Abstract: The structural characteristics of the main part of metal cutting CNC machine tools are analyzed, and the appearance characteristics of mechanical products from the perspective of industrial art modeling are discussed.
1 Characteristics of CNC machine tools
The definition of numerical control in GB is "a method of controlling the movement of the machine tool and its machining process with digital signals". Modern CNC machine tools are typical mechatronics processing equipment that integrates high technology. CNC machining equipment is mainly divided into three categories: cutting, pressure processing and special processing (such as CNC EDM machine tools). The machining process of the CNC machine tool for cutting can be automatically performed according to a predetermined procedure, eliminating artificial operation errors and achieving control precision that is difficult to achieve by manual operation. The machining accuracy can also be corrected and compensated by software. Therefore, the machining accuracy and the repeating positioning accuracy higher than the machine tool precision can be obtained; after the workpiece is clamped, the workpiece can be successively roughed and finished, and after the automatic tool change device is arranged, the auxiliary machining time can be shortened and the productivity can be improved; Since the machine's motion trajectory is controlled by programmable digital signals, it is possible to process single-piece and small-volume, complex-form parts, and the production preparation cycle is greatly shortened. In summary, CNC machine tools are characterized by high precision, high efficiency, high degree of automation and good flexibility.
From the production status and development trend of CNC machine tools, due to the penetration and application of new technologies and new technologies such as microelectronics technology and information processing technology in the machine tool industry, it has not only “quality†in terms of mechanical structure performance compared with ordinary machine tools. And the "shape" changes, and its appearance also formed its own unique style and characteristics.
2 Characteristics of mechanical structure design of CNC machine tools
Although CNC machine tools also have the bed and columns, guide rails, work tables, tool holders and other components of ordinary machine tools. However, in order to match the high-precision and high-speed control of the control system, the structural design of the main part of the machine tool also requires high precision, high stiffness, low inertia, low friction, no gap, high resonant frequency, proper damping ratio, etc. . Since the mechanical structure is a concrete means to reflect its performance and is the core factor to achieve performance (of course, the structure is also affected by materials and processes), therefore, the key components of CNC machine tools have also undergone major changes in structural design.
2.1 Structural features of the basic components
The basic components of the numerical control machine tool mainly include support members such as a bed body, a column, a work table, etc., and their basic function is to support the bearing and holding the relative positions of the respective executing organs. The CNC machine tool integrates rough machining in one, which is capable of withstanding the maximum cutting force of the large knife and the large knife during roughing, and the high precision during finishing. Therefore, the structural design of the basic parts has high requirements on strength, stiffness, vibration resistance, thermal deformation and internal stress. The main measures adopted by the current production of CNC machine tools are: the fully-closed section of the casting, the reasonable arrangement of internal partitions and ribs, the sand-filled or filled concrete, the widened rail surface, and the inclined bed and guide rails of the lathe are also beneficial for platooning. The scraps, the bed and the column are made of steel welded structure, which can significantly improve the rigidity. According to the thermal symmetry principle, the heat dissipation and heat insulation effect can be increased.
2.2 Structural characteristics of the main drive system
The main drive system achieves the cutting power required for various tools and workpieces, and guarantees constant power output in the widest possible speed range. At the same time, in order to achieve the best cutting speed for CNC machine tools, the main drive must be in a wide range. Infinitely variable speed is achieved within. The current CNC machine tools use high-performance DC or AC stepless speed-regulating spindle motors, which is much simpler than the mechanical step-change transmission chain of ordinary machine tools. The accuracy, stiffness, vibration resistance and thermal deformation performance requirements of the spindle components that have a direct impact on the machining accuracy can be ensured by the structural design of the spindle components and the reasonable bearing combination and the selection of high-precision special bearings. In order to increase productivity and automation, the spindle should have automatic clamping, loosening, chip cleaning and spindle quasi-stop mechanism for the tool or workpiece. Recently, Japan has developed a new type of ceramic spindle, which is light in weight and low in thermal expansion rate. It is used in machining centers and has high rigidity and precision.
