JP2022161355A - Method and device for deriving motion error in machine tool - Google Patents

Abstract

To provide a motion error derivation method and derivation device capable of measuring a motion error (positioning error, etc.) of a machine tool useful for improving machining accuracy, easily, accurately and appropriately in a short time without waste.SOLUTION: When deriving a positioning error in a machine tool, "machine state check 1" regarding a collision history of the machine tool is performed in S1 under control of a numerical controller 21, and then in S2, the current state of the machine tool is determined by performing "machine state check 2" regarding a temperature of the machine tool. After that, it is determined in S3 whether the state of the machine tool is normal based on check results of "machine state check 1" and "machine state check 2". If it is determined to be normal, "positioning error measurement" is performed in S4, and then in S5, it is determined whether or not the measured positioning error is valid.SELECTED DRAWING: Figure 3

Description

The present invention derives motion errors (geometric errors) such as positioning errors, straightness, squareness, etc., which are used to prevent a decrease in machining accuracy in a machine tool (i.e., measures/calculates and determines whether or not they are appropriate). It relates to a derivation method and a derivation device for determining

In numerically controlled machine tools, motion errors (i.e., positioning errors, straightness, squareness, etc.) are transferred to the shape of the workpiece during machining, and the shape and dimensions of the workpiece to be machined (workpiece) are affected. It is a factor that causes an error in Therefore, at the stage of manufacturing and assembling machine tools, efforts are being made to improve accuracy in order to reduce these errors. However, since it is impossible to avoid a situation in which the motion error becomes large due to thermal deformation due to heat generation of the tool/workpiece during machining, various correction techniques have been developed to correct the thermal deformation.

As such a correction method, Patent Literature 1 discloses that a positioning error that changes with temperature is measured by measuring two circular pockets (with a known center-to-center distance) provided in the invar with a touch probe. Then, a method of correcting the positioning error based on the measurement results has been proposed. In addition, Patent Document 2 describes a 5-axis control machine tool having 3 translational axes and 2 rotation axes, using a position measurement sensor and a target sphere to automatically measure and calculate the geometric error of the 5-axis control machine tool. A method to do so is proposed.

As in Patent Documents 1 and 2 above, when the motion error is automatically measured using a touch probe and a precision master such as Invar or a target ball, the measured motion error may be caused by machine tool troubles or measurement errors. It is necessary to confirm that it is not inappropriate. As a method of confirming the validity (whether or not it is appropriate) of the motion error thus measured, as in Patent Document 3, the geometrical error measured in a 5-axis control machine tool is measured in advance. A method of comparing with a set threshold value and determining that the measured motion error is not valid when the geometrical error exceeds the threshold value and notifying the operator of the situation is known. .

JP 2006-212765 A Japanese Unexamined Patent Application Publication No. 2011-038902 Japanese Unexamined Patent Application Publication No. 2012-107900

However, it is difficult to always and accurately determine the validity (whether or not it is appropriate) of the measured motion error in the method as disclosed in Patent Document 3 above. For example, if the elapsed time from the previous measurement of the motion error to the current measurement is long, the state of the machine tool may have changed significantly due to failures or repairs during that time. Even if motion errors such as degrees and positioning errors exceed thresholds, they may not be considered inappropriate. Also, if the machine tool is partially deformed due to uneven temperature in each part, motion errors such as straightness and positioning errors tend to increase. Even if the measured motion errors exceed thresholds, motion errors above those thresholds may not be considered inappropriate.

An object of the present invention is to solve the problems of the conventional motion error measuring method (effectiveness confirmation method) such as the above-mentioned Patent Document 3, and to shorten the motion error of a machine tool useful for improving machining accuracy without waste. It is an object of the present invention to provide a motion error derivation method and a derivation device capable of easily, accurately and appropriately measuring in time.

