ME14 Introduction to Mechanical Engineering Design Schedule Updates Design Artifacts for Group Project Tuesday, April 22 Artifacts: objective tree, function

ME14Introduction to Mechanical Engineering Design

Schedule Updates

Design Artifacts for Group Project • Tuesday, April 22• Artifacts: objective tree, function diagram(s), specs.,

morphology chart• Grading: how extensive/complete are your artifacts?• Breadth of the objectives, functions, specs., designs• Depth of ideas, where appropriate• Evidence of integration across your process.• Quality of presentation in the documents

Group Design Project Demonstrations• Thursday, April 24, in class


Grading Updates

You can retrieve your posters from the shop.

Three teams did not have team member names on poster.

• El Secreto Del Volcano• Hawai’ian Roller Coaster• Hell and Heaven


Generating and Evaluating Concepts

Brainstorming, Morphology Charts,

Weighted Design Matrices


Design Process

Recognition of a Need

Problem Definition

Solution Generation

Analysis & Evaluaton


Common Features

• Problem definition stage• Concept generation and evaluation stage• Preliminary design stage• Detailed design stage

• Feedback and iteration between stages• Documentation and reviews along the way


Design Process


Problem Definition

Clarify Objectives

Establish Functions

Set SpecificationsSolution Generation

Generate Concepts

Embodiment

Evaluate Concepts


Design Spaces and Concepts

• Design Space– A design space is an abstract space that bounds all the

possible solutions to a design problem. The size of the space reflects the freedom available to the designer to solve the problem.

– The problem definition defines the boundary of the design space.

• Design Concept– A design concept an idea (potential solution) that is

sufficiently developed to evaluate the physical principles that govern its behavior


Quantity Leads to Quality

• There is a tendency to derive a solution immediately based on intuition, and then refine it until it works. – THIS IS A POOR WAY TO DO DESIGN

• Studies and experience have shown that the more ideas you explore, the better solutions you derive– 1 in 10 ideas is a good idea– 1 in 100 ideas is a great idea– The pathway to great ideas is to generate lots of them

• Our objective is to explore as many concepts as possible (divergence) and then select the best few for more detailed evaluations (convergence).


Generating Concepts

• Objective – To develop as many partial or end-to end potential solutions to

the design problem as possible– To describe features and principles in words and sketches– To understand (flesh out) the relationship between the

specifications (functions and constraints) and potential solutions (form, physical realizations)

– Explore, explore, explore

• Basic Techniques– Creative Thinking (individuals)– Brainstorming (groups)– Morphology charts


Free Your Mind…

• Creativity and Problem Solving– Develop a creative attitude and an open mind– Unlock your imagination (think outside the box)– Be persistent– Suspend your judgment

• Ask yourself:– How can I solve the problem?– How ELSE can I solve the problem?– What are the assumptions?– Are the assumptions valid?


Start with what you know

• Sources of design information– Experience– Observation (be curious about how things work)– Reverse engineering– Trade magazines– Machine components distributors (McMaster-Carr)– Source books– Patents– Experts


Brainstorm for new ideas

• Procedure– State the problem– Come up with as many ideas as possible

• Rules– Record all ideas– “Think Different” - wild and crazy ideas are welcome and

encouraged– Build on previous ideas– Do NOT judge, criticize, evaluate, berate, chastise, belittle...


Explore Extremes and Inverses

• Transform current concepts into others by taking them to extremes or inverses (look at them from a different perspective and challenge assumptions)

• Suggestions– Make one dimensions very short or very long– Take the current order of things and switch them around– Try taking what is the inside of something and making it the outside

or vise versa– Make something that is rigid, flexible or flexible,rigid– Take a motion that is linear and see if it can be accomplished by

almost linear motion– Take something that is assumed straight and make it curved


Try the SCAMPER Checklist

• Substitute• Combine• Adapt• Modify, Magnify, Minify• Put to other uses• Eliminate• Rearrange, Reverse


Can Crusher

• What is the first thing you think of when you see/hear the words Can-Crusher?

• Is your first impression to draw up the basic, well-established slider-crank design?

• Let’s brainstorm on how we might implement and improve on the basic design.


