WO2011024840A1 - Procédé de correction de déplacement thermique dans une machine-outil, et dispositif de correction de déplacement thermique - Google Patents

Procédé de correction de déplacement thermique dans une machine-outil, et dispositif de correction de déplacement thermique Download PDF

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Publication number
WO2011024840A1
WO2011024840A1 PCT/JP2010/064346 JP2010064346W WO2011024840A1 WO 2011024840 A1 WO2011024840 A1 WO 2011024840A1 JP 2010064346 W JP2010064346 W JP 2010064346W WO 2011024840 A1 WO2011024840 A1 WO 2011024840A1
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WIPO (PCT)
Prior art keywords
thermal displacement
amount
shaft
correction
ball screw
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PCT/JP2010/064346
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English (en)
Japanese (ja)
Inventor
治夫 小林
初 倉橋
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ブラザー工業株式会社
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Priority to CN201080037053.0A priority Critical patent/CN102481674B/zh
Publication of WO2011024840A1 publication Critical patent/WO2011024840A1/fr

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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/404—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/49—Nc machine tool, till multiple
    • G05B2219/49212—Using lookup table, map, position error, temperature and position

Definitions

  • the present invention relates to a thermal displacement correction method and a thermal displacement correction apparatus for machine tools.
  • Machine tools use a ball screw mechanism as a positioning mechanism.
  • the ball screw mechanism causes a pitch error between the amount of rotation of the ball screw shaft and the amount of movement of the nut due to manufacturing tolerances and the like. Therefore, the machine tool corrects the pitch error based on a preset table of pitch error correction amounts.
  • the ball screw mechanism causes thermal expansion due to temperature rise due to the frictional resistance between the ball screw shaft, the nut, and each bearing, causing thermal displacement.
  • the thermal displacement of the ball screw shaft results in a positioning error.
  • the machine tool uses a system in which pre-tension is applied to the ball screw shaft to absorb thermal expansion.
  • the machine tool uses a thick ball screw shaft and the feed rate is very fast, so the heat generation increases.
  • the machine tool must apply a very large tension to the ball screw shaft.
  • a very large tension is applied to the machine tool, there is a problem that the ball screw mechanism is deformed.
  • an excessive force is applied to the thrust bearing and seizes.
  • the method for correcting the thermal displacement of the ball screw shaft disclosed in Patent Document 1 does not apply excessive tension to the ball screw shaft and does not require a special measuring device.
  • the amount of heat generated by the ball screw shaft is calculated from the product of the armature current and voltage of the servo motor. Based on the heat generation amount of the ball screw shaft and the ratio (heat distribution coefficient) obtained in advance, the heat generation amount of nut movement due to the movement of the nut, the heat generation amount of the front bearing due to the rotation of the front bearing, and the rotation amount of the rear bearing Calculate the rear bearing heat value.
  • the temperature distribution is obtained from the unsteady heat conduction equation based on the calculated calorific value.
  • the method of correcting the thermal displacement of the ball screw shaft while the machine tool is operating predicts the thermal displacement amount of the ball screw shaft from moment to moment, and gives the predicted thermal displacement amount to the numerical controller as a correction amount for correcting the pitch error correction amount.
  • This method has a problem that the correction amount becomes larger than the actual elongation when the number of times of acceleration / deceleration of the servo motor is large.
  • Patent Document 2 focuses on the fact that the acceleration / deceleration energy of the servo motor itself is included in the calorific value as a factor of the problem in Patent Document 1.
  • the thermal displacement correction method disclosed in Patent Document 2 calculates the heat generation amount of the ball screw shaft from the rotation speed of the servo motor, and based on the heat generation amount of the ball screw shaft, the nut movement heat generation amount, the front bearing heat generation amount, and the rear bearing Calculate calorific value.
  • Patent Document 2 does not take into account the amount of heat generated by the servo motor when a drive current flows through the servo motor.
  • the amount of heat generated by the servo motor is applied to the ball screw shaft through the front bearing. Therefore, in order to perform highly accurate thermal displacement correction, not only the nut movement heat generation amount, the front bearing heat generation amount, and the rear bearing heat generation amount are calculated, but also the servo motor heat generation as in the method of Patent Document 1. It is necessary to consider the amount.
  • a fixed bearing 18 is fixed to a support base 10 via a bearing holder 20.
  • the fixed bearing 18 supports an end portion 81 e (end portion on the X-axis motor 71 side) of the X-axis ball screw shaft 81.
  • the movable bearing 19 is movable in the axial direction of the X-axis ball screw shaft 81.
  • the movable bearing 19 supports an end portion 81 f of the X-axis ball screw shaft 81 on the side opposite to the fixed bearing 18.
  • a path for radiating a part of the heat generated by the X-axis motor 71 includes a path for radiating heat to the periphery of the X-axis motor 71, a path for radiating heat from the X-axis motor 71 to the support base 10 via the bearing holder 20, and an X-axis motor.