In order to achieve the above object, according to the first aspect of the present invention, a table holding a workpiece and a spindle holding a tool are moved relative to each other under control of a numerical control device to move a workpiece on the table. A derivation method for deriving a motion error by measuring the position of an object to be measured placed on the table with a position measurement sensor mounted on the spindle, in a machine tool that performs the machining of a machine state determination step of determining the state of the machine tool from the history of collisions of the machine tool recorded in the machine tool and/or the temperature detected by a temperature sensor provided in each component of the machine tool; and a measurement execution determination step of determining whether or not to measure the position of the object to be measured by the position measurement sensor based on the determination result of the determination step.

The invention according to claim 2 is the invention according to claim 1, wherein the machine condition determination step determines the condition of the machine tool based on an unrepaired collision history in the collision history recorded in the recording means. It is characterized by

The invention according to claim 3 is the invention according to claim 1, wherein the machine condition determination step includes a temperature acquisition step of acquiring the temperature of each component by the temperature sensor, and and a temperature comparison step of obtaining a temperature difference between the constituent elements from the temperatures of the constituent elements and comparing the temperature difference with a preset temperature difference threshold. do.

The invention according to claim 4 is the invention according to claim 1, wherein the machine condition determination step includes a temperature acquisition step of acquiring the temperature of each component using the temperature sensor, and A change speed comparison step of calculating a temperature change speed in each component from the temperature of the component and comparing the temperature change speed with a preset change speed threshold is performed. do.

According to a fifth aspect of the present invention, there is provided a machine tool for machining a workpiece on a table by relatively moving a table holding the workpiece and a spindle holding the tool under control of a numerical control device, A derivation method for deriving a motion error by measuring the position of an object to be measured installed on the table with a position measurement sensor mounted on the spindle, wherein the position measurement sensor mounted on the spindle mounted on the table an error measuring step of measuring and calculating a motion error of the machine tool by measuring an accuracy master; a motion error measured and calculated in the error measuring step; a date and time when the error measuring step was performed; a recording step of recording the temperature of each component detected by a temperature sensor provided in each component in the recording means of the numerical control device; and the collision history of the machine tool recorded in the recording means and/or Alternatively, the motion error is measured from the temperature of each component recorded in the recording step, the motion error recorded in the recording step, and the execution date and time of the error measurement step recorded in the recording step. and an error determination step of determining the validity of the result.

The invention according to claim 6 is the invention according to claim 5, wherein the error determination step is performed by comparing the measurement result of the motion error in the error measurement step with the previous motion error recorded in the recording step. an error comparison step of calculating a difference and comparing the motion error difference with a preset error difference threshold; and an interval comparison step of comparing the time interval between the execution date and time of the error measurement step recorded in the recording step and the current date and time, and a preset time difference threshold. It is characterized by judging the validity of the motion error.

The invention according to claim 7 is the invention according to claim 5, wherein the error determination step includes the difference between the measurement result of the motion error in the error measurement step and the previous motion error recorded in the recording step. is calculated, and an error comparison step of comparing the motion error difference with a preset error difference threshold; a temporal temperature difference comparison step of calculating a difference and comparing the temperature difference with a preset temporal temperature difference threshold; and an interval comparison step of comparing the time difference threshold.

According to an eighth aspect of the invention, there is provided a machine tool for machining a workpiece on a table by relatively moving a table holding the workpiece and a spindle holding the tool under control of a numerical control device, A derivation device for deriving a motion error by measuring the position of an object to be measured placed on the table with a position measurement sensor attached to the spindle, wherein the motion error is recorded in the recording means of the numerical control device. Machine state determination means for determining the state of the machine tool from the history of collisions and/or temperatures detected by temperature sensors provided in each component of the machine tool; and measurement execution determining means for determining whether or not the position of the object to be measured is to be measured by the position measuring sensor.

