Reverse Engineering: An Excellent Opportunity for Student Team
Projects in Engineering Graphics
R. Barr, T. Krueger, B. Wood, T. Aanstoos, and M. Pirnia
Department of Mechanical Engineering
University of Texas, Austin, TX 78712
ABSTRACT - Our group at the University of Texas at
measurements and sketches, build 3-D solid models,
Austin
apply the solid models to various analyses, and make
has
developed
the
current
version
of
Engineering Graphics based on the pedagogical triad
rapid prototypes.
of: 1. engineering graphics fundamentals, 2. computer
documented with sketches, 3-D model printouts,
graphics modeling fundamentals, and 3. computer
analysis reports, prototypes, and final drawings. The
graphics applications.
The engineering graphics
attached Appendix I outlines the various tasks for each
fundamentals part covers the traditional topics of
student team. This paper briefly discusses the current
sketching, projection theory, orthographic drawing
version of our Engineering Graphics course at UT,
layout, sectioning, and dimensioning. The computer
which has evolved significantly over the last two
graphics modeling component teaches 2-D computer
decades, and then outlines in detail the reverse
sketching, 3-D solid modeling of parts, assembly
engineering project using an example student team
modeling, and the projection of an engineering drawing
project.
The whole project is eventually
directly from the 3-D model. The graphics application
part includes kinematics animation, finite element
I. Introduction to Modern Engineering
analysis, and generation of a rapid prototype directly
Graphics Instruction
from the 3-D data base. In order to motivate the
Within the past two decades, the teaching of 3-D solid
freshmen students, and to tie the three pedagogical
modeling has become the central theme in most
components into a unifying theme, we have instituted a
engineering graphics programs. This recent paradigm
team project in the course based on the concept of
shift to 3-D has been facilitated by the development and
reverse engineering.
Reverse engineering is the
low-cost availability of solid modeling software that
dissection of a common mechanical assembly into its
allows the student to focus on the “bigger-picture”
individual parts, studying the geometry and design
approach to engineering graphical communication. In
function of each part, and then reconstructing the parts
this Concurrent Engineering approach [Barr, et al.
into 3-D solid model data bases. The team activities in
1994], the 3-D geometric database serves as the hub for
the reverse engineering project have been carefully
all engineering communication activities (Figure 1).
scheduled by our group so that the teams systematically
These communications include engineering analysis,
accomplish various phases of the project over the
simulation, assembly modeling, prototyping, and final
duration of the course, with intermediate due dates for
drafting and documentation.
major tasks. The student teams select a mechanical
In the Concurrent Engineering paradigm for
assembly, dissect it into individual parts, make
graphical communication, the student starts with a
63rd Annual ASEE/EDGD Mid-Year Conference Proceedings, Berkeley, California – January 4-7, 2009
sketch of an idea. The sketch can then be used to build
a solid model of the part. The solid model not only
serves as a visualization modality, but it also contains
the solid geometry data needed for engineering
analysis. Typical of these analyses are finite element
meshing, stress and thermal studies, mass properties
reports, and clearance-interference checking.
After
analysis, the same geometric database can be used to
generate
final
communications
like
engineering
drawings, marketing brochures, and even rapid physical
prototypes that can be held in one’s hand. Indeed, an
Table 1: The Triad of Modern Engineering Graphics
Instruction
A. Engineering Graphics Fundamentals
Freehand Sketching
Generation of Engineering Drawings
Dimensioning
Sectioning
B. Computer Graphics Modeling Fundamentals
Creation of 2-D Computer Geometry
Creation of 3-D Computer Models
Building Computer Assembly Models
C. Computer Graphics Applications
entire Engineering Graphics curriculum could be
Digital Analysis
developed around three major aspects of instruction:
Animation and Simulation Presentations
engineering graphics fundamentals, computer graphics
Rapid Prototyping and Manufacturing
modeling
Design Projects/Reverse Engineering
fundamentals,
and
computer
graphics
applications. This triad of modern engineering graphics
Presentation Graphics
instruction is listed in Table 1.
Figure 1: The Concurrent Engineering Design Paradigm.