  • 71 is a path for radiating heat from 71 to the surroundings via the bearing holder 20.
  • the amount of heat radiation is determined by a temperature difference between two objects, such as a temperature difference between the motor temperature and the ambient temperature.
  • the method of Patent Document 1 does not take into consideration that a part of the heat generated by the servo motor radiates heat.
  • the temperature of the X-axis motor 71 rises.
  • the increased temperature enters the bearing holder 20, and the temperature of the bearing holder 20 increases.
  • the temperature of the bearing holder 20 enters the motor side end 81e of the ball screw shaft 81, and the temperature of the motor side end 81e rises.
  • the temperature rise of the motor side end portion 81e is after a predetermined time has elapsed since the X-axis motor 71 was driven.
  • the front bearing heat generation amount is calculated based on the heat generation amount supplied from the X-axis motor 71 to the ball screw shaft 81 and the heat distribution coefficient, but the predetermined time is not taken into consideration.
  • the heat distribution coefficient is a constant value. Therefore, the method of Patent Document 1 cannot accurately calculate the temperature change of the motor side end portion 81e and cannot accurately correct the thermal displacement.
  • An object of the present invention is to provide a thermal displacement correction method and a thermal displacement correction apparatus for a machine tool capable of performing highly accurate thermal displacement correction.
  • the machine tool thermal displacement correction method is a ball screw mechanism for feed driving, a servo motor that rotationally drives a shaft into which a nut of the ball screw mechanism is screwed, and a control device that controls the servo motor based on control data And calculating a heat generation amount generated in a plurality of sections obtained by dividing the overall length of the shaft into a plurality of sections at predetermined intervals based on the rotation speed of the servo motor and control data.
  • the unsteady heat conduction equation uses an increase in the temperature of the bearing holder that is increased by the amount of heat input from the servo motor. Therefore, the amount of heat displacement can be calculated using the amount of heat generated in consideration of the amount of heat released from the amount of heat generated by the servo motor.
  • the temperature rise of the bearing holder is calculated every predetermined time. Therefore, it is possible to calculate the amount of thermal displacement taking into account the time delay from when the current flows to the servo motor until the end of the shaft on the motor side is thermally affected by the servo motor. Since the thermal displacement correction method of the machine tool can calculate the thermal displacement amount considering the heat radiation of the servo motor and the time delay, the thermal displacement correction can be performed with high accuracy.
  • the temperature rise of the bearing holder is calculated based on a rotation speed and a drive current value of the servo motor.
  • the thermal displacement correction method for a machine tool according to claim 2 calculates the temperature rise of the bearing holder based on the rotation speed of the servo motor and the drive current value. Therefore, highly accurate thermal displacement correction can be performed using an existing sensor without newly providing a sensor or the like.
  • a thermal displacement correction device for a machine tool is a ball screw mechanism for driving driving, a servo motor that rotationally drives a shaft into which a nut of the ball screw mechanism is screwed, and a control device that controls the servo motor based on control data
  • a thermal displacement correction device for a machine tool having a speed detection device for detecting the rotational speed of the servo motor, and the amount of heat generated in a plurality of sections obtained by dividing the overall length of the shaft, the rotational speed of the servo motor
  • a calorific value calculation unit to obtain every predetermined time based on the control data, a temperature calculation unit to detect a temperature rise of the bearing holder that rotatably supports the motor side of the shaft via a bearing, at each predetermined time; Instead of the total calorific value of the calorific value of the plurality of sections accumulated for a predetermined period and the temperature rise at the motor side end of the shaft, the bearing ho A temperature distribution calculation unit that calculates a temperature distribution of a pluralit
  • a correction amount for correcting the control data for each of a plurality of correction sections obtained by dividing a plurality of nut movement ranges of the shaft based on the thermal displacement amount calculation section for each predetermined period and the plurality of sections.
  • a correction amount calculation unit that calculates the value for each predetermined period.
  • the thermal displacement correction device for a machine tool includes a temperature calculation unit for calculating a temperature rise of the bearing holder every predetermined time, a total heat generation amount obtained by accumulating a heat generation amount of a plurality of sections for a predetermined period, and a motor side of the shaft
  • a temperature distribution calculation unit that calculates the temperature distribution of a plurality of sections for each predetermined period based on the unsteady heat conduction equation using the temperature increase of the bearing holder instead of the temperature increase of the end portion. 1 has the same effect.
  • the temperature calculation unit calculates a temperature rise of the bearing holder based on a rotation speed and a drive current value of the servo motor.
  • the temperature calculation unit calculates the temperature rise of the bearing holder based on the rotation speed of the servo motor and the drive current value. Therefore, the manufacturing cost can be reduced by using an existing sensor without newly providing a sensor or the like.
  • FIG. 1 is an overall perspective view of a machine tool M.
  • FIG. The side view of the machine tool M.
  • the graph which shows the relationship between time t and the temperature rise (theta) 0 (t) of a bearing holder.
