CNC System Automatic Tool Change System Process

- May 24, 2018 -

The wide application of CNC machine tools in production has led more and more processing companies to discover their advantages. Although the cost of CNC machine tools is relatively high, there are still many companies engaged in processing, which rely on their efficient processing. The high efficiency of the CNC system is mainly due to the advanced nature of the system, such as the automatic tool change system, which effectively shortens the machining time to a certain extent, which is of great help in improving the machining efficiency.


First, the tool change principle


The magazine consists of a knife holder rotation mechanism and a tool changer. The magazine is disc-shaped and has an indexing plate inside. The rotary motion of the magazine is powered by a three-phase asynchronous motor with a brake. The three-phase power supply is provided to the motor through the AC contactor. At this time, the brake is opened and the magazine is operated. When the three-phase power supply is cut off, the brake is locked and the magazine immediately stops operating. Through the movement of the indexing disk and the logical combination of the relevant detection element groups, each tool sleeve can be accurately stopped at the tool change position. After the tool holder is stopped at the tool change position, the tool holder is controlled by the air cylinder to be in the horizontal or vertical state to facilitate the robot's tool change. The knife holder indexing table can be rotated clockwise or counterclockwise so that the tool to be replaced can be searched in the shortest possible time.


The movement of the magazine change tool manipulator is also powered by a three-phase asynchronous motor with holding brake. Through the gear transmission mechanism, the uniform rotating motion generated by the motor is converted into the regular advance, stop and rotation motion of the manipulator. The gear transmission is equipped with a micro switch. The micro switch group is used to control the robot gripping the tool, the robot removing the tool from the spindle and the sheath, and the robot being in the original position.


A torque limiter is built into the rotary tool holder of the tool magazine and the deceleration transmission mechanism of the manipulator to prevent damage to the internal mechanical structure.

Second, the knife knife automatic tool change implementation


The magazine robot is the main mechanism for automatic tool change. Its task is to return an unused tool from the spindle and return it to the tool magazine when a process is completed. At the same time, the next process tool is loaded into the spindle, and then the robot returns to its original position to wait for the next work cycle.


The regular movement of the magazine robot is achieved by three-phase asynchronous motors and gear transmission mechanisms, but these actions also need to be implemented through electrical systems. The tool holder in the magazine moves to the tool change position according to the T code command, and then performs tool exchange. During the working of the machine tool, the tool is commanded to make the robot pick or load. Therefore, it is required that the electrical system must perform each action accurately and reliably in accordance with the sequence of movement of the tool change process.


Electrical operation sequence:


(1) Start the tool selection. The tool changer is turning or reversing the nearest tool.

(2) The knife sleeve counting and indexing disc positioning signal make the knife cover motor stop, and a knife cover exactly stops at the tool change position.

(3) The electroporation valve that controls the turning of the knife sleeve (vertical) is energized.

(4) The tool holder is in vertical position and sends an in-position signal. The spindle orientation gives the position arrival confirmation signal.

(5) The robot starts from its original position and rotates 90° to reach the robot gripper position.

(6) The robotic knives are in place to issue a stop signal, the tool is removed from the spindle and the tool holder, and the robot motor stops.

(7) Knife confirmation and tool release give place signal.

(8) After the tool clamp is loosened, the robot starter rotates 180° to reach the tool change position.

(9) The robot motor stop signal stops the robot motor.

(10) Tool loading confirmation and tool clamping give an in-position signal.

(11) The robot motor starts and returns the robot to its original position.

(12) The robot motor stop signal stops the robot motor.

(13) The robot's home position switch signals.

(14) The electromagnetic valve that controls the turning of the tool sleeve (horizontal) is energized.

(15) Turning the proximity switch in the horizontal position signals the completion of the magazine change operation.


The movements of the magazine and manipulator can be controlled by the NC, or controlled by the PLC, depending on the actual machining conditions of the magazine.

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