Requirements for the Structure of a Machining Center

Requirements for the Structure of Machining Centers (1) Higher Static and Dynamic Stiffness. The machining centers from Shenyang Machine Tool Factory are expensive, and their processing costs exceed those of traditional machine tools. Therefore, measures must be taken to significantly reduce the processing time for individual workpieces. Reducing the processing time includes two aspects: on one hand, the development of new cutting tool materials has greatly increased cutting speeds, significantly shortening cutting times; on the other hand, the use of automatic tool change systems and accelerated clamping operations has considerably reduced auxiliary time. These measures have greatly improved productivity and achieved good economic benefits, but they have also significantly increased the load and operating time of the machine tools. Moreover, the structural stiffness of components such as the machine bed, guide rails, work table, tool holder, and spindle box will affect the geometric accuracy of the machine and the errors caused by deformation. All these factors require CNC machine tools to have higher static stiffness. Vibration during the cutting process not only directly impacts the machining accuracy and surface quality of parts but also reduces tool life and affects productivity. As machining centers operate continuously, it is not possible to make manual adjustments (such as changing cutting parameters or altering tool geometry) during processing to eliminate or reduce vibration. Therefore, it is also necessary to enhance the dynamic stiffness of machining centers. In designing the structure of machining centers, these considerations lead to the use of closed box structures for the main components, a reasonable layout of reinforcement plates, and strengthening the contact stiffness of various parts, effectively enhancing the static stiffness of the machine. Additionally, adjusting the mass of components may change the system's natural frequency, and increasing damping can improve the damping characteristics of the machine, which is an effective measure to enhance the machine's dynamic stiffness. (2) Smaller Thermal Deformation. During machining, machining centers are influenced by internal and external heat sources such as cutting heat and friction heat, resulting in varying degrees of thermal deformation in different components, which affects the machining accuracy of workpieces. Since the spindle speeds, feed rates, and cutting amounts of machining centers are greater than those of traditional machine tools, combined with automated and often continuous processing, the heat generated is also substantial. Effective methods such as liquid cooling and air cooling are employed to control temperature rise; improving machine structure to ensure that thermal deformation occurs in non-error-sensitive directions is also crucial. For instance, the vertical columns of horizontal machining centers often adopt a double-column frame structure that is symmetrically arranged. The thermal deformation causes a shift in the direction of the spindle axis, which can be compensated through coordinate correction, minimizing heat generation and attempting to separate the heat source from the main unit. (3) Reduced Friction Between Moving Parts and Elimination of Drive System Clearance. The displacement of the machining center's work table is measured in pulse equivalents as small units, and during tool setting and similar operations, the work table often moves at extremely low speeds. This requires the work table to accurately respond to commands from the CNC system, which is related to the friction characteristics of moving parts. Machining centers use rolling guides, which have lower static friction than sliding guides, and under the action of lubricating oil, their friction decreases as the speed increases, effectively avoiding low-speed crawling phenomena, thereby enhancing the motion stability and positioning accuracy of the machining center. The use of ball screws instead of sliding screws in the feed system is based on the same principle. Furthermore, employing pulse compensation devices for pitch compensation eliminates the clearance in the feed drive system, and some machines utilize backlash-free drive systems. (4) High Longevity and Good Precision Retention. A good lubrication system ensures the longevity of machining centers, while the guide rails, feed screws, and spindle components utilize new wear-resistant materials, allowing machining centers to maintain good precision over long-term use. (5) User-Friendly Design. Machining centers employ spindles, multi-tool holders, and automatic tool change devices to complete multiple processes in one clamping setup, significantly saving time on clamping and tool changes. Since manual operation is not required, closed or semi-closed processing is utilized, creating a clear, clean, and coordinated human-machine interface. The machine has strong interlocking capabilities to prevent accidents, improving the operator's conditions for observation, operation, and maintenance, and is equipped with emergency stop devices to avoid unforeseen accidents. All operations are centralized on a single control panel, making it clear and reducing the chances of operational errors. For more information about gantry machining centers, please visit: http://www.yxskkj.com.cn