The movement of nc machine tools to achieve high accuracy, positioning accuracy and high automation performance, the characteristics of its mechanical structure is mainly manifested in the following several aspects.
1. High stiffness
CNC machine to work under high speed and heavy load conditions, therefore, the machine tool bed, column, spindle, workbench, tool post, such as main components, all needs to have high rigidity, to reduce the deformation and vibration in the work.For example: some lathe bed, double-wall structure is adopted, and equipped with inclined to the floor and strengthening rib, make it has high bending stiffness and torsional stiffness;As the increase of the stiffness in the spindle assembly, Chen spindle assembly to take the necessary steps in the structure, but also high stiffness of bearing, and appropriate preloaded.Increase the tool post base size, reduce the overhanging cutter, to adapt to the stability of heavy cutting, etc.
2. High sensitivity
The moving parts of nc machine tools should have high sensitivity.Usually use rolling guide rail components, plastic guideway and hydrostatic guideway, in order to reduce friction, without crawling phenomenon in the low speed movement.Workbench, head and other parts of mobile, driven by ac or dc servo motor, the ball screw transmission, reducing the drive torque needed to feed system, the positioning precision is improved and the running smoothness.
3. High vibration
Some of nc machine tool moving parts, besides should have high rigidity, high sensitivity, also should have high vibration, namely under the condition of high speed cutting, reduce vibration, to ensure high precision and high surface quality of machining parts.Paying special attention to is to avoid the resonance when cutting, therefore, the dynamic characteristics of nc machine tools is put forward the higher request.
4. Small thermal deformation

Machine tool spindle, workbench, head of the moving parts in motion will produce heat, resulting in a corresponding thermal deformation.And process automation and the development of precision machining, the machining precision of machine tools and precision stability higher and higher demands are proposed.To ensure the movement precision of parts, require less calorific value of the moving parts, to prevent excessive thermal deformation.For this purpose, the machine according to the principle of thermal symmetric structure design, and to improve the spindle bearing, lead screw nut pair. The friction characteristics of high-speed linear motion guide.Such as mj - 50 CNC numerical control lathe spindle box shell design, in accordance with the principle of thermal symmetry and in the outer shell casting with intensive cooling fin structure, main shaft bearing adopts high performance grease lubrication, and strictly control the injection rate, make the spindle temperature rise is very low.To produce a large number of scraps of nc machine tools, are generally good with a automatic chip removal device, etc.
5. High accuracy keep sex
In order to speed up the numerical control machine tool investment recycling, must keep the machine high start than (two to three times higher than common machine tool), therefore, must increase the service life of machine tool and accuracy stable, in guarantee as much as possible to reduce the electrical and mechanical failure at the same time, nc machine tools in the process of long-term use of no loss of accuracy.
6. High reliability
Numerical control machine tool under the condition of automatic or semi-automatic work, especially in the flexible manufacturing system (FMS) in the numerical control machine tool, can realize unmanned management in running 24 hours a day, which requires the machine has high reliability.Therefore, to improve the reliability of CNC equipment and machine tool structure, such as frequent actions in the working process of the tool change mechanism, tray, workpiece switching device, such as components, must ensure that in the long-term work very reliable.In addition, the introduction of machine tool fault diagnosis system and adaptive control system, optimization of cutting parameter, etc., are also helps to machine work in a reliable way.
7. Modular
Flexible machine configuration of modular design thought, the user in terms of the function of nc machine tools, specifications have more choices, do both can satisfy the processing requirements of users, and as far as possible, don't assume additional costs for redundant functions.
Nc machine tool is usually composed of lathe bed, column, spindle box, workbench, tool holder system and electrical assembly parts.If the basic unit of various parts as the foundation, according to different functions, design specifications and prices into a variety of modules, the user can according to need to choose the most reasonable function module configured to the machine.It can not only reduce the numerical control machine tool design and manufacturing cost, and can shorten the design and manufacturing cycle, ultimately win the market.At present, the concept of modularity has started from the function modules to develop in the direction of the modularity, it is not limited to the function modular, but expanded into modular parts and raw materials.
8. Mechanical and electrical integration
Mechanical and electrical integration of the nc machine tool is the important requirements for the overall design and structure design.It is to point to in the realization of the function of the nc machine tool and general layout must consider the combination of both mechanical and electrical.New type of nc machine tool of the system is no longer their associated independent system.One of the most typical example is the nc machine tool spindle system is no longer the pure mechanical drive gears and pulleys, and more is on the basis of motorized spindle by ac servo motor.Electrical assembly and is no longer a pure free independent from the machine tool parts, but on the layout and organically combined machine tool structure., thanks to the development of anti-jamming technology has now put the power of the high voltage module and microelectronics computer weak current modules are combined into an organic whole, both reduced volume, and improve the reliability of the system.
Compared to common machine tool, CNC machine though rather than have a lot in common in terms of structure, but or improvements in the structure, automation, higher sensitivity, etc.