Generally, there are two kinds of Multi head cnc router: synchronous type and asynchronous type(non-synchronous type).

Synchronous type means we can deal with more than one workpieces, it is very suited for bulk production; by asynchronous type, we process one workpiece without or with less tool/bit changing;

Concerning auto tool/bit changing, there are another kind cnc machine for your reference, pls click: ATC CNC Router Machine.