Vibration suppression measures during the processing of end mills

Vibration during the machining process of end mills is a key factor affecting machining accuracy, surface quality and tool life. To effectively suppress vibration, comprehensive measures need to be taken from multiple dimensions such as tool design, optimization of cutting parameters, workpiece clamping and machine tool status. The following is the specific technical solution and analysis:

First, tool design and selection

Optimization of tool geometric parameters

Selection of main deflection Angle: When processing thin-walled parts or slender shafts, tools with a main deflection Angle close to 90° (such as 90° face milling cutters) should be preferred to reduce radial cutting force and lower the risk of vibration.

The radius of the tool tip arc: Reducing the radius of the tool tip arc can lower the radial cutting force, especially suitable for the processing of slender bar tools or thin-walled parts.

Helix Angle design: Using a large helix Angle (such as above 40°) can reduce the radial component force on the cutting edge and lower the vibration tendency. For deep cavity processing, it is recommended to use an unequal helix Angle design to suppress vibration through an asymmetric cutting force distribution.

Improvement of tool structure

Vibration-reducing tool holders: For processing scenarios where the overhanging length exceeds four times the diameter, vibration-reducing tool holders with built-in dampers (such as the Silent Tools™ series) are adopted. By absorbing vibration energy through damping materials, stability is significantly enhanced.

Unequal pitch milling cutter: By means of non-uniform pitch design, it breaks the periodicity of cutting force, suppresses self-excited vibration, and is especially suitable for high-speed milling.

Second, optimization of cutting parameters

Feed strategy adjustment

Feed per tooth (fz) : To prevent the fz from being too small, which may cause the chips to be too thin and lead to the “tool letting” phenomenon. At the same time, prevent the cutting force from surging due to excessive fz. It is recommended that the fz range be 0.05 to 0.2 mm/z (the specific range should be combined with the material and the cutting tool).

Axial depth of cut (ap) and radial depth of cut (ae) :

When processing thin-walled parts, a small diameter depth of cut (ae≤25% of the tool diameter) and a large axial depth of cut (ap close to the tool diameter) are adopted to disperse the cutting force.

For deep cavity processing, the plunge milling process is preferred. By reducing the radial force through axial feed, the rigidity of the tool holder is enhanced.

The rotational speed matches the feed rate

Avoid resonant rotational speed: Determine the safe rotational speed range through the machine tool Stability Lobe Diagram and avoid the critical rotational speed corresponding to the system’s natural frequency.

High feed rate: Under the premise of ensuring surface quality, appropriately increasing the feed rate (such as using high-speed milling technology) can reduce cutting time and lower the accumulation of thermal deformation and vibration.

Third, workpiece clamping and fixture design

Strengthening of clamping rigidity

Multi-point clamping: For large workpieces, diagonal clamping or distributed clamping is adopted to ensure uniform distribution of clamping force and avoid local suspension.

Auxiliary support: When processing thin-walled parts, elastic support (such as rubber strips, springs) can be added between the fixture and the workpiece, or vacuum suction cups can be used to achieve surface contact to enhance the overall rigidity.

Fixture optimization

Specialized fixture design: For workpieces with complex shapes, specialized fixtures are designed to reduce clamping deformation. For example, through the combination of modular fixture units, the transformation from point contact to surface contact is achieved.

Clamping force direction: Ensure that the direction of the main cutting force is consistent with that of the clamping force to prevent the workpiece from moving due to insufficient clamping force.

Fourth, machine tool status and maintenance

Rigidity inspection of machine tools

Main shaft and guide rail: Regularly inspect the wear of the main shaft bearings, lead screw nut pairs and guide rails to ensure the accuracy of the transmission system. For machine tools that have been in use for more than five years, it is necessary to focus on evaluating the bearing conditions of the spindle and the transmission box.

Dynamic balance calibration: During high-speed milling (with a rotational speed >5000 rpm), dynamic balance tests are conducted on the tool system to ensure that the unbalance is below the G2.5 standard.

Cutting fluid and cooling

Efficient cooling: High-pressure internal cooling of the tool is adopted, and the cutting fluid is directly sprayed into the cutting area to reduce the cutting temperature and minimize the vibration caused by thermal deformation.

Lubrication optimization: For difficult-to-machine materials (such as titanium alloys), extreme pressure cutting fluid is selected to reduce the coefficient of friction and lower the fluctuation of cutting force.

Fifth, process path planning

Tool path optimization

Arc transition: Use an arc path to cut in at the corner to avoid sudden changes in cutting force caused by right-angle turns.

Layer-by-layer milling: For workpieces with large allowances, the step milling method is adopted to remove the material step by step, reducing the load of a single cutting.

Selection between climb milling and reverse milling

Advantage of climb milling: When the lead screw clearance of the machine tool is controllable, climb milling is preferred to reduce tool wear.

The application scenarios of reverse milling: For workpieces with hardened surfaces or uneven allowances, reverse milling can avoid the “gnawing” phenomenon, but attention should be paid to the fluctuation of cutting force.

Sixth, vibration monitoring and real-time adjustment

Online monitoring system

Acceleration sensor: Install a three-directional acceleration sensor on the machine tool spindle or cutting tool to monitor the vibration amplitude and frequency in real time, and combine spectral analysis to locate the vibration source.

Adaptive control: By integrating a vibration monitoring module into the numerical control system, cutting parameters (such as rotational speed and feed rate) are dynamically adjusted to achieve closed-loop control.

Trial cutting verification

Stability test: Before formal processing, determine the boundaries of safe cutting parameters through trial cutting tests, and optimize the process plan in combination with vibration monitoring data.

Through the comprehensive application of the above measures, the vibration level during the processing of end mills can be significantly reduced, and the processing efficiency and surface quality can be improved. In practical applications, parameter fine-tuning should be carried out in combination with specific working conditions (such as materials, cutting tools, and machine tool models), and the best processing effect should be achieved through continuous monitoring and optimization.