  • the configuration of the machine tool M will be described with reference to FIGS.
  • the lower right of FIG. 1 is the front of the machine tool M.
  • the workpiece (not shown) and the tool 6 are independently moved relative to each other in the XYZ rectangular coordinate system to perform desired machining (for example, “milling”, “drilling”, “ Cutting "etc.).
  • the X-axis direction, Y-axis direction, and Z-axis direction of the machine tool M (machine main body 2) are the left-right direction, front-rear direction, and vertical direction of the machine tool M (machine main body 2), respectively.
  • the machine tool M includes a base 1, a machine body 2, and a cover (not shown) as main constituents.
  • the base 1 is a substantially rectangular parallelepiped casting that is long in the Y-axis direction.
  • the machine body 2 is provided on the upper part of the base 1.
  • the machine body 2 performs a cutting process on the workpiece.
  • the cover is fixed to the upper part of the base 1.
  • the cover has a box shape covering the machine body 2 and the upper part of the base 1.
  • the machine body 2 includes a column 4, a spindle head 5, a spindle 5A, a tool changer 7, and a table 8 as main constituents.
  • the column 4 has a substantially prismatic shape and is fixed to a column seat portion 3 provided at the rear portion of the base 1.
  • the spindle head 5 can be moved up and down along the column 4.
  • the spindle head 5 rotatably supports the spindle 5A.
  • the tool changer 7 is provided on the right side of the spindle head 5.
  • the tool changer 7 exchanges the tool 6 at the tip of the spindle 5A and the tool stored in the tool magazine 14.
  • the table 8 is provided on the upper part of the base 1.
  • the table 8 fixes the work so as to be detachable.
  • the control box 9 is box-shaped.
  • the control box 9 is provided on the back side of the column 4.
  • the numerical control device 50 (see FIG. 4) is provided inside the control box 9.
  • the numerical controller 50 controls the operation of the machine tool M.
  • An X-axis motor 71 that is a servomotor drives the table 8 to move in the X-axis direction.
  • the X-axis motor 71 is provided on the rectangular parallelepiped support base 10.
  • a Y-axis motor 72 which is a servo motor, drives the table 8 to move in the Y-axis direction.
  • the Y-axis motor 72 is provided on the base 1.
  • the support base 10 is provided below the table 8.
  • the support base 10 includes a pair of X-axis feed guides (not shown) extending along the X-axis direction on the upper surface thereof.
  • the pair of X-axis feed guides support the table 8 movably on the upper part thereof.
  • the nut portion 8 a is arranged on the lower surface of the table 8.
  • the nut portion 8a is screwed with the X-axis ball screw shaft 81 to constitute an X-axis ball screw mechanism.
  • the X-axis ball screw shaft 81 is connected to the X-axis motor 71 via the coupling 17.
  • the fixed bearing 18 is fixed to the support base 10.
  • the fixed bearing 18 supports a fixed-side end portion 81e of the X-axis ball screw shaft 81 on the X-axis motor 71 side (fixed side).
  • the movable bearing 19 supports the movable side end 81f.
  • the movable end 81f is on the opposite side (movable side) of the fixed end 81e.
  • the movable bearing 19 is movable along the axial direction of the X-axis ball screw shaft 81.
  • a pair of Y-axis feed guides (not shown) are provided on the upper side of the base 1 and extend along the Y-axis direction.
  • the pair of Y-axis feed guides support the support 10 so as to be movable.
  • the table 8 moves in the X-axis direction along the pair of X-axis feed guides when the X-axis motor 71 is driven.
  • the support base 10 is moved in the Y-axis direction along the pair of Y-axis feed guides when the Y-axis motor 72 is driven.
  • the Y-axis moving mechanism is a ball screw mechanism, similar to the X-axis moving mechanism.
  • Covers 11 and 12 cover the X-axis feed guide on the left and right sides of the table 8.
  • the covers 11 and 12 can be expanded and contracted.
  • the cover 13 and the Y-axis rear cover (not shown) cover the Y-axis feed guide on both the front and rear sides of the support base 10, respectively. Even when the table 8 moves in either the X-axis direction or the Y-axis direction, the covers 11, 12, 13 and the Y-axis rear cover always cover the X-axis feed guide and the Y-axis feed guide.
  • the covers 11, 12, 13 and the Y-axis rear cover prevent chips and coolant liquid scattered from the processing area from falling on the rails of the respective feed guides.
  • the lifting mechanism of the spindle head 5 will be described with reference to FIGS.
  • the column 4 supports a Z-axis ball screw shaft (not shown) extending in the vertical direction.
  • the nut portion (not shown) is screwed with the Z-axis ball screw shaft.
  • the nut portion supports the spindle head 5.
  • a Z-axis motor 73 (see FIG. 4) rotates the Z-axis ball screw shaft in forward and reverse directions. Based on the forward / reverse rotation drive of the Z-axis ball screw shaft, the spindle head 5 is driven up and down in the Z-axis direction.
