With the side mount swing arm type tool changers, the tools do not stay in assigned "pots" on the belt/magazine the way they do on the umbrella types. With umbrella type machines, Tool 1 is always stored in position 1 on the carousel.

On swing arm machines. the purpose of loading the tools through the spindle is to give each tool to the machine via the spindle and let the machine assign it a "pot" on the belt/magazine. However, once a program has been cycled and the tools have been sequenced, the tools will not necessarily be in their original "pots". For example, suppose the machine starts with T1 in the spindle, pot1 on the belt/magazine is sitting empty, and T2-Tx are in pot2-potx on the belt/magazine. When running a part program, T2 is called. The belt/magazine places T2/pot2 at the ready postion. When M6 is commanded, the swing arm puts T2 into the spindle and puts outgoing T1 into pot2. Pot1 remains empty. The tool number will no longer match the pot number. Gets very confusing if the program skips around with tools, like going from T1 to T14 to T23. In that instance, T1 winds up in T14's pot, then T14 goes to T23's pot.

I think there are some machines which have an intermediate pot between the belt/magazine and the swing arm. This permits the tools to stay in assigned pots on the belt/magazine. I think this style is only found on really big horizontal machines.

As a useless tangent, this is why machine tool builders will sometimes claim tool capacity on swing arm machines to be xx + 1 as the belt/magazine can be full and one tool in the spindle and the tool changer will still work properly. All pots can be occupied and a tool in the spindle. Umbrella types must always have an open spot in the carousel to accept the tool currently in the spindle.