According to a ninth aspect of the invention, in the eighth aspect of the invention, the machine condition determining means determines the condition of the machine tool based on the unrepaired collision history in the collision history recorded in the recording means. It is characterized by

The invention according to claim 10 is based on the invention according to claim 8, wherein the machine condition determination means comprises temperature acquisition means for acquiring the temperature of each component by the temperature sensor, and the temperature acquired by the temperature acquisition means. and temperature comparison means for obtaining a difference in temperature between the constituent elements from the temperatures of the respective constituent elements, and comparing the difference in temperature with a preset temperature difference threshold. do.

According to an eleventh aspect of the invention, in the eighth aspect of the invention, the machine condition determination means includes temperature acquisition means for acquiring the temperature of each component by means of the temperature sensor, and and a change speed comparing means for calculating a temperature change speed in each component from the temperature of the component and comparing the temperature change speed with a preset change speed threshold. .

According to a twelfth aspect of the invention, there is provided a machine tool for machining a workpiece on a table by relatively moving a table holding the workpiece and a spindle holding the tool under control of a numerical control device, A motion error derivation device for identifying the motion error, comprising error measuring means for measuring and calculating the motion error by measuring an accuracy master placed on the table with a position measurement sensor mounted on the spindle. , the motion error measured and calculated by the error measuring means, the date and time when the motion error was measured and calculated, and the temperature of each component obtained by a temperature sensor provided in each component of the machine tool. the collision history of the machine tool recorded in the recording means and/or the temperature of each component recorded in the recording means; and the motion error recorded in the recording means; The apparatus is characterized by comprising error determination means for determining the accuracy of the measurement result of the motion error from the date and time when the motion error was measured and calculated.

According to a thirteenth aspect of the invention, in the twelfth aspect of the invention, the error determination means compares the measurement result of the motion error by the error measuring means with the previous motion error recorded in the recording means. error comparison means for calculating a difference and comparing the difference in motion error with a preset error difference threshold; history determination means; and interval comparison means for comparing the time interval between the measurement/calculation date and time of the motion error by the error measurement means recorded in the error measurement means and the current date and time with a preset time difference threshold. It is characterized by being

In the invention according to claim 14, in the invention according to claim 12, the error determination means compares the measurement result of the motion error by the error measurement means with the previous motion error recorded in the recording means. error comparing means for calculating a difference and comparing the difference in motion error with a preset error difference threshold; and a temperature comparison means for comparing the temperature difference with a preset temperature difference threshold; measurement and calculation date and time of the motion error by the error measurement means recorded in the recording means and the current date and time; and an interval comparing means for comparing the time interval between and a preset time difference threshold value.

According to the motion error derivation method and derivation device for a machine tool according to the present invention, by determining the state of the machine tool before calculating the motion error by measuring and measuring the object to be measured, it is possible to obtain an appropriate motion error at the present time. can be derived, and the accuracy of the derived motion error can be estimated. As a result, the motion error can be easily calculated accurately and appropriately in a short time by avoiding useless motion error calculation. can be calculated. In addition, according to the motion error derivation method and derivation device for a machine tool according to the present invention, the difference between the motion error measured last time and the motion error measured this time, the time interval between measurements, the history of machine tool collisions, the machine tool Considering the temperature variation of each component of the machine, it is determined whether the measured and calculated motion error is valid (whether or not it includes disturbance), so the motion error can be derived extremely accurately. can do.

1 is a schematic diagram of a machine tool (numerically controlled machine tool); FIG. It is a block diagram showing a control configuration of the machine tool. 4 is a flow chart showing the details of processing when deriving a motion error; FIG. 10 is a flow chart showing processing details when determining a machine state caused by a collision of the machine tool; FIG. 4 is a flow chart showing the processing contents when determining the machine state caused by the temperature of each part of the machine tool. FIG. 4 is a schematic diagram showing how the dimensions of an accuracy master are measured by a touch probe attached to a spindle; 4 is a flow chart showing the details of processing when determining the validity of the measured motion error.

An embodiment of the motion error derivation method and derivation device according to the present invention will be described by taking the case of measuring the positioning error in a numerically controlled machine tool having three translation axes (X-axis, Y-axis, and Z-axis) as an example. will be explained based on In this embodiment, the case where the machine tool to which the present invention is applied is based on a machining center as shown in FIG. Instead, it may be a lathe-based machine tool or the like.

