MET 210W:
Instructor:
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B. Michael, P.E.
230 REDC Building
898-6192
rxm61@psu.edu
Consultant:
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Elastomer design
Structural Analysis
FEA
Vibration Analysis
MET 210W Machine Design
Lecture – 6:00 – 7:15 pm - Mon/Wed (106 REDC)
Lab Section 1 – 7:30 – 9:20 pm - Mon (106 REDC)
Lab Section 2 – 12:20 – 2:10 pm - Fri (101 REDC)
MET 210W:
What is this course???
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Mott Text: Machine Elements in Mechanical Design – 4th Edition.
– Part I focuses on reviewing and upgrading readers' understanding of design
philosophies, the principles of strength of materials, the design properties of
materials, combined stresses, design for different types of loading, FAILURE
THEORIES, and the analysis and design of columns. BASICALLY A REVIEW
OF 213!!
– Part II is organized around the design of a complete power transmission system,
emphasizing the interrelationships among machine elements in addition to their
unique characteristics. Included are belt drives, chain drives, gears, shafts, keys,
couplings, seals, rolling contact bearings, and completion of the design of a power
transmission. BASICALLY A GEAR DRIVE
– Part III presents methods of analysis and design of plain surface bearings, linear
motion elements, fasteners, springs, machine frames, bolted connections, welded
joints, electric motors, controls, clutches, and brakes. BASICALLY MISC.
Machine Elements!!
A CD-ROM for the mechanical design software MDESIGN is included with each book.
This powerful software enables users to quickly complete the design of many of the
machine elements discussed in the book.
MET 210W
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Review Syllabus
Review Course Schedule
Review Homework Guidelines!
Chapter 1 – The Nature of Mechanical
Design
Course
Title
Page
Name & Date
Chapter &
problem no.
Sketch of
situation
What you are
to find
Always include
UNITS
FBD’s as
necessary
No more than TWO
problems per page
LATE HOMEWORK
NOT ACCEPTED
Engineering
Calculation
Paper
Box or underline
answers
Homework
Use this as a
model!!
Chapter 1 – The Nature of
Mechanical Design
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Markets
Design process/flowchart
Skills needed in mechanical design
Functions, design requirements, etc.
Misc: preferred sizes, units
Brief Intro:
http://www.youtube.com/watch?v=7zB6E2Fm7zg&feature=related
Why Design???
•Only true wealth a country can
create is through manufactured
goods and technology!!
•Innovation and technology
brought to life thru Design
(improve quality of life).
• Design/Innovation makes us dominant
nation. Manufacuring?
– Manufacturing 1970 vs Current:
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Machine Tools
Color Televisions
Semiconductors
1970 100% US
1970 100% US
1997 25% US
1997 5% US
2000 30% US
• US still leads in innovation (rest of world catching up):
IBM – consistent record holder with 3,148 (‘07 # patents awarded. Other
companies catching up!!): source: http://www.baselinemag.com/c/a/ProjectsEnterprise-Planning/IBM-Samsung-Churn-Out-Most-Patents-in-2007/
Mechanical Design Markets:
Consumer Products – lawnmowers, household appliances, et.
1.
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Cost and safety major issues (o’head blade deck)
2.
Manufacturing systems/ general industrial equipment – machine tools, conveyers,
test machines, inspection machines, et.
3.
Construction Equipment/ Agriculture Equipment – loaders, scrapers, vibratory
rollers, pavers, tractor, harvester, et.
4.
Aerospace Industry – commercial airliners, helicopters, military jets, et.
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Performance, safety, weight major issues (o’head helicopter rotor)
5.
Transportation – truck, bus and automotive
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Focus of this class on machine design/ machine elements (2/3 above)
A Typical Mechanical
Design:
Skills needed in mechanical
design?? Sect 1-3)
Phases of Design
Phases of Design:
(similar to Mott, F 1-11)
Recognize the Need
Definition of Problem
(function, requirements, and evaluation criteria)
Synthesis
Analysis & Optimization
Evaluation
ITERATION
From:
Presentation
Shigley, Mechanical Engineering
Design, 2nd Ed, McGraw-Hall, 1972
The Design Process:
1. Recognize need:
– Can be system or component
– OEM vs. supplier (big difference)
2. Define Problem and Requirements:
– Requirements fall under 3 categories (see text):
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Functions
Design Requirements
Evaluation Criteria
2. Problem Definition
Functions
• Tell what the device is supposed to do.
• Can be one or more somewhat general nonquantitative statements
• Use action phrases:
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To support…
To lift…
To regulate…
To bend…
- To constrain…
- To orient…
- To change…
- To limit…
2. Problem Definition
Design Requirements
• Detailed & Specific requirements of the project
giving quantitative data where possible.
– Expected performance levels
– Environmental conditions in which the thing
operates
– Limitations on space and weigh
– Available materials or components that may be used.
Generic design requirements: strength, reliability, wear, corrosion, thermal properties,
surface appearance, finish, color, life, size, shape, NVH, maintenance, manufacturability,
recyclability, safety, weight, shape, size, flexibility (stiffness), lubrication, liability, friction,
etc…
The Design Process:
2. Define Problem and Requirements:
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Evaluation Criteria (RANKING) – statements of
desirable qualitative characteristics of a design that
assist the designer in ranking various designs and
determining which one is optimum. Examples:
cost, safest, easiest to manufacture, stiffness to
weight ratio, strength to weight ratio, etc.
Sometimes called design index (MET 470)
Show drawing!
