With the rapid development of the global economy and technology, the aerospace and automotive industries are gradually becoming the focus of attention.
As a world manufacturing power, China’s manufacturing industry is bound to become one of its pillar industries.
CNC machining centers have become indispensable equipment in mechanical production, while automatic tool changer is an important part of CNC machining centers, with the advantages of continuous tool change and short tool change time.
Automatic tool changer significantly improves productivity and reduces production costs by reducing non-cutting time, thus enhancing the productivity of the machine tool and the entire production line.
In the future, CNC machine tools will be developed towards high performance, high precision, and high reliability, which will raise the ents for the precision, operating speed, and, reliability of automatic tool changers.
At present, developed countries have successfully developed five-axis and six-axis linkage machine tools, which significantly improve processing efficiency and precision.
China is also actively promoting the equipment manufacturing industry, putting forward the strategic goal of independent development of CNC machine tools, aimed at shortening the R & D cycle and improving the technical level.
At the same time, Chinese scholars have begun to pay attention to the performance of CNC machine tools and their auxiliary components, set up independent research and development teams, and strive to produce high-performance CNC machine tools with independent intellectual property rights.
However, the current domestic auxiliary manufacturing components, such as automatic tool changers, automatic inspection devices, and computerized control systems, still have problems such as low precision, and inaccurate and unreliable operation, which need to be solved urgently.
Overview of tool changer system
A tool magazine system is an automated machining device responsible for storing and changing tools. This system consists of a tool magazine that can store multiple tools and an automatic tool changer. The main function of the tool magazine is to prepare the required tools in advance during machining and to provide storage space for unused tools.
1. Working Principle
The operation of the tool magazine is controlled by the computer program. When receiving the command of tool change, the system will start the drive device and begin to run the tool magazine.
During the running process, the position detection device will feedback on the position of the tool to the computer.
When the tool reaches the specified tool change position, the computer will receive a stop signal, then the tool change device will cooperate with the robot to complete the tool change operation.
After the tool change is completed, the drive device continues to work, and the tool magazine to the standby state.
2. The relationship between the tool magazine and the tool change mechanism
An important part of the tool magazine system is the tool changer, which is responsible for the implementation of tool replacement. Tool magazines and tool changers complement each other, indispensable.
If there is no tool magazine, the tool change time will increase, resulting in the extension of non-cutting time; and if there is no tool changer, the tool can not be completed when the tool reaches the tool change position, and can not improve productivity.
4. Influence of tool magazine system
In recent years, the importance of the tool magazine system in the machining process has gradually emerged.
Its performance on the machining efficiency of the impact is becoming more and more obvious, is no longer regarded as an auxiliary part of the machine tool, but in the field of technology is playing an increasingly large role.
At present, the development direction of global CNC machine tools is to pursue high performance, high precision, and high reliability, and the quality of the tool magazine system directly affects the overall performance of CNC machine tools.
Types of tool magazines
According to different designs and functions, tool magazines can usually be categorized into the following main types.
1. Bucket type tool changer
Characteristics: This small tool magazine usually holds up to 24 tools and is compact.
Principle of operation: During tool change, the tool magazine moves toward the spindle. When the tool on the spindle enters the tool slot in the magazine, the spindle relaxes the clamping device and moves upward, leaving the tool in the magazine.
After the tool magazine rotates to the correct position, the spindle moves downward to clamp the new tool and complete the tool change.
Figure 1 Bucket hat type tool magazine
2. Disc type tool magazine
Characteristics: Also known as disk-type tool magazine, usually used in small vertical integrated processing machines, with a tool capacity of about 30.
Principle of operation: the general diameter of the tool magazine is 1 meter, the tool magazine rotation will be selected to move to the tool position, at the same time the spindle also moved to the correct position, the robot clamped the tool in use and the selected tool to complete the tool change.
Figure 2 Disc type tool magazine
3. Chain-type tool changer
Features: This type of tool magazine has a large tool capacity, usually up to 120, suitable for large machining centers.
Principle of operation: chain tool magazine through the drive device driven sprocket rotation, the chain will be transferred to the correct position of the tool, by the knife device with the robot to complete the tool change action.
