Loading a magazine rack without a jam

A loader that jams gets blamed on the machine. Most of the time the machine is doing exactly what it was told, and the fault went into the magazine before it ever reached the conveyor.

Boards that are not fully seated

The most common cause and the easiest to miss. A board pushed most of the way into its slot sits proud at the back. The loader indexes to the slot and finds the board is not where geometry says it should be.

What makes it hard to catch is that it looks correct from the front. A partly seated board and a fully seated board present the same face to the operator.

Load from a consistent direction and check the rear of the magazine, not the front, because that is the face where the error is visible.

Skipped and doubled slots

An empty slot in the middle of a run is usually harmless. A slot with two boards in it is not, and it happens more often than people expect when boards are thin and loading is quick.

Two thin boards can enter one slot and feel like one. The loader then attempts to take a single board and gets two, which is where edge damage happens on top of the jam.

Loading by count, and checking that the count matches the slot span used, catches this in a few seconds.

Boards that are not what the magazine expects

Slot pitch is fixed. Board thickness is not, and a mixed batch is where trouble starts.

A board thinner than the magazine was set up for has room to move and can tilt inside the slot. A tilted board presents an edge rather than a face to the mechanism.

Warp does the same thing without any thickness variation at all. A board with a bow in it occupies more vertical space than its thickness suggests, and a batch that has been through reflow is not the same shape it was going in.

The magazine itself

Worn rails let boards sit imprecisely. Debris in a slot, usually a fragment of a break-out tab, stops a board seating. A magazine that has been knocked can be out of square in a way that is invisible standing next to it and obvious to a machine working to a fixed index.

The check that finds nearly all of this is to slide an empty test board through every slot by hand before a production run. Any slot that feels different is telling you something. The interface requirements are covered in the SMT loader interface guide.

The order to check in

Seating first, because it is the most common and takes seconds. Then count against slots. Then board condition, particularly warp if the boards have been through a thermal process. Then the magazine, by hand, slot by slot.

Calling the machine unreliable is the last step, not the first, and it is rarely where the fault turns out to be.

Magazines built to loader tolerances are in magazine racks, and worn rail parts are in rack spares.