Malfunctions and repairs of CNC machine tool manipulator tool changing device

In the maintenance of CNC machine tools, faults related to tool change are extremely common. This article is based on the structure and action control of the manipulator tool changer, combined with maintenance examples, summarizes common failure phenomena, causes and treatment measures. It has greater practical significance in the maintenance and transformation of CNC machine tools, and is worthy of serious exploration, communication and promotion.

　　One of the important reasons for the high precision and efficiency of CNC machine tools, especially CNC machining centers, is its one-time clamping and multi-process automatic processing. The key to achieving this function is the automatic tool changer. Due to the high working frequency of the automatic tool changer and the complex control mechanism, including the tool magazine, tool exchange and drive, the probability of failure is also high, and it occupies a considerable proportion of the maintenance of CNC machine tools. Understand its structural characteristics and control mechanism, familiarize with the action flow of tool change, summarize and summarize common failure phenomena, causes and solutions, and learn from related maintenance examples, which will help to quickly and accurately diagnose and eliminate failures, and improve the quality and efficiency of maintenance work .

1. The structure of the robot tool changer

Figure 1 Multi-spindle tool change

Figure 2 Dual spindle tool change

Figure 3 Turret head type tool change

Figure 4 Hat type tool change

Figure 5 Manipulator tool change

　　There are many ways to realize the automatic tool change function of CNC machine tools, such as multi-spindle tool change (see Figure 1), dual-spindle tool change (see Figure 2), turret head type tool change (see Figure 3), and hat type tool change. (See Figure 4) and robot tool change (See Figure 5) and so on. It can be divided into two categories according to whether the tool is changed by a manipulator: the tool change without a manipulator (such as a hat type) mostly relies on the axial relative movement between the spindle and the tool magazine to realize the tool extraction and insertion. When the tool is changed, the tool magazine is moved to the change. Tool position, the spindle returns the tool to the empty tool holder of the tool magazine change position, and then the tool magazine rotates to make the tool needed for the next process enter the tool change position, and the spindle removes the new tool from the tool magazine and returns the tool. The two actions of taking the tool can only be carried out in steps. In addition to the axial movement of the spindle and the movement and rotation of the tool magazine, the tool change time is long, the processing efficiency is low, and the capacity of the tool magazine is also small. At present, CNC machine tools use more It is a manipulator for tool change, which uses the manipulator to quickly and accurately adjust the tool change position in the tool magazine and the tool on the spindle. The tool is returned and taken at the same time, the tool change time is greatly shortened, and the capacity of the tool magazine is not limited by the tool change mechanism.

Figure 6 Disc tool magazine

Figure 7 Chain Tool Library

Figure 8 Grid type tool magazine

1. Tool holder 2. Tool holder 3. Tool change manipulator

4. Tool holder for tool change position 5. Longitudinal guide rail of the tool taking robot

6. Transverse guide rail of knife taking manipulator

　　According to the layout of the tools, the tool magazine can be divided into three types: disc type, chain type and grid type. The disc-type tool magazine tools are distributed in a circular shape (see Figure 6), the chain-type tool magazine tools are arranged on each link of the chain (see Figure 7), and the grid-type tool magazine tools are arranged vertically and horizontally (see Figure 8). Disc tool magazines have low space utilization and small capacity, and are generally used in small machining centers. Chain-type and grid-type tool magazines have high space utilization and large capacity, and are used in medium and large CNC machining centers. The function of the tool magazine is not only to store the tools needed in the machining process, but also to accurately send the tools to be used in the next process to the tool change position.

Fig. 9 Schematic diagram of cam type tool change manipulator structure

　　There are three drive modes of the tool changer: hydraulic, servo and AC asynchronous motor drive. Hydraulic drive requires sufficient hydraulic power, and the speed and accuracy of movement are affected by factors such as oil quality, oil pressure, oil temperature, and environment. It is generally used for large and medium-sized machine tools that do not require frequent tool changes. The tool changing device driven by the servo motor has fast tool changing speed, high precision and strong stability, but the cost is relatively high. The tool change device driven by AC asynchronous motor, with the help of a cam mechanism (see Figure 9), has fast tool change speed, accurate positioning, high stability, good continuity and low cost. It is widely used in small and medium-sized machining centers that frequently change tools.