How to control vibration during cutting on CNC machine tools? Very particular!
Cutting vibration
Cutting vibration usually occurs in the turning of slender shafts and thin-walled parts.
Once the vibration intensifies, the amplitude will exceed several tens μ The intense vibration of m is usually accompanied by significant noise. In cutting, vibration may exceed 100 μ m. Although it can be processed, there will be obvious vibration scratches remaining on the processed surface, which is not allowed on precision machined surfaces.
The harm of cutting vibration is that the vibration generated during metal cutting is a very harmful phenomenon.
1. If vibration occurs during machining, there will be relative displacement between the tool and the workpiece, which will cause vibration marks on the machining surface and seriously affect the surface quality and performance of the parts;
2. When reducing the lifespan of the machine tool and cutting tool, the process system will continue to withstand the dynamic alternating load, which makes the tool extremely prone to wear (even blade breakage), and the connection characteristics of the machine tool are damaged. In severe cases, it may even make the cutting process unable to continue;
3. Noise generation poses a threat to the operator's physical health. The noise generated during vibration will also pose a threat to the operator's physical health. To reduce vibration, sometimes it is necessary to reduce the cutting amount, which reduces the production efficiency of machine tool processing.
Therefore, in order to ensure the normal operation of such mechanical processing equipment, the control of cutting chatter has become increasingly important. The classification of cutting vibration The causes of cutting vibration when cutting a workpiece require the following three conditions to exist simultaneously:
The first issue is that the insufficient rigidity of the process system, including the cutting tools, leads to a low natural frequency,
The second is that cutting generates a sufficiently large external excitation force,
The third is that the frequency of this external excitation force is the same as the natural frequency of the process system, and resonance occurs immediately.
How to eliminate cutting vibration?
(1) The first solution is to minimize cutting force, and the second is to enhance the static rigidity of the tool system or fixture with the workpiece as much as possible; The third method is to create another vibration inside the tool holder to disrupt the vibration frequency of the external cutting force, thereby eliminating tool vibration.
(2) Countermeasure 1: The first is to reduce the cutting force to the minimum
(1) Use sharp blades to reduce cutting force
(2) When the cutting depth is constant, use a small tool tip arc radius
(3) For boring and turning slender shaft parts with slender tool holders, a 90 degree main deviation angle tool should be used
(4) For milling cutters with slender rods, circular blade milling cutters are more conducive to vibration reduction
(5) Insertion milling method is often used for milling deep cavities with slender end mills
(6) The face milling cutter adopts sparse teeth and unequal spacing milling cutters to reduce milling vibration
(7) When boring inner holes, the smaller the blade shape angle, the better. 2. Improve the static rigidity of the tool holder (StaticToughness)
Use integral hard alloy or heavy metal tool holders to improve the static rigidity of the tool holder. 3. Improve the dynamic rigidity of the tool - passive damping and vibration avoidance tool holder!