  • the axis controller 63a drives the Z-axis motor 73 based on a control signal from the CPU 51 (see FIG. 4) of the numerical controller 50. Therefore, the spindle head 5 is driven up and down by driving the Z-axis motor 73.
  • the tool changer 7 includes a tool magazine 14 and a tool change arm 15.
  • the tool magazine 14 stores a plurality of tool holders (not shown) that support the tool 6.
  • the tool exchange arm 15 grasps a tool holder attached to the main shaft 5A and another tool holder, and conveys and exchanges them.
  • the tool magazine 14 includes a plurality of tool pots (not shown) and a transport mechanism (not shown) inside.
  • the tool pot supports the tool holder.
  • the transport mechanism transports the tool pot in the tool magazine 14.
  • the numerical controller 50 includes a microcomputer.
  • the numerical controller 50 includes an input / output interface 54, a CPU 51, a ROM 52, a flash memory 53, axis control units 61a to 64a and 75a, servo amplifiers 61 to 64, differentiators 71b to 74b, and the like.
  • the axis controllers 61a to 64a are connected to the servo amplifiers 61 to 64, respectively.
  • the servo amplifiers 61 to 64 are connected to an X-axis motor 71, a Y-axis motor 72, a Z-axis motor 73, and a main shaft motor 74, respectively.
  • the shaft control unit 75 a is connected to the magazine motor 75.
  • the X-axis motor 71 and the Y-axis motor 72 are motors for moving the table 8 in the X-axis direction and the Y-axis direction, respectively.
  • the Z-axis motor 73 is a motor for driving the spindle head 5 up and down in the Z-axis direction.
  • the magazine motor 75 is a motor for rotating the tool magazine 14.
  • the main shaft motor 74 is a motor for rotating the main shaft 5A.
  • the X-axis motor 71, Y-axis motor 72, Z-axis motor 73, and main shaft motor 74 are provided with encoders 71a to 74a, respectively.
  • the axis controllers 61a to 64a receive the movement command amount from the CPU 51 and output a current command (motor torque command value) to the servo amplifiers 61 to 64.
  • the servo amplifiers 61 to 64 receive a current command and output a drive current to the motors 71 to 74.
  • the axis controllers 61a to 64a receive position feedback signals from the encoders 71a to 74a and perform position feedback control. Differentiators 71b to 74b differentiate the position feedback signals output from the encoders 71a to 74a and convert them into speed feedback signals. Differentiators 71b to 74b output speed feedback signals to the axis controllers 61a to 64a.
  • the axis controllers 61a to 64a receive the speed feedback signal from the differentiators 71b to 74b and control the speed feedback.
  • the current detectors 61b to 64b detect drive currents output from the servo amplifiers 61 to 64 to the motors 71 to 74.
  • the current detectors 61b to 64b feed back the detected drive current to the axis controllers 61a to 64a.
  • the shaft controllers 61a to 64a perform current (torque) control based on the drive current fed back by the current detectors 61b to 64b.
  • the shaft control unit 75 a receives the movement command amount from the CPU 51 and drives the magazine motor 75.
  • the ROM 52 is a main control program for executing a machining program for the machine tool M, a control program for thermal displacement correction control (see FIG. 12), and a control program for correction amount calculation processing for calculating the correction amount of the pitch error correction amount (FIG. 13). Etc.) are stored.
  • the flash memory 53 stores parameters relating to the mechanical structure, parameters relating to physical properties, heat distribution coefficients (ratio) ⁇ N , ⁇ F and ⁇ B , a table of pitch error correction amounts, and the like.
  • the parameter relating to the mechanical structure is, for example, the length and diameter of the ball screw shaft 81. Parameters relating to physical properties are, for example, density and specific heat.
  • the flash memory 53 includes a data area for updating and storing the heat generation amount, the total heat generation amount, the rotation speed and driving current of the motor 71, and the distributed heat generation amount shown in FIG.
  • the flash memory 53 also appropriately stores a plurality of machining programs for machining various workpieces.
  • the pitch error correction amount table is a table for correcting pitch errors of the ball screw mechanisms of the X axis, the Y axis, and the Z axis.
  • the pitch error of the ball screw mechanism is caused by manufacturing tolerances.
  • the pitch error between the rotation amount of the ball screw shaft 81 and the movement amount of the nut portion 8a is corrected based on a preset pitch error correction amount table.
  • the thermal displacement correction method of this embodiment is performed by correcting the pitch error correction amount using the calculated thermal displacement when correcting the thermal displacement.
  • This embodiment is an example in which the thermal displacement of the X-axis ball screw shaft 81 is corrected, but basically the same applies to the Y-axis ball screw mechanism and the Z-axis ball screw mechanism.
  • the nut portion 8 a is movable in the nut portion moving range 81 b of the X-axis ball screw shaft 81.
  • Pitch error correction is performed for each correction section.
