2.810 Final Report
Manufacturing Processes in Systems
Instructor: Dr. Tim Gutowski
Submitted December 13, 2000
Group B: Qing Cao, David Freeman, Jeremy Levitan, Carolyn Phillips, Cagri Savran, Eric
Wilhelm, Jin Yi
Website: web.mit.edu/~geneyee/www/index.htm
As we began the task, our primary objective was to design a vehicle that has a one-inch
road clearance, is robust and easy to drive. Our focus is on manufacturing the vehicle and
its quick-change power-control component system. We will demonstrate its ability to
function repeatedly without failure under rigorous conditions.
Figure 1. Group B: from left to right. Jin Yi , Qing Cao, Carolyn Phillips (seated), David
Freeman, Jeremy Levitan (seated), Cagri Savran, Eric Wilhelm.
A quick dimensional analysis reveals that our one-inch speed bump is comparable to bump
one-fifth of the height of an actual car. From this, incurred that it is reasonable to assume
that a typical suspension system, under high-speed conditions, is unlikely to greatly
enhance drivability and our time and effort would be better utilized on the remaining
systems.
Dimensional analysis of suspension system.
h
Suspension effectiveness =  sb ,…
Hc
hsb = height of speed bump
Hc = height of vehicle
Model (
h
1 .0
)  Full Scale ( sb ), hsb  9.4 inches
5 .5
51.5
Design Issues
Figures 2 & 3. Completed vehicles modeled after the Porsche 911.
Overall Objectives
Functional Requirements
Design Parameters
Drivability
Servo responsiveness, driving practice, suspension?
Rapid change of power & controls
Parts in one unit, quick change mechanical
coupling
Robustness
Material selection, protective elements, Minimize
Mass Momentum,
Table 1. Functional requirements and design parameters for overall vehicle system.
Efforts were made to minimize the interdependence of parameters through design.
Our design approach was to divide the vehicle into four systems; shell, chassis, steering
and the interchangeable power-control (IPC) box. Team members choose to participate in
two or more of these system groups. This allowed each group to focus on its design issues
with feedback from the other systems.
Cagri
Carolyn David
Eric
Jeremy
Jin
Qing
Shell
X
X
X
Chassis
X
X
X
X
X
X
Steering
X
X
X
X
IPC Box
X
X
X
X
Table 2. All members participated in system groups. Systems groups each had distinct
design and manufacturing phases.
Figure 2. Interchangeable Power-Control (IPC) Box. Time estimate for change out 3.5
seconds.
IPC Box
Interface
IPC Box to Chassis Servo output to
Power to motor
steering
mechanisms
Mechanical
Mechanical
Electrical
Type
Approach 1
Coupled
Coupled
Independent
Approach 2
Independent
Independent
Independent
Table 3. Three critical interfaces of the Interchangeable Power-Control (IPC) Box. A
range of alternatives were considered within approach 1 and approach 2.
Figures 4. Chassis taken from water jet. Figure 5. Solid model of chassis and IPC Box.
(Locking shaft not shown)
Chassis
Functional Requirements
Design parameters
Minimize momentum
Cut out excess material
Bend ability
Design so that there is less material at desired point of bending
Design so that bending can be done without damaging parts
that should not be bent.
Minimize number of parts
Easy to Manufacture &
Assemble
Table 4. FR’s and DP’s for the sheet metal chassis.
Steering Mechanism
Functional Requirements
Design parameters
Transfer servo input to
Design interface to minimize friction within the desired
wheels.
operating range.
Easy interface with servo
Design self aligning features
Drivability
Adjust servo sensitivity
Table 5. FR’s and DP’s for steering mechanism.
Figures 6 & 7. Solid model of shell and final thermoformed part.
Shell
Functional Requirements
Design parameters
Pleasing aesthetics
Design an attractive shell
Quick access to IPC Box
Hinged top, Snap able top, hole in shell
Protect IPC components
Design an enclosed shell
Table 6. Designing a new mold for our shell allowed us to gain experience using the CNC
milling machine. Mold was made of wood and cut with a ball-milling tool.