<Composition of the machine tool>
FIG. 1 shows a numerically controlled machine tool (hereinafter simply referred to as machine tool) having three translational axes (X-axis, Y-axis, and Z-axis), and FIG. 2 shows the control mechanism of the machine tool. It is a thing. The machine tool M includes a bed 11 as a base, a spindle 12 capable of holding and rotating a tool, a table 13 holding a workpiece, a column 14 movably holding the spindle 12, and the like. ing. That is, the machine tool M is provided with an inverted U-shaped column 14 near the rear end of a rectangular flat bed 11 so as to be perpendicular to the surface of the bed 11 . A rectangular plate-like table 13 is placed on the bed 11 , and is moved in the Y-axis direction along a pair of rails provided on the surface of the bed 11 by a Y-axis translation servomotor 32 . It is possible to move in parallel. On the other hand, a rectangular plate-shaped support plate 15 is installed on the front surface of the column 14 , and is moved in the X-axis direction along a pair of rails provided on the front surface of the column 14 by an X-axis translation servomotor 31 . It is possible to move in parallel. Further, on the front surface of the support plate 15, a longitudinal rectangular parallelepiped main shaft 12 is installed so as to be translatable in the Z-axis direction by a Z-axis translation servomotor 33. As shown in FIG. Temperature sensors 1 to 5 are provided on the front and side surfaces of the bed 11, spindle 12, table 13, and column 14, respectively.

The machine tool M is controlled by a command from the numerical controller 21 to operate an X-axis translation servomotor 31, a Y-axis translation servomotor 32, a Z-axis translation servomotor 33, and a servomotor for rotating the main shaft 12 (Fig. (not shown) can be driven to machine a workpiece (workpiece) fixed to the table 3 into an arbitrary shape using a tool attached to the spindle 12 . Further, according to commands from the numerical controller 21, the temperature of each part can be acquired from the temperature sensors 1-5. Furthermore, by attaching a touch probe, which is a position measurement sensor, to the spindle 2 instead of a tool, it is possible to measure the coordinates and position of an object to be measured such as a workpiece placed on the table 3.

<Configuration of Numerical Controller>
On the other hand, a numerical control device 21 for controlling the machine tool M includes a recording means (storage means) 22 composed of RAM, ROM, etc., a detection means 23, a display means 24 such as a monitor, a timer 27, etc., and an interface (not shown). , an input means 25 such as a numeric keypad, a receiver 26, and temperature sensors 1 to 5 are connected. In addition, the numerical control device 21 uses an X-axis translation servomotor 31 to translate the support plate 15 (and the main shaft 2) in the X-axis direction, and a Y-axis translation servomotor 31 to translate the table 13 in the Y-axis direction, via an interface (not shown). Axis translation servomotor 32 and Z-axis translation servomotor 33 for translating the main shaft 12 in the Z-axis direction are connected.

The numerical controller 21 configured as described above can detect a situation such as when the main shaft 12 and the table 13 collide with each other by means of the detection means 23 . When the main shaft 12 and the table 13 collide with each other, the translational movement of each axis is stopped, and the fact of the collision and the date and time of the collision ("machine collision history") are recorded by recording means. 22 is recorded (stored). Furthermore, when repair is performed after the occurrence of an accident as described above, the effect of the repair ("machine repair history") can be recorded in the recording means 22 by the input means 25. there is The recording means 22 also records the temperature of the bed 11, the spindle 12, the table 13 and the column 14 detected by the temperature sensors 1 to 5, the motion error of the machine tool M measured and calculated by a method described later, and the measured (Calculation) Date and time can be recorded. In addition, the numerical control device 21 uses the input means 25 to set a "temperature difference threshold", a "change speed threshold", an "error difference threshold", and " Numerical values such as "time difference threshold" can be input (set) in advance by the input means 25, and the numerical values can be recorded in the recording means 22. FIG.

