Maixin's MR series high-performance vector control frequency converter adopts a brand-new hardware platform with flexible and diverse terminal functions, independent air duct design, and more stable operation. The product has a complete braking circuit solution, built-in adaptive PID function module, and comprehensive protection and oscillation suppression functions.
1. Scope of application
Application of frequency converter debugging for CNC machine tool spindles.
2. Principle Overview
CNC machine tools
CNC machine tools , short for Computer Numerical Control machine tools, are automated machine tools equipped with a program control system. This control system can process programs with control codes or other symbolic instructions, decode them, input them into the CNC device via an information carrier, and after processing, the CNC device sends control signals to control the machine tool's movements to perform various metal processing operations.
frequency converter
Currently, Maixin Electric's new vector control frequency converter has automatic detection, automatic identification , and adaptive functions for motor parameters. Before the asynchronous motor starts normal operation, the frequency converter automatically identifies the parameters and adjusts the relevant parameters in the control algorithm according to the identification results, thereby performing vector control on the asynchronous motor.
System structure and operation mode of CNC machine tool spindle frequency conversion
Basic Principles of Spindle Frequency Control
According to the theory of asynchronous motors, the formula for the spindle motor speed is:
n = (60f/p) × (1-s)
Where p : number of pole pairs of the motor, s : slip, f : frequency of the power supply, and n : speed of the motor.
As can be seen from the above formula, motor speed is directly proportional to frequency. Changing the frequency can smoothly adjust the motor speed. For frequency converters, the frequency adjustment range is very wide, and it can be adjusted arbitrarily between 0 and 600Hz (or even higher frequencies). Therefore, the spindle motor speed can be adjusted within a wide range. Of course, when the speed is increased, the impact on its bearings and windings should also be considered to prevent excessive wear and overheating of the motor. This can generally be limited by setting a maximum frequency.
2.1 Hardware Wiring
Inverter model: MR500-4T-7.5B
Spindle motor voltage: Y380V
Current: 15.5A
Power: 7.5kW
Rotation speed: 6000 r/min
Frequency: 200Hz
The wiring components include: main circuit and control circuit.
Note: The above is a schematic diagram of the inverter wiring terminals. Please refer to the actual product for the terminal definitions.
2.2 Parameter Settings
Note 1 : The above are the parameters for modifying and confirming the frequency converter . "/" represents the default value.
Note 2 : The above are the basic settings for inverter parameters. For function details, please refer to the instruction manual. Parameter F01.09 is the value determined after debugging. Please refer to the debugging test for details.
2.3 Debugging and Testing
Connection between the motor shaft, main shaft, and external encoder shaft:
The motor shaft and the main shaft are connected by a V-belt pulley. The motor shaft is on the left and the main shaft is on the right. The specific size of the pulley depends on the actual site conditions.
The main shaft is connected to the external encoder via a timing belt. The encoder shaft is on the upper side, the main shaft is on the lower side, and the two timing pulleys have the same module.
Debugging process:
Turn on the CNC machine tool system;
The program manually inputs the code to start the spindle and set the speed G.
Run the program and observe the given speed and the actual spindle speed value fed back by the encoder.
Adjust the system parameters to match the given speed value with the actual speed value. Adjust the P055 parameter (for Heidemann CNC systems; parameters may vary for different CNC systems) via the motor shaft pulley and spindle pulley.
Limit the maximum spindle speed by adjusting the inverter parameter F01.09.
References
MR Series Frequency Inverter Manual
MR Series Frequency Inverter Selection Manual