Figures 8, 9 & 10. The classic Porsche 911.
Manufacturing Processes
Manufacturing operations were typical with the exception of the IPC Box. Design for the
IPC Box was completed before decisions were made regarding its manufacture. The issues
that lead to the decision to use an additive process were 1.) only one part was needed, and
2.) a subtractive process would lead to a tremendous waste of material. Therefore, the
FDM 2000 rapid prototyping technology was used.
Figure 11. The chassis underwent four redesigns before the bending problems were solved
and an easy to reproduce chassis was developed.
Process
Milling
Sheet Metal Cutting
Turning/Winding
Machine
CNC Machine
Water jet
Lathe
Rapid Prototyping
Technology
Bending
Injection Molding
Cutting
FDM 2000
CNC Machine, Vertical
Drill/Hole saw
Table 7. Primary manufacturing processes
Manual and Secondary Processes
Cutting
Tapping
Fitting
Table 8. Manual and Secondary Processes.
Part
Mold for shell
Chassis, steering bar
Locking Shaft
Handle
Shaft
Spring
IPC Box, Aligners,
Electrical connector support
Chassis
Wheels
Shells & wheel wells
Assembly Processes
Figure 12 . Assembled vehicle.
Method
Job Shop Assembly
Process
Press fitting bushings into
front wheels, adhering foam
tires to wheels.
Issues
Fixing & drilling required
before fitting bushing &
attaching foam wheels.
Assembly of locking shaft.
Fitting required. One time
job.
Fitting Power/control
components and wiring IPC
Box.
Simple assembly, one time
job.
Painting
Electrical connector
assembly - soldering motor
connection
Cellular Assembly
Parts to chassis: electrical
connector supports, IPC
Box aligners, front wheel &
steering assembly, motor,
rear end (axel, wheels,
gears) hinges, shells
Table 9. List of assembly processes and issues incurred.
Flow line assembly
Individual preference.
Soldering iron required (one
available)
Lean process, all members
familiar with vehicle.
Assembly Processes
Job Shops. Figure 13. Press fitting bushing into chassis and fitting axels (note part
waiting). Figure 14. Fitting at stationary machine.
Figure 15. Flow line manufacture assembly; soldering & shell to chassis assembly.
Figures 16 & 17. Cellular assembly of vehicles after completion of other processes.
Redesign
During the production of our vehicle, we were required to redesign several features because
of manufacturing or assembly issues. The Servo receiver, for example, was produced using
the rapid prototyping process, but system software interpreted our original design as two
features added together. This caused a weakened plane, which intersected the loaded
threaded region. The receiver was designed such that it could only be interpreted as a
single feature.
Figure 18. Rework
Redesign Issues
Part
No. of redesigns
IPC Box
1
Chassis
4
IPC Box aligners
1
Servo receiver
1
Banana clip solder connection
1
Rear axel assembly
1
Table 10. Features, issues and the number of redesigns.
Issue
Assembly
Manufacturing
Assembly
Manufacturing
Assembly
Assembly
Performance Issues
System
Issues
Remediation
Battery
Inability to maintain charge Recharge after 8 minutes
Speed controller
Thermal sensitivity
Employ heat sink
Table 11. As we completed our vehicle and began testing, performance issues surfaced
regarding the components we were provided.
Lessons Learned by the Team
Qing Cao
I gained a lot of knowledge about manufacturing, especially on those processes in making
our cars. Being quite unfamiliar in this field (I was not a ME major before), everything
seems so challenging to me. From cutting the mold, thermal forming the shell, injection
molding the wheels, using the water-jet and bending the chassis, and the whole assembly
process, I got not only the basic ideas on how parts are made, but also the first hand
experience on the real manufacturing process itself.
Secondly, I learned the value of teamwork. This is really the first teamwork exercise for me
in America, especially in this world ranked institute. I know, as a team, everybody should
be not only aggressive, but also communicate and coordinate. Due to my language barrier, I
have to admit I was not doing so well in communicating with other team members as I
expected, but it was really a good experience for me.
