A machining center is a machine tool equipped with a knife lib, can change knives automatically, and carries out multiple procedures after a fixture on the workpiece. It's highly mechanically and electrically integrative, after fixtures on workpieces, the CNC can control the machine tool to automatically choose and change knives, automatically change the spindle's rotational speed, feeds and etc, and can continuously finish procedures such as drilling, boring,milling,hinge and tapping. Therefore, time for auxiliary procedures such as fixtures on workpieces, tests, machine tools adjustment and etc is reduced, and it has a good economic effect on the process of accessories which have complicated shapes, require a high degree of precision, and change breeds high frequently. Machining centers are often sorted into horizontal ones, vertical ones, and all-purpose ones according to the relative positions of the spindles and the work platforms. Horizontal machining center is the one whose spindle and the work platform are parallel, and is mainly used to process trunk accessories.