Reasons for lathe cutting vibration and improvement measures

This article introduces the main occasions, causes, and countermeasures of tool vibration, which can help you deal with tool vibration problems in daily processing.
When using a lathe for mechanical processing, there are several situations where the so-called "vibration knife" may occur:
Using Formed Blades for Forming Turning
External Turning of Slender Round Rod
Turning the Outer Circle of Thin Taiwanese Meatballs Rod
Turning of box shaped parts (such as sheet metal welded structural components)
Cutting of superhard materials
The bearing has been damaged and cutting continues
When the vibration of the cutting tool occurs, the vibration of the cutting tool, workpiece, and lathe often leads to harsh noise inside the factory, and its amplitude can reach tens of micrometers or more on one side, sometimes as high as 100 micrometers or more. This type of vibration knife not only causes loosening of the tool or workpiece clamping, but also has a negative impact on the operator's physical and mental health due to its noisy noise. As a result, the machining accuracy cannot meet the customer's requirements. Therefore, all tool manufacturers are hesitant to eliminate the vibration knife problem as a great challenge.
01
Basic methods
1. Forced Vibration
This is a forced vibration caused by intermittent cutting or vibration caused by defective rotating parts. Common phenomena such as abnormal noise caused by bearing damage, poor gear meshing, poor workpiece clamping, and excessive spindle swing belong to this category.
In this type of problem, intermittent turning belongs to the processing technology problem, and the defects of the parts mainly come from the assembly technology of the machine tool and the quality control of its key components, and are also related to the design concept of the machine tool structure. The characteristics of its vibration are directly related to the magnitude of the revolution.
2. Self excited vibration
This is due to the periodic unevenness of the cutting process, which causes a slight deviation and repeated overlapping of the periodic phases, resulting in a regenerative effect. It can generally be called "resonance", which is mainly caused by the excitation of the natural frequency of the machine tool structure or the excitation of the self frequency of the workpiece clamping system being too low.
Due to the fact that the natural frequency of the structure only changes with the clamping or fixing method, changing the cutting conditions (such as changing the speed) can often improve cutting vibration when vibration occurs. However, in certain situations where the cutting speed cannot be changed (such as tapping or cutting of certain materials), only by changing the clamping method, or even changing the tool or tool fixing method, can such problems be solved.
02
Countermeasures for Suppressing Vibration Knives
Based on the vibration knife principle obtained from research, there are currently some specific and practical methods applied in machining sites:
1. Try to choose all conditions with lower cutting impedance, that is, the most appropriate tool feed rate and cutting speed (or spindle speed).
2. Adjust the cutting speed to avoid resonance.
3. Reduce the working weight of the part that causes vibration, and the smaller the inertia, the better.
4. Fix or clamp the areas with the highest vibration, such as center frames, work retainers, etc.
5. Improve the rigidity of the machining system, such as using tool holders with higher elastic coefficients or using special seismic forces with added dynamic dampers to absorb impact energy.
6. Put effort into the direction of blade and work rotation (the work presses down the tool while also increasing its stability).
7. Change the appearance and angle of the cutting tool, for example: the smaller the nose radius, the better, to reduce cutting resistance. The inclination angle must be taken as a positive value to make the cutting direction closer to perpendicular. It is best to have a positive inclination angle, but the ability to remove chips and chips is relatively poor. Therefore, slot cutters can generally be used to make the inclination angle negative, but still maintain a positive cutting effect.
8. The smaller the lead angle, the better, preferably zero.