Lecture 1 - Mechanical Engineering

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ME110- Introduction to CAD
Craig R. Ronald
Gavett 244
Course Format

PTC Creo
» Industry recognized leader in
mechanical design software.

Focus on solid modeling,
detailing and assemblies.
Design Examples
Paintball Mask
LeMans Race Car
Dentist Chair
Design Examples
Automatic Bus Transmission
John Deere Combine
About the Instructor
MS Mechanical Engineering U of R 1990
 Taught ME110 since 1987
 Used PTC Creo since 1997

Importance of Course
Only a 2 credit course but...
 Teaches the language of engineering
 Skill that is most likely to help job
search

Web Site

http://www.me.rochester.edu/courses/ME110
The web site will be kept up to date
 Check frequently! You are responsible for
knowing the information on the site.

Blackboard
Log on at: http://my.rochester.edu/
 Assignments
 Grades

Course Outline
Phone numbers 259-6119 Cell(‘til 10PM)
 E-mail: [email protected]

Teaching Assistants
Hannah McCullough
 Gina Bolanos
 Carolyn John
 Rachel Melnyk
 Thomas Kittross
 Thomas Barrett

Grading
6 Homework worth 8 points each,
Lowest grade is dropped!
 1 midterm test worth 30 points, no
curving.
 Final exam worth 30 points.

Saving Work for Course

Flash Drive
– you will need to have a USB flash drive by
next lecture.
– All HW and test files must be saved
– Must be able to show the original files in
case of grading disputes.
Academic Honesty


All assignments and activities associated with this
course must be performed in accordance with the
University of Rochester's Academic Honesty Policy.
Suspected violations will be pursued vigorously
following the College’s procedures for suspected
cases of academic dishonesty.
– Collaboration on homework is encouraged
– Each student must create and submit their own file
– Sharing files, data, or accounts on homework or tests is
prohibited.
Conclusion
SAVE
YOUR WORK
DON’T CHEAT
Six View Orthographic
Projection
Three views are usually sufficient

Choice of views
– least hidden lines
– clarity
– only necessary
views
Precedence of Lines
Visible
 Hidden
 Center


Meaning of lines
– intersection of 2 surfaces
– edge view of a surface
– contour of a curved surface
Section Views



Use section views
to eliminate
hidden lines.
All visible lines
behind plane
shown.
Hidden lines are
rarely shown.
Types of CAD systems




Wireframe- modeling the curves of the part
Surface modeling- Model the surfaces of the
part, but without knowledge of material.
Solid modeling- full solid representation
Parametric Modeling- dimension driven solid
modeling.
Solid Modeling

What is a solid model?
– A three dimensional representation of
geometry that includes the shape definition
of the geometry as well as a definition of
inside and outside.
Why use a solid modeler?

Intelligent modeling- modeler can
understand concept like through,
through until, etc.
Accurate Detailing
– Hidden lines
– Section views
– Auxiliary views
Manufacturing
Tool paths may be made directly from
the model.
Interference checking
Finite Element Analysis
Ability to do Deflection and stress
analysis on complex parts/assemblies.
 Complex problems are discritized into
simple shapes.

Rapid Prototyping

Stereo Lithography
– Light setting polymer is built up layer by
layer with a laser.
3D Printing
Inkjet printer glues together layers of
Plastic or Stainless steel powder.
 Sintering binds the powder.

Demo
Types of Solid Modeling

B-REP– Boundary representation
– The solid is defined by the surfaces bounding the volume as well as
inside and outside definition. (outward unit normal)
Types of Solid Modeling

CSG- Constructive Solid
Geometry
– Primitive solid shapes joined together with Boolean
operators define the solid. The model is stored with a
tree structure.
– Boolean operators are three-dimensional set operators
(union, difference, and intersection).
Set Theory
Union
Difference
Intersection
CSG- Constructive Solid Geometry
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