The choice of CNC machine tools, the general should consider the following aspects: (1) The size of the main specifications of CNC machine tools should be compatible with the outline size of the workpiece. That is, a small workpiece should choose a small size of the machine tool, while the large workpiece is the choice of large-scale machine tool processing, so that the rational use of equipment. (2) The structure of the machine depends on the size of the machine tool, the weight of the workpiece and other factors. The following table lists the most common CNC equipment, the important specifications and performance specifications. (3) The working accuracy of the machine is compatible with the machining accuracy required by the process. According to the parts machining accuracy requirements of the machine, such as the low precision of the roughing process, should choose the low precision machine tools, high precision finishing process, should use high precision machine tools. (4) The power and rigidity of the machine and the range of maneuver should be compatible with the nature of the process and the most appropriate cutting. Such as roughing process to remove the rough margin, choose the larger cutting allowance, it requires the machine has a large power and better stiffness. (5) easy clamping, fixture structure is also a choice of numerical control equipment is a factor to be considered. Choose to adopt horizontal CNC machine tools, or select vertical CNC machine tools, will directly affect the structure of the selected fixture and the processing coordinate system is directly related to the ease of NC programming and CNC machining reliability. It should be noted that in the choice of CNC machine tools should take full advantage of the functions of CNC equipment, according to the need for a reasonable development to expand the functions of CNC machine tools to meet product needs. Then, according to the selected CNC machine tools, further optimization of CNC machining programs and process routes, according to the need to properly adjust the process. Select the processing machine, we must first ensure the technical requirements of processing parts, able to process qualified parts. The second is to help improve production efficiency and reduce production costs. Choose to process machine tools generally take into account the structure of the machine, load, power, travel and accuracy. Should also be based on the processing of parts of the material state, technical state requirements and process complexity, the selection of appropriate and economical CNC machine tools, considering the impact of the following factors. (1) Machine type (car, milling, machining center, etc.), specifications (travel range), performance (processing materials). (2) CNC machine tool spindle power, torque, speed range, tool and tool system configuration. (3) CNC machine tool positioning accuracy and repeat positioning accuracy. (4) Parts positioning and clamping methods. (5) linkage between machine coordinate system and coordinate axis. (6) control system tool parameter settings, including the tool alignment, tool compensation and ATC related functions.