<Derivation method and derivation device for motion error>
Next, the motion error derivation method and derivation device according to the present invention will be described with reference to the flow chart of FIG. 3, taking the measurement of the positioning error in the machine tool M as an example.

In the "positioning error derivation process" of FIG. 3, first, in steps (hereinafter simply denoted by S) 1 and 2, a "machine state determination step" is executed to determine the state of the machine tool M. FIG. That is, first, in S1, "machine condition check 1" is performed regarding the collision history of the machine tool M, and if measurement is performed at the present time, inappropriate measurement results (measurement results including large errors due to disturbances, etc.) ). After that, in step 2, "Machine condition check 2" is performed regarding the temperature of the machine tool M, and, in the same manner as in "Machine condition check 1", if the measurement is performed at the present time, it is determined whether or not an inappropriate measurement result will be obtained. to check. Details of checks in "machine condition check 1" and "machine condition check 2" will be described later.

Then, as described above, after the "machine condition determination step" is executed in S1 and S2, the "measurement execution determination step" is executed in S3 to measure the position, coordinates, etc. of the object to be measured by the position measurement sensor. Determine whether or not That is, in S3, the check results of "machine condition check 1" and "machine condition check 2" are both "appropriate measurement results can be obtained if measurement is performed at this time (that is, machine tool M state is normal)”. If "YES" is determined in S3, "measurement of positioning error" is executed in S4. "Positioning error check" ("error determination step") is executed to determine whether the The details of "measurement of positioning error" and "checking of positioning error" will also be described later.

[Details of machine condition check 1]
The "machine state check 1" relating to the collision of the machine tool M performed in S1 will be described below with reference to the flowchart shown in FIG.

In the "machine state check 1", first, in S11, the collision/repair history of the machine tool M recorded in the recording means 22 of the numerical controller 21 ("machine collision history" and "machine repair history", hereinafter , simply referred to as "machine collision/repair history"). In the machine tool M, every time the "positioning error derivation process" of FIG. The "machine collision/repair history" at the time of measurement (during execution) is updated.

As described above, after acquiring the "machine collision/repair history" in S11, it is determined in S12 whether or not there has been a collision (such as contact between the spindle 12 and the table 13) in the machine tool M in the past and the repair has not been completed. determine whether If there was no collision, or if there was a collision but repairs have already been made, it is determined that there is no problem with the state of the machine tool M ("NO" in S12), and the check process is completed. do. On the other hand, if there has been a collision in the past and it remains unrepaired, it is determined that there is a problem with the state of the machine tool M (that is, no effective motion error can be obtained even if it is measured at this time), and in S13. , the display means 24 displays a message A (not repaired after collision, etc.) to notify the operator.

[Contents of machine condition check 2]
Next, the "machine state check 2" regarding the temperature of the machine tool M performed in S2 will be described based on the flowchart shown in FIG.

In the "machine condition check 2", first, in S21, under the control of the numerical controller 21, temperature data T1 0 before operation (initial) temperature data T1 ₀ , Obtain T2 ₀ , T3 ₀ , T4 ₀ , and T5 ₀ (“Temperature Acquisition Step”). In the machine tool M, each temperature sensor 1 to 5 samples the temperature (temporal change) of each part under the control of the numerical controller 21 and records it in the recording means 22, and the data is updated every predetermined time. It is designed to be After the temperature sensors 1 to 5 have obtained the temperature data T1 ₀ , T2 ₀ , T3 ₀ , T4 ₀ , and T5 ₀ as described above, the difference between the maximum value and the minimum value of the obtained temperature data is dT ₀ is calculated, and in subsequent S23, the difference dT ₀ is compared with a threshold A (temperature difference threshold) previously recorded (set) in the recording means 22 ("temperature comparison step").