Example: Function, Design Requirements,
Evaluation Criteria (Helicopter Rotor)
• Functions:
– Receive power from transmission
– Rotate to create lift
– Flexible blades for manuevering
• Design Requirements:
– Flight critical parts must have infinite life.
– Max weight and package size not to exceed ……
– Operating temperature ……… (-40 to +200 F)
– Maximum rotor blade angle = …… degrees (60)
– Blades must be able to rotate +/- ……. Pitch (+/- 20 deg)
– Rotor speed = …….. (4.5 Hz)
– Must be able to climb 4000 ft I, 95 F in 30 sec
– Etc……………….
Show drawing!
Example: Function, Design Requirements,
Evaluation Criteria (Helicopter Rotor)
• Evaluation Criteria:
– Best design: highest strength to weight ratio
– Best design: most durable
– Best design: highest stiffness to weight ratio
3. Synthesis:
The Design Process –
cont’d:
– The stage where you come up with options and
ideas or basically BRAINSTORMING!!
Always ask: can a vendor supplied component
be used?? Ex: Lord product selection guide:
http://www.lord.com/Home/ProductsServices/VibrationShockMotionControlProducts/Industrial
Catalog/tabid/3300/Default.aspx
Alternatives
• Brainstorm and come up with as many different solution
schemes as is possible.
• Never settle on your first idea.
• The most off-the-wall initial idea can lead to a unique and
innovative solution.
• Design is an iterative solution to a problem.
The Design Process –
cont’d:
4. Analyze and Optimize – Finalize design,
create drawings, analyze stress, weight,
FEA, etc..
– If designing series or families of parts – look
at automating (spreadsheets, ANSYS macro,
etc.)
The Design Process –
cont’d:
5.
Evaluation:
– Build prototypes and TEST!! Is design
acceptable? Areas of improvement/refinement
– may go back to 3!
6. Presentation:
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Generally an oral presentation to the customer and/or upper management
The opportunity to sell the design
Good designs lead to better pay and esteem for the designer.
My experience? Most iterations occur between 3 – 4 – 5!! Example seismic isolator: brainstorm, analyze,
build prototype and test, start over!!!! Show design summary
How does this design process
work??
• NVH Caster: http://www.jarviscaster.com/pdfs/News%20Release%20Stealth.pdf
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Functions: Support payload while providing compliance for shock inputs.
Design Requirements:
1.
Must support load of 1,000 lb
2.
Must have vertical mounting height of 6.24”
3.
Wheel diameter must be 4”
4.
Static vertical deflection of wheel = 0.5”
5.
Max vertical deflection of wheel = 1.0”
6.
Hole pattern for mounting = ………
7.
Fatigue life = 20,000 cycles at 0.5” +/- .2”
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Next Generation
Caster
Communicate the Details
As the field requested it
As marketing ordered it
As engineering designed it
As installed
As the plant manufactured it
What the customer wanted
CASE STUDY – Drill Bit
Isolator
• Drill bit isolators for underground mining –
all metal components and elastomer must be
safe!
• Design requirement: 8,000 lb thrust load
and 300 lb-ft (3,600 lb-in) torque – these are
basically the cutting forces.
• Must have adequate life (2 – 4 weeks).
• Must provide noise attenuation (4 – 7 dBA).
– Stiffness and damping requirements
Bit
Isolator
Drill Depth
up to 48”
Chuck
Isolator
1 3/8" DBI, R. Michael, PE
Results showed that in combination, the bit isolator
and the drill chuck isolator provided a 7 dB(A)
reduction in sound pressure level at the operator
position.
Ref: Noise controls for roof bolting machines, P. Kovalchik, A. Smith, R. Matetic and J.
Peterson
1 3/8" DBI, R. Michael, PE
FULLY BONDED: 1
3/8””
Chuck
isolator:
1 3/8” Drill Bit
Isolator – Design
Review:
Drill Bit
isolator:
4/10/2015
30
1 3/8" DBI, R. Michael, PE
Critical
Area!!
Look at metal components: Where would
you expect max stress to occur?
4/10/2015
31
1 3/8" DBI, R. Michael, PE
Integration of Machine Elements
(ref 1-5)
• Aka: Design coupling. Design of one
machine element impacts the others.
• Happens a lot in mechanical design
(examples:…..)!
• Speed reducer (F 1-12) what design first?
Most critical component!! What would you
design last??
Preferred Sizes and Shapes
-see appendix 2
-use standard sizes
-use standard shapes (ASTM A36
structural steel)
Review section 1-9
You will need to solve problems in both unit systems but bulk of
MD problems will be in English units.
Bob Michael – Sputz Design Philosophy:
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Get as much input as you can from your customer – do not start the design
process until you get from them (IN WRITING) design requirements and
functions (i.e. Make sure you’re both on the same page). Send them a
“generic” design requirement form (See example). And while you’re at it:
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Brainstorm as many ideas as you can. Create several designs (CAD, hand
sketch, etc.)
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IMMEDIATELY ADDRESS: Prototype costs (including tooling), target production costs,
intellectual property ownership, business agreement.
Make sure your customer understands several iterations could be involved to “get it right”
Send these designs to your customer and get their input. If feasible, incorporate one or more of
their recommendations into the design (Joint Ownership!!!).
Refine your design
Brainstorm some more (while you’re cutting the grass, in church, wherever, think about your
design until you’ve exhausted all possibilities).
Talk to the “experts”: manufacturing, vendors, metallurgist, material scientist, etc…
Don’t reinvent the wheel (check existing patents, old drawing archives, senior level engineers)
Finalize design and send to customer for approval
Prototype, Test (Field evaluations should be done as well)
Refine, prototype test, etc.
DONE! File patent and Start Selling!!!!