2.3 Feed system structure characteristics
The feed system of the CNC machine is driven by a servo motor, and the ball or the workpiece is driven by the ball screw to complete the feed motion in each coordinate direction. In order to determine the transmission accuracy and working stability of the feed system, when designing the mechanical device, the principle is “no gap, low friction, low inertia, high stiffnessâ€. The specific measures are as follows: 1 Low friction, light drag, high Efficiency ball screw and linear rolling guide; 2The servo motor with high torque and wide speed is directly connected with the screw to shorten and simplify the feed chain; 3 Eliminate the gear, screw and coupling through the anti-backlash device Drive clearance; 4 pairs of rolling guides and lead screws preloaded, pre-stretched.
2.4 CNC rotary table and automatic exchange workbench
The CNC boring, CNC milling and machining center adopts a rotary table with internal structure and the characteristics of the CNC feed drive mechanism to realize the indexing and feeding motion at any angle of the circumference. For multi-step CNC machine tools, an automatic exchange table is configured to further reduce auxiliary machining time.
2.5 tool holder system
Rotary tool holders, replacement of spindle tool change and automatic tool change system with tool magazine, multi-tool holder and multi-spindle layout play an important role in improving production efficiency and automation. In order to quickly position and clamp the tool on the machine, the standard tool system and the machine clamp are commonly used.
2.6 CNC accessories
The function of the machine tool attachment is to achieve automatic machining with the machine tool. The special accessories for CNC machine tools are: 1 tool setting instrument, 2 automatic programming machine, 3 automatic chip conveyor, 4 material storage and loading and unloading device, 5 automatic cooling, lubrication and various new matching parts such as guide rail cover.
3 appearance characteristics of CNC machine tools
The appearance of CNC machine tools mostly adopts a simple and straight-line plate-type fully enclosed safety cover. It is equipped with a modern operation panel that integrates operation, display and control. It eliminates various operating handles, handwheels and line types of ordinary machine tools. Complex and fragmented multifaceted surface morphology. The safety shield can prevent high pressure, large flow of coolant and iron filings from splashing, reduce dust intrusion, and reduce sound and noise. It is conducive to the precision maintenance and environmental protection of the machine tool, and truly reflects the integration of machine, electricity and liquid.
The desktop or hanging CNC operating panel designed according to the principle of ergonomics is the only interface for machine tool and operator contact and information exchange. The number and arrangement of indicators, buttons and buttons and CRT design are suitable. The human operation characteristics are also conducive to the coordination and communication between human and machine. Through the visually good key surface color and the standardized pictogram symbol extraction, the information between the two can be accurately reflected and transmitted.
4 Conclusion
The structural design of the CNC machine tool reflects the deep characteristics of the intrinsic function of the product. The appearance expresses the surface layer characteristics of the product. For the user, the deep structural properties closely related to the product use are transmitted and expressed through the appearance of the surface layer. Although the fully enclosed protective cover covers the main structure of the machine tool, it at least conveys the deep inner content of the CNC machine tool: 1 advanced numerical control digital display device; 2 reliability and safety protection for the precision and rigidity of the machine tool And environmental protection and other strict requirements; 3 using advanced standard tool system and automatic tool changer with reasonable installation position; 4 using a complete set of commercialized, standardized new matching parts, automatic chip removal, lubrication and cooling devices. It is summarized as high precision, high efficiency, high automation and electromechanical integration.
About the author: Cai Jingzhi, female, 36 years old, associate professor, graduated from Lanzhou Railway Institute in 1984, majoring in mechanical manufacturing, and now engaged in the teaching of electromechanical relics.
Author: Cai Jingzhi Lanzhou Industrial College, Lanzhou 730050, China;
Zhu Yahong Lanzhou Changzheng Machinery Factory, Lanzhou 730050, China)
references:
[1] Editorial Board of "Practical CNC Machining Technology". Practical CNC Machining Technology [M]. Beijing: Ordnance Industry Press, 1995.
[2] Gao Min, ed. The basis of artistic modeling of mechanical products [M]. Beijing: Academic Press, 1989.