Then, if the difference _dT0 is smaller than the threshold value A, the temperature change rate is calculated in the following S24. That is, under the control of the numerical controller 21, the temperatures T1 _b , T2 _b , T3 _b , T4 _b , and T5 _b of the respective parts recorded in the recording means 22 for T seconds before the current time are acquired, and the following equations 1 to 5, temperature change rates RT1, RT2, RT3, RT4, and RT5 are calculated (absolute values). Note that the time T is a parameter for calculating the temperature change rate recorded in the recording means 22 in advance.

RT1=(T1 ₀ −T1 _b )/T Equation 1
RT2=(T2 ₀ −T2 _b )/T Equation 2
RT3=(T3 ₀ −T3 _b )/T Equation 3
RT4=(T4 ₀ −T4 _b )/T Equation 4
RT5=(T5 ₀ −T5 _b )/T Equation 5

After calculating the temperature change rates RT1, RT2, RT3, RT4, and RT5 as described above, the temperature change rates RT1, RT2, RT3, RT4, and RT5 are recorded (set in advance) in the recording means 22 in subsequent S25. ) is compared with a preset threshold value RT (change speed threshold value) (“change speed comparison step”). If all of the temperature change rates RT1, RT2, RT3, RT4, and RT5 are smaller than the threshold value RT, it is determined that there is no problem with the state of the machine tool M, and the check process is completed. On the other hand, if it is determined in S23 that the difference _dT0 is equal to or greater than the threshold value A, and if it is determined in S25 that any one of RT1, RT2, RT3, RT4, and RT5 is equal to or greater than the threshold value RT, It is determined that there is a problem with the state of the machine M, and in S26, a message A (such as a large temperature change) is displayed on the display means 24 to notify the operator.

[Details of positioning error measurement]
Next, the "positioning error measurement" performed in S4 will be described by taking the case of measuring the positioning error in the X-axis direction in the machine tool M as an example.

When measuring the positioning error in the X-axis direction, as shown in FIG. 6, a touch probe 41 is attached to the spindle 12, and an accuracy master 42 is placed on the table 13 so as to be parallel to the X-direction. . The touch probe 41 has a target ball (stylus) at the lower end thereof provided with a sensor (not shown) for detecting contact with the object to be measured. 21, signals such as infrared rays and radio waves can be transmitted. On the other hand, when the receiver 26 receives the detection signal from the sensor of the touch probe 41, the numerical controller 21 changes the position (coordinates) of each axis (X-axis, Y-axis, Z-axis) at that time to the contact position. As a result, the position (coordinates) of a predetermined portion of the object to be measured (accuracy master 42) can be measured. The accuracy master 42 is a gauge used as a dimensional reference, and the calibrated value of the distance ML between both end surfaces is known.

In S4 "measurement of positioning error", based on the control from the numerical controller 21, the touch probe 41 detects the X- (minus) side end face position (X _- , Y _- , Z _- ) of the precision master 42. and X+ (plus) side end face positions (X ₊ , Y ₊ , Z ₊ ) are measured, and the distance between both end faces ML′=(X ₊ )−(X ₋ ) is calculated. Then, a positioning error dX in the X direction is calculated as the difference between the calculated ML′ and the calibration value ML (“error measurement step”). In the machine tool M, every time the "positioning error measurement" of S4 is executed under the control of the numerical controller 21, the numerical value of the positioning error and the measurement (calculation) date and time are stored in the recording means 22. It is to be recorded (cumulatively recorded) ("recording step").

[Details of positioning error check]
Next, the "positioning error check" performed in S5 will be described based on the flowchart shown in FIG.

In the "checking of positioning error", first, in S31, the difference ddX between the positioning error dXn measured in S3 and the previously measured positioning error dXc recorded in the recording means 22 is calculated. In the machine tool M, the measured positioning error dXc is recorded in the recording means 22 every time the "positioning error derivation process" in FIG. The positioning error dXc is updated.

