Momentum - April 2020 - 8

STUDENT
GENERATION

Rear sprockets, wheel hubs, wheel uprights, differential uprights,
and swan neck rear wing supports are programmed in Mastercam
Mill and verified using the software's Verify and Backplot features to
anticipate and correct any machining problems before the parts are
actually made.

Simulation functions
within the software
virtually run toolpaths
based on geometry
provided by uploaded
STL files, saving time
and allowing the
students to run the
machining operation
prior to loading the
billet on the machine.
with Mastercam CAD/CAM software (CNC Software, Inc.,
Tolland, CT).
"I think the feature we find most beneficial is the
simulation," said Dewey, "We can model the toolpaths to
see if there's going to be any unexpected failures due to
the tool maybe not being long enough or running into
the tool holder. It also helps us estimate time and figure
out what would be the best way to simplify the toolpath
and maybe save some time on the machining." The
Simulator feature within Mastercam includes Verify and
Backplot options to anticipate and correct any machining
problems before they occur. Verify is especially useful in
customizing parts with specific tolerances, modeling the
finished part, and comparing the preview with an external
STL model.
This simulation is invaluable when the crew works
on difficult parts. The drivetrain and suspension
components, such as the suspension uprights, were a
source of strain for the Purdue team on their 2019 car.
"This was a tricky piece of geometry. The uprights
8 April 2020

2004_SG_4-13.indd 8

connect a lot of different points of the suspension together, and they
have to be perfect so we can fasten as much of the other components
on the racecar as possible. We make it in two halves and then we'll flip
it over so we can get the other half of the part," explained senior Alex
Roberts, suspension team leader. To machine a billet of 7055 aluminum
into the uprights, the team relied on the software's Contour toolpaths
and pocketing solutions. Contour toolpaths use high-speed strategies
to remove material along walls, supporting multiple passes and even
allowing finishing passes.
The differential supports were made in a similar fashion. "We machine
the uprights in two set-ups," continued Dewey. "We bore out a pocket
for the bearing and we leave about 30/thousandths (0.0030") off of it
so we can bore the upright out for a pressed fit on a manual mill. We try
to get that within 1/thousandth (0.001"), ideally. We use 3/8" end mills
for many of the pockets as well as ¾" end mills for the larger bearing
pocket. And then in terms of fixturing, we're using a sacrificial aluminum
block that we've modeled in CAD, and we'll bolt our uprights to that.
When we're machining the outer geometry of the upright, we can bolt
the upright to the sac-block so that part doesn't come flying out at us."
The result is a part that is just as functional as it is safe.
Roberts explained that, while speed and maneuverability are
paramount to a good competition racecar, the Purdue team places most
importance on strength and safety. Chief Engineer and senior Adam
Christopherson clarified, "Aside from safety, strength in the sense that
something does not fail during our entire season is our next biggest
priority because as soon as something fails, that means we lose our
testing time. Obviously, we try to reduce weight as much as possible, but
we don't want to reduce weight to the point where we're sacrificing our
chances of being able to run the car."
During the four days of the Formula SAE Michigan competition in
May 2019, the student engineers not only had to drive their racecar
in multiple events to test every facet of their design, they were also
expected to deliver presentations to the judges. During the Design
Event, judges with decades of experience in the racing and auto
industries asked the students to explain all their design choices for
the vehicle, including detailed design on individual components. This
explanation had to include a detailed overview of the manufacturing
process, the design parameters, and the empirical reasons behind the
design and manufacturing choices.
The teams were also expected to have a cost report and a sales
presentation prepared. The goal of assigning these projects each
year is to mimic how a real racecar designing firm might pitch its
prototype to a manufacturing company. The car with the lowest
retail cost automatically wins 30 points. The students are not only
responsible for tracking expenses and weighing financial decisions,
they are also in charge of securing much of the project's funding.
Every year, the team raises $35,000-$40,000 through fundraising
and establishing sponsorships.
"This is a team that does a lot of outreach, and the responsibility is
distributed across the whole team to do their best to get the resources,
get good people, and see what additional options we could have in the
design and competition," said Roberts.
The Purdue FSAE team finished the 2019 Michigan competition in
33rd place Overall. The car earned 17th in Cost, 45th in Design, 50th in
Presentation, 49th in Acceleration, 44th in Skid-pad, 44th in Autocross,
and 32nd in Endurance. After the competition closed, the Purdue
team wasted no time. The 2020 design started immediately for those
returning to the university, regardless of summer break.

MOMENTUM

3/19/20 11:25 AM
Momentum - April 2020

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