David Freeman
Having a background in both, architectural and civil engineering, I am familiar with the
typical issues that arise during the design phase. Not, until this class, however, did I have
the opportunity to understand how the design decisions affect manufacturing and assembly.
This project really helped to drive home the DFM/DFA concepts discussed in class in
addition to the manufacturing methods. We learned that by developing a schedule, taking
more time and care with the design phase, we were able to do the manufacturing and
assembly with minimum difficulty, finishing two weeks before the contest date. The
course was also valuable in teaching project management as well as an understanding of
how products are manufactured and assembled.
Jeremy Levitan
I learned a few important things from this class and the car construction project. Perhaps
most tangible is that acrylic shells are very fragile. When car flips over and the shell flips
with it, it's time for a new shell. Fixing cracked acrylic is also very difficult. On a more
personal note, I also further developed skills of working in teams, setting deadlines and
goals, and project review. It felt really nice to see everything come together and the cars
completed with 2 weeks of time left to get the kinks out.
Carolyn Phillips
Since this has been my first manufacturing class, suffice to say I have learned a lot about
how products are built, or how an engineer’s design goes from a CAD drawing to a product
on the market. More importantly, when my roommate recently approached me with an
electronic object she had broken, carefully examined it, determined how the parts had been
made and then assembled, and from that figured out how the piece could be taken apart and
repaired, and then reasoned out a few simple changes the manufacturers could have made
to make the object less likely to break in the first place. So aside from all else, I have at
least learned to impress my friends and family.
Cagri Savran
The main point that I learned in this project is the fact that manufacturing is full of
surprises. In the beginning of the semester, when Prof. Gutowski gave a description of the
project, I thought machining of the chassis would consume most of the time. However, the
utilization of the water jet device made this one of the least troublesome steps, i.e., all we
needed was a CAD drawing with the appropriate format. Water jet cutting indeed
eliminated many machining steps that would otherwise be needed. Also, a 3-D printer was
used to manufacture the power box that contains the battery, the servo and other relevant
utilities. This tool also eliminated many machining steps. Nevertheless, certain simple
machining steps such as tapping and drilling were experienced. By the same token, I would
have never thought that bending a sheet metal would be as difficult as it turned out for us.
Aligning the sheet metal with the bender properly required several iterations on the chassis
design. The first couple of bending trials became unsuccessful. Either, the rest of the
chassis hit the bending tool, making it difficult to press the handle, or the bending occurred
at an undesired spot. I also learned the importance of design for assembly, and the
importance of having a simple design. We experienced only minor problems during the
assembly. This was mainly because our design was quite simple and required minimum
number of parts. This is probably why we did not have to build a prototype, and base the
production of the rest of the cars on that prototype. All of our cars were produced at the
same time and every single one worked! This also surprised me a lot because in the
beginning of the project I had anticipated that most problems would occur during assembly
and the troubleshooting of those problems. On the contrary, having a simple design and
thinking through the assembly ahead of time prevented us from having a lot of problems
and saved us a lot of time.
Eric Wilhelm
Designing and bending sheet metal is not trivial! One of the key manufacturing related
things I learned during this project was how to design sheet metal parts so that they bend as
expected. The chassis went through 4 revisions just to get the bends correct and it was not
just to get the bends to bend at the correct position, but also making the chassis so that it
could be bent on the bender in the LMP shop. Material had to be cut from just the right
areas making the weakest point the desired bend while other material had to be cut from
just the right spot so that it did not hit the bender during the operation and destroy some
part of the chassis. CAD models were helpful for the first revision, but the next three were
done after taking notes on the actual bending operation.
Jin Yi
All the chasses were cut using the water jet. The chassis has many complicate features for
reducing weight and fitting the battery-radio box, the motor, gear, and the steering system.
It brought these difficulties to the water jet. First, for the small pieces which are cut need to
be picked up after the nozzle finishing cutting them, because sometime the small pieces
will block the traveling path of the nozzle. Secondly, the sand feeding system should be
clear, of any obstacles. A sand clog will cause the water to beam out of the machine since
it cannot cut though the aluminum sheet without the sand.