Vibration suppressing method and vibration suppressing device for us in machine tool
In a machine tool having a rotary shaft for use in rotating a tool or a workpiece, a plurality of stable rotation speeds at which the chatter vibrations are expected to be suppressed, and at least one switching rotation speed across which a dynamic characteristic of a rotary shaft system changes are stored. The plurality of stable rotation speeds may be determined from chatter vibrations detected using a vibration detection unit. Optimum rotation speed that is a rotation speed to which a rotation speed of the rotary shaft is changeable without crossing the switching rotation speed is selected from the plurality of stable rotation speeds, and the rotation speed of the rotary shaft is changed to the optimum rotation speed. Thus, chatter vibrations generated during rotation of the rotary shaft can be suppressed effectively.
1. A vibration suppressing method implemented in a machine tool having a rotary shaft for use in rotating a tool or a workpiece, for suppressing chatter vibrations generated during rotation of the rotary shaft, the vibration suppressing method comprising:
a first step of detecting chatter vibrations using a vibration detection unit;
a second step of storing a plurality of stable rotation speeds at which the chatter vibrations are expected to be suppressed, and at least one switching rotation speed across which a dynamic characteristic of a rotary shaft system changes;
a third step of selecting an optimum rotation speed from the plurality of stable rotation speeds, the optimum rotation speed being a rotation speed to which a rotation speed of the rotary shaft is changeable without crossing the switching rotation speed; and
a fourth step of changing the rotation speed of the rotary shaft to the optimum rotation speed.
2. The vibration suppressing method according to claim 1 , further comprising steps, in the second step, of:
determining a chatter frequency of the chatter vibrations detected in the first step; and
determining the plurality of stable rotation speeds using the determined chatter frequency.
3. The vibration suppressing method according to claim 1 , further comprising, a step, in the second step, of storing at least one of an upper limit rotation speed and a lower limit rotation speed for at least one of a type of the rotary shaft and a type of the tool or the workpiece to be mounted on the rotary shaft,
wherein the optimum rotation speed to be selected in the third step is a rotation speed to which a rotation speed of the rotary shaft is changeable without crossing the switching rotation speed and which is within a range defined by at least one of the upper limit rotation speed and the lower limit rotation speed.
4. The vibration suppressing method according to claim 2 , further comprising, a step, in the second step, of storing at least one of an upper limit rotation speed and a lower limit rotation speed for at least one of a type of the rotary shaft and a type of the tool or the workpiece to be mounted on the rotary shaft,
wherein the optimum rotation speed to be selected in the third step is a rotation speed to which a rotation speed of the rotary shaft is changeable without crossing the switching rotation speed and which is within a range defined by at least one of the upper limit rotation speed and the lower limit rotation speed.
5. The vibration suppressing method according to claim 1 , further comprising, a step, in the third step, of displaying a warning on a display device when no rotation speed to which a rotation speed of the rotary shaft is changeable without crossing the switching rotation speed is found in the plurality of stable rotation speeds stored in the second step.
6. The vibration suppressing method according to claim 2 , further comprising, a step, in the third step, of displaying a warning on a display device when no rotation speed to which a rotation speed of the rotary shaft is changeable without crossing the switching rotation speed is found in the plurality of stable rotation speeds stored in the second step.
7. The vibration suppressing method according to claim 3 , further comprising, a step, in the third step, of displaying a warning on a display device when no rotation speed to which a rotation speed of the rotary shaft is changeable without crossing the switching rotation speed is found in the plurality of stable rotation speeds stored in the second step.
8. The vibration suppressing method according to claim 4 , further comprising, a step, in the third step, of displaying a warning on a display device when no rotation speed to which a rotation speed of the rotary shaft is changeable without crossing the switching rotation speed is found in the plurality of stable rotation speeds stored in the second step.
9. A vibration suppressing device provided in a machine tool having a rotary shaft for use in rotating a tool or a workpiece, for suppressing chatter vibrations generated during rotation of the rotary shaft, the vibration suppressing device comprising:
a vibration detection unit configured to detect chatter vibrations;
a storage unit configured to store a plurality of stable rotation speeds at which the chatter vibrations are expected to be suppressed, and at least one switching rotation speed across which a dynamic characteristic of a rotary shaft system changes;
an optimum rotation speed selection unit configured to select an optimum rotation speed from the plurality of stable rotation speeds, the optimum rotation speed being a rotation speed to which a rotation speed of the rotary shaft is changeable without crossing the switching rotation speed; and
a rotation speed change unit configured to change the rotation speed of the rotary shaft to the optimum rotation speed.