# US 7,245,983 B2 · Method and apparatus for correcting thermal displacement of machine tool > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,245,983 B2 - Document ID: US7245983B2 - Status: Granted - Kind: B2 - Application number: 11/255,649 - Filed: 2005-10-20 - Published: 2006-04-27 - Granted: 2007-07-17 - Earliest claimed: 2004-10-22 - Assignees: Yamazaki Mazak Corporation - Inventors: Yasuhiko Suzuki; Makoto Tanahashi - Web page: https://patentgrep.com/patent/US7245983B2 ## CPC - G05B 19/404: characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia (G05B19/19, G05B19/41 take precedence) - G05B 2219/49204: Control of heat to compensate for dilatation, thermal displacement - G05B 2219/49214: Estimate error from heat distribution model and drive current, correct error - G05B 2219/49219: Compensation temperature, thermal displacement - G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G) ## Abstract A method corrects thermal displacement of a machine tool having a rotational spindle. The method includes detecting a rotation speed of the spindle. A thermal displacement amount of the spindle in the current cycle of execution of a program is estimated by using an arithmetic expression that is based at least on the spindle rotation speed and a thermal displacement amount that has been estimated in the preceding cycle of execution of the program. The estimated thermal displacement amount in the current cycle is used as a correction amount for canceling the thermal displacement of the spindle. Therefore, thermal displacement of a machine tool is corrected with no complicated processes when a spindle rotation speed changes. ## Claims ### Claim 1 A method for correcting thermal displacement of a machine tool having a rotation spindle, comprising: detecting a rotation speed of the spindle; detecting a load on the spindle; estimating a thermal displacement amount of the spindle in the current cycle of execution of a program by using an arithmetic expression that is based at least on the spindle rotation speed, the spindle load, and a thermal displacement amount that has been estimated in the preceding cycle of execution of the program; and using the estimated thermal displacement amount in the current cycle as a correction amount for canceling the thermal displacement of the spindle. ### Claim 2 (depends on 1) The method according to claim 1, wherein a first member is attached to the spindle, the first member being one of a working attachment and a workpiece, a second member, which is the other one of the working attachment and the workpiece, is arranged to face the spindle, wherein the machine tool includes a feed rod for moving the first member or the second member, the method further comprising controlling the feed rod in such a manner as to correct a relative position relationship between the first member and the second member based on the correction amount. ### Claim 3 (depends on 1) The method according to claim 1, further comprising: detecting a temperature of the spindle; estimating an estimated spindle temperature in the current cycle of execution of the program by using a temperature computation expression that is based on the spindle rotation speed and an estimated spindle temperature that has been estimated in the preceding cycle of execution of the program; and estimating the thermal displacement amount in the current cycle by using an arithmetic expression that is based on the spindle rotation speed, the precedingly estimated thermal displacement amount, the spindle load, and a difference between the estimated spindle temperature estimated in the current cycle of execution of the program and the detected spindle temperature. ### Claim 4 (depends on 1) The method according to claim 1, wherein the arithmetic expression for estimating the thermal displacement amount in the current cycle at least includes the following terms a) to d): a) a term having the precedingly estimated thermal displacement amount as a variable; b) a term having the rotation speed of the spindle, which is detected at a predetermined interval, as a variable; c) a term having the square of the spindle rotation speed as a variable; and d) a term having the cube of the spindle rotation speed as a variable. ### Claim 5 (depends on 4) The method according to claim 4, wherein the arithmetic expression for estimating the thermal displacement amount in the current cycle further includes a term having, as a variable, an amount obtained by multiplying the spindle rotation speed by the precedingly estimated thermal displacement amount. ### Claim 6 (depends on 1) The method according to claim 1, further comprising obtaining the arithmetic expression for estimating the thermal displacement amount in the current cycle based on a response surface methodology. ### Claim 7 (depends on 3) The method according to claim 3, further comprising obtaining the temperature computation expression for estimating the estimated spindle temperature in the current cycle based on a response surface methodology. ### Claim 8 An apparatus for correcting thermal displacement of a machine tool having a rotation spindle, the apparatus comprising: a spindle rotation speed detection section for detecting a rotation speed of the spindle; a spindle load detection section for detecting a load on the spindle; a thermal displacement estimation section for estimating a thermal displacement amount of the spindle in the current cycle of execution of a program by using an arithmetic expression that is based at least on the spindle rotation speed, the spindle load, and a thermal displacement amount that has been estimated in the preceding cycle of execution of the program; and a correction section for using the estimated thermal displacement amount in the current cycle as a correction amount for canceling the thermal displacement of the spindle. ### Claim 9 (depends on 8) The apparatus according to claim 8, wherein a first member is attached to the spindle, the first member being one of a working attachment and a workpiece, a second member, which is the other one of the working attachment and the workpiece, is arranged to face the spindle, wherein the machine tool includes a feed rod for moving the first member or the second member, wherein the correction section controls the feed rod in such a manner as to correct a relative position relationship between the first member and the second member based on the correction amount. ### Claim 10 (depends on 8) The apparatus according to claim 8, further comprising a spindle temperature detection section for detecting a temperature of the spindle, wherein the thermal displacement estimation section: estimates an estimated spindle temperature in the current cycle of execution of the program by using an estimated spindle temperature computation expression that is based on the spindle rotation speed and an estimated spindle temperature that has been estimated in the preceding cycle of execution of the program; and estimates the thermal displacement amount in the current cycle by using an arithmetic expression that is based on the spindle rotation speed, the precedingly estimated thermal displacement amount, the spindle load, and a difference between the estimated spindle temperature estimated in the current cycle of execution of the program and the detected spindle temperature. ### Claim 11 (depends on 8) The apparatus according to claim 8, wherein the arithmetic expression for estimating the thermal displacement amount in the current cycle at least includes the following terms a) to d): a) a term having the precedingly estimated thermal displacement amount as a variable; b) a term having the spindle rotation speed, which is detected at a predetermined interval, as a variable; c) a term having the square of the spindle rotation speed as a variable; and d. a term having the cube of the spindle rotation speed as a variable. ### Claim 12 (depends on 11) The apparatus according to claim 11, wherein the arithmetic expression for estimating the thermal displacement amount in the current cycle further includes a term having, as a variable, an amount obtained by multiplying the spindle rotation speed by the precedingly estimated thermal displacement amount. ### Claim 13 (depends on 8) The apparatus according to claim 8, wherein the arithmetic expression for estimating the thermal displacement amount in the current cycle is obtained based on a response surface methodology. ### Claim 14 (depends on 10) The apparatus according to claim 10, wherein the temperature computation expression for estimating the estimated spindle temperature in the current cycle is obtained based on a response surface methodology. ### Claim 15 A method for correcting thermal displacement of a machine tool having a rotation spindle, comprising: detecting a rotation speed of the spindle; estimating a thermal displacement amount of the spindle in a current cycle of execution of a program by using an arithmetic expression that at least includes the following terms a) to d): a) a term having a thermal displacement amount that has been estimated in a preceding cycle of execution of the program as a variable; b) a term having the rotation speed of the spindle, which is detected at a predetermined interval, as a variable; c) a term having the square of the spindle rotation speed as a variable; and d) a term having the cube of the spindle rotation speed as a variable; and using the estimated thermal displacement amount in the current cycle as a correction amount for canceling the thermal displacement of the spindle.