Development of CH360 turning center

The turning center is a CNC lathe with compound processing capability. It combines the processing performance of CNC lathes and machining centers. It is a variety of CNC machine tools that are currently developing in industrialized countries. The utility model has the advantages that the utility model has the advantages of small multi-purpose, small floor space, saving investment, ensuring processing precision, reducing workpiece in-process, and improving processing efficiency.
The CH360 turning center is a key scientific and technological project of the “Ninth Five-Year Plan” in Zhejiang Province. Its biggest feature is precision, high efficiency, practicality and economy. It is easy to accept for the majority of users under the market economy conditions, in line with China's national conditions.

1 Determination of the design plan


According to the current level of international and domestic economic and technological development and the relationship between supply and demand determined by the market economic system, it is currently appropriate to develop a turning center with many functions and simple structures. Therefore, the number of controllable axes should be developed first (ie C axis, X). The turning center of the shaft and the Z-axis) will be developed on the basis of this to develop a turning center with more controllable number of axes and more functions.
  • The main motor adopts a servo motor with C-axis function. The same drive chain is used to switch and interlock the analog signals through the built-in PLC to realize the main motion and C-axis motion of the main shaft respectively. This solution is different from the two commonly used transmission chain schemes, the mechanical structure is greatly simplified, the manufacturing is easier, and the cost is relatively low.
    The main bearing is grease-lubricated and relies on the contact labyrinth seal. The amount of grease enclosed has a great influence on the life of the spindle bearing and the temperature rise during operation. Generally, the sealing amount of each bearing is controlled within the range of 10 to 14 g. The structure of the main shaft portion is shown in Fig. 1.

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    Figure 1 Spindle structure

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    Figure 2 Feed transmission structure

  • The machine adopts the structure of the flat bed inclined slide, which not only facilitates chip removal, but also has the advantages of small footprint, easy operation, pleasant appearance and good manufacturing process.
  • The 12-station rotary power tool holder from SAUTER, Germany. The CNC turret tool holder is a key component for multi-process machining such as turning, drilling, boring and milling. In order to ensure the working accuracy of the machine and shorten the manufacturing cycle, the power tool holder of SAUTER of Germany is used.

      2 Determination of technical parameters

      1. According to the actual needs of domestic users and the development trend of similar foreign products, the main parameters of the machine tool are determined as follows:

      1. The maximum turning diameter of the bed body: 360mm;
      2. Maximum processing length: 750mm;
      3. Spindle through hole diameter: 80mm;
      4. Spindle speed (stepless): 0-3500r/min;
      5. Number of knives loaded with knives: 12;
      6. Z-axis feed rate (stepless): 0-20m/min;
      7. X-axis feed rate (stepless): 0-10m/min;
      8. Power tool spindle speed: 0-2500r/min;
      9. Main motor power: 12kW;
      10. X, Z axis minimum setting unit: 0.001mm;
      11. C axis minimum output increment: 0.001 °
      12. Z-direction repeat positioning accuracy: 0.007mm;
      13. X-direction repeat positioning accuracy: 0.002mm;
      14. Tool holder repeat positioning accuracy: 0.002mm;
      15. Processing roundness: 0.002mm;
      16. Dimensions (length × width × height): 2000mm × 800mm × 1600mm;
      17. Net weight of machine tool: 4800kg.

