drill holes in materials. The
product is intended for household
use (e.g., DIY projects). The
product needs to use standard
drill bits. The product specifically
needs to make it easier to drill
straight holes.
How would you solve this
problem?
2
How would you solve this problem?
3
Mechanical Design Process
• Class discussion: What is the mechanical design
process?
Question: What was the record speed for a vehicle in
1899 and how was the vehicle powered? Answer
given later in the class.
4
Mechanical Design Process
• Literature – There are some variations
• Shigley’s Mechanical Engineering Design (Chapter 1: See
Figure 1-1)
• Ullman (Mechanical Design Process: See Figure 4.5)
• Ulrich and Eppinger (Product design and development: See
Figure 2-2)
• Wilke (A Personal Perspective on the Engineering Design
Process and Design Qualification – See
https://medium.com/@wilkedn/a-personal-perspective-on-
the-engineering-design-process-and-design-qualification-
d6352a5cca55 )
• …
Resources were selected that are either freely available
on the web or in the library
5
Mechanical Design Process:
Resources
• Shigley’s Mechanical Engineering Design
https://UnivofPretoria.on.worldcat.org/oclc/1226062640
• Ullman: Mechanical Design Process
https://www.davidullman.com/mechanical-design-process-
6ed
https://UnivofPretoria.on.worldcat.org/oclc/1018479235
• Ulrich and Eppinger: Product design and product
development
https://UnivofPretoria.on.worldcat.org/oclc/770864718
• Wilke: A personal perspective on the engineering design
process and design qualification
https://medium.com/@wilkedn/a-personal-perspective-
on-the-engineering-design-process-and-design-
qualification-d6352a5cca55
• Norton: Design of Machinery: An Introduction to the
Synthesis and Analysis of Mechanisms and Machines.
https://UnivofPretoria.on.worldcat.org/oclc/682145222
6
Mechanical Design Process
How do different resources see the design process?
Class discussion using examples
7
Shigley’s
https://UnivofPretoria.on.worldcat.org/oclc/1226062640
• Read through Shigley’s “Phases and
Interactions of the Design Process”
in Chapter 1.
• Specifications are obtained during
the problem definition process.
• Synthesis of the design is
conceptual design
• Analysis and optimization are
performed using appropriate
models
• Evaluation checks whether the
design meets the specifications.
This is usually tested in an
experiment according to Shigley’s
• Note iterative nature of design is
highlighted here.
• Iterative nature of the design vs.
Design reporting (See discussion
later)
8
Wilke
https://medium.com/@wilkedn/a-personal-perspective-on-the-engineering-design-process-
and-design-qualification-d6352a5cca55
11
Norton
Robert L. Norton. 2008. Design of Machinery: An Introduction to the Synthesis and Analysis of Mechanisms
and Machines. McGraw-Hill
https://UnivofPretoria.on.worldcat.org/oclc/682145222
• Identification of need
• Background research
• Goal statement
• Performance specifications
• Ideation and invention
• Analysis
• Selection
• Detailed design
• Prototyping and testing
• Production
12
Systems Engineering Process
Systems engineering book: https://apps.dtic.mil/sti/pdfs/ADA387507.pdf
13
Mechanical Design Process
• What is the need or what is the problem? (opportunity
identification)
• Requirements -> Specifications -> Concepts -> Detail ->
Manufacturing -> Product.
• Constraints (time, resources, financial, …)
• Impact of the design (social, environmental, legal,
health, safety)
• After detail design, we need to evaluate or verify: Does
the design meet the requirements?
• We need to think about the life cycle functions of the
design: Cradle-to-grave
14
What are the life cycle functions?
Cradle-to-grave or Development-to-Disposal
Systems Engineering Fundamentals
https://apps.dtic.mil/sti/pdfs/ADA387507.pdf
https://commons.wikimedia.org/wiki/File:Turbine_Blades_Head_to_Mu
irhall_Wind_Farm.jpg
Rudolf Ammann from Tsu-shi, Japan
15
We must consider the impact of the
design during the design process
During each phase of the design process, we must consider the potential
impact of the design during its life cycle:
• Social impact
• Health and Safety impact
• Legal impact
• Environmental impact
It is not an afterthought!
Think about the full life-cycle of the product when evaluating these
aspects.
Products can have significant positive and significant negative impacts
MIA 320
16
Impact of the design: ECSA perspective
Copied from “Subject: Competency Standard for Registration as a Professional: Engineer”
Document No.: R-02-PE
https://www.ecsa.co.za/register/Professional%20Engineers/R-02-PE.pdf
(Accessed 2023-07-23)
5. GROUP C OUTCOMES: IMPACTS OF ENGINEERING ACTIVITY
Outcome 6: “Recognise and address the reasonably foreseeable social, cultural
and environmental effects of complex engineering activities.”