[3] Bi Jiejie editor. Machine tool numerical control technology [M]. Beijing: Mechanical Industry Press, 1991.
1 Characteristics of CNC machine tools
The definition of numerical control in GB is "a method of controlling the movement of the machine tool and its machining process with digital signals". Modern CNC machine tools are typical mechatronics processing equipment that integrates high technology. CNC machining equipment is mainly divided into three categories: cutting, pressure processing and special processing (such as CNC EDM machine tools). The machining process of the CNC machine tool for cutting can be automatically performed according to a predetermined procedure, eliminating artificial operation errors and achieving control precision that is difficult to achieve by manual operation. The machining accuracy can also be corrected and compensated by software. Therefore, the machining accuracy and the repeating positioning accuracy higher than the machine tool precision can be obtained; after the workpiece is clamped, the workpiece can be successively roughed and finished, and after the automatic tool change device is arranged, the auxiliary machining time can be shortened and the productivity can be improved; Since the machine's motion trajectory is controlled by programmable digital signals, it is possible to process single-piece and small-volume, complex-form parts, and the production preparation cycle is greatly shortened. In summary, CNC machine tools are characterized by high precision, high efficiency, high degree of automation and good flexibility.
From the production status and development trend of CNC machine tools, due to the penetration and application of new technologies and new technologies such as microelectronics technology and information processing technology in the machine tool industry, it has not only “quality†in terms of mechanical structure performance compared with ordinary machine tools. And the "shape" changes, and its appearance also formed its own unique style and characteristics.
2 Characteristics of mechanical structure design of CNC machine tools
Although CNC machine tools also have the bed and columns, guide rails, work tables, tool holders and other components of ordinary machine tools. However, in order to match the high-precision and high-speed control of the control system, the structural design of the main part of the machine tool also requires high precision, high stiffness, low inertia, low friction, no gap, high resonant frequency, proper damping ratio, etc. . Since the mechanical structure is a concrete means to reflect its performance and is the core factor to achieve performance (of course, the structure is also affected by materials and processes), therefore, the key components of CNC machine tools have also undergone major changes in structural design.
2.1 Structural features of the basic components
The basic components of the numerical control machine tool mainly include support members such as a bed body, a column, a work table, etc., and their basic function is to support the bearing and holding the relative positions of the respective executing organs. The CNC machine tool integrates rough machining in one, which is capable of withstanding the maximum cutting force of the large knife and the large knife during roughing, and the high precision during finishing. Therefore, the structural design of the basic parts has high requirements on strength, stiffness, vibration resistance, thermal deformation and internal stress. The main measures adopted by the current production of CNC machine tools are: the fully-closed section of the casting, the reasonable arrangement of internal partitions and ribs, the sand-filled or filled concrete, the widened rail surface, and the inclined bed and guide rails of the lathe are also beneficial for platooning. The scraps, the bed and the column are made of steel welded structure, which can significantly improve the rigidity. According to the thermal symmetry principle, the heat dissipation and heat insulation effect can be increased.
2.2 Structural characteristics of the main drive system
The main drive system achieves the cutting power required for various tools and workpieces, and guarantees constant power output in the widest possible speed range. At the same time, in order to achieve the best cutting speed for CNC machine tools, the main drive must be in a wide range. Infinitely variable speed is achieved within. The current CNC machine tools use high-performance DC or AC stepless speed-regulating spindle motors, which is much simpler than the mechanical step-change transmission chain of ordinary machine tools. The accuracy, stiffness, vibration resistance and thermal deformation performance requirements of the spindle components that have a direct impact on the machining accuracy can be ensured by the structural design of the spindle components and the reasonable bearing combination and the selection of high-precision special bearings. In order to increase productivity and automation, the spindle should have automatic clamping, loosening, chip cleaning and spindle quasi-stop mechanism for the tool or workpiece. Recently, Japan has developed a new type of ceramic spindle, which is light in weight and low in thermal expansion rate. It is used in machining centers and has high rigidity and precision.