  • the correction sections are 15 sections obtained by dividing the nut portion movement range 81b by a set length of 20 mm, for example.
  • the pitch error correction amount for correcting the pitch error is a value obtained by the following procedure in the adjustment stage before shipment.
  • the nut portion 8a moves from the position X0 to the position X300 for each correction section at intervals of 20 mm in the X-axis direction according to the movement command value. In this embodiment, an error (target value ⁇ actual movement amount) with respect to the movement command value is accurately measured.
  • a table of pitch error correction amounts is created based on the measurement results.
  • the created table is stored in advance in the flash memory 53 and shipped.
  • a table of pitch error correction amounts is similarly created for the Y-axis and Z-axis directions.
  • the amount of thermal displacement is generated along with the numerical control during the operation of the machine tool M. As shown in FIG. 5, in this embodiment, the amount of heat generated in three regions of the front shaft portion 81 a of the ball screw shaft 81, the nut portion moving range 81 b, and the rear shaft portion 81 c of the ball screw shaft 81 is obtained.
  • the section from the end 81e to the end 81f of the ball screw shaft 81 is divided into four.
  • the calculation sections 1 to 3 are divided into 120 mm (six times the set length of the correction section), and the calculation section 4 is divided into 140 mm (seven times the set length of the correction section).
  • the four divisions are merely an example, and the present embodiment is not limited to the four divisions.
  • the calorific value for each calculation section is obtained for each of the plurality of calculation sections at a predetermined time (for example, 50 ms).
  • the flash memory 53 is a predetermined time period (e.g., 6400ms) calorific value of the total generated in the arithmetic section 1-4 Q 1 ⁇ Q 4, the total heat generation of the calorific value Q 1 ⁇ Q 4
  • a data area for storing the quantity Q T , the rotational speed ⁇ of the X-axis motor 71 and the drive current i is provided.
  • the calorific value is calculated according to the following equation based on the feed speed of the table 8.
  • the feed speed of the table 8 is determined based on the actual rotational speed of the X-axis motor 71.
  • the actual rotational speed of the X-axis motor 71 is determined based on the detection signal of the encoder 71a.
  • the data area of the flash memory 53 stores the calculated heat generation amount.
  • the calorific value is calculated according to the following equation.
  • Q K 1 ⁇ F T (1)
  • Q is a calorific value.
  • F is the feed speed of the table 8.
  • K 1 and T are predetermined constants.
  • the calorific value due to the movement of the nut portion 8a in each calculation section is calculated 128 times every 50 ms for a predetermined period (for example, 6400 ms).
  • the calorific values calculated during a predetermined period are totaled for each computation interval, and calorific values Q 1 to Q 4 for each computation interval are calculated.
  • the heat generation amounts Q 1 to Q 4 are stored in the flash memory 53 in association with the calculation sections 1 to 4.
  • the total calorific value Q T is calculated and stored in the flash memory 53.
  • the total calorific value Q T is a calorific value obtained by summing the calorific values Q 1 to Q 4 .
  • the data of the rotational speed ⁇ that is, ⁇ 0 , ⁇ 1 ,..., ⁇ 127
  • the data of i that is, i 0 , i 1 ,... i 127
  • the data of i is stored in the flash memory 53 respectively.
  • the distribution method of the total calorific value Q T shown below is based on the same method as that of Japanese Patent Publication No. 1992-240045. That is, the nut portion moving range 81b, the front shaft portion 81a, and the rear shaft portion 81c of the ball screw shaft 81 are regarded as being thermally independent from each other without causing heat conduction to other portions. The ratio of each heat generating portion to the total heat generation amount Q T is substantially constant regardless of the change in the feed rate.
  • the CPU 51 calculates the distributed heat generation amount of each heat generating part according to the following equation.
  • Q F ⁇ F ⁇ Q T
  • Q N ⁇ N ⁇ Q T
  • Q B ⁇ B ⁇ Q T
  • the calorific value Q F is the calorific value of the front shaft portion 81 a due to the rotation of the fixed bearing 18.
  • the heat generation amount Q N is the heat generation amount of the nut portion moving range 81b.
  • the heat generation amount Q B is the heat generation amount of the rear shaft portion 81 c due to the rotation of the movable bearing 19.
  • Ratio eta F is the ratio of the calorific value Q F with respect to the total heat generation amount Q T.
  • Ratio eta N is the ratio of the calorific value Q N to the total heat generation amount Q T.
  • Ratio eta B is the ratio of the calorific value Q B to the total heat generation amount Q T.
  • the ratios ⁇ F , ⁇ N and ⁇ B are constant as shown in the method. Therefore, the ratios ⁇ F , ⁇ N , and ⁇ B are values obtained in advance by measuring Q F , Q N , and Q B using an actual machine.
  • the heat generation amount Q N of the nut portion movement range 81b is distributed to the bearing holder 20 and four calculation section separation positions (positions corresponding to ⁇ 2 to ⁇ 5 in FIG. 5).
