Behind efficient machining: Technology and application of CNC automatic tool changer

In the field of high-end manufacturing, the automatic tool changer (ATC) of CNC machine tools is the key to achieving multi-process continuous machining. From aerospace to automobile manufacturing, the application of CNC automatic tool changers has significantly shortened the machining cycle and reduced the need for manual intervention. This article will start from the technical principles, analyze the core technology of CNC automatic tool changers, and explore its actual application cases in different industries.

1. Working principle of CNC automatic tool changer

(1) Tool access and exchange process

The basic process of automatic tool change is as follows:

●After the CNC system detects that the current tool is worn or the tool needs to be replaced in the machining process, it sends a tool change command.

●The machine tool spindle stops rotating and releases the tool, while ensuring that the inner taper of the spindle remains clean to ensure the clamping accuracy of the new tool.

●The tool changer takes out the new tool from the tool magazine, removes the old tool at the same time, and puts it back to the specified position in the tool magazine.

●The robot installs the new tool on the spindle and clamps it to ensure that the tool and the spindle fit tightly to prevent shaking during high-speed rotation.

●After the CNC system confirms that the tool has been installed, performs position verification, and adjusts the processing parameters, the machine tool continues processing.

(2) Sensors and feedback control mechanisms

Modern CNC automatic tool changers are usually equipped with a variety of sensors to ensure that the tool change process is accurate and correct:

1) Position sensor:

Monitors whether the tool is correctly positioned to avoid misalignment or tool change failure.

2) Pressure sensor:

Real-time monitoring of tool clamping force to prevent processing errors or tool damage caused by insufficient or excessive clamping.

3) Vibration sensor:

Detects the installation status of the tool after tool change to avoid a decrease in processing quality due to excessive vibration.

4) RFID intelligent tool management system:

Automatically records the tool's service life, wear status, and historical processing data to enable more accurate tool management and improve the intelligence of tool change.

2. Introduction to key technologies of CNC automatic tool changers

The performance and reliability of CNC automatic tool changers (ATCs) depend on a number of key technologies that directly affect tool change speed, accuracy, and stability. The following are the core technologies of ATC and their functions:

(1) High-speed tool change drive technology

1) Servo motor + cam mechanism:

Modern high-speed ATC usually uses a servo motor to drive the cam mechanism to achieve fast and accurate positioning of the manipulator, and the tool change time can be shortened to less than 0.8 seconds.

2) Linear motor drive:

Some high-end models (such as the DMG HSC series) use linear motors to directly drive the tool change arm to reduce transmission chain errors and improve response speed.

3) Hydraulic/pneumatic assistance:

Heavy-duty machine tools may use hydraulic or pneumatic assistance to loosen the tool to ensure stable gripping of large-mass tools.

(2) High-precision tool positioning technology

1) Spindle orientation and accurate stop:

Before changing the tool, the spindle must stop precisely at a fixed angle (usually controlled by an encoder with an accuracy of up to ±0.001°) to ensure that the keyway of the tool holder is aligned.

2) HSK/BT tool holder taper fit:

The high-precision ground tool holder taper (such as HSK63) fits tightly with the spindle taper hole, with a radial runout of ≤0.002mm.

3) Tool pre-adjustment and compensation:

The tool length and diameter are automatically measured by laser probe or contact probe, and input into the CNC system for compensation to ensure the consistency of processing dimensions.

(3) Intelligent tool management and identification technology

1) RFID tool identification:

The RFID chip is embedded in the tool holder to store tool parameters (such as length, wear status, life), and automatically read and adjust the processing parameters when changing tools.

2) Barcode/QR code scanning:

The tool number is identified by optical scanning to prevent tool change errors.

3) Tool life monitoring:

The tool wear is predicted based on cutting force, vibration signal or processing time, and the replacement is alarmed in advance to avoid the risk of tool breakage.

(4) Quick tool release and locking technology

1) Butterfly spring tensioning system:

Under normal conditions, the tool holder is tightened by a high-strength butterfly spring (tension 5~15kN) to ensure processing rigidity.

2) Hydraulic tool release mechanism:

When changing tools, the hydraulic cylinder pushes the pull rod to overcome the spring force to release the tool, and the action time is <0.3 seconds.

3) Pneumatic chip blowing function:

When changing tools, high-pressure gas cleans the spindle taper hole to prevent chips from affecting positioning accuracy.