2.3 Feed system structure characteristics
The feed system of the CNC machine is driven by a servo motor, and the ball or the workpiece is driven by the ball screw to complete the feed motion in each coordinate direction. In order to determine the transmission accuracy and working stability of the feed system, when designing the mechanical device, the principle is “no gap, low friction, low inertia, high stiffnessâ€. The specific measures are as follows: 1 Low friction, light drag, high Efficiency ball screw and linear rolling guide; 2The servo motor with high torque and wide speed is directly connected with the screw to shorten and simplify the feed chain; 3 Eliminate the gear, screw and coupling through the anti-backlash device Drive clearance; 4 pairs of rolling guides and lead screws preloaded, pre-stretched.
2.4 CNC rotary table and automatic exchange workbench
The CNC boring, CNC milling and machining center adopts a rotary table with internal structure and the characteristics of the CNC feed drive mechanism to realize the indexing and feeding motion at any angle of the circumference. For multi-step CNC machine tools, an automatic exchange table is configured to further reduce auxiliary machining time.
2.5 tool holder system
Rotary tool holders, replacement of spindle tool change and automatic tool change system with tool magazine, multi-tool holder and multi-spindle layout play an important role in improving production efficiency and automation. In order to quickly position and clamp the tool on the machine, the standard tool system and the machine clamp are commonly used.
2.6 CNC accessories
The function of the machine tool attachment is to achieve automatic machining with the machine tool. The special accessories for CNC machine tools are: 1 tool setting instrument, 2 automatic programming machine, 3 automatic chip conveyor, 4 material storage and loading and unloading device, 5 automatic cooling, lubrication and various new matching parts such as guide rail cover.
3 appearance characteristics of CNC machine tools
The appearance of CNC machine tools mostly adopts a simple and straight-line plate-type fully enclosed safety cover. It is equipped with a modern operation panel that integrates operation, display and control. It eliminates various operating handles, handwheels and line types of ordinary machine tools. Complex and fragmented multifaceted surface morphology. The safety shield can prevent high pressure, large flow of coolant and iron filings from splashing, reduce dust intrusion, and reduce sound and noise. It is conducive to the precision maintenance and environmental protection of the machine tool, and truly reflects the integration of machine, electricity and liquid.
The desktop or hanging CNC operating panel designed according to the principle of ergonomics is the only interface for machine tool and operator contact and information exchange. The number and arrangement of indicators, buttons and buttons and CRT design are suitable. The human operation characteristics are also conducive to the coordination and communication between human and machine. Through the visually good key surface color and the standardized pictogram symbol extraction, the information between the two can be accurately reflected and transmitted.
4 Conclusion
The structural design of the CNC machine tool reflects the deep characteristics of the intrinsic function of the product. The appearance expresses the surface layer characteristics of the product. For the user, the deep structural properties closely related to the product use are transmitted and expressed through the appearance of the surface layer. Although the fully enclosed protective cover covers the main structure of the machine tool, it at least conveys the deep inner content of the CNC machine tool: 1 advanced numerical control digital display device; 2 reliability and safety protection for the precision and rigidity of the machine tool And environmental protection and other strict requirements; 3 using advanced standard tool system and automatic tool changer with reasonable installation position; 4 using a complete set of commercialized, standardized new matching parts, automatic chip removal, lubrication and cooling devices. It is summarized as high precision, high efficiency, high automation and electromechanical integration.
About the author: Cai Jingzhi, female, 36 years old, associate professor, graduated from Lanzhou Railway Institute in 1984, majoring in mechanical manufacturing, and now engaged in the teaching of electromechanical relics.
Author: Cai Jingzhi Lanzhou Industrial College, Lanzhou 730050, China;
Zhu Yahong Lanzhou Changzheng Machinery Factory, Lanzhou 730050, China)
references:
[1] Editorial Board of "Practical CNC Machining Technology". Practical CNC Machining Technology [M]. Beijing: Ordnance Industry Press, 1995.
[2] Gao Min, ed. The basis of artistic modeling of mechanical products [M]. Beijing: Academic Press, 1989.
[3] Bi Jiejie editor. Machine tool numerical control technology [M]. Beijing: Mechanical Industry Press, 1991.
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