The Application of Frequency Converter in CNC Machine Tools of Machine Tool Plant

I. Introduction

Digital control machine tools, abbreviated as numerical control machine tools (NC, Numerical Control), are integrated electromechanical products integrating mechanical, electrical, hydraulic, pneumatic, microelectronics, and information technologies for more than 30 years, and are used in the production of modern machine tools. Generally, multi-motor drag is used, and the spindle and each feed system are respectively dragged by their own motors. Due to the wide range of machine tools, different workpieces, different processes, and different tools, the execution components of machine tools are required to have different speeds of motion. Therefore, the main movement of the machine tool should be capable of stepless speed regulation. The spindle speed control system generally uses AC spindles. system.

With the development of variable frequency speed control technology, the AC drive of the spindle of the CNC machine tool can meet the needs as well. The main drive motor drives the spindle to rotate through the belt drive, or through the belt drive and the reduction gear in the spindle box (to obtain more torque) to drive the spindle to rotate. Due to the wide speed range of the spindle motor and stepless speed regulation, the structure of the spindle box is greatly simplified.

Second, the technical requirements of CNC machine tools

1 motor requirements

Usually requires the use of variable frequency motor, or ordinary motor plus fan to meet the motor cooling requirements at low frequencies, and requires a wide range of motor speed.

2 Technical requirements for the frequency converter

a requires low-frequency torque

At low frequency (1~10Hz), it can come out with 150% of rated torque.

b Fast dynamic response of torque, high precision of steady speed

Can achieve a very good dynamic response effect, according to the load changes, through the output torque changes quickly respond, so as to achieve the stability of the shaft speed.

c Fast deceleration and stop speed

Generally, the accelerating and decelerating time of the CNC machine tool is relatively short. The accelerating time depends on the performance of the inverter and the decelerating time depends on the external braking resistor or the braking unit.

d High reliability

Inverter's low failure rate, stable and reliable operation

e EMC issues

CNC machine tools for industrial applications, not only requires the inverter itself strong anti-interference ability, but can not interfere with the peripheral control equipment.

It can be known from the working principle of the inverter that the output of the inverter contains certain harmonic components. If it is handled improperly, it will cause interference to other devices. The most easily disturbed device on CNC machine tools is the CNC controller. Once the CNC controller is disturbed, the system will not work properly. In particular, the inverter frequency command and operation command may also be disturbed. Severe interference may cause frequency command instability and inverter malfunction. The solution to this type of problem is to undergo rigorous EMC testing at the factory of the inverter and use EMC-qualified inverter products.

Third, the system composition

1 CNC numerical control system structure as shown below:



2 Configuration:

Inverter: ALPHA6000-37R5GB

Braking resistor: 80Ω/750W

7.5KW speed regulating motor

Fourth, wiring and inverter system settings

1 Inverter wiring schematic



2 Inverter parameter setting:

P0.01 =2 Terminal AI1 is analog input

P0.04=1 External terminal control

P0.07=150 (maximum output frequency)

P3.03=14 (External fault shutdown)

P3.17=2 (speed arrival)

P3.14=19 (fault output)

P2.06=6 (carrier frequency)

P9.00=100 (slip frequency compensation gain)

P3.01=1 (X1 forward)

P3.02=2 (X2 reverse)

P3.04=6 (X4 reset)

Fifth, the characteristics of ALPHA6000 series inverter

ALPHA6000 series inverters, low output torque, high speed accuracy, reasonable price, complete functions, stable and reliable quality, are ideal for machine tool equipment. ALPHA6000 series inverter has the following features
1 dedicated motor control CPU, space vector PWM control, ultra-quiet and stable operation.

2 The low-frequency torque characteristics are good, and the low-speed rated torque output operates stably. .

3 Through EMC test, the anti-interference ability is strong.

4 advanced automatic torque compensation function design, load adaptability.

5 Real-time prosecution of output current, with good dynamic response capability.

6 Full-featured, up to 40 protection and alarm functions.

Six, the use of effects

After the ALPHA6000 series inverters were tested in batches by Shenyang Machine Tool Plant, the ALPHA6000 series of inverters were fully tested. The user's proof of use with the ALPHA6000 inverter can fully meet the requirements of the spindle control of the machine tool. The low-speed operation output torque is stable and can meet different parts. Machining needs, can completely replace the traditional structure of the rolling bearing spindle, and this spindle structure is simple, compact, can achieve true stepless speed regulation. The speed of this spindle is controlled by an external analog signal to control the output frequency. Different machining processes (such as roughing, finishing, etc.) require different rotation speeds. At this time, the digital control system can output different analog voltage signals to the inverter. The realization of different speeds, at the same time the start-stop signal is also controlled by the numerical control system, which improves the degree of automation and prolongs the service life of the tools. At present, ALPHA6000 inverter has been equipped with a large number of Shenyang machine tools, the user response is excellent, and the failure rate is almost zero.

Seventh, conclusion

Through the successful application of the ALPHA 6000 series frequency conversion on the spindle of CNC machine tools, the situation of relying on imported products in the past has changed and the product cost has been greatly reduced. ALPHA6000 series inverters are rapidly used in CNC machine tools because of their unique performance and superior cost performance.