Machining center is a numerical control machine tool with tool magazine, automatic tool changing function, and multi process processing after one clamping of workpiece. The machining center is a highly mechatronic product. After the workpiece is clamped, the CNC system can control the machine tool to automatically select and replace the cutting tool according to different processes, automatically set the cutting tool, automatically change the spindle speed, feed rate, etc., and continuously complete various processes such as drilling, boring, milling, reaming, tapping, etc. Thus greatly reducing the workpiece clamping time, measurement and machine tool adjustment and other auxiliary process time, the processing shape is more complex, high precision requirements, varieties of frequent replacement parts, has a good economic effect. Machining centers are usually classified according to the relative position of spindle and worktable, which can be divided into horizontal, vertical and universal machining centers.

1. Horizontal machining center: it refers to the machining center with the spindle axis parallel to the workbench, which is mainly suitable for machining box parts.

2. Vertical machining center: it refers to the machining center with the spindle axis perpendicular to the worktable. It is mainly suitable for processing plate, plate, mold and small shell complex parts.

3. Universal machining center (also known as multi axis linkage machining center): it refers to the machining center that can control the linkage change through the angle between the spindle axis and the rotary axis of the worktable to complete the machining of complex spatial surface. It is suitable for the impeller rotor, die and mould with complex space surface

Cutting tools and other workpiece processing.

Inspection standard machining center adopts the internal control standard of machine tool industry. There are mainly JB / gq1140-89 machining center precision, JB / gq1140-89 machining center precision annex, JB / gq1141-89 machining center technical conditions. The standard specifies the requirements and inspection methods for geometric accuracy and working accuracy of machining centers. The machining center inspection should also refer to jb2670-82 general rules for precision inspection of metal cutting machine tools and gb9061-88 general technical conditions for metal cutting machine tools.

Inspection items machining center can be divided into ordinary level and precision level according to its precision level. The inspection items are generally more than 30, and the details, inspection conditions and methods are clearly specified in the standard. The whole acceptance of a machining center is relatively complex. Generally, large high-precision instruments such as laser interferometer and three coordinate measuring machine are used to test the mechanical, electrical, hydraulic, pneumatic, microcomputer control parts of the machine tool and the running performance of the whole machine. Finally, the comprehensive technical evaluation of the machine is obtained.

1. Geometric accuracy: including the comprehensive reflection of the relative and mutual position accuracy of the spindle and the worktable, spindle radial jump, end face run out (movement), worktable flatness, rotation accuracy, etc.

2. Positioning and repeated positioning accuracy of machine tool: that is, the difference between the set value and the actual value (measured value) of the table or spindle motion position, or the average value of the difference between multiple measurements. It is a comprehensive index reflecting the control and compensation accuracy of the machine tool numerical control system and the setting of the machine tool itself.

3. Working accuracy: refers to the inspection of the finishing dimensions of representative workpieces, and the dimensional accuracy is the comprehensive assessment of the geometric accuracy and positioning accuracy of the machine tool under certain cutting and processing conditions. It mainly includes boring accuracy, parallel hole spacing accuracy, coaxiality of turning boring, milling accuracy of surrounding surface, arc interpolation milling accuracy, etc.

4. Appearance: it can be inspected according to relevant standards of general machinery, but the appearance requirement of machining center is higher than that of general machine tool because of its high price.