63rd Annual ASEE/EDGD Mid-Year Conference Proceedings, Berkeley, California – January 4-7, 2009
a rigorous analytical challenge, but rather allows them
II. What is Reverse Engineering?
Reverse engineering is a systematic methodology
to apply all the tools that they have learned in the
for analyzing the design of an existing device or
graphics course to a real-world design problem. The
system. It can be used as a means to study the design,
checklist in Appendix I outlines all the activities
and is a prerequisite for re-designing the device or
expected for the student reverse engineering team
system.
Reverse engineering is used to gain
project. The following sections detail the chronological
information about the functionality and sizes of existing
events that occur during this reverse engineering
design components. It should be noted that, for student
project.
projects, reverse engineering is a legitimate activity.
Determining “how something works” is not stealing
III(a) Assigning Teams
someone’s ideas, but rather is a beneficial way to
At the start of the semester, the students are asked
enhance the learning process of engineering design for
to fill out a form that includes information like section
the novice.
number, class level, gender, dormitory name, and other
Reverse
engineering
is
sometimes
called
scheduling data. They are also required to take the
mechanical dissection because it involves taking apart
Myers-Briggs Type Indicator (MBTI) on-line, and then
or “dissecting” a mechanical system. Mechanical
to indicate their four-letter MBTI personality rating on
dissection has been promoted for many years as an
the information form. These data are then used by the
acceptable activity for engineering students [Sheppard,
instructor and teaching assistant (TA) to assign the
1992; Mickelson, et al. 1995; Lieu and Sorby, 2009].
teams (nominally four students per team) in an
When the student dissects the system, careful sketches
equitable fashion that balances team factors such as
of the parts are made.
gender, academic backgrounds, and MBTI types. The
These sketches convey the
geometry of the part, and show how the parts fit and
team will then have an inaugural meeting in class to
work together.
exchange contact information, to pick a team leader,
This facilitates reassembling of the
whole system at a later date. The student needs to
and to then begin the project.
carefully measure all of the features on each part during
the dissection process so that solid models can be
created. Since correct measurements are a significant
part of the reverse engineering process, the students
learn to use common measurement tools such as scales
and calipers.
III(b) Selecting the Engineering Object to be Reverse
Engineered
The first team task is to pick the engineering object
to be reversed engineered. Some judgment is needed to
select an object that matches the task at hand. Usually,
the instructor will give some advice on what types of
III. Student Reverse Engineering Project
objects work well and will interact with the teams so
The reverse engineering project serves as a semester-
that they can select a feasible object. Table 2 lists some
long, culminating experience for engineering graphics
engineering objects that have been successfully used in
students at the University of Texas at Austin.
the past for this reverse engineering team project. For
Typically, these students are freshmen engineers who
purpose of illustrating the reverse engineering project, a
have very little background in design or analysis.
Trailer Winch student report has been selected for this
Hence, the reverse engineering project does not serve as
paper.
63rd Annual ASEE/EDGD Mid-Year Conference Proceedings, Berkeley, California – January 4-7, 2009
Table 2: Examples of Acceptable Reverse
Engineering Objects
Shower
Differential Master
Massage
Baby Toy
Gear
Cylinder
Head
Spinning
Bathroom
Doorknob
Model Car
Disk
Scale
Assembly
Drive Train
Launcher
Beer
Sprinkler
Flashlight
Oil Pump
Faucet
Head
Bicycle
Pump
students are encouraged to not only look at the
operation of the product, but to expand the way they
consider the use of the product in terms of customer and
engineering specifications. A black box diagram is a
convenient technique to identify and organize inputs
and relate them to the corresponding outputs. Figure 3
shows the Black box diagram for the Trailer Winch. It
is recommended that the Black box diagram be
Fuel Pump
Oscillating
Sprinkler
Stapler
Bolt Cutter
Gate Valve
Pencil
Sharpener
Toy Gun
Can
Opener
Hand Tool
Pepper
Grinder
Trailer
Hitch
The dissection process will allow for a better
Corkscrew
Hose
Nozzle
Piston
Assembly
Trailer
Winch
may have been misunderstood and other subsystems
Deadbolt
Lock
Kitchen
Timer
Pipe Clamp
Vise Grip
was exposed. The dissection of the product can be
Desktop
Clamp
Ratchet
Tie-Down
Water
Faucet
Valve
performed with simple tools. For those dissections that
Lug Wrench
developed before the physical dissection takes place.
Subsystems of the product should be identified or
surmised before the physical dissection takes place.
understanding of the subsystems.