      3 main measures to improve performance

      1. Measures to improve accuracy
        1. The headstock components are made of high quality and high precision NSK bearing support spindles from Japan, double row short cylindrical roller bearings and two ball bearings for front bearings, and double row short cylindrical roller bearings for rear bearings, so that the front and rear bearings are evenly heated and reduced. Spindle angular displacement reduces thermal distortion of the machine tool. The main drive is lubricated with high-speed grease to reduce the heat generated by the main bearings and other bearings and extend bearing life. The spindle system is precisely balanced to ensure that the spindle box components have low vibration, good rigidity and high precision.
        2. The bed has a barrel-like rib structure and is integrated with the bed to enhance rigidity. The bed rail surface adopts super-audio quenching and peripheral grinding technology, and the depth of the quenching layer is maintained at 2.5 mm or more, which effectively improves the precision and precision retention of the machine tool.
        3. The longitudinal and lateral feed servo motor output ends of the machine are respectively provided with elastic coupling and synchronous toothed belt connection to make the transmission more stable. The vertical and horizontal feeds are all driven by the internal circulation ball screw drive, so that the X and Z direction repeat positioning accuracy of the machine tool reaches 0.002mm and 0.007mm respectively.
        4. The minimum setting unit of X-axis and Z-axis is 0.001mm, the minimum output increment of C-axis is 0.001°, the repeating positioning accuracy of turret is 0.002mm, and the CNC system has tool compensation, clearance compensation, pitch compensation, etc. The function fully guarantees the machining accuracy of the machined parts.
      2. Measures to improve efficiency
        1. In the turning center, the rotary body can be compositely processed, and the processes of turning, drilling, milling and tapping are integrated into one machine tool, and the parts have small clamping error, which improves the processing quality and efficiency, saves equipment costs, and simplifies. Production management.
        2. The maximum speed of the spindle reaches 3500r/min, the maximum speed of the power tool spindle reaches 2500r/min, the rapid feed of the X-axis and the Z-axis reaches 10m/min and 20m/min respectively, and the conversion time of the Z-direction from 0 to 20m/min is only 0.06s. The conversion time of the spindle from 0 to 3500r/min is only 2.5s, and the adjacent tool change time of the turret is only 0.3s, which ensures the improvement of machining efficiency.
      3. Improve the practicality of machine tools
        1. The CNC system has more complete cycle functions, such as linear interpolation, circular interpolation, taper cutting cycle and thread cutting cycle, which makes the machine programming simple. At the same time, it can also perform man-machine dialogue programming, perform motion trajectory and dynamic simulation, and have a rich database of turning technology.
        2. The machine tool is easy to set up. There are many ways to directly process the parts with the tool and input the measured values ​​into the system to automatically generate the tool offset value. Tool adjustments are quick and easy to install.
        3. The function keys on the operation panel are defined by the factory itself. They are relatively simple and intuitive. The PLC controls the three-jaw clamping and relaxation, the tailstock sleeve is extended and retracted, the tool holder is selected, the positioning, the power tool is effective, the spindle and C The axis is effective, etc., and the functions required for electromechanical coupling are realized in the simplest operation.
        4. A turning center can replace multiple and multiple machine tools. It has the cutting function of ordinary lathe. It can drill longitudinally, drill eccentric hole, tap thread, longitudinal milling, milling end face and milling with C axis and rotary tool. The circumferential groove, the end face thread, the milling polygon, the milling circle, the milling longitudinal spiral groove, the milling contour and the lettering can achieve the purpose of finished machining on one machine.
      4. Measures to reduce machine tool costs

        5. Since we have tried to replace the complexity with the simplification in the overall scheme and structural performance design, for example, the number of control axes is 3, the servo motor with C axis function is used as the main motor, and the longitudinal and horizontal feeds are respectively used as couplings. And the synchronous toothed belt drive makes the machine tool simple and reasonable in structure, and reduces the cost. The cost of the machine tool is about 400,000 yuan, and the price is about 550,000 yuan, while the price of other similar turning centers in China is more than 700,000 yuan.

      4 Conclusion

      The successful development of the CH360 turning center provides a precise, efficient, practical and economical technical equipment for the mechanical processing industry in China. This product has been used by users such as Jiangsu Xiangyang Internal Combustion Engine Parts Factory, and it has been verified by actual tests that the automation of the machine tool is high. The work is reliable, the performance of the whole machine is close to the level of similar foreign products, and it can replace imported.

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