With the robot to complete the tool change action. The drive device is usually a hydraulic or mechanical drive, with high efficiency and flexibility.
4. Side-mounted tool magazine
Characteristics: The tools are hung vertically or obliquely, which is convenient for quick change and management of tools.
Application: This type of tool magazine is often used in the need for frequent replacement of tool processing occasions, such as mold processing.
5. Automatic tool magazine
Features: Integrated with robot technology, it can automatically recognize and change tools.
Advantages: Increased speed and accuracy of tool change, suitable for complex machining tasks.
Table 1 Types of tool magazines
China’s external research status and development direction
1. The origin of the automatic tool changer
Since the 1950s, the United States successfully launched a machining center with an automatic tool changer, and countries have invested in research and development of their machining centers.
By the 1970s, CNC machine tools ushered in the golden period of development, and a variety of high-performance, high-reliability, and high transmission-accuracy machining centers continued to emerge.
Germany Japan and other developed countries have made remarkable achievements in this regard. For example, Austria successfully developed a tool change time of only 0.4 seconds for automatic tool change machine tools, creating a world record.
By configuring independent drive motors for each spindle on multi-spindle machines, tool change time can be significantly reduced.
2. Current status of research and development in China
Compared with these countries, China’s research and development of automatic tool changers started relatively late. Developed countries started their research in the 1950s, while China only started to follow suit 30 years later. Due to the late start, China’s automatic tool changer production technology is still immature, and the performance gap is obvious compared with developed countries.
However, China is increasing its emphasis on the equipment manufacturing industry, clarifying the development direction of CNC machine tools and striving to shorten the research and development cycle.
At the same time, more and more scholars began to pay attention to CNC machine tools and their auxiliary components, set up independent research and development teams, and strive to develop high-performance CNC machine tools with independent intellectual property rights.
3. Composition of automatic tool changer
Automatic tool changer mainly consists of tool magazines, robots, and drive devices, usually divided into bucket hat type tool magazines, disk type tool magazines, chain type tool magazines, side hanging type tool magazines, and automatic tool magazines 5 types.
The operation of the tool magazine is controlled by a computer program, the computer sends commands to the motor of the drive unit, and the position detection device continuously monitors the position of the tool after startup.
When the tool reaches the specified position, the computer receives a feedback signal and instructs the motor to stop, at which point the robot will complete the tool change under control.
4. Current Challenges
Currently, the main problem facing the tool changer system is that the transmission accuracy decreases over time. For example, the cam mechanism may wear out due to prolonged operation, leading to a reduction in transmission accuracy.
In addition, the tool change time is an important indicator for evaluating the performance of the tool magazine, which is strongly influenced by the sensitivity of the knife-flipping device. Currently, tool change times are generally long, which poses a productivity challenge.
5. Types of drives
The knife magazine drive device is mainly divided into a knife turning device, a manipulator drive device, and a knife storage bin drive mechanism. Common drive methods include pneumatic drive, hydraulic drive, and mechanical-hydraulic linkage drive.
Researchers have found that the cam mechanism is excellent in dynamic characteristics and can maintain high transmission accuracy at high speeds, so the automatic tool changer for tool magazines using the cam mechanism is gradually becoming a trend.
However, cams require high machining accuracy and relatively high costs.
Fig. 3 Types of drives
6. Future development trend
With the continuous progress of CNC technology and automatic control technology, CNC machine tools are developing in the direction of high-speed, high-precision, and multifunctionalization. This will certainly put forward higher requirements for the tool magazine system.
In the future, the tool magazine system needs to be able to store more tools to meet diversified machining needs, and at the same time realize faster tool change speed and more accurate tool change positioning.
Conclusion
In conclusion, the continuous development of the tool magazine system is not only the inevitable result of the technological progress of CNC machine tools but also an important way to enhance the competitiveness of China’s manufacturing industry.
Through continuous technological innovation and research, we have reason to believe that China’s future in the field of automatic tool changers will be brighter and can occupy a place in the global manufacturing industry.