CNC machines are inevitably affected by various factors during the processing process, which causes certain deviations in their processing accuracy and brings some inconvenience to production and life. How to improve the processing accuracy of CNC machines is a matter of great concern to experts.
Position error refers to the amount of change or degree of deviation between the actual surface, axis or symmetry plane of the processed parts relative to their ideal position, such as verticality, position, symmetry, etc. Position error in CNC machine processing usually refers to dead zone error. The main reasons for position error are the clearance and elastic deformation caused by transmission during the processing of machine tool parts, and the position error caused by the friction force and other factors of the machine tool head during processing. In the open-loop system, the position accuracy is greatly affected, while in the closed-loop follow-up system, it mainly depends on the accuracy of the displacement detection device and the speed amplification factor of the system, and the influence is generally small.
In CNC machine processing, the geometric accuracy of the machine tool is affected by external factors such as external forces and heat generated during processing, and the parts processed on the machine tool are geometrically deformed, resulting in geometric errors. According to research, the main reasons for geometric errors in CNC machines are nothing more than the following two: internal factors and external factors. The internal factors of geometric errors in machine tools refer to geometric errors caused by factors of the machine tool itself, such as the horizontality of the machine tool's worktable, the horizontality and straightness of the machine tool's guide rails, and the geometric accuracy of the machine tool's tools and fixtures. External factors mainly refer to geometric errors caused by factors such as external environment and thermal deformation during processing. For example, during the cutting process, the tool or parts expand and deform due to heat, resulting in geometric errors, which affect the machining accuracy of the machine tool and the machining accuracy of parts.
Through long-term data analysis and practical operations of parts processing, it can be seen that machine tool positioning has a great influence on the machining accuracy of CNC machines. From a structural point of view, the machining error of CNC machines is mostly caused by positioning accuracy, among which the feed system of the machine tool is the main link affecting the positioning accuracy. The feed system of CNC machines usually consists of two parts: a mechanical transmission system and an electrical control system. The positioning accuracy is related to the mechanical transmission system in the structural design. In a closed-loop system, CNC machines can usually prevent the main components of the feed system from generating position deviations, such as ball screws, through positioning detection devices. For open-loop systems, due to the large number of influencing factors and the complexity of the situation, positioning monitoring cannot be performed, so the machining accuracy of CNC machines is greatly affected.
In the machining process of CNC machines, the accuracy of the parts they process directly affects the quality of the product. Some mechanical parts and parts of precision equipment have very high requirements for machining accuracy. Improving the machining accuracy of CNC machines is the key to solving the problem. Through extensive research and analysis, it is concluded that there are roughly the following countermeasures to improve the machining accuracy of CNC machines:
During the machining process of CNC machines, errors themselves are inevitable. There is an inevitable error between the processed parts and the CNC machines. This error that must exist is called the original error.
Therefore, to improve the machining accuracy of CNC machines, controlling the original error of CNC machines is one of the important countermeasures. A systematic analysis should be conducted on the possibility of generating original errors, and corresponding improvement measures should be formulated according to the causes and types of errors. During the machining of mechanical parts, the position accuracy and geometric accuracy of CNC machines have an important influence on the machining accuracy of parts. Position control and geometric accuracy control should be used to reduce the influence of position error and geometric error on parts. At the same time, for the deformation error generated during the machining process, air cooling, water cooling and other methods should be used to control the thermal deformation during the machining process to reduce the influence of thermal deformation error on machining accuracy. At the same time, for position errors, it is necessary to reasonably select tools suitable for the material of the parts to avoid tool deformation. At the same time, select reasonable fixtures according to the shape of the blank of the processed parts. If necessary, the fixtures should be specially designed according to the shape and size of the parts to avoid position errors.
The positioning accuracy of machine tools has an important influence on the accuracy of parts. The core components that affect the positioning accuracy of machine tools include the straightness and horizontality of the feed system, guide rails, and worktables. When designing CNC machines, it is necessary to reasonably select core components. For example, when selecting ball screws that are currently widely used in machine tools, the accuracy of ball screws should be fully considered, and relatively mature ball screw technology should be selected and installed. The support of ball screws should also not be ignored. The support of ball screws is closely related to the transmission accuracy of the system. The support of ball screws is mainly determined by axial loads and rotation speeds, which has an important influence on the processing accuracy of CNC lathes. High-precision fixing and support methods are usually selected. In addition, the bearing capacity of ball screws should be strictly checked during the design process.
As part of the external protection of machine tools, drag chains are now indispensable to machine tools. Due to its chain link structure, it will also generate certain vibrations when following the tool holder movement. This vibration will be directly transmitted to the tool, and will eventually have a certain impact on the processing accuracy.
Therefore, the performance of the drag chain greatly determines the accuracy of the machine tool. The E6 series drag chain of igus has been specially designed to greatly reduce vibration and noise, and minimize the impact of the drag chain movement on the accuracy of the machine tool.
In addition, the E6 series drag chain of igus uses a small pitch, non-pin connection method of aggregate springs, zero wear, suitable for high-speed and high-acceleration applications. At a speed of V=1.8m/s, the noise is only 37Db(A), and it can also be used in industries such as clean rooms.
With the continuous improvement of CNC technology, the machining process of CNC machines can be monitored in real time, the error links in the machining process can be adjusted in time, and the error data of each link in the machining process can be collected and fed back to the control terminal. The corresponding error compensation mechanism can be adopted through the error data to make timely error compensation, which can effectively improve the machining accuracy of parts.
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