  • distribution ratios X 1 to X 4 are obtained according to the following equations based on the calorific values Q 1 to Q 4 and the total calorific values Q T of the four calculation sections stored in the data area.
  • the distribution ratios X 1 to X 4 are ratios for distributing the calorific value Q N to the calorific values of the four calculation sections.
  • the heat generation amounts Q 1 to Q 4 and the total heat generation amount Q T are stored in the data areas, respectively.
  • the distribution heat generation amounts Q N1 to Q N4 for the four calculation sections 1 to 4 are calculated from the distribution ratios X 1 to X 4 of the four calculation sections and the distribution heat generation amount Q N of the nut portion movement range 81b by the following equation. Is calculated.
  • the temperature distribution is calculated from each distribution heat generation amount.
  • the temperature distribution can be obtained by solving the following unsteady heat conduction equation.
  • [C] is a heat capacity matrix
  • [H] is a heat conduction matrix
  • ⁇ is a temperature distribution
  • ⁇ Q ⁇ is a calorific value
  • t is time.
  • the temperature distribution multiplied by the heat conduction matrix is called a temperature rise matrix.
  • the temperature distribution ⁇ and the calorific value ⁇ Q ⁇ can be expressed by the following equations, respectively.
  • the conventional method using the unsteady heat conduction equation of Equation (3) uses a calorific value Q F calculated based on a calorific value supplied from the X-axis motor 71 to the ball screw shaft 81 and a heat distribution coefficient. .
  • the heat distribution coefficient is a constant value. Therefore, the conventional method cannot accurately estimate the temperature change of the ball screw shaft end portion 81e.
  • the conventional method does not consider the time delay from when the current flows to the X-axis motor 71 until the temperature of the ball screw shaft end portion 81e rises.
  • the conventional method does not take into consideration that part of the heat generated by the X-axis motor 71 radiates heat.
  • a point that a part of the heat generation amount of the X-axis motor 71 dissipates heat and the time delay are considered.
  • the temperature rise ⁇ 0 of the bearing holder 20 is used instead of the temperature rise ⁇ 1 of the ball screw shaft end portion 81e in the temperature rise matrix of the expression (3).
  • a time variable is added as will be described later.
  • the unsteady heat conduction equation is as follows.
  • Equation (4) can be transformed and expressed as the following equation (5).
  • Equation (5) is obtained by using a time variable with respect to the temperature of the bearing holder 20, the ball screw shaft end portion 81e, and four calculation section separation positions (positions corresponding to ⁇ 2 to ⁇ 5 in FIG. 5). It can be expressed as (6). In this embodiment, a known value is substituted for the right side of the equation (6). In the present embodiment, it is possible to calculate the gradient of the temperature rise at the ball screw shaft end portion 81e and the four calculation section break positions at the time n ⁇ t on the left side.
  • the temperature rise ⁇ 0 (t) of the bearing holder 20 is calculated.
  • the temperature rise ⁇ 0 (t) of the bearing holder 20 is calculated based on the drive current of the X-axis motor 71 and the rotational speed of the X-axis motor 71.
  • the current detector 61b detects the drive current of the X-axis motor 71.
  • the rotational speed of the X-axis motor 71 is based on the detection signal of the encoder 71a.
  • ⁇ i ( ⁇ t) ⁇ i (0) + d ⁇ i (0) / dt ⁇ ⁇ t (7)
  • i 1 to 5
  • the temperature distribution ⁇ with the passage of time can be calculated at the ball screw shaft end portion 81e and the four calculation section break positions.
  • the temperatures ⁇ 1 to ⁇ 5 of the ball screw shaft end portion 81e and the four calculation section break positions are calculated.
  • the thermal displacement amounts of the ball screw shaft end portion 81e and the four calculation section break positions are calculated.
  • the thermal displacement amount between the ball screw shaft end portion 81e and the four calculation section break positions is calculated from the following equation (8).
  • ⁇ L ⁇ L 0 ⁇ ⁇ ⁇ (L) dL ⁇ (8) ⁇ L is the amount of thermal displacement. ⁇ is the coefficient of linear expansion of the ball screw shaft material.
  • the integration symbol indicates integration over a range of 0 to L. L indicates the length up to the four calculation section break positions. Specifically, the integration over a range of 0 to 120, 0 to 240, 0 to 360,.
  • FIG. 11 is an explanatory diagram for calculating a correction amount for correcting the pitch error correction amount.
  • the vertical axis represents the amount of thermal displacement based on the position of the fixed bearing 18.
  • the upper horizontal axis is the position of each part of the ball screw shaft 81 with respect to the fixed bearing 18.
  • the horizontal axis on the lower side is a delimiter position (X0, X20..., X300) of 15 correction sections.
  • D F1 is a thermal displacement amount in the calculation section 1.
  • D F2 is the total amount of thermal displacement in the calculation section 1 and the calculation section 2.
  • D F4 is the total amount of thermal displacement in the calculation section 1 to the calculation section 4.
