Chatter vibration detection method, chatter vibration avoidance method, and machine tool
AssigneeMakino Milling Machine Co., Ltd.
InventorEiji Kondo
Life of this patent
Estimating the term…
Abstract
A chatter vibration detection method includes acquiring vibration data of a tool (4) at a time of machining a workpiece at a predetermined sampling period (Δt), calculating an autocorrelation coefficient (Rxx′) corresponding to a time required for a cutting edge (4a, 4b) to contact the workpiece (W) several times based on acquired time series vibration data and calculating a period (Tx) of characteristics of the calculated autocorrelation coefficient (Rxx′), and deciding that chatter vibration occurs when a contact period (T1) at which the cutting edge (4a, 4b) contacts the workpiece (W) is not an integral multiple of the calculated period (Tx).
Claims8
A regenerative chatter vibration detection method for detecting regenerative chatter vibration, the regenerative chatter vibration occurring when a tool having a cutting edge is attached to a rotary spindle and this tool is moved relative to a workpiece to machine the workpiece, comprising:
- a data acquiring step of acquiring vibration data, which has a correlation with vibration of the tool at a time of machining the workpiece, at a predetermined sampling period;
- a calculating step of calculating an autocorrelation function corresponding to a time required for the rotary spindle to rotate at least twice so that the cutting edge contacts the workpiece several times based on time series vibration data acquired by the data acquiring step, and calculating a period or frequency of characteristics of the calculated autocorrelation function;
- and
- a deciding step of deciding that the regenerative chatter vibration occurs when a contact period at which the cutting edge contacts the workpiece is not an integral multiple of the period calculated by the calculating step or when the frequency calculated by the calculating step is not an integral multiple of a product of a number of cutting edges of the tool and a rotational speed of the rotary spindle.
A regenerative chatter vibration avoidance method for avoiding regenerative chatter vibration, the regenerative chatter vibration occurring when a tool having a cutting edge is attached to a rotary spindle and this tool is moved relative to a workpiece to machine the workpiece, comprising:
- a data acquiring step of acquiring vibration data, which has a correlation with vibration of the tool at a time of machining the workpiece, at a predetermined sampling period;
- a calculating step calculating an autocorrelation function corresponding to a time required for the rotary spindle to rotate at least twice so that the cutting edge contacts the workpiece several times base on time series vibration data acquired by the data acquiring step, and calculating a period or frequency of characteristics of the calculated autocorrelation function;
- a deciding step of deciding that the regenerative chatter vibration occurs when a contact period at which the cutting edge contacts the workpiece is not an integral multiple of the period calculated by the calculating step or when the frequency calculated by the calculating step is not an integral multiple of a product of a number of cutting edges of the tool and a rotational speed of the rotary spindle;
- and
- a rotational speed adjusting step of calculating a phase difference determined from the contact period of the cutting edge and the period calculated by the calculating step or a phase difference determined from the product of the number of cutting edges of the tool and the rotational speed of the rotary spindle and the frequency calculated by the calculating step when the deciding step decides that the regenerative chatter vibration occurs, increasing and decreasing the rotational speed of the rotary spindle by a predetermined ratio based on the calculated phase difference, and repeating the increasing and decreasing of the rotational speed of the rotary spindle until the calculated phase difference becomes substantially 0.
A machine tool for machining a workpiece, in which a tool having a cutting edge is attached to a rotary spindle, and this tool is moved relative to the workpiece, comprising:
- a data acquiring portion acquiring vibration data, which has a correlation with vibration of the tool at a time of machining the workpiece, at a predetermined sampling period;
- a calculating portion calculating an autocorrelation function corresponding to a time required for the rotary spindle to rotate at least twice so that the cutting edge contacts the workpiece several times based on time series vibration data acquired by the data acquiring portion, and calculating a period or frequency of characteristics of the calculated autocorrelation function;
- and
- a deciding portion deciding that the regenerative chatter vibration occurs when a contact period at which the cutting edge contacts the workpiece is not an integral multiple of the period calculated by the calculating portion or when the frequency calculated by the calculating portion is not an integral multiple of a product of a number of cutting edges of the tool and rotational speed of the rotary spindle.
Dependencies are inferred from the claim text.