As described above, after the difference ddX between the positioning error dXn and the previously measured positioning error dXc is calculated in S31, the difference ddX and the threshold value B ( error difference threshold) ("error comparison step"). If it is determined in S32 that the difference ddX is equal to or greater than the threshold value B, then in S33, the "machine collision/repair history" recorded in the recording means 22 is acquired, and It is determined whether or not there has been a collision or repair of the machine tool M up to (at present) ("repair state determination step").

If it is determined in S33 that the machine tool M has had a collision between the previous measurement and the current measurement, but it has not been repaired yet, the measurement error is caused by the collision and is calculated in S31. In S38, a message B to that effect (i.e., that the difference ddX may contain a measurement error) is displayed on the display means 24 to inform the operator. inform.

On the other hand, if it is determined in S33 that there is no history of collision or that there was a collision but repairs are being made, then in S34, the current date and time and the previous measurement of the positioning error are recorded. The "time interval" of measurement (that is, the time interval from the previous measurement to the current measurement) is calculated from the date and time recorded in means 22 . Thereafter, in subsequent S35, the calculated "time interval" is compared with a threshold value C (time difference threshold value) recorded (set) in advance in the recording means 22 ("interval comparison step"). Then, when it is determined in S35 that the "time interval" is less than the threshold value C, in subsequent S36, the temperature data T1 ₀ , T2 ₀ , T3 ₀ , T4 ₀ , T5 ₀ acquired in S21 and the previous "Temperature difference ΔT" between the temperature data T1 _c , T2 _c , T3 _c , T4 _c , and T5 _c recorded in the recording means 22 at the time of measurement of the positioning error is calculated for each installation portion of the temperature sensors 1 to 5. ("temperature differences ΔT ₁ to ΔT ₅ ").

As described above, after the temperature difference ΔT from the previous measurement of the positioning error to the current measurement is calculated for each installation portion of the temperature sensors 1 to 5 in S36, the calculated "temperature difference ΔT ₁ to ΔT ₅ ” is compared with a threshold value D (temporal temperature difference threshold value) recorded (set) in advance in the recording means 22 (“temporal temperature difference comparison step”). Then, if it is determined in S37 that the "temperature differences ΔT ₁ to ΔT ₅ " of each part are less than the threshold value D, there are factors such as troubles and disturbances of the machine tool M (that is, collision of the machine tool M, measurement failure, etc.). It is determined that the difference ddX calculated in S31 has increased due to a measurement error caused by a factor other than the lengthening of the time interval and the increase in temperature change of each part. , etc.) is displayed on the display means 24 to notify the operator.

On the other hand, if it is determined in S32 that the difference ddX is smaller than the threshold value B, if it is determined in S35 that the "time interval" is equal to or greater than the threshold value C, and in S37, the "temperature differences ΔT ₁ to ΔT ₅ is equal to or greater than the threshold value D, it is determined that there is no measurement error in the positioning error measured and calculated this time, and in subsequent S39, the positioning error, the current date and time, and the temperature of each part are recorded by the recording means 22 is recorded (updated) to complete the process.

In the machine tool M, as described above, the numerical control device 21 functions as a device for deriving the motion error, and the functions of the recording means 22, the detection means 23, the display means 24, and the timer 27 of the numerical control device 21 receive Machine 26, temperature sensors 1 to 5, input means 25, X-, Y-, and Z-axis translational servomotors 31-33, etc., and send/receive signals to obtain collision history of machine tool M and temperature sensor "Machine state determination means" for determining the state of the machine tool M from the temperatures obtained from 1 to 5, and "Measurement execution determination" for determining whether or not to measure the motion error based on the determination result of the "machine state determination means" means", "temperature acquisition means" for acquiring the temperature of each component from temperature sensors 1 to 5, and "temperature "Temperature comparison means" for comparing with "difference threshold"; , "error measuring means" for measuring and calculating the motion error of the machine tool M by measuring the accuracy master installed on the table 13 with the touch probe 41 attached to the spindle 12, the collision history of the machine tool M and each configuration "Error judgment means" for judging the validity of the motion error measurement result from the temperature of the element, the motion error of the machine tool M, and the measurement/calculation date and time of the motion error, the motion error measurement result of the machine tool M and the previous ``Error comparison means'' and ``Error measurement means'' that calculate the difference between the motion error and the motion error and compare the difference with a preset "error difference threshold". 'interval comparing means' for comparing the time interval of and a preset 'time difference threshold', calculating the difference between the temperature of each constituent element in the previous time and the temperature of each constituent element at the present time, and comparing the difference with the preset A "temperature comparison means" for comparing with the set "temperature difference threshold" is configured.

