Mechanical Engineering Design

Group # 2September 7, 2005

Weston Dooley General Design, Design Elements

Robert Todd Miner Functional Design, Material Design, Visual Design

Zachariah Ratzlaff Industrial Design, Design Process, Benchmarking

Moises Narvaez Engineered Products

General Design History

EXISTENCE

MATERIALCAUSE

FORMALCAUSE

EFFICIENTCAUSE

FINALCAUSE

Aristotle’s 4 Causes That Give Rise To Existence.

Defining Design

• Very hard to create a clear meaning of design• Approximately 8 different definitions listed in our

textbook on page 51• Order & Organization is common to all of these

definitions• “Design is the conscious, human process of planning

physical things that display a new form in response to some predetermined need”

Guiding Design

• A well designed product will not only function properly, but will also look good and be very durable

• Three Requirements: Functional, Material, Visual

Guiding Design

Functional• Most important of the 3 guiding design principles• Bad Examples: Tools that fail to perform and chairs

that are not comfortable• Good Examples: Punch type can-openers and

hacksaws

Guiding DesignPunch Type Can Opener Example

Functionality:• Cuts Safe opening in top of can • Effective, Reliable, and Simple to use• 2 tools in one: bottle top opener opposite can opener

Manufacturability:• Simple two-step shearing and bending

Guiding DesignMaterial• A good choice of materials will: reduce weight, maintain

structural integrity, and will be aesthetically pleasing.• Too many materials of contrasting form make an object appear

“busy”

Guiding Design

Visual Requirements• Most difficult of the 3 guiding design principles to fulfill• The following sum up the context of visual

requirements: Proper Balance, Correct Proportion, Compatible Colors & Textures, Structure

Design Elements

There are four basic elements of design:• Lines• Planes• Forms• Surface Qualities

Design Elements

LinesAn expression of continuity between 2 points• When lines are properly spaced and joined they create surfaces• Lines are significant in directing attention and determining form• Lines convey feelings and determine basic shapes• Outlines, contours, shapes, openings, appointments and plane

openings are all established by lines.

Design Elements

Form• Three-Dimensional constructions comprised of

combinations of lines and planes

Design Elements

Surface Qualities• Faces of planes and solids can be enhanced, embellished, or

modified by coloring or texturing.• Value = The ability of a surface to reflect the light striking it• Certain combinations of color and texture can change the

apparent shape and size• Texture can alter the relative quality of something• Individual Reactions to colors

Design Elements

Unity and Variety• Must be enough similarity to show unity, but there

must also be enough variety to display interest

Rhythm• Flow or movement of the viewing eye by the repetition

of either similar or varying elements.• Product Safety & Convenience issues

Design Elements

Balance & Proportion• The quality of equilibrium achieved and sustained

through the proper proportioning of the parts of any whole

• The Greeks “Golden Section”

Design Guidelines

• Functional Requirements

• Material Requirements

• Visual and Aesthetic Requirements

Functional Requirements:• A product must fit the purpose which it is needed or

intended for• An example of a functional product would be a C-clamp or

a hammer these are simple objects but functionally they work great.

• They are easy to manufacture, inexpensive, easy to use, durable.

Important to keep in mind when considering functionality• Never let aesthetics interfere with functionality• Form follows function

Questions to ask oneself when considering functionality

• What is it to be used for?• Where is it to be used?• How is it to be used?• Who will be using it?

These questions must be considered when designing a product.

Material Requirements:• The project or product should reflect a simple direct

and practical use of the substance it is made of.• The designer should achieve maximum benefit from a

minimum amount of judiciously selected materials• Materials should be used for there own intrinsic

properties • Knowing the particular functions and applying proper

analysis will lead to logical material choices.• There are a variety of materials out there, there is

wood, plastics, metals, ceramics, composites and many more so choosing the right material for the job can be a difficult task.

• Considering the materials properties should be one of the first steps to making a decision about what material should be used.

Material Properties:• Physical Properties- Melting Point, density, porosity

and surface texture.• Chemical Properties- resistance to corrosion and

dissolution.• Thermal Properties- measures of the effects of

temperature on materials• Electrical Properties- conductivity, resistance • Acoustical Properties- reaction to sound, frequency,

resonance• Optical Properties- reactions to different types of light• Mechanical properties- Indicators of strength,

durability, (ex: Tension is a force that tends to stretch, compression applies pressure, torsion is a twisting force, shear force fractures a material)

Metals:• Two basic classifications; ferrous and non-ferrous • Ferrous: Metal comprised primarily of iron• Non-ferrous: Metals that contain little or no iron• Most metals used are alloys which are metals

combined with other metals and chemicals.

Iron: A ferrous metal that is soft and ductile and has good corrosive resistance so it is used in pipes, fire hydrants etc.

Steel: Carbon and other elements are added to iron in order to make steel. Steel is strong durable malleable ductile corrosion resistant. Steel is extremely versatile and is used in many applications the most important being structural I beams.

Copper: One of the oldest metal known still used in a variety of industrial and mechanical products. Soft metal; it has high thermal and electrical conductivity which makes it great for communications and for wiring in houses.

Alloys: There are many alloys out there with there own intrinsic properties they are usually stronger, lighter, ductile and are very commonly used.

Plastics:• Synthetic materials they are made from a variety of materials• Plastics can be machined, cast, molded and worked in a variety of

ways• Plastics are strong colorful, corrosion resistant odorless lightweight and

convenient to use.• Two basic groups of plastics: Thermoplastic (thermoplasts) and

Thermosetting all plastics fall into one of these two groups

Composites:• Another material used in many modern applications are composites.• There are a variety of composites that exist out there.• They are used in cars, airplanes, spaceships and a variety of

common objects• Composites influenced by the types of fibers, type of matrix, the

process used.

