Although CNC milling machine has many different types and the control is simple and complex, the basic control of CNC milling machine includes spindle control, feed control and auxiliary function control.
1. Spindle control
The basic functions of spindle control include spindle reversing and spindle speed control. Control of the spindle, in fact, the spindle motor control, that is, the spindle motor forward and reverse determines the steering of the spindle; spindle motor speed determines the spindle speed. The drive of the spindle motor is realized by the spindle drive. The basic requirement for spindle control is to keep the spindle speed stable. For this reason, an encoder is provided on the spindle motor or spindle for speed detection and feedback.
In order to ensure the accuracy of position control, usually in the spindle to install the encoder for spindle position detection and feedback. With the development of technology, some milling machines use electric spindle technology.
2. Feed control
Feed control includes point control and trajectory control, as shown.
(1) point control
Machining center drilling, reaming, reaming, tapping and boring are all point control. In the point control, the tool is not cut during the rapid movement from the current position to the next position. The movement path can be set artificially, but the position accuracy between the point and the point is guaranteed.
(2) trajectory control
CNC milling machine for contour processing are trajectory control. Trajectory control, the tool according to the provisions of the path cutting the workpiece, it is necessary to ensure the accuracy of the location, but also to ensure the stability of the tool movement speed.
The control target of the feed movement is the position control and the speed control, and the accuracy of the position control, the stability of the feed speed and the fastness of the command response are ensured. To achieve this goal, the CNC milling machine has a feed motion control for position detection and speed detection, such as gratings and encoders. With the development of technology, some CNC milling machine adopts linear motor drive, eliminating the ball screw, shortening the feed mechanical transmission chain, improve the mechanical transmission stiffness and accuracy, and the rapid response speed of the servo system.
3. Auxiliary function control
The auxiliary function is controlled by the M command and the T command through PLC control of the CNC system. It involves milling machine side input and output switch, such as button, key switch, proximity switch, proximity switch, relay, contactor and solenoid valve, and PLC ladder diagram. Among them, the spindle is reversing and stopping, lubrication and cooling are all CNC milling machine with auxiliary functions, the other also includes the knife knife selection, machining center tool change, machining center spindle tensioner, and rotary table and tray exchange, etc.