After the mid-1980s, a series of high-speed, high-precision machine tools came out one after another. In the first ten years, people mainly focused on the large-scale and high-speed of feed axes and spindle motors, and the heat treatment technology and high-speed numerical control devices that were generated, and achieved significant results in these areas. However, in the following five years, the search for high speed and high precision technology has embarked on a different path. The increase in speed has only shortened the processing time a little, and if you want to pursue the processing accuracy and the quality of the processing surface, you must compromise on speed. The center of gravity drive is a technology based on the theory of mechanical motion dynamics. Every machine tool engineer understands that pushing the center of gravity is the ideal method, but it does not fully understand its importance and reasons. The center-of-gravity drive technology can be said to achieve more substantial improvements in processing time, machining accuracy, machining quality, and tool life. It can be used not only in the machining center but also for all machine tools that perform the relative movement of the tool and the workpiece. The machine tool adopting the center-of-gravity drive technology can operate accurately according to the instructions issued by the CNC to avoid unnecessary consumption. The center of gravity drive principle exerts force on one end of the component, which will destroy the balance and cause vibration. Applying force on the center of gravity can be straightened without vibration. However, due to the presence of an object at the center of gravity of the machine, force cannot be applied directly to it. If you apply an average force at both ends of the center of gravity, you can move straight. Center-of-gravity drive The center-of-gravity drive is a technology that can shorten the processing time, improve the accuracy of contour processing, and improve the quality of the processing surface. It is well-known that not pushing the object in the middle may cause the object to rotate and become unstable when the object is pushed. "But if you press in the middle ...", the focus of the drive is such a simple truth. Ball screws are usually used in machine tools to move the tool and the workpiece. If it can be pushed in the middle of its center of gravity, there is no problem. As long as the center of gravity is placed between the two driving points, this problem can be well solved. Connect the center of the two ball screws. It is appropriate to coincide with the center of gravity of the moving object. The vibrational vibration accompanying the axis movement over time is shown in the figure. The center-of-gravity drive device quickly eliminates vibration, whereas the vibration of other devices lasts longer. Using a tool located on the top of a vibrating device to machine a workpiece can result in a significant deterioration of the quality of the machined surface. In addition, if the tool is used to cut the workpiece during vibration, the tip will also be slightly worn. Therefore, vibration is a real enemy to the tool life. What is more, if the vibration occurs, the numerical control device will detect it as an action other than the normal command, and drive the feed motor in order to correct the error. Repeatedly, it further exacerbates the vibration. A technician familiar with this situation will adjust the numerical control device at startup and passivate its reaction to the action. However, even if there are some errors, fine adjustments cannot be made, resulting in a loss of accuracy. And to maintain accuracy, it will reduce speed. After all, mechanical vibration is a natural enemy of precision and processing time. Why does the center of gravity drive have specific advantages in terms of not generating vibration? To sum up, it is that it can reduce vibration and the effect is obvious. The improvement of the quality of the processing surface is also very effective in improving the quality of the working surface. Let us try to analyze it. In machining, surface or curve machining is essential. We can think of the surface as a link to a small polyline. Each time you change the angle of each line, the direction of movement changes. If the direction is changed without reducing the speed, even a slight change in direction requires a large acceleration. At the beginning of the acceleration, all the oscillating vibrations are proportional to the distance between the driving point and the center of gravity. This phenomenon is more pronounced when the processing point in the lower side of the cavity reaches the bottom surface and the direction of movement is rapidly changed. Using original organic-type workpieces, there are many irregularities in the cuts produced after the direction of movement of the processing point is changed. The center-of-gravity drive technology more closely approaches the nature of the deterioration of the quality of the machined surface. Another example of rapid changes in the direction of movement is the reversal of circular cutting, that is, the problem of transitional cutting at 0, 90, 180, and 270 degrees. If the boring diameter correction is to be replaced with a simple end mill for contour machining, the degree of perfect circle becomes extremely important. This also involves the problem of vibration caused by changes in the direction of movement. Center-of-gravity drive can also be used to improve the roundness of circular cutting. Shortening the machining time and driving the center of gravity has a significant effect on shortening the processing time. With a center-of-gravity-driven machine tool, since the vibration generated at the beginning of acceleration is small, it can be immediately accelerated from the initial force to the greater force. Instead of using a center-of-gravity driven machine, you can only slowly increase the force to prevent vibration at the beginning of acceleration. As shown in the figure, the non-center-of-gravity drive and the center-of-gravity drive are used. The yellow curve represents the time difference from the start of acceleration to a higher speed, and it can be seen that the time difference between the two reaches a higher speed. In summary, the application of gravity center drive technology in large-format engraving and milling machines has obvious advantages over traditional drive technology, and is the development direction of middle-grade engraving and milling machines.
