CNC cutting vibration usually occurs in turning of slender shafts, turning of thin-walled parts, etc. Once the vibration is intensified, there will be intense vibration with an amplitude of more than tens of μm, usually accompanied by a lot of noise. In the cutting process, the vibration may exceed 100 μm. Although it can be processed, obvious vibration scratches will remain on the machined surface, which is not allowed on the finished surface.
Vibration generated during metal CNC cutting is very harmful
1. Affect the surface quality of the parts. If vibration occurs during processing, there will be relative displacement between the tool and the workpiece, which will cause vibration marks on the processed surface, which will seriously affect the surface quality and performance of the parts;
2. When reducing the CNC cutting vibration of the machine tool and tool life, the process system will continue to bear the dynamic alternating load, the tool is easily worn (even chipped), the connection characteristics of the machine tool are damaged, and even the cutting process cannot continue in severe cases;
3. The noise generated is harmful to the health of the operator. The noise generated in the vibration will also endanger the health of the operator. In order to reduce vibration, sometimes the cutting amount has to be reduced, which reduces the production efficiency of machine tool processing.
Therefore, in order to ensure the normal operation of this kind of machining equipment, the control of cutting chatter becomes more and more important.
Causes of cutting vibration
The vibration of the tool when CNC cutting the workpiece requires the following three conditions to exist at the same time:
The first is that the rigidity of the process system including the tool is insufficient, resulting in a low natural frequency.
The second is that the cutting produces a sufficiently large external force,
The third is that the frequency of the external excitation force is the same as the natural frequency of the process system and then resonates.
How to Eliminate Cutting Vibration
The first is to reduce the CNC cutting force to a minimum,
The second is to enhance the static rigidity of the tool system or the fixture and the workpiece as much as possible;
The third is to create another vibration inside the tool holder to disrupt the vibration frequency of the externally driven cutting force, thereby eliminating tool vibration.
1. The first is to reduce the CNC cutting force to the minimum
(1) Use sharp blades to reduce cutting force
(2) When cutting a certain depth, use a small radius of the tool nose arc
(3) For boring cutters with slender tool bars and turning slender shaft parts, 90-degree leading angle tools should be used
(4) For milling cutters with slender rods, round blade milling cutters are the most conducive to vibration reduction
(5) The plunge milling method is often used for milling deep cavities with slender rod end mills
(6) The face milling cutter adopts a coarse-tooth unequal distance milling cutter to reduce milling vibration
(7) The smaller the edge angle of the insert when boring the inner hole, the better
2. Improve the static rigidity of the tool holder (Static Toughness)
3. Improve the dynamic rigidity of the tool—passive damping and vibration-proof tool holder