(5) Tool magazine management and optimization technology

1) Servo-driven tool magazine:

Adopting servo motor indexing, the tool magazine tool change position positioning accuracy is ±0.01mm.

2) Tool preselection function:

The CNC program can instruct the next tool to move to the tool change position in advance to reduce waiting time.

3) Random tool change algorithm:

Optimize the tool magazine movement path, reduce empty stroke, and improve tool change efficiency.

(6) Fault diagnosis and safety protection

1) Tool drop detection:

Confirm whether the tool is installed in place through a pressure sensor or photoelectric switch.

2) Robot anti-collision:

Adopt torque limitation or infrared detection to prevent interference during tool change.

3) Self-diagnosis system:

Real-time monitoring of the status of each ATC component (such as motor load, hydraulic pressure), automatic alarm or shutdown in case of abnormality.

3. Application field of CNC automatic tool changer

With the development of intelligent manufacturing, the application of CNC automatic tool changer is becoming more and more extensive. Different types of CNC machine tools and the high-precision processing needs of multiple industries have put forward higher requirements for automatic tool changing technology. CNC automatic tool changing devices not only improve processing efficiency, but also promote the development of manufacturing industry towards intelligent and unmanned directions.

(1) Applicable to different types of CNC machine tools

CNC automatic tool changing devices are mainly used in the following types of machine tools:

1) Machining center:

Machining centers usually need to perform multiple processes on the same workpiece, such as milling, drilling, tapping, etc. Different processes require different tools, so automatic tool changing devices are crucial. Especially in high-end five-axis machining centers, multi-faceted processing of complex parts requires frequent tool changes to ensure production continuity and accuracy.

2) Turning center:

In the modern CNC turning process, in addition to traditional turning tools, a variety of tools such as drills and milling cutters are also required to achieve multi-functional processing. Automatic tool changing devices can quickly switch tools, making CNC turning more flexible and efficient.

3) Five-axis linkage machine tools:

Used for complex surface processing, such as high-precision parts in the aerospace and medical device industries. The processing flow of five-axis machine tools is relatively complex and the tool change frequency is high, so it is an inevitable trend to equip them with intelligent automatic tool changers.

4) Composite machining machine tools:

Integrated with multiple processing methods such as milling, turning, and drilling, multiple processing steps can be completed in one clamping. The automatic tool changer can greatly reduce manual intervention and improve production efficiency.

(2) Typical application industries

CNC automatic tool changers are widely used in the following industries, promoting the development of manufacturing industry towards high efficiency and high precision:

1) Aerospace:

The manufacturing of aircraft engine parts and fuselage structural parts requires extremely high precision, and the workpiece materials are mostly difficult-to-process metals (such as titanium alloys, nickel-based alloys, etc.), requiring different types of tools for rough processing, fine processing and surface treatment. The automatic tool changer can ensure the rapid replacement of tools during the processing process, improve production efficiency, and reduce human operation errors.

2) Automobile manufacturing:

The processing of complex structures such as engine blocks, gearbox housings, and chassis parts requires efficient automated production. The application of automatic tool changers greatly shortens the tool replacement time, improves the utilization rate of machine tools, meets the needs of mass production, and ensures product quality consistency.

3) Medical devices:

Precision medical devices (such as artificial joints, dental implants, orthopedic surgical tools, etc.) require extremely high processing accuracy and surface finish. Automatic tool changers can ensure error-free tool change, improve production consistency, and meet the high standards of the medical industry.

4) Mold manufacturing:

Mold processing often requires a variety of tools, including roughing tools, finishing tools, and micro-tools. The automatic tool changer can complete tool changes at different stages within one processing cycle, improve mold processing efficiency, and reduce tool change errors caused by human factors.

5) Electronic product manufacturing:

The processing of parts such as housings and connectors of precision electronic products requires high-precision and efficient tool change. The automatic tool changer can ensure that the tool change process is accurate and fast, improve processing quality, and meet the needs of high-end electronic manufacturing.

5. Summary

The technological progress of CNC automatic tool changers is driving the manufacturing industry to a higher level of automation. By optimizing tool change speed, accuracy, and reliability, ATC will continue to provide efficient solutions for the processing of complex parts and become an indispensable part of smart factories.