Some subsystems
may be found that could not be seen until the interior
require more than just screwdrivers and pliers, the
students may
III(c) Charts and Diagrams
utilize the services of the ME
department’s machine shop.
The students need to
As part of the process to get started, the team
document the dissection with notes, sketches, and
selects a product for the reverse engineering project and
digital pictures. An exploded assembly of the product
then submits a proposal for approval of that product.
will also be developed.
The students learn within the same week whether their
As the product is being dissected, the students
proposal was approved. The students have to quickly
identify the subsystems first, then the individual
plan how to utilize the remainder of the semester,
components are identified. Students assign a name and
efficiently, to complete the project. To do this, students
number to each part of the product, and create a parts
prepare a Gantt chart for the team to follow. The
list.
students first review the team activities that are to be
individual parts can be organized into a fishbone
completed during the semester.
Some of the
diagram. The fishbone diagram shows the relationship
assignments have multiple activities. The due dates
between the subsystems and the parts. The head of the
specified in the course syllabus are the deadlines for
fish is labeled the project name, Trailer Winch in this
completion of each activity. Figure 2 shows the Gantt
case, and a spine is drawn. Ribs angle off of the spine
chart that is used for the Trailer Winch design.
to represent each subsystem. Minor ribs come off of
From this information the subsystems and
The initial step in the reverse engineering of a
each subsystem rib to represent every component part
product is to analyze the product in terms of inputs and
of the subsystem. Figure 4 shows the Fishbone bone
outputs. The exact analytical operation that converts an
diagram for the Trailer Winch.
input into an output is not important at this time. The
63rd Annual ASEE/EDGD Mid-Year Conference Proceedings, Berkeley, California – January 4-7, 2009
Figure 2: Gantt Chart for Planning the Reverse Engineering Project.
Figure 3: Black Box Diagram Showing the Major Function of the Trailer Winch.
Figure 4: Fishbone Diagram for the Trailer Winch.
63rd Annual ASEE/EDGD Mid-Year Conference Proceedings, Berkeley, California – January 4-7, 2009
III(d) Sketching the Parts
Throughout
the
entire
Reverse
Engineering
process, much thought has been given to the possible
changes that could improve the efficiency and
durability of the whole system as well as individual
subsystems and parts. This starts with the students
taking apart the mechanical system, studying the
subsystems that allow it to function, and inspecting the
individual parts.
Part of this process includes
measuring geometry and sketching isometric pictorials
of the individual parts, as well as sketching the parts
assembled together.
The following preliminary
documents are then produced in order to better
understand and visualize each individual part as well as
the overall mechanical assembly:
1. Isometric sketches of all individual parts,
2. An exploded-assembly sketch that depicts all the
parts (see Figure 5), and
3. A parts list of all components of the assembly
Figure 6: Parts List for the Assembly.
(see Figure 6).
Figure 5:Conference
ExplodedProceedings,
Assembly Berkeley,
Sketch. California – January 4-7, 2009
63rd Annual ASEE/EDGD Mid-Year
III(e) Building Solid Model Parts and Assemblies
The students will have a good understanding of the
parts after the exploded assembly sketches and the
individual isometric sketches of each part have been
made.
The students generally have a team meeting
during the next lab session and request digital calipers
from the professor. The students utilize the calipers to
get the gross dimensions of the individual parts and the
size and location dimensions for the details.
The
students sketch the dimensions onto the isometric
sketches until there is enough detail present to construct
an accurate computer model of each part. Figure 7
shows the computer model of the handle for the Trailer
Figure 7: Computer Model of the Winch Handle.
Winch.
The students divide the dimensioned sketches
among the team members.
Each team member is
responsible for modeling several component parts. The
students work together to model their individual parts
and make sure that the parts are oriented properly so an
assembly drawing can be made by compiling the part
files into a single assembly file. Care is taken to adhere
to the dimensions taken from the real parts to assure
accurately sized and constructed components. Properly
constructed parts will mate in the assembly as they
mate in the real product.
The course prepares the students to make intricate
computer models.
Figure 8: Computer Model of the Winch Pinion Gear.
The students have had concerted
The students will use the individual part files to
practice in making difficult profiles into extruded and
reconstruct the product as an assembly. The parts can
revolved parts. The students are capable of making
be aligned and mated to resemble the finished product,
accurate internal and external threads.
