We know that error is a major indicator for testing the qualified rate of workpiece processing. In the cnc vertical Machining Center 1165, the accuracy is mainly represented by the size of the error, and the specific accuracy is divided into two types, including static accuracy and dynamic accuracy. Among them, the static accuracy refers to the detection when the machining center is not working and not cutting. The main indicators are the geometric accuracy and positioning accuracy of the machining center itself. This accuracy can only show the accuracy of the machining center for the detection of the accuracy of the machining center. Original accuracy; as the name suggests, dynamic accuracy is the accuracy detected and achieved by the machining center during the cutting process. The measurement of this accuracy value includes the original accuracy of the machining center and the accuracy expression after the impact of environmental and technological issues during the machining process, including Errors caused by the selection of tools, workpieces, vibration, etc. during the machining process. In the production process of the machining center, the dynamic accuracy of the machining center cannot be effectively controlled. What can be guaranteed is the static accuracy of the machining center, the accuracy of the original manufacturing, and the machining accuracy of the CNC machining center. The main discussion content below.
Factors Affecting Machining Precision of CNC Machining Center
The error of the machining center itself is shown in a large amount of data and statistics that more than 65.7% of the machining center cannot fully meet its relevant index standards during installation, and 90% of the CNC machining centers are in an inaccurate working environment during work. In the same state, this situation determines the importance of monitoring the working status of the machining center. The accuracy test of the machining center is a necessary basis for the guarantee of the accuracy of the machining center, which can better guarantee the machining accuracy of the parts.
In addition to the accuracy error of the machining center itself, the operation of the machining center in the workshop environment will also be affected, including the temperature fluctuation of the workshop, the heating of the motor, the friction of the connecting and unloading, and the influence of the medium. These problems will all affect the machining center. The shape and accuracy have a certain degree of influence, and the temperature change of the machining center will cause the loss of adjustment accuracy, which will affect the accuracy of the machining center and the size and accuracy of the workpiece. At the same time, the temperature rise also changes the bearing clearance, which in turn affects the machining accuracy. On the other hand, the temperature rise makes the temperature distribution uneven, causing changes in the mutual positional relationship between the parts or parts of the parts, thereby causing the displacement or distortion of the parts.
Reverse deviation The so-called reverse deviation refers to the error phenomenon caused by the reverse dead zone or backlash caused by the coordinate axis in the transmission process in the work of the CNC machining center. It can also be the backlash or loss of momentum. For CNC machining centers using semi-closed-loop servo systems, the existence of reverse deviation will affect the positioning accuracy and repeat positioning accuracy of the machining center, thereby affecting the machining accuracy of the product.
Clearance error The transmission chain is needed in the machining process of the CNC machining center. The operation of the transmission chain will produce some gaps. These gaps are easy to cause errors, especially when the machining center does not move during the motor operation, which will cause CNC machining Oscillation of the center or a large error problem.
Measures to Improve the Machining Accuracy of CNC Machining Center
The selection of machining center is different due to the accuracy of the machining center itself, which requires us to pay attention to the selection of machining center model and accuracy in the selection of machining center. At present, the inspection of the position accuracy of CNC machining center usually adopts the international standard ISO230-2 or the country. Standard GB10931-89 and so on. In the selection of machining center, attention should be paid to the standard, because the difference of the standard will also cause the difference in accuracy.
The machining center of the control sliding bearing of the parts can choose the bearing with better wear resistance, so as to ensure the working accuracy of the machining center.
The control of the workshop environment reduces the heat source: the focus is on the rotation speed of the spindle bearing, the adjustment of the gap and the reasonable preload. For thrust bearings and tapered roller bearings, because of their poor working conditions, they generate more heat. If necessary, they can be replaced by thrust angular contact ball bearings to minimize the friction and heat generation of certain parts. Heat insulation: keep the heat source away from the main shaft, such as isolating the motor and transmission, using separate transmission, etc. Heat dissipation: Strengthen lubrication and cooling, adopt oil cooling, air cooling, etc., to speed up heat dissipation. Reduce the influence of thermal deformation: No matter what method is used, it can only reduce thermal deformation and it is difficult to completely eliminate thermal deformation. Therefore, measures should be taken to reduce the impact of thermal deformation.
The control of the reverse deviation will cause the accuracy of the equipment to become lower due to the reverse deviation, and the longer the application time of the machining center, the greater the wear and the greater the error, which requires the application of the machining center. Periodic detection and compensation of the reverse deviation are carried out to reduce errors as much as possible and improve the accuracy of the machining center.
Error compensation Error compensation refers to the corresponding recording of the position of the fixed axis in the processing of the CNC machining center. In addition, the relevant recorded data is compared with the actual measurement results to understand the error value and to be on the axis during operation. Select the reference point for measurement, record the error value during operation, and input it into the relevant control system, so that the axis movement and error time at different points can be well controlled. If the number of measured points is larger, the error effect that needs to be compensated for the pitch is more obvious. The premise of this error compensation technology is based on the coordinate system of the CNC machining center, and the important parameters of the coordinate system of the CNC machining center are a reference. Therefore, it is necessary to ensure that the error value of the selected reference point is zero.
Compensation of backlash error Due to the influence of backlash error in CNC machining center, it is necessary to pay full attention to backlash error in the design of CNC machining center and take effective measures to solve it. But it is undeniable that the gap exists, so what we have to do is to record the backlash of each point during the operation of the machining center through the pitch error compensation technology, and directly control the reverse movement through the control system of the CNC machining center. Carry out the error compensation operation, thereby using the parameter setting and the numerical control system setting to reduce the error.
Technical improvement The accuracy of machining centers is constantly improving and progressing with the development of science and technology. The accuracy of machining centers has improved from the original micron level to the nano level. More research and development are needed, especially in bearing technology. Avoiding the hysteresis of bearing technology is one of the problems of development. The hysteresis phenomenon is particularly important for the accuracy of positioning. In the research, it is found that the hydrostatic bearing technology can solve the hysteresis of the machine. Therefore, it is processed in a high-precision CNC machining center. A large number of applications have been obtained.
In summary, there are many factors affecting the accuracy of the CNC machining center in the machining work of the CNC machining center. We must comprehensively analyze these effects and reduce the error as much as possible from many aspects to achieve an effective improvement in the machining accuracy.
