Collecting Foam Rings Sure is Hard Work!
For the 2020-2021 FIRST FTC challenge we were presented with a problem; our robot had
to pick up foam ring-shaped game pieces from the playing field. We gathered as a team to brainstorm various strategies for gathering the game pieces cleanly and efficiently. From those brainstorming sessions emerged several prototypes.
Our first model was a ramp with a bottom-mounted conveyor belt to lift the rings from the floor and carry them to the shooting mechanism. However, this design featured too thick of a contact point with the playing surface and failed to lift the rings from the floor to the conveyor belt. For our second prototype, we stayed with a ramp design, but altered the conveyor to be top-mounted. Both of the conveyor belt designs were unreliable, but we still felt our best design would involve the use of a ramp to gather the rings and move them into position for firing.
Eventually we tested and decided on using latex tubing for “noodle arms,” top-mounted on four chain driven axles. The “noodle arms” were effective in coaxing the rings up the ramp toward the shooting mechanism. However, the surface material of the
ramp was a critical variable in our designs. The team tried plywood, but the material featured too much friction. The next material tested was whiteboard material, but the material was too thin for the ramp. Finally, the team purchased some Ultra-High Molecular Weight (UHMW) polyethylene for the ramp material. We found the UHMW material cut and could be drilled cleanly. The UHMW material was also very rigid and withstood the stresses of the operations better than the plywood and the whiteboard. Most significantly, UHMW material features very low friction. The result was smooth and reliable movement of the ring pieces on the ramp.
Despite the improvements, the robot struggled in quickly transferring ring pieces from the playing floor to the ramp. In the midst of our league qualifying matches, we incorporated a drop-down assembly of three “gecko” wheels mounted on a chain-driven axle. The “gecko” wheels were excellent at gripping the foam ring pieces and significantly improved our robot’s ability to collect ring pieces from the playing field.
Throughout the journey of finding a solution to our problem, we prototyped and tested many different intake designs and materials. This experience of seeking any adjustment to improve the performance of the robot will serve us well as we prepare for next year’s challenge.