We succeeded in connecting an inverted spherical Geneva mechanism to a four-bar mechanism with speed control to perform a 3-point pick-and-place, but had difficulty adding the electromagnetic end-effector.
The challenge with the end-effector came down to weight and torque. The weight of the electromagnet made the arm immovable, stalling the motor. It also tilted the mechanism, but that was easily solved with counterweights. To make the arm movable, we needed more torque, but we were at the limits of our simple geartrain. We needed a compound geartrain in order to smoothly run the mechanism at lower speeds with more torque than the 10:1 ratio of our simple geartrain. At the end we decided to remove the electromagnet but the keep the end effector on the arm to show proof of concept.
An additional challenge was preventing shafts from slipping on components. The press-fits weren’t always enough for the high torque in the mechanism. When the parts were designed with a long hole, like the Geneva sphere, the friction seemed strong enough, but as soon as we disassembled and reassembled the mechanism the friction would no longer be strong enough. Reassembly is important for a complicated prototype such as ours. We tried implementing more robust hubs with set-screws, but even this failed because we didn’t have D-shafts, which we should have ordered early on.