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Maanshan Iron and Steel is an important production base for train wheels and tires in China. In order to meet the requirements of heavy-duty and high-speed trains, the company introduced a wheel processing line from Germany in 2006. The production line consists of 12 CNC machining centers and auxiliary equipment. Each machining center (hereinafter referred to as a machine tool) can perform machining such as car and boring on various parts of the wheel. The machine tool is a double-turret vertical structure with a horizontal X-axis and a vertical Z-axis on the right side, a horizontal U-axis and a vertical W-axis on the left side, and a magazine on each of the left and right sides. CNC system This is an article about equipment operation. The paper introduces the control method of the automatic tool change by using the PLC program in the double-tool library of the machining center, and briefly explains the tool magazine management. In this column, articles on practical operation and maintenance of equipment will be added in the future, and readers and authors are welcome to pay attention.
For the 840DE powerline. The two tool holders and the magazine are controlled by two channels of the CNC system. Using the disc type tool magazine produced by MIKSCH, Germany, each tool magazine can hold 12 tools and realize automatic tool change by robot. This achieves the goal of completing multiple processes on a single machine.
I. Overview of the automatic tool change principle of the tool magazine The machine tool adopts the CTM50/52 type tool magazine produced by MIKSCH of Germany with a capacity of 12 knives. The tool magazine includes a knife sleeve rotation mechanism and a tool change robot as shown. The shape of the magazine is disc-shaped and has an indexing plate inside. The rotary motion of the tool magazine is powered by a three-phase asynchronous motor with a brake. The three-phase power supply is supplied to the motor through the AC contactor. At this time, the brake is opened and the tool magazine is operated. When the three-phase power supply is cut off, the brake is closed and the tool magazine is immediately stopped. Through the movement of the indexing disc and the logical combination of the relevant detection component groups, each pocket can be accurately stopped at the tool change position. After the knife sleeve stops at the tool change position, the knife sleeve is controlled by the cylinder to be horizontal or vertical to facilitate the robot to change the knife. The knife 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 tool changer is also driven by a three-phase asynchronous motor with a brake. Through the gear transmission mechanism, the uniform rotational motion generated by the motor is converted into the regular forward, stop and rotary motion of the manipulator. The gear drive is equipped with a micro switch group. This switch group includes three sets of micro-motion cams and three proximity switches, and each set of micro-motion cams is equipped with three micro-motion cams. The micro switch group is used to control the robot to clamp the tool, the robot to remove the tool from the spindle and the knife sleeve, the robot in the original position, and the like.
A torque limiter is built into the rotary cutter sleeve of the magazine and the reduction gear of the robot to prevent damage to the internal mechanical structure.
Second, the tool magazine automatic tool change The implementation of the tool magazine robot is the main mechanism to achieve automatic tool change. Its task is to remove the unused tool from the spindle and return it to the magazine when a process is completed. At the same time, the tool of the next process is loaded into the spindle, and then the robot returns to the original position for the next working cycle. For the robot movement sequence diagram. The regular movement of the magazine robot is realized by a three-phase asynchronous motor and a gear transmission mechanism, etc., but these actions also need to be realized by an electrical system. The tool holder in the magazine runs to the tool change position according to the command of the T code, and then the tool exchange is performed. During the operation of the machine tool, the tool makes the robot take the knife or load the knife according to the instruction. Therefore, the electrical system is required to perform each action accurately and reliably in accordance with the motion sequence of the tool change process.
The following is the sequence of electrical operation: (1) start the selection of the knife, the tool magazine rotates forward or reverse to find the knife; (2) the knife sleeve count and the index plate positioning signal stop the knife sleeve motor, and one knife sleeve stops at the tool change (3) The electric phosphorus valve that controls the turning (vertical) of the knife sleeve is powered; (4) the knife sleeve is vertically positioned, and the in-position signal is issued, the spindle orientation gives the position arrival confirmation signal; (5) the robot starts from the original position, rotates 90° reaches the position of the robot chuck; (6) The mechanical button is in place to send a stop signal, the tool is taken out from the spindle and the knife sleeve, and the robot motor stops; (7) the knife confirmation and the tool release give the in-position signal; (8) After the tool clamp is relaxed, the starter rotates 180° and reaches the tool change position; (9) the robot motor stop signal stops the robot motor; (10) the tool confirmation and the tool clamp give the in-position signal; (11) the robot motor starts. , so that the robot returns to the original position; (12) the robot motor stop signal, so that the robot motor stops; (13) the robot's original position switch signals; (14) control the knife sleeve flip (horizontal) electromagnetic valve is energized; (15) the tool holder turns over the proximity switch in the horizontal position (the tool change is completed).