  • correction amount of X0 thermal displacement amount of calculation section 1 ⁇ ⁇ (length between left delimiter position of calculation section 1 and X0) / length of calculation section 1 ⁇
  • Correction amount of X20 thermal displacement amount of calculation section 1 ⁇ ⁇ (length between the left delimiter position of calculation section 1 and X20) / length of calculation section 1 ⁇ ⁇ correction amount of X0
  • correction amount of X40 calculation section 1 Heat displacement amount + heat displacement amount in computation interval 2 ⁇ ⁇ (length between left separation position of computation interval 2 and X40) / length of computation interval 2 ⁇ ⁇ correction amount of X20
  • correction amount calculation interval 1 Thermal displacement amount + thermal displacement amount in computation interval 2 ⁇ ⁇ (length between left delimiter position of computation interval 2 and X60) / length of computation interval 2 ⁇ ⁇ correction amount of X20
  • the numerical control device 50 functions as a thermal displacement correction device of the present invention.
  • the thermal displacement correction control executes the above-described thermal displacement correction method. Therefore, since this control has many parts which overlap with the above-mentioned content, it demonstrates easily. Numerical control of machining on the workpiece is executed in parallel with thermal displacement correction control.
  • the CPU 51 of the numerical controller 50 first performs initial setting in S1 (S1).
  • S1 initial setting
  • a matrix and an initial temperature necessary for calculation by the finite element method are set from setting data such as parameters.
  • the CPU 51 executes processing such as clearing the related area of the flash memory 53.
  • the CPU 51 divides the ball screw shaft 81 into four calculation sections 1 to 4 (S2).
  • the CPU 51 sets the counter I to 0 (S3).
  • the CPU 51 reads the X-axis feed data, the detection signal of the encoder 71a, and the drive current value of the current detector 61b (S4).
  • the CPU 51 calculates the amount of heat generated every 50 ms in the calculation sections 1 to 4 and the temperature ⁇ 0 of the bearing holder 20 and stores them in the flash memory 53 (S5).
  • the CPU 51 adds “1” to the counter I (S6).
  • the CPU 51 determines whether or not the counter value of the counter I is “127” (S7). While determining that the counter value of the counter I is not “127” (S7: NO), the CPU 51 returns to S4 and repeats the processes of S4 to S6.
  • the CPU 51 determines that the counter value of the counter I is “127” (S7: YES)
  • the CPU 51 calculates the heat generation amounts Q 1 to Q 4 and the total heat generation amount Q T for 6400 ms in the calculation sections 1 to 4.
  • the data is stored in the flash memory 53 (S8).
  • the CPU 51 calculates the calorific values Q N and Q B of each part described above, stores them in the flash memory 53, and computes the calorific values Q N1 to Q N4 distributed to the calculation sections 1 to 4 distributed to the calorific values Q N. And stored in the flash memory 53.
  • the CPU 51 also calculates the distribution heat generation amount shown in FIG. 7 for the bearing holder 20 and the four calculation section break positions and stores them in the flash memory 53 (S9).
  • the CPU 51 calculates the temperatures ⁇ 1 to ⁇ 5 of the ball screw shaft end portion 81e and the four calculation section break positions based on the distributed heat generation amount shown in FIG. 7, and stores them in the flash memory 53 (S10).
  • the CPU 51 calculates the thermal displacement amount at the calculation section break position for the four calculation sections based on the above formula (8) and stores it in the flash memory 53 (S11).
  • the CPU 51 calculates the correction amounts at the 16 correction section break positions as described above based on the correction amount calculation formula described above (S12).
  • the CPU 51 uses the correction amount calculated in S12 to execute correction processing for the preset pitch error correction amount for the 16 correction section break positions, and performs feed amount correction processing using the corrected pitch error correction amount. (S13).
  • the CPU 51 determines whether or not to end the thermal displacement correction process (S14). When it is determined that the thermal displacement correction process is not to be ended (S14: NO), the CPU 51 returns to S3 and repeatedly executes the processes after S3. When it is determined that the thermal displacement correction process is finished (S14: YES), the thermal displacement correction control is finished.
  • the following formula simply represents the correction amount calculation formula described above.
  • D F The total amount of thermal displacement generated in the calculation section on the fixed side with respect to the position Xn.
  • ⁇ D n thermal displacement amount generated in the calculation section including the position Xn.
  • X F Left separation position of the calculation section including the position Xn.
  • L n the length of the calculation section including the position Xn.
  • ⁇ M ⁇ 20 used for obtaining ⁇ M 0 is 0.
  • the CPU 51 adds 20 to n (S22).
  • Encoder 71a corresponds to “speed detection device”.
  • the CPU 51 that executes S3 to S7 corresponds to a “heat generation amount calculation unit” and a “temperature calculation unit”.
  • the CPU 51 that executes S8 to S10 corresponds to a “temperature distribution calculation unit”.
  • the CPU 51 that executes S11 corresponds to a “thermal displacement calculation unit”.
