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Solutions

Solutions for servo drives in digital machine tools

Classification of machine tools

    CNC machine tools are classified according to technological purposes. CNC machine tools can be divided into CNC drilling machines, lathes, milling machines, boring machines, grinders and gear processing machine tools, as well as presses, punches, pipe benders, shearing machines, etc.

Description

According to the control mode of numerical control system, it can be divided into open-loop control, semi-closed-loop control and full-closed-loop control.

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      The feature of the open-loop control system is that there is no detection feedback device in the system, the command information is transmitted in one direction, and after the command is issued, no feedback is returned, so it is called open-loop control. At present, most common CNC lathe spindles, high-speed milling machines, precision engraving machines, etc. are such open-loop controls. Features in such occasions: small speed fluctuations when sudden load is required; fast acceleration and deceleration performance (improving processing efficiency); large low-speed heavy cutting torque; wide speed adjustment range; multiple CNC speed setting methods (-10v ~ + 10v analog or pulse input); large fluctuation range of power grid environment, large oil pollution in physical environment, etc.


The semi-closed-loop control CNC machine tool does not directly detect the displacement of the worktable, but uses a corner displacement detection element to measure the rotation angle of the servo motor or screw, calculate the actual displacement of the worktable, and feed it back to the CNC for position control. Turning machining centers, compound turning and milling machines, high-speed tapping machines, centering machines, deep hole drilling machines, semi-automatic boring and milling machines, etc. are mostly such semi-closed loop controls. Characteristics in such occasions: small speed control fluctuations; wide speed range; fast acceleration and deceleration performance; large low-speed heavy cutting torque; small position error during high-speed position control; large low-speed lock shaft force; accurate positioning;


The characteristic of the full closed-loop control (double closed-loop) system is that the actual displacement of the table is fed back to the computer using the detection elements installed on the table, compared with the required position command, and controlled with the difference until Until the difference is eliminated. It can be seen that the closed-loop control system can eliminate the effects of various errors of mechanical transmission components and the interference generated during the processing of the workpiece, thereby greatly improving the processing accuracy. High-end turning and milling machines, automatic boring and milling machines, corrugated paper shearing machines, steel bar (steel pipe) bending (shearing) machines, etc. are mostly such closed-loop controls. In addition to the requirements mentioned above, the most important features of this type of machine tool are high machining accuracy and fast moving speed.


The MT series inverters and SVM series servo drives launched by our company for the machine tool industry meet the various CNC machine tools of open-loop control system, semi-closed-loop control system and full-closed-loop control system.


Features

The advantages of the MT series for open loop system solutions:

1. Super adaptability to the power grid, which can be used in the occasions where the power grid is low for a long time or the power grid fluctuates, etc.
2. Strong environmental adaptability, completely independent air duct design greatly improves the resistance to harsh environments such as oil pollution, dust and heat, and the unique coating thickening process provides double protection
3. Excellent control performance, not only ensure the rapid acceleration and deceleration performance, but also effectively reduce the frequency conversion overload, overcurrent protection, and maximize the guarantee of production continuity
4. Excellent low-frequency torque characteristics, low-speed recutting speed fluctuation is less than 1RPM
5. Unique field weakening control technology, so that the commonly used low-frequency high-torque motor (fundamental frequency 33.3Hz) can run at 0-200Hz


The advantages of SVM series for semi-closed loop control system and full closed loop control system:
1. Super adaptability to the power grid, which can be used in the occasions where the power grid is low for a long time or the power grid fluctuates, etc.
2. Strong environmental adaptability, completely independent air duct design greatly improves the resistance to harsh environments such as oil pollution, dust and heat, and the unique coating thickening process provides double protection
3. Excellent control performance, which not only guarantees rapid acceleration and deceleration performance, but also effectively reduces frequency conversion overload and overcurrent protection, ensuring maximum production continuity
4. Excellent low-frequency torque characteristics, low-speed recutting speed fluctuation is less than 1RPM
5. Unique field weakening control technology, so that the commonly used low-frequency high-torque motor (fundamental frequency 33.3Hz) can run at 0-200Hz, closed-loop control can reach 1300Hz
6. The drive can drive synchronous and asynchronous spindles (motors), and optimized current control reduces the heating of the spindles (motors)
7. High positioning accuracy, ± 1 pulse, multi-point indexing positioning function
8. The zero-speed lock has a large shaft force, and it is very good to complete the tool change or cutting action
9. Full pulse position control range speed can reach 0 ~ 8000rpm, no speed control position control switch
10. Double PG full-closed control to achieve higher control accuracy and corresponding speed