Morphological Charts

• Procedure– List the features or functions that are essential to

the product– For each feature or function, list the means by

which it might be achieved (in words or sketches)– Draw up a chart containing all the possible sub-

solutions– Identify feasible combinations of sub-solutions


Do This…


Using Nothing But This…


Objective Tree






Solutions


Can-Crusher Redux

• Break the can crusher up into its three primary sub-functions– Hold can– Crush can (or dimple can, then crush can)– Release can

• Let’s create a morphology chart based on achieving these functions…


Design Process


Problem Definition

Clarify Objectives

Establish Functions

Set SpecificationsSolution Generation

Generate Concepts

Embodiment

Evaluate Concepts


Selecting Concepts for Evaluation

• The concept generation phase ideally produces numerous potential solutions to design problems and sub-problems

• The first step in converging to a final solution is to prune the concepts based on feasibility and technology readiness, and go/no-go screening.


Initial Concept Screening

• Is the concept feasible, infeasible, or need further work? – Is it complete (end-to-end)– Is it physically possible and practical

• Is the technology required to realize the concept ready for implementation?

• Does the concept seem like it has the potential to satisfy the requirements?


Initial Concept Representation

• In practice we try to select 3-5 concepts for further evaluation

• At this stage the concepts should be roughly the same level of abstraction or detail– Concepts are ideally presented as a single sketch which captures

the conceptual layout and functionality of the solution.– An effective way to do this is to provide a perspective sketch with

key components and features labeled

• The goal of this stage is to more closely compare the concepts and evaluate them with respect to the requirements


Weighted Objectives Method

• This method provides a way to systematically evaluate and compare concepts

• Procedure– List the design objectives– Rank-order the list of objectives– Assign relative weightings to the objectives– Evaluate and compare the relative utility values of

the alternative designs


Ranking and Weighting Objectives

• This part of the process is highly subjective• Ranking can be done using a pair-wise comparison

– This becomes more cumbersome with more objectives

• Weighting can be done based on the ranking– This is even more subjective

• A simple way to perform these steps is to examine the objective tree and weight each level and sub-level. – The ranking and weighting will drop out of this examination


Weighted Objective Tree


Weighting Matrix

Attribute Level 1 Level 2 Level 3 Total

Hold Can 0.3 0.1 1 0.03

Crush Can 0.3 0.8 1 0.24

Release Can 0.3 0.1 1 0.03

Fast 0.7 0.4 0.2 0.056

Portable 0.7 0.4 0.1 0.028

Low force 0.7 0.4 0.5 0.14

East to Clean 0.7 0.4 0.2 0.056

Limit Access 0.7 0.3 0.9 0.189

Hands Free 0.7 0.3 0.1 0.021

Cheap 0.7 0.3 1 0.21


Ranking Matrix with Weights

Attributes Level 1 Level 2 Level 3 Weight

Crush Can 0.3 0.8 1 0.24

Cheap 0.7 0.3 1 0.21

Limit Access 0.7 0.3 0.9 0.189

Low force 0.7 0.4 0.5 0.14

East to Clean 0.7 0.4 0.2 0.056

Fast 0.7 0.4 0.2 0.056

Release Can 0.3 0.1 1 0.03

Hold Can 0.3 0.1 1 0.03

Portable 0.7 0.4 0.1 0.028

Hands Free 0.7 0.3 0.1 0.021


Putting it all together

1. Choose the criteria for comparison (leaves of the objective tree)

2. Develop relative importance weighting (ranking and weighting based on objective tree)

3. Select the alternatives to be compared (from pruning the initial concepts)

4. Evaluate alternatives (relative comparison +,–,0)• Pick one to be the datum or baseline concept, and

compare all designs to that one

5. Compute the satisfaction (add ‘em up)


Decision Matrix


References

• D. Ullman• The Mechanical Design Process, Third Edition• McGraw-Hill, San Francisco, 2003

• C. Dym and P. Little• Engineering Design: A project based introduction, second edition• John Wilely & Sons, New York, 2004

• G. Deiter• Engineering Design: A Materials and Process Approach, 3rd Edition• McGraw-Hill, San Francisco, 2000

• N. Cross• Engineering Design Methods: Strategies for Product Design, Second, Ed• John Wiley & Sons, New York, 2000

Documents

ME14 Introduction to Mechanical Engineering Design Schedule Updates Design Artifacts for Group Project Tuesday, April 22 Artifacts: objective tree, function