Outcome 7: “Meet all legal and regulatory requirements and protect the health
and safety of persons in the course of his/her complex engineering activities”
“Range statement for outcomes 6 and 7
Impacts and regulatory requirements include
- Direct, indirect, immediate and long-term effects of engineering solutions
- Due regard for the principles of sustainability
- Regulatory requirements that are explicit for the context and are generally
applicable
- Recognition that protection of society is the highest priority”
These were copied from the ECSA documents to provide context
17
Impact of the design: Examples
Pollution: Automation:
“One study estimates that about 400,000 jobs were lost to
automation in U.S. factories from 1990 to 2007.”
“Robots could replace as many as 2 million more workers in
manufacturing alone by 2025”
https://time.com/5876604/machines-jobs-coronavirus/
(Retrieved: 2023-07-20)
“This review of health/safety intervention case studies
indicates that advanced (programmable) manufacturing
automation, including industrial robots, reduced workplace
musculoskeletal risk factors, and improved process
productivity in most cases.” (Lowe et al., 2023)
Lowe, B.D., Hayden, M., Albers, J. and Naber, S., 2023. Case
studies of robots and automation as health/safety
interventions in small manufacturing enterprises. Human
Factors and Ergonomics in Manufacturing & Service
Industries, 33(1), pp.69-103.
18
Impact of the design
We need to think of the impact of the product across
its entire life cycle.
For example:
• Electric vehicles
• Wind turbines
• Class discussion using examples from headlines
19
Mechanical Design Process
Mechanical design process is
used to solve the problem,
while increasing the positive
impact and reducing negative
impact of the design (and
related ecosystem) on the
- Environment
- Health and safety
- Legal
- Social
22
Opportunity identification/Problem
identification
• Products are driven by needs and
opportunities
• Updates/changes to existing
products
• Technological developments
• Gap in the market
• Project identification
• Project planning
• Resource planning and allocation
23
Opportunity identification/Problem
identification
• Rechargeable batteries: Planté’s Lead-acid battery
(1859) & Faure’s improvement (1881) lead to electric
vehicles that can run on rechargeable batteries in late
1880s
• La Jamais Contente (1899) electric car breaking the
record by going 105.9 km/h.
• Lithium-ion battery development for laptops and
consumer electronics leads to first commercial lithium-
ion batteries in early 1990s.
• Tesla Roadster (2008)
• Highway legal
• Uses lithium-ion battery cells
• More than 300km range
24
Product definition
• We start with an initial problem/need
• Often in the language of the customer/client.
• Technical vs. Non-technical.
• Vague or over-prescriptive.
• Implicit needs.
• Identify and analyse the requirements (Requirements
analysis)
• Unambiguous and complete.
• Transform needs into technical language.
• A successful product shall conform to this.
• Identify and analyse the functions that need to be
performed (Functional analysis)
• Functions that the product should perform to meet the
requirements.
• NOT functional realisations (e.g., electrical motor, switch).
• Identify and define measurable quantities that specifies
how well a successful design needs to perform specific
tasks (Specifications)
• Metrics are measurable with units.
• Range of feasible values for target specifications.
• Target specifications vs. Final specifications.
• Information collection (e.g. surveys, literature review,
searching for existing products, …)
• Iterative process
25
Product definition
Example Problem to illustrate the differences between
requirements, functions and specifications:
• Customer needs: ”I need a device that can accurately
launch a rugby ball to practice catching”
• A requirement: The product can launch a standard
rugby ball in the air to practice catching the ball.
• Some functions: To accept ball, To support ball, To
accept signal to launch ball. To launch ball.
• A specifications: A rugby ball between 350 – 450g can
be launched between 10 – 40m with an accuracy of 1m.
26
Product definition
We now have technical design specifications that quantify
what the product needs to do to address the requirements.
What is the next step?
27
Conceptual design
• Concept generation
• Hand sketches with annotations
• Function to form: Create realisations of functions
• Neat & clear -> Used to communicate the design to team, manager and
client
• Concept should address the functions.
• Concept should be able to meet TDS (and requirements).
• Concept selection criteria
• Linking the criteria to previous steps
• Weighting the criteria
• Establishing a screening and evaluation approach
• Concept screening (pruning, combining and refining)
• Comparison using criteria, but identifying shortcomings, infeasible
concepts, concepts that can be improved, concepts that can be
combined etc.
