As with machining center tool-carrying configurations, cnc machining centrers are just as diverse, ranging from relatively simple geneva-mechanisms for turret indexing with a small tooling complement, to highly complex and sophisticated tool storage and delivery methods. Typical of the drum-type of tooling carousels is the one shown , where a large machining center is fitted with twin rotary carousels holding a considerable tooling inventory. 

The tool transfer mechanism is situated above the machine's horizontal spindle in vertical cnc milling machine and can extract tools from both magazines by preselecting the next tool to be used whilst cutting continues. These tool magazines are bi-directional, meaning that the quickest time for indexing the carousel results from it taking the shortest route to the tool-change position. Tool pre-selection in such a manner means that the non-productive idle-times are reduced to a minimum. A different approach to tool storage is shown in Fig. 1.26, where the chain-type of magazine is depicted. 

This type of tooling configuration lends itself nicely to the "banking of magazines". With the "banking" approach to tool storage, the inventory of tools held can be increased by positioning side-by-side similar tool magazines allowing the capacities to be increased in steps of 60. Thus with only one magazine 60 tools can be held, with two 120 tools may be carried, with three "banks" 180 tools can be used on the cnc machining center.

What's the most advanced machining center you can think of ? 

The newly back door type cnc gantry machining center, which gained many patents and is unique in the world: