Roller ball cam follower

  Our engineering students make automata to learn about how motion can be graphed and translated to a cam/follower system. Some of these motion studies produce some oddly-shaped cams that aren't amenable to a flat pad follower, which will not engage, or worse, get stuck. This follower has a roller ball that is free to spin inside the cup, for (hopefully) better engagement. 
  Mine are printed in PLA. They feature three tiny points of attachment inside, which can be broken loose when the print is removed from the plate. Rolling the ball firmly against a grabby surface like a rubber mat has worked for me. If the ball is not round enough, roll it on sandpaper in multiple directions until it acts the way you want it to. This tiny print benefits by being printed on a dialed-in system! No support needed--stand them on the 'hole' end.

  Human Intelligence badge courtesy of Beth Spencer, The Introvert Drawing Club.