The development of science and technology has put forward the requirements of high precision and high complexity for mechanical products, and the upgrading of products is also accelerating. This not only puts forward the requirements of precision and efficiency for machine tools, but also puts forward the versatility and Flexibility requirements. CNC machine tools are a new type of automated machine tool for this requirement. CNC machine tools integrate microelectronics technology, computer technology, automatic control technology, servo drive technology and precision mechanical technology, which are typical products of high mechatronics. It is an important part of mechatronics and an important indicator of the level of modern machine tool technology. CNC machine tools represent the mainstream of the world's machine tool technology advancement, and are an important indicator for measuring the level of mechanical manufacturing technology. They play an important and fundamental role in advanced manufacturing technologies such as flexible production and computer integrated manufacturing. Therefore, how to use CNC machine tools is a very important issue. Since CNC machine tools are expensive and expensive equipment, their maintenance cannot be ignored.
First, CNC machine tools
1. The concept of CNC machining
The working principle of CNC machine tools is to carry out various operations required for the machining process (such as spindle shifting, workpiece loosening and clamping, feeding and retracting, driving and stopping, automatic shutdown of coolant) and steps and workpiece shape. The size is represented by a digital code. The digital information is sent to the numerical control device through a control medium (such as a punched tape or a magnetic disk). The numerical control device processes and calculates the input information, and issues various control signals to control the servo system of the machine tool or Other drive components allow the machine to automatically machine the required workpiece. Therefore, the key to CNC machining is the acquisition of machining data and process parameters, namely CNC programming. CNC machining generally includes the following contents:
(1) Analyze the drawings to determine the parts that require CNC machining;
(2) Using graphics software (such as CAXA manufacturing engineers) to shape parts that require CNC machining;
(3) According to the processing conditions, select appropriate processing parameters to generate machining trajectories (including roughing, semi-finishing, finishing trajectories);
(4) Simulation test of the trajectory;
(5) generate a G code;
(6) Passed to the machine tool for processing.
2. Characteristics of CNC machine tools
(1) Highly flexible
Machining parts on CNC machine tools depends mainly on the machining program. It is different from ordinary machine tools. It is not necessary to manufacture or replace many tools and fixtures. It is not necessary to adjust the machine frequently. Therefore, CNC machine tools are suitable for occasions where parts are frequently replaced. It is suitable for the development of single-piece, small batch production and new products, shortening the production preparation cycle and saving the cost of a large number of process equipment.
(2) High processing accuracy
The machining accuracy of CNC machine tools can generally reach 0.005~0.1mm. The numerical control machine tool is controlled in the form of digital signals. Each time the numerical control device outputs a pulse signal, the moving parts of the machine tool move by one pulse equivalent (generally 0.001mm), and the machine tool advances. The average error of the backlash and the screw pitch of the transmission chain can be compensated by the numerical control device. Therefore, the positioning accuracy of the numerically controlled machine tool is relatively high.
(3) Processing quality is stable and reliable
Machining the same batch of parts, using the same tool and machining program under the same machining conditions on the same machine tool, the tool's path is exactly the same, the parts have good consistency and the quality is stable.
(4) High productivity
CNC machine tools can effectively reduce the machining time and auxiliary time of parts. The range of spindle speed and feed rate of CNC machine tools is large, which allows the machine tool to carry out powerful cutting with large cutting amount. CNC machine tools are now entering the era of high-speed machining, moving parts of CNC machine tools. The fast moving and positioning and high-speed cutting process reduces the turnaround time between the semi-finished products and improves the production efficiency.
(5) Improve working conditions
After the CNC machine tool has been adjusted before machining, the program is started and started, and the machine tool can automatically and continuously process until the end of the process. The operator is mainly the input of the program, editing, loading and unloading parts, tool preparation, observation of the processing state, inspection of the parts, etc., the labor intensity is greatly reduced, and the labor of the machine tool operator tends to be an intellectual work. In addition, the machine tool is generally closed, that is, clean and safe.
(6) Conducive to the modernization of production management
The machining of CNC machine tools can accurately estimate the machining time in advance, and the tools and fixtures used can be standardized and modernized. CNC machine tools use digital signals and standard codes as control information, which is easy to standardize processing information. It has been organically combined with computer-aided design and manufacturing (CAD/CAM) and is the basis of modern integrated manufacturing technology.
3. Things to be aware of when using CNC machine tools
Before using the CNC machine, you should carefully read the machine manual and other relevant information in order to operate the machine correctly, and pay attention to the following points:
(1) The operation and maintenance personnel of the machine tool must be professionals who have mastered the relevant professional knowledge of the machine tool or those who have been trained in technology, and must operate the machine tool according to the safety operation rules and safe operation regulations;
(2) Non-professionals are not allowed to open the electric cabinet door. Before opening the electric cabinet door, it must be confirmed that the main power switch of the machine has been turned off. Only professional maintenance personnel are allowed to open the electric cabinet door for power-on maintenance;
(3) In addition to some parameters that can be changed by the user, other system parameters, spindle parameters, servo parameters, etc., cannot be modified by the user, otherwise the equipment, workpiece, personal injury, etc. will be brought to the operator;
(4) After modifying the parameters, when the first machining is performed, the machine tool is tested with the machine lock and single block without the tool and the workpiece, and the machine tool is confirmed after the machine is normal;
(5) The PLC program of the machine tool is designed by the machine tool manufacturer according to the machine tool and does not need to be modified. Improper modification, operating the machine may cause damage to the machine and even damage the operator;
(6) It is recommended that the machine tool run continuously for up to 24 hours. If the continuous running time is too long, it will affect the life of the electrical system and some mechanical components, which will affect the accuracy of the machine tool;
(7) All connectors, joints, etc. of the machine tool are not allowed to be pulled or inserted, otherwise serious consequences will result.
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