  • the CPU 51 that executes S12 corresponds to a “correction amount calculation unit”.
  • the amount of heat generated in a plurality of sections obtained by dividing the entire length of the ball screw shaft 81 is calculated every 50 ms based on the rotational speed of the X-axis motor 71 and control data.
  • the temperature rise of the bearing holder 20 is calculated every 50 ms.
  • the present embodiment is based on the unsteady heat conduction equation using the total heat generation amount accumulated for 6400 ms and the temperature rise of the ball screw shaft end portion 81e instead of the temperature rise of the bearing holder 20 based on the unsteady heat conduction equation.
  • the temperature distribution is calculated every 6400 ms.
  • the thermal displacement amount of a plurality of sections of the ball screw shaft 81 is calculated every 6400 ms based on the temperature distribution.
  • a correction amount for correcting the control data is calculated every 6400 ms for each of a plurality of correction sections obtained by dividing the nut movement range 81b of the ball screw shaft 81 based on the thermal displacement amounts of the plurality of sections. Therefore, the present embodiment can obtain the following effects.
  • the unsteady heat conduction equation uses the temperature rise of the bearing holder 20 that has risen due to the amount of heat input from the X-axis motor 71. Therefore, in this embodiment, the heat displacement amount can be calculated using the heat generation amount considering the heat radiation amount in the heat generation amount of the X-axis motor 71.
  • the temperature rise of the bearing holder 20 is calculated every predetermined time. Therefore, this embodiment can calculate the amount of thermal displacement taking into account the time delay from when the current flows to the X-axis motor 71 until the ball screw shaft end portion 81 e is thermally affected by the X-axis motor 71.
  • the thermal displacement amount is calculated in consideration of the fact that a part of the heat generation amount of the X-axis motor 71 dissipates heat and the occurrence of the time delay. Therefore, highly accurate thermal displacement correction can be performed.
  • the temperature rise of the bearing holder 20 is calculated based on the rotational speed of the X-axis motor 71 and the drive current value. Therefore, in this embodiment, it is possible to perform highly accurate thermal displacement correction using an existing sensor without newly providing a sensor or the like, and to reduce the manufacturing cost.
  • the above embodiment uses the drive current of the X-axis motor 71 and the rotational speed of the X-axis motor 71 when calculating the temperature rise of the bearing holder 20.
  • the modification example may be calculated using only the drive current of the X-axis motor 71 or only the rotation speed of the X-axis motor 71.
  • a temperature sensor may be attached to the bearing holder 20, and the temperature rise of the bearing holder 20 may be calculated using the detection result of the temperature sensor.
  • the calculation cycle for calculating the calorific value is described as an example, but the calculation cycle is not limited to 50 ms.
  • the predetermined period of 6400 ms is only an example. In the modified example, for example, the predetermined period may be set in units of seconds longer than that of the present embodiment.

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  • Engineering & Computer Science (AREA)
  • Human Computer Interaction (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Automatic Control Of Machine Tools (AREA)
  • Numerical Control (AREA)

Abstract

Un dispositif de commande numérique obtient la chaleur produite dans une pluralité d’intervalles en lesquels est segmentée une tige de vis à bille, ladite obtention étant réalisée toutes les 50 ms sur la base de données de commande et de la vitesse de rotation d’un moteur d’axe X, et calcule l’augmentation de température d’un support de palier toutes les 50 ms. La distribution de température de la pluralité d’intervalles est calculée toutes les 6400 ms sur la base d’une équation de conduction de chaleur instable qui utilise l’augmentation de température du support de palier et la quantité totale de chaleur produite qui correspond à 6400 ms des quantités cumulées de chaleur produite de la pluralité d’intervalles. Les amplitudes de déplacement thermique de la pluralité d’intervalles de la tige de vis à bille sont calculées toutes les 6400 ms sur la base de la distribution de température. Une valeur de compensation value est calculée toutes les 6400 ms pour chaque intervalle de compensation en lequel est segmentée la plage de mouvement nette, ledit calcul étant réalisé sur la base de l’amplitude de déplacement thermique de la pluralité d’intervalles.
PCT/JP2010/064346 2009-08-28 2010-08-25 Procédé de correction de déplacement thermique dans une machine-outil, et dispositif de correction de déplacement thermique WO2011024840A1 (fr)

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JP6747894B2 (ja) 2016-07-08 2020-08-26 ファナック株式会社 ネットワークを利用した診断サービスシステム及び診断方法
JP6612704B2 (ja) * 2016-09-26 2019-11-27 ファナック株式会社 工場監視システム、工場監視方法、及び制御装置
CN107065771B (zh) * 2017-05-05 2019-02-01 大连理工大学 半闭环进给轴的热膨胀误差建模及补偿方法
CN110045681B (zh) * 2019-03-12 2020-10-23 浙江大学 一种基于位置预测的数控机床位置相关型误差的外置补偿方法

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