Each part is
or they may be aligned but exploded. To construct the
constructed and saved as a part (.SLDPRT) file. Each
assembly the students bring their files to one computer
part is also saved as a stereo-lithography (.STL) file to
and sequentially open them and insert them into an
be emailed to the teaching faculty member for later
assembly file. Parts are mated as necessary, with the
printing.. Figure 8 shows the computer model of the
most common mate being cylindrical components and
Trailer Winch pinion gear. Each part will be submitted
the holes they fit into concentrically. Figure 9 shows
with the original sketch, the CAD model, the mass
the Trailer Winch computer assembly model with all
properties report, and dimensioned orthographic views.
the parts mated properly.
63rd Annual ASEE/EDGD Mid-Year Conference Proceedings, Berkeley, California – January 4-7, 2009
Figure 9: The Trailer Winch Computer Assembly Model.
III(f) Mass Properties Report and Design Analysis
One objective of the project is to have the students
volume-averaged over all parts in the assembly. Figure
10 shows a Mass Properties report.
assess the overall suitability of a design from a
Some projects also include a finite element study
materials performance point of view. The starting point
of key parts or on the assembly as a whole. In such
for this assessment is the Mass Properties Report. After
studies, student teams assign realistic boundary
a part model is complete, the students assign material
constraints as well as fixed or distributed loads on the
properties, including the material type and mass or
part or assembly so as to mimic what the real assembly
weight density, depending on system of units used.
might see in normal duty.
Stock materials can be chosen from a library or custom
and/or deformation color 3-D plots are then studied to
materials can be defined.
reveal high stress areas.
The software then
Resulting stress, strain,
Alternately, design check
automatically generates the Mass Properties Report,
studies can also be run to show performance of the
which includes the calculated mass, volume, and
assembly against a stated margin of safety criterion.
surface area of the part, as well as principal axes and
Students are asked to evaluate the efficiency of their
moments of inertia at various locations (center of mass,
model, and to suggest ways in which the design of parts
output coordinate system). The mass properties report
could be modified to improve overall design efficiency
can also be generated for an assembly, in which case
of their project (e. g. reduce peak stress concentrations,
overall properties are given and the resulting density is
reduce total mass, etc).
63rd Annual ASEE/EDGD Mid-Year Conference Proceedings, Berkeley, California – January 4-7, 2009
Mass properties of CRANK ARM (2) ( Part Configuration ‐ Default ) Output coordinate System: ‐‐ default ‐‐ Density = 0.2854 pounds per cubic inch Mass = 0.4896 pounds Volume = 1.7153 cubic inches Surface area = 18.9277 inches^2 Center of mass: ( inches ) X = ‐0.3781 Y = 0.1050 Z = ‐0.5578 Principal axes of inertia and principal moments of inertia: ( pounds * square inches ) Taken at the center of mass. Ix = (0.9603, 0.0001, 0.2789) Px = 0.1290 Iy = (0.2789, 0.0003, ‐0.9603) Py = 1.5414 Iz = (‐0.0002, 1.0000, 0.0003) Pz = 1.5879 Moments of inertia: ( pounds * square inches ) Taken at the center of mass and aligned with the output coordinate system. Lxx = 0.2388 Lxy = 0.0001 Lxz = 0.3782 Lyx = 0.0001 Lyy = 1.5879 Lyz = 0.0000 Lzx = 0.3782 Lzy = 0.0000 Lzz = 1.4316 Moments of inertia: ( pounds * square inches ) Taken at the output coordinate system. Ixx = 0.3966 Ixy = ‐0.0193 Ixz = 0.4815 Iyx = ‐0.0193 Iyy = 1.8102 Iyz = ‐0.0286 Izx = 0.4815 Izy = ‐0.0286 Izz = 1.5069
Figure 10: Mass Properties Report for the Crank Arm.