Wood:• Wood is used in construction and has been a crafting material for

centuries• There are a variety of woods that one can choose from depending on

the application the look.• There are Hardwoods such as Oak, Hickory, Maple, Ash, Birch• There are Softwoods such as White pine Cedar and Douglas fir

Visual Requirements:

• Visual correctnessFive Guidelines to Visual Requirements1. Proper Balance2. Correct Proportion3. Compatible Colors4. Texture5. Structure

Visual requirements are the hardest to control since everyone has a different interpretation of what is visually pleasing.

Summary:

• There are certain requirements when designing to consider which are functionality, materials and aesthetics.

• Functionality- Form follows function, design for the needs and use of the object

• Materials- There are a lot of materials out there that can do the job but are the right ones, consider the materials intrinsic properties and how it will be used

• Visual/Aesthetic- keep in mind the five guidelines to visual requirements try to keep in mind the visual element of the product when designing it for functionality

Industrial Design

• “Art in Industry” • Optimizing function, value, and appearance of

products• Industrial Designers are especially capable of working

with the visual aspects of a design problem

The Process of Design

Design Brief

• Typically this is the stage where you make a statement of intent.

• Define what you want to do.

Product Design Specifications

The PDS is the guide for the design team

and should contain all important information.

• Defines the problem in detail with possible solutions.

• Competition based research and analysis.

PDS

Things to consider• Function• Appearance• Materials• Construction• Safety

Conceptual Design

• Concept Generation

• Concept Evaluation

Conceptual Design

Concept Generation• Develop a number of different possible solutions

based on the requirements in the PDS.• Sketch ideas.• Focus on key components and their relations.• Keep the rest of the process in mind.

Conceptual Design

Concept Evaluation• Analyze all the concepts for strengths and

weaknesses.• Consider cost and feasibility.• Consider the design that best fulfils the need defined

in the PDS.• Select the design that is most suitable to develop

further.

Detailed Design

• Beginning stage of development for chosen design.• Details are defined including dimensions, materials,

and all other specifications needed to make a prototype.

• Work with manufacturing to ensure that designs are able to be built.

Prototyping and Testing

• Does the design actually work?• Does it meet the requirements of the design brief?• Would other modifications make the design a better

solution to the problem.

Production and Sales or Design Implementation• If the design is successful then the marketplace saw it

as a good solution to the problem. • The ultimate goal of the design process.

Benchmarking

• One process of searching out and studying the best

practices that produce superior performance.

Benchmarking

Internal Benchmarking • Established within the same organization. External Benchmarking• Looking outside of the organization at another

organization that produces the same service or product.

Functional benchmarking• Reference to a similar function or process in another

industry.

Engineering Design:

• Process by which a need is transformed into an actuality. Achieving this actuality may involve some or all the disciplines of engineering.

• The design process may be accomplished individually or in groups, according to the complexity of the need to be satisfied and its constraints.

• The something created may be a machine, a chemical, an electronic circuit, a process, or any other thing that is designed to satisfy a need.

Design Guidelines:

In the act of designing, primary considerations must be given to the users needs. The needs to be satisfied provide the guidelines and constraints for the design.

*Functional requirements: A product must satisfy the need or purpose for which it was created.

*Material Requirements: The project or product should use the substance of which it is made in a simple and practical manner. The structure should be as strong as necessary, without any waste of materials.

To accomplish this, the designer must consider the following Design Factors:

1 Strength 12 Processing 2 Reliability 13 Control 3 Thermal considerations 14 Maintenance 4 Corrosion 15 Size 5 Wear 16 Noise 6 Friction 17 Styling 7 Flexibility 18 Utility 8 Stiffness 19 Surface finish 9 Cost 20 Lubrication 10 Safety 21 Shape 11 Weight 22 Volume

Failure to consider the above mentioned Designing Factors can lead to a failure of the project or product. In some cases this can lead to great economic loss and/or the loss of lives.

On November 7, 1940, the first Tacoma Narrows suspension bridge collapsed due to wind-induced vibrations. Situated on the Tacoma Narrows in Puget Sound, near the city of Tacoma, Washington, the bridge had only been open for traffic a few months.

Strength of Material

• Strength is a static property of the material, and depends upon the treatment and processing of the material.

• The type of material to be use in the production of each part of a system or product, should be based on tension, compression, torsion, shear, stress, and thermal analyses, and on the mathematical models performed during the design process.

Things to consider• The public today requires faster, cleaner, safer and

quieter machines (products) at very low prices.• The cost of production is a very important factor when

it comes to designing a product or project.• At the same time, design engineers must follow the

safety standards and design constraints when it comes to deciding what materials and the production process to use in the project.

Every single component of this highly efficient and reliable natural gas turbine (designed to convert pressure differential in gas distribution stations to electrical energy) was carefully planned to withstand the extreme temperatures, shears, stresses, etc. that

are found in gas turbines.

References

• Shigley, Joseph E., Mechanical Engineering Design, 3rd ed., New York:McGraw-Hill, 1977

• Lindbeck, John R., Product Design And Manufacture, Upper Saddle rives, NJ:Prentice Hall, 1994

• http://www.ptc.com/award/2002/winners/international.htm

• http://www.enm.bris.ac.uk/research/nonlinear/tacoma/tacoma.html