When the vibrating knife occurs, the vibration of the tool, workpiece and lathe often causes harsh noise inside the factory, and its amplitude is tens of microns or more on one side, sometimes up to 100 microns or more. This vibrating knife not only causes the clamping of the tool or the workpiece to become loose, but also causes a bad physical and mental impact on the operator due to its noisy noise, and the machining accuracy cannot meet the requirements of the customer, so the tool machine manufacturers do not It is a great challenge to eliminate the problem of vibrating knives.
First, the basic method (a) forced vibration (ForcedVibration)
This is the forced vibration caused by intermittent cutting or the vibration caused by the turning of the rotating parts. Generally, the abnormal sound or gear meshing caused by the damage of the bearing and the poor clamping of the workpiece, the spindle pendulum This phenomenon is such a phenomenon that the size is too large.
Among such problems, intermittent turning is a problem of machining technology, and most of the parts are derived from the assembly technology of the machine tool and the quality control of its key components, and also related to the machine structure design concept. The vibration characteristics are directly related to the number of revolutions.
(2) Self-excited vibration (Self-excitedUibration)
This is because the periodic work unevenness during cutting processing causes the effect of the repetitive effect of repeated overlap of the periodic phase, which is generally called "resonance". The main cause comes from The natural frequency of the machine tool structure is excited or caused by the low frequency of the workpiece clamping system being excited.
Since the natural frequency of the structure changes only with the change of clamping or fixing mode, changing the cutting conditions (such as changing the speed) can often improve the cutting vibration when the vibrating knife occurs. However, in some occasions where the cutting speed cannot be changed (such as attacking) Tooth or cutting of certain materials, it is often only possible to solve such problems by changing the clamping method or even changing the tool or tool fixing method.
Second, the countermeasures to suppress the vibrating knife According to the vibration knife principle obtained from the research, there are some more specific and practical methods applied to the processing site:
(1) Try to choose all the conditions with small 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) Reducing the working weight of the part causing the vibration, the smaller the inertia, the better.
(4) Fix or clamp the place with the largest vibration, such as the center frame, work holder, etc.
(5) Improve the rigidity of the processing system, for example, using a tool holder with a high modulus of elasticity or using a special shock resistance added to the dynamic damper to absorb the impact energy.
(6) Working hard from the direction of the blade and the work rotation (the work will lower the tool while also increasing the stability of the tool).
(7) Change the shape and advance angle of the tool. For example, the smaller the nose radius, the better, to reduce the cutting resistance. The roll angle must be positive so that the cutting direction is closer to vertical. The back rake angle is preferably positive, but the chip removal ability is relatively poor. Therefore, a groove cutter is generally used to make the inclination angle negative, but still has a positive cutting effect.
(8) The smaller the lead angle, the better, preferably zero.
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Label: What are the reasons for the cutting knife and the improvement measures?
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