III(g) Making Rapid 3-D Prototypes of the Object
III(h) Creating Dimensioned Orthographic Drawings
Once the solid models are produced in a computer
Another objective of the project is to familiarize
modeling software package, the parts can be saved in
the student with the purpose and practice of engineering
the stereolithography (.STL) format. There are various
orthographic drawings from solid models. The student
ways to then produce physical models.
sets drawing preferences (e. g. ANSI or ISO style,
Physical
models can be made using CAM, laser sintering, or by
units,
means of a 3-D printer. In our program, we print the
part/assembly 3-D model into a set of orthographic
students’ STL files on a Stratasys Dimension BST 3-D
views in a 2-D drawing document. Then, the student
printer.
constructs
consistent,
instructor, who load the printers and control what is
dimensions
in
being printed. In some cases, more than one part can be
conventional dimensioning practice. Shaded isometric,
printed in a single run, so the instructor tries to optimize
auxiliary, and/or section views should be added to the
the print output by nesting the files on a print board.
drawing for clarity if needed. To document assembly
Figure 11 shows examples of 3-D parts from the Trailer
properties, an overall annotated exploded assembly
Winch assembly that were produced on our 3-D
drawing should be included, with a bill of materials
Stratasys printer system. The footprint for printing a
defining the individual parts of the assembly. Figure 12
part is about 8” x 8” x 8”.
shows the individual part drawing of the Crank Arm.
The students send their STL files to their
tolerance,
precision)
the
and
complete,
appropriate
converts
the
non-redundant
views
63rd Annual ASEE/EDGD Mid-Year Conference Proceedings, Berkeley, California – January 4-7, 2009
following
Figure 11:
1 3-D Rapid
d Prototypes of
o Several parrts for the Win
nch Assembly.
Figure
F
12: Dim
mensioned Orrthographic Drrawing of the Crank Arm.
63rd Annual AS
SEE/EDGD Midd-Year Conferencce Proceedings, Berkeley, Califoornia – January 4-7, 2009
III(i). Submission of the Final Team Report
Nonetheless, these hurdles were overcome, and the
At the end of the semester, the students compile all
Concurrent Engineering Design paradigm (as originally
of the interim reports along with their dimensioned
envisioned in earlier versions of Figure 1) is now fully
drawings and their redesign recommendations, and bind
functional for graphics education [Krueger and Barr,
them into a final report. The students are required to
2007]. Even more noteworthy is that, while the
find a suitable box that will hold the bound report and
educational paradigm itself has been realized, achieving
the printed prototypes (Figure 13). We have found that
it has now opened a rich opportunity for graphics
unless you have these items turned in together as a unit,
applications and projects for our engineering students
it is hard to keep all of the parts of the project in the
beyond the graphics fundamentals.
same place.
building solid models and assemblies, they can also
The checklist in Appendix I helps the
In addition to
students in this final submission requirement.
analyze the models, perform kinematic animations, and
IV. Conclusions
print 3-D parts.
Our current educational paradigm for Engineering
This paper illustrates a reverse engineering student
Design Graphics is a fulfillment of 20 years of work to
project that not only exercises the graphics and
deliver a robust course based on the solid modeling
modeling fundamentals, but also extends the student
approach to engineering design. During this journey,
activities to analysis and prototyping. In doing so, the
many obstacles were encountered.
These obstacles
teaching environment for Engineering Graphics can
included incompatible software and hardware systems,
now be extended deeper into design practices that will
user-unfriendly
serve the students well in later engineering courses.
analysis
software
that
frequently
crashed, and high costs for prototyping equipment.
Figure 13: Submission of the Final Project Report.
63rd Annual ASEE/EDGD Mid-Year Conference Proceedings, Berkeley, California – January 4-7, 2009
V. References
Barr, R., Juricic, D., and Krueger, T. (1994). The Role
of Graphics and Modeling in the Concurrent
Engineering Environment, Engineering Design
Graphics Journal, 58(3):12-21.
Mickelson, S.K., Jenison, R.D., and Swanson, N.
(1995). Teaching Engineering Design Through Product
Dissection,” Proceedings of the 1995 ASEE Annual
Conference, Anaheim.
Krueger, T. and Barr, R. (2007). The Concurrent
Engineering Design Paradigm is Now Fully Functional
for Graphics Education, Engineering Design Graphics
Journal, 71(1):22-28.
Sheppard, S.D. (1992). Dissection as a Learning Tool,
Proceedings of the 1992 Frontiers in Education
Conference, IEEE.
Lieu, D.K. and Sorby, S. (2009). Visualization,
Modeling, and Graphics for Engineering Design
(Chapter 8: Design Analysis), Delmar Cenage
Learning, New York.
Appendix I
63rd Annual ASEE/EDGD Mid-Year Conference Proceedings, Berkeley, California – January 4-7, 2009