• Concept evaluation
• Transparent
• Objective comparison using criteria and scores
• Select best concept
• Reflect on the best concept.
• System level vs. Sub-system level concept generation and selection
• If the system becomes too complex, it is best to draw concepts of
subsystems, do selection and combine.
28
Detail design
• Design is context dependent (e.g., design of a bicycle for everyday use or design a bicycle that
will be used in the Tour de France).
• Duty cycle analysis
• Identify essential calculations that need to be performed to ensure that the product will successfully
perform the required tasks:
• Think about the operation of the system over its lifetime (e.g. loading conditions, environmental
conditions)
• Identify load cases that should be used for design & selection of components and subsystems.
• Identify critical cases/limiting cases that need to be considered.
• Design calculations:
• System, subsystem, component analysis
• Model fidelity (“the degree of exactness with which something is copied or reproduced.” Oxford
Languages)
• Failure modes
• Boundary conditions
• Loading conditions
• Safety factors
• …
• Consideration of applicable standards and codes
• We must consider Manufacturing Processes when performing a detail design. These also inform
• Manufacturing drawings
• Assembly drawings
29
Manufacturing, assembly and
beyond
• Manufacturing process
• Milling
• Turning
• Casting
• CNC
• …
• Additive manufacturing
Custom components – Components that need to be manufactured.
Communicated with a manufacturing drawing
Cost: Material, Labour, Equipment
Reflect: Can your component be manufactured?
• Assembly process
• Assembly process of components
• Standard + Custom components
• Permanent (Welding) vs. Temporary (Bolts)
Communicated with an assembly drawing
Reflect: Can the system be assembled?
MGC 110 & MOW 217
30
Simulation-based design
• What is simulation-based design?
• Why would we want to perform simulation-based
design?
• Does simulation-based design remove the need to
perform product testing?
• Is understanding the fundamental theory (e.g., solid
mechanics, thermodynamics) more or less important
when using simulation-based design?
31
What is simulation-based design?
Simulations play an active role in the design process:
- Conceptual design (e.g. comparison between concepts)
- Detail design (e.g. evaluation, improvement,
optimization)
- Design evaluation (e.g. testing)
- Verification and validation of simulations are critical
Verification: Did I implement and solve the intended
model, BC, loads, initial conditions correctly?
Validation: Is the model (BC, loads, constitutive
equations, contact …) correct for the actual system?
32
What is simulation-based design?
What is a simulation?
• “imitation of a situation or process”
(Oxford Languages via Google)
Examples of computer-based simulations:
Diesel Engine Intake Flow (Top figure)
https://www.youtube.com/watch?v=mcJWK0N6i-o
Rear Underride Crash (Middle figure)
https://www.youtube.com/watch?v=Jq9qCcijCAU
Flow simulation – Heat transfer (Bottom figure)
https://www.youtube.com/watch?v=QRi6qaq0IF0
Correlation between test & simulation
https://www.youtube.com/watch?v=YEFVnmFqyJs
2D CFD simulation
https://www.youtube.com/watch?v=r9n6zouU7Tc
Simulations refer to computer-based simulations in this
course.
33
Some simulation software
(https://en.wikipedia.org/wiki/List_of_computer_simulation_softwa
re - Retrieved on 2023-07-20)
It is impossible to teach you all the simulation packages,
however, we can focus on the process
and establish software independent principles to transfer to
new software in this course. 35
Now that we have simulations, is it still
necessary to understand the core theory in
mechanical engineering?
• Yes – it is VERY important to have a good fundamental
understanding of the core theory
• Structural mechanics
• Fluid mechanics
• Heat transfer
• Thermodynamics
• Dynamics
• Vibrations
• …
• For example, how can you interpret/evaluate the stress
field if you do not have an expectation how the stress
field should look like?
• Garbage in-> State-of-the-art software -> Garbage out
36
Design process vs. Design report
High-level process Example of
documentation: • Design process is iterative
• Iteration: Large jumps =
Cost + Delay
• Design report and drawings
are to communicate the
work
• To team
• Iterative design process • To other teams
not caused by mistakes, • To client
but non-linearity of the
problem.
• To suppliers
• Iterations within phases • ….
(Expected) • The design report should
• Iterations between
phases (Potentially very therefore be
expensive) • Logically structured
• Coherent
• Golden thread
37
Next steps
We will discuss the following aspects in more detail
in the next lecture slides:
• Product definition
• Conceptual design
• Detail design
• Manufacturing and design evaluation
38
