When a turntable beats a rack

A rack and a turntable get grouped together as ESD-safe board handling, which hides the fact that they solve opposite problems. One holds the boards you are not touching. The other holds the board you are.

The line between them

A rack is storage between operations. Its job is to keep boards apart, protected and identifiable while nothing is happening to them.

A turntable is a work surface. Its job is to present one board, at a workable height, in an orientation that can be changed without picking the board up.

The distinction matters because the expensive handling damage on most floors does not happen during storage. It happens during the small movements: picking a board up to turn it around, setting it down on a bench, picking it up again.

Every rotation avoided is a handling event avoided

Inspection, rework, touch-up and conformal coating all involve looking at a board from more than one angle. Without a turntable, changing the angle means lifting the board and putting it back down.

That is where boards get flexed, where they get set down on something they should not be set down on, and where they meet the edge of a bench. A turntable removes the lift entirely. The board stays put and the view changes.

Where a turntable is the wrong tool

For anything involving quantity. A turntable holds one board, so using them as a place to leave work between operations means boards sitting out in the open, occupying bench space, being handled again to clear the bench.

For anything that has to feed a machine, where the magazine interface decides the hardware.

And for anything that has to move. A turntable is a bench fixture, not a transport device.

The ESD requirement is the same either way

A turntable is in direct contact with a board for the entire time somebody is working on it, usually with a person leaning over it and touching it. That is a longer and more intimate contact than most storage.

It needs the same attention to material and to grounding path as any rack. The mechanism has to be part of the grounded path rather than an insulated bearing sitting between an ESD top and a grounded base, which is a real failure mode in general-purpose turntables that were not built for this work.

If it moves and it touches boards, it needs a path to ground through the moving part.

How they work together

The normal arrangement is a rack at the operation holding the queue, and a turntable at the bench holding the board currently being worked on. Boards come out of the rack one at a time, go onto the turntable, get worked, and go back.

The board is only lifted twice, and both lifts are short and deliberate.

Our ESD turntables are built for the bench-side half of that arrangement, and the universal racks range covers the queue.