I. Introduction:

 

Digitally controlled lathes, referred to as CNC lathes (CNC lathes), are mechatronics products that integrate mechanical, electrical, hydraulic, pneumatic, microelectronics and information technologies in the past 30 years. Due to the wide range of machine tools, Different workpieces, different processes, and using different tools require the execution parts of the machine tool to have different movement speeds. Therefore, the main motion of the machine tool should be able to adjust the speed. The main drive motor drives the spindle to rotate through the belt drive, or through the belt drive and the spindle The reduction gear in the box (to obtain greater torque) drives the spindle to rotate. In the mechanical manufacturing industry, when using ordinary machine tools to process complex parts or batch products with high accuracy, skilled technical workers are required to perform manual operations. This inefficient traditional processing method can no longer meet the requirements of modern manufacturing. demand. With the rapid development of computer technology, advanced machining centers and CNC machine tools have emerged, and have gradually become mainstream machine tools.

 

2. Working principle:

 

　　 CNC lathe, turning center, is a high-precision, high-efficiency automatic machine tool. It has a wide range of processing performance, can process linear cylinders, oblique cylinders, arcs and various threads, has linear interpolation, arc interpolation and various compensation functions, and has played a good role in the mass production of complex parts. Economic effect.

 

The working process of CNC system

 

1) Input: The part processing program is usually imported from the upper-level computer through DNC.

 

2) Decoding: The decoding program translates the part processing program into a language that can be recognized inside the computer.

 

3) Data processing: including tool radius compensation, speed calculation and processing of auxiliary functions.

 

4) Interpolation: After knowing the type, starting point, ending point and feed speed of a curve, the data points are densified between the starting point and the ending point.

 

5) Servo output: The function of the servo control program is to complete the position servo calculation of this interpolation cycle and send the result to the servo drive interface.

 

Three, frequency converter application

 

Due to the high cost performance of frequency converters, frequency converters are commonly used on lathes. The application of frequency converters for speed regulation is a development trend of CNC machine tools. It has the following characteristics:

 

(1) The adjustment range of frequency conversion speed regulation is very wide. Generally, general-purpose inverters can realize stepless speed regulation within the range of 0-400Hz.

 

(2) Inverter + ordinary motor (or variable frequency motor) drive has harder mechanical characteristics, and can generally provide 150% load torque capacity at low frequencies.

 

(3) After using frequency conversion speed regulation, the original complicated mechanical drag mechanism such as gear box can be simplified, with high degree of automation, simple operation and convenient maintenance.

 

(4) The inverter has analog voltage (0-10V) and analog current input interfaces, which can be well matched with the control signal of the CNC system.

 

Fourth, the advantages of GT620 inverter

 

(1) The spindle frequency conversion speed regulation has a wide range, which can realize stepless speed regulation in the range of 0-400Hz, which can fully meet the requirements of the spindle for the speed regulation range.

 

(2) The use of frequency converters for CNC lathes can simplify the original complex mechanical transmission mechanisms such as gear boxes, and is simple to operate and easy to maintain.

 

(3) The frequency converter can provide 150% load torque capacity at low frequency, which meets the requirements of the machine tool spindle motor with harder mechanical characteristics, and can provide 150% overload protection (60s), 175% for 15 seconds, making the machine tool at low speed It has a strong overload capacity at times.

 

(4) The voltage and current analog input ports of the inverter, and the control signal of the CNC machine tool can be used well with the inverter.

 

(5) GT620 can realize full-closed-loop servo control of the spindle motor, integrating speed control, position control, and torque control. It can easily realize high-precision turning processing and is better than traditional variable frequency drives in heavy cutting.

 

(6) It can be used in conjunction with an encoder to enable the spindle to have a servo function, participate in the interpolation control of the coordinate axis, and complete functions such as rigid tapping and thread cutting.