Most are stainless steel tubs, anchored to a base by spring steel strips around
the periphery. Electromagnets power the tub. If the strips are vertical, the tub
motion is rotational only. If they are horizontal, the tub motion is vertical
only. If they are at a 45 degree angle, the motion is a combination of both,
e.g. CW rotation + UP then CCW rotation + DOWN. Often, a linear version is used
to offload the parts from the tubs. The main use of such devices is part
orientation. I worked on a machine that assembled hinges for Motorola cell
phones. Those tiny parts had to be oriented exactly so the machine could
assemble them. For example, screws are easy. A track is added inside the tub
with V-cross section, rising gradually along the inner wall, from the tub bottom
to the top rim. On this track, the screws can be head-first or thread-first.
Near the top, the track changes to 2 flat rails with a slot between them. When
a screw reaches the slot, the threaded part falls in, and presto, the screw is
oriented head-up.
Complex parts can be oriented by added more tracks, and doing it in stages. Some
designs can even do minimal inspection, rejecting malformed parts. Design and
fabrication of such machines is an art not likely to be computerized soon.
I spent my whole career in factory automation, and I am still impressed by these
simple but amazing devices.
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