The movement of the tool magazine and the robot can be controlled by the NC or by the PLC. Since the common three-phase asynchronous motor is selected for the tool magazine, the PLC is used to control the movement of the tool magazine and the robot. Since the machine numerical control system is 840DE powerline, it integrates the S7?315?2DP PLC system internally, which provides convenience for PLC programming to control the movement of the tool magazine and robot. The PLC program design adopts modular, parameterized and standardized programming methods. According to the control function, the program block is divided into different function blocks, and the control function program is standardized by the parameter programming features in the form of block. The program structure is as shown.
The PLC program can better meet the operating sequence of the tool holder and the manipulator during the tool change, and shorten the tool change time by perfecting the nearby tool. Since the two left and right magazines have channel 1 and channel 2 controls respectively, the operation of the right magazine is controlled by the function block FB96 and the background data block DB103 during programming. Similarly, the operation of the left magazine is controlled by the function block FB96 and the background data block DB112. When programming, consider a number of protection factors, such as the protection of the knife sleeve motor and the robot motor (), the protection of the knife-turned electric phosphorus valve. In addition, in order to facilitate the manual replacement of the tool, each tool magazine is equipped with an OP7 operation panel, which greatly facilitates the operator's manual tool change and tool magazine debugging and maintenance.
It can be seen from the PLC program structure diagram that the PLC program consists of the user program and the Siemens standard block. These standard blocks of Siemens are the interfaces for tool management. In terms of tool management, Siemens has other standard blocks to choose from. The purpose of these standard blocks is to improve the man-machine interface of the tool magazine management, in order to better use the tool changer to automatically change the tool.
Third, the tool management The CNC system of the machine is equipped with MMC103/PCU50 man-machine interface, which has a relatively complete tool management function. The operator can clearly see the condition of the tool in the entire tool magazine from the man-machine interface, and can adjust the knife. Information in the library, such as manual tool change. Standard Siemens tool management functions are numerous, such as tool list, load/unload function, random tool change/fixed tool change. The following is a brief introduction to the use of the tool magazine management.
It can be seen that the movement of the tool holder and the robot, that is, the control of the tool magazine and the tool management are inseparable.
The tool magazine management software of this machine is defined as the No. 1 tool magazine for the right tool magazine and the No. 2 tool magazine for the left tool magazine. The position of the knife in the knife table corresponds to the actual knife sleeve. The buffer of the spindle, the gripper 1 and the gripper 2 is defined as the magazine No. 9998.
At each stage of the tool change, as long as the tool exchange occurs, the tool data is between the tool pocket No. 1 of the tool table and the tool holder of the No. 9998 tool magazine (the spindle, the robot hand 1 and the hand 2). exchange. And each time the tool data transfer is required, it must be confirmed by the PLC interface, and the MMC is started to exchange the displayed tool table data. The PLC interface of the tool data transfer is confirmed by the Siemens standard function FC8-TM?TRNS. The relevant data of the new and old knives on the magazine side and the spindle side are stored in the data block DB90, and DB90 is the background data block of FB90. When changing the tool, FB90/DB90 calls FC8, so that the new tool on the spindle side, the old knife on the tool magazine side and the tool list information on the man-machine interface are updated in time, so that the tool change action and the tool list display information are accurate. The following are some of the PLC programs for tool information exchange: IV. Conclusion The machine tool effectively automates the tool change and spindle tool change, and makes the tool change process very flexible and reliable, and the failure rate is extremely low. The application of two magazines greatly increases productivity. The interface of the tool magazine management makes automatic tool change and management safer.
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