The company I work for has a patented product that requires very, very fine glass beeds to be precisely dispensed into a cavity in the body of the platic molded part.
We've used a semi-automatic mechanism with a gated drop, very similar to a good powder drop for years.
We're dropping a six digit number of bills (and the first digit isn't 1) on a completely automated assembly line this summer, and are scheduled to take delivery of it in a couple weeks.
The drop uses long channels machined in to a plate that is mounted on a vibrating plate with very precise control of amplitude and frequency of vibration (similar to vibratory feed bowls).
The designers prototyped this module of the machine ealier in the spring to prove the concept out and it gets getting amazingly consistant and precise drops.
There is NO gate. The channels are open to the drop tubes at all times. When the vibration stops, the movement of the beads in the channels stops and secures the drop.
The control of the vibratory plate is programed into the PLCs that run the entire line.
I can't take credit for any of this, but I took part in the design review meetings (looking for obvious hiccups in ergonomics and procedures) and the set up was VERY impressive.
We refer to the lead mechanical designer at this vendor as the "mad scientist" and he really looks the part, with a bald top and bushy hair pushing out in all horizontal directions.