Vibration Mechanism Analysis
The vibration of NC Spiral Cutter during processing is mainly caused by the periodic change of cutting force. During the milling process, the cutting force will fluctuate when the tool cuts into and out of the workpiece material. When the frequency of the cutting force change is close to or equal to the natural frequency of the machine tool-tool-workpiece system, resonance is easily induced. The helix angle characteristics of the spiral milling cutter make the degree of participation of the cutting edge in the cutting process constantly change, which further leads to the complexity of the dynamic characteristics of the cutting force. For example, when the spiral milling cutter with a larger helix angle is processed, its axial cutting force component is relatively large, and the distribution along the tool axis is uneven, which is easy to cause axial vibration of the tool. At the same time, factors such as the motion accuracy of the machine tool, the installation accuracy of the tool, and the clamping stiffness of the workpiece will also affect the dynamic characteristics of the system. If there are deficiencies in these aspects, the generation and propagation of vibration will be aggravated.
Tool-related improvement measures
From the perspective of the tool, a variety of measures can be taken to improve the surface quality. First, optimize the geometric parameters of the spiral milling cutter, such as the reasonable selection of the helix angle and the cutting edge radius. Appropriately reducing the helix angle can reduce the axial cutting force and reduce the possibility of axial vibration; while a smaller cutting edge radius can make the cutting sharper and reduce the fluctuation of the cutting force. Secondly, adopt a vibration-reducing tool structure, such as designing a vibration-reducing device inside the tool, such as a damper or a vibration-reducing cavity, to suppress the vibration of the tool by consuming vibration energy. In addition, improve the manufacturing accuracy and dynamic balance performance of the tool, reduce the centrifugal force caused by the unbalanced mass of the tool itself, and thus reduce the excitation source of vibration.
Process parameter optimization
The reasonable selection of process parameters is crucial to suppress vibration and improve surface quality. In terms of cutting speed, it should be avoided to choose near the critical cutting speed, because resonance is easily induced in this area. Vibration can be effectively reduced by determining the appropriate cutting speed range through experiments and simulations. The feed rate will also affect the cutting force. Appropriately reducing the feed rate can reduce the amplitude of the cutting force, but at the same time, the processing efficiency must be taken into account. The cutting depth should be reasonably determined according to the workpiece material and tool performance. Excessive cutting depth will cause a sharp increase in cutting force, resulting in increased vibration. For example, when processing materials with higher hardness, using a smaller cutting depth and appropriate feed rate, combined with a suitable cutting speed, can reduce the vibration level while ensuring the processing quality.
Machine tool and clamping optimization
The performance and clamping method of the machine tool have a significant impact on the processing vibration and surface quality. Ensure that the machine tool has sufficient rigidity and precision, regularly maintain the machine tool, check the wear of key components such as guide rails and lead screws, and adjust or replace them in time. When clamping the workpiece, use reasonable clamping methods and fixtures to improve the clamping rigidity of the workpiece and reduce the vibration caused by the deformation of the workpiece. For example, for thin-walled workpieces, special auxiliary support devices or vacuum adsorption clamping methods can be used to enhance the stability of the workpiece. At the same time, optimize the clamping method of the tool to ensure the installation accuracy and coaxiality of the tool in the tool holder, reduce the vibration factors caused by the tool installation error, and thus create good conditions for improving the surface quality of NC Spiral Cutter processing.
