Team F
Contents
Members
Preliminary Designs
Team Fα
Team members: Isaac, Christine, Lindsay
Team Fα's initial design involved several triangle cut-outs across the robot arm template. The triangles would provide support to the arm while removing much of the extraneous mass. The results of this design were as follows: Volume: .88 Displacement: .3653 Score: .3214
Team FΩ
Team members: Greg, Andrew
The premise of Team FΩ's design was to do away with extraneous portions of the given design. The result was a curved, s-shape piece that cut off the portions past the pre-cut notches under the hypothesis that these areas did not help the piece resist deformation. The curved structure was intended to eliminate the corners created by the notches so that stress could not focus on any particular spot.
Synthesis of Designs
The team decided to base the final design primarily on Team Fα's preliminary design because it performed better with virtually the same volume. The main quality that we tried to incorporate into our new design was the use of triangles in the central region of the piece, between each of the notches. We also cut away the portions past the notches, like in Team FΩ's design.
Design Development
Step 1 was to find the ideal arrangement and orientation of two triangle cuts in the center of the arm.
Middle Bar Test 1: Displacement: .298 Volume: .95 in^3 Score: .280
Middle Bar Test 2: Displacement: .2922 Volume: .95 in^3 Score: .277
Middle Bar Test 3: Displacement: .2682 Volume: .95 in^3 Score: .255
Middle Bar Test 4: Displacement: .2824 Volume: .95 in^3 Score: .268
Middle Bar Test 2 provided the lowest score and became the base model for step 2, which was to cut out a substantial, trapezoidal section near the applied force. An additional trapezoidal section was
added towards the top of the arm as well. Each of the Cut Tests we performed involved different arrangements and sizes of the trapezoidal cuts.
Cut Test 1:
Displacement: .358
Volume: .7 in^3
Score: .250
Cut Test 2: Displacement: .29 Volume: .72 Score: .209
Cut Test 3: Displacement: .277 Volume: .72 Score: .199
Cut Test 3 provided the lowest score and was used as the base model for the step 3, where we tested different depths of shelling.
Shelling Test 1:
Displacement: .4195
Volume: .50
Score: .210
Shelling Test 2: Displacement: .323 Volume: .61 Score: .197
Shelling Test 2 provided a better score; however, it was only marginally better than the score without any shelling at all. The small difference was still desirable, so Shelling Test 2 provided the base for the fourth and final step: lightening holes and filleting.
Lightening Holes and Filleting Test 1:
Displacement: .3339
Volume: .59
Score: .196
Lightening Holes and Filleting Test 2: Displacement: Volume: Score:
Final Design
After testing the different cuts, shelling, and filleting options that were possible, we realized that the ultimate design included rounded edges. We kept the triangle and trapezoidal cut-outs in the center of the arm, but we filleted every edge possible on the inside and outside edges. We also added lightening holes through the sides to reduce the mass as much as possible while maintaining the same low displacement value.