In order to meet the requirements of the main transmission of CNC lathe machining, CNC machine tools (attribute: automated machine tools) often use a motor stepless speed regulation system. In order to expand the speed adjustment range and meet the requirements of low speed and large torque, gear stepped speed regulation and motor control The method of combining multi-level speed regulation realizes spindle speed regulation. In the numerical control machining, the control system issues instructions to make the tool perform various movements that meet the requirements, and the shape and size of the workpiece are expressed in numbers and letters in the form of technical requirements and machining requirements. It generally refers to the process of machining parts on CNC manufacturing machine tools. In order to improve production automation, shorten programming time and reduce CNC machining costs, a series of advanced CNC machining technologies have been developed and used in the aerospace industry.
- 1. Mechanical gear shift
In the main transmission system of CNC lathe machining, the traditional spindle box structure is greatly simplified due to the stepless speed regulation of the motor. However, due to the limitation of the spindle motor and the driving power supply, the output of constant torque is often in its low speed range. In order to possibly enable the spindle to provide the maximum output power of the main motor in the entire speed range and meet the needs of CNC machine tools (attributes: automated machine tools) for low-speed and powerful cutting, 1 to 4 gears and stepless speed regulation are often used The combined method is the so-called stepless speed regulation. The use of mechanical gear reduction not only amplifies the output power, but also expands the speed range.
When CNC lathe machining is cutting, the spindle runs automatically at the speed specified by the S command in the part machining program (procedure). Therefore, there must be two types of spindle speed command signals in the numerical control system, that is, analog (definition: virtual for real things or processes) or digital signals (S code (code)) to control the drive adjustment of the spindle motor. Speed circuit, while using switch signal (M code) to control the actuator (organization) of mechanical gear speed automatic shift. The automatic shift actuator is an electric-mechanical conversion device, commonly used hydraulic shift fork and electromagnetic clutch (Clutch). - 2. Motor speed regulation
The speed-regulating motors used for the spindle drive of CNC lathes are mainly divided into two categories: DC and AC.
(1) DC motor speed regulation-usually CNC manufacturing machine tools have a large speed regulation range, and the DC motor speed regulation adopts both voltage regulation and magnetic regulation. The characteristic curve of its typical DC spindle motor is shown in Figure 61. From its characteristic curve, it can be seen that the motor below the speed n0 belongs to constant torque speed regulation, that is, it is realized by changing the armature voltage; above the speed n0, it belongs to the constant power (referring to the work done by the object in unit time). How much) speed regulation is achieved by changing the excitation current (Electron flow).
The more commonly used FANUC DC-excited spindle motor adopts a three-phase fully controlled thyristor (zhá) tube non-circulating current reversible speed regulation system, which can realize voltage and magnetic speed regulation, and the speed range is 35 ?~3500r/min. CNC machining General CNC machining usually refers to computer digital control precision machining, CNC machining lathe, CNC machining milling machine, CNC machining boring and milling machine, etc. The feed route of finishing is basically carried out along the part contour sequence. Therefore, the focus of determining the feed route is to determine the feed route of rough machining and idle stroke.
(2) AC motor speed regulation
At present, cage induction motors are used in AC spindle drives of CNC machine tools, and vector control (control) frequency conversion (frequency conversion) speed regulation methods are widely used.
With the improvement of new DC and AC spindle speed control motors, motor speed control will be widely used, but in economical CNC machine tools (attributes: automated machine tools) in order to reduce the cost, mechanical gear shifting is often used Method to change the spindle speed. In the numerical control machining, the control system issues instructions to make the tool perform various movements that meet the requirements, and the shape and size of the workpiece are expressed in numbers and letters in the form of technical requirements and machining requirements. It generally refers to the process of machining parts on CNC manufacturing machine tools. In order to improve production automation, shorten programming time and reduce CNC machining costs, a series of advanced CNC machining technologies have been developed and used in the aerospace industry.