<Effects of positioning error derivation method and derivation device>
According to the positioning error derivation processing/derivation device described above, the currently effective (appropriate) Since it is determined whether or not the motion error can be derived, as a result, useless measurement of the motion error can be avoided, and the motion error can be measured and calculated easily, accurately and appropriately in a short period of time. In addition, according to the motion error derivation method and derivation device of the machine tool M according to the present invention, the difference between the motion error measured last time and the motion error measured this time, the measurement time interval, the collision history of the machine tool M, Since it is determined whether or not the measured/calculated motion error includes a measurement error due to disturbance in consideration of the variation in temperature of each component of the machine tool M, the motion error can be derived very accurately. can.

<Motion error derivation method/example of modification of derivation device>
The motion error derivation method according to the present invention is not limited to the aspects of the above-described embodiments. , can be changed as appropriate without departing from the scope of the present invention. Further, the motion error derivation device according to the present invention is not limited to the aspects of the above-described embodiments, but includes the contents of the machine state determination means, the measurement execution determination means, the error determination means, etc., and the motion error measurement method. etc. can be changed as appropriate without departing from the gist of the present invention.

For example, the motion error derivation method and derivation device according to the present invention are not limited to those for measuring positioning errors as in the above embodiment, but also for measuring straightness and geometrical errors of five-axis control machine tools. etc. can also be applied. Further, the motion error derivation method and derivation device according to the present invention derives the motion error by measuring the accuracy master with a sensor (touch probe, infrared sensor, etc.) as in the above embodiment (i.e., the device to be measured). The object is not limited to the accuracy master), but the one that derives the motion error by measuring multiple positions (coordinates) of the machined workpiece with a sensor (touch probe, infrared sensor, etc.) (i.e., the object to be measured It is also possible to change the object to a workpiece).

11 Bed 12 Spindle 13 Table 14 Column 41 Touch probe 42 Accuracy master 1, 2, 3, 4, 5 Temperature sensor M Machine tool 21 Numerical controller

Claims (14)

In a machine tool that processes a workpiece on the table by relatively moving a table that holds the workpiece and a spindle that holds the tool under the control of a numerical controller, a position measurement sensor mounted on the spindle A derivation method for deriving a motion error by measuring the position of an object to be measured placed on the table,
Machine state for determining the state of the machine tool from the collision history of the machine tool recorded in the recording means of the numerical control device and/or the temperatures detected by temperature sensors provided in each component of the machine tool. a determination step;
and a measurement execution determination step of determining whether or not to measure the position of the object to be measured by the position measurement sensor based on the determination result of the machine state determination step. method of derivation. The machine state determination step includes:
2. A method for deriving a motion error in a machine tool according to claim 1, wherein the state of said machine tool is determined based on an unrepaired collision history in the collision history recorded in said recording means. The machine state determination step includes:
a temperature acquisition step of acquiring the temperature of each of the components by the temperature sensor;
a temperature comparison step of obtaining a temperature difference between the constituent elements from the temperatures of the constituent elements obtained in the temperature obtaining step, and comparing the temperature difference with a preset temperature difference threshold; 2. A method for deriving a motion error in a machine tool according to claim 1, wherein: The machine state determination step includes:
a temperature acquisition step of acquiring the temperature of each component by the temperature sensor;
a change speed comparison step of calculating a temperature change speed in each component from the temperature of each component acquired in the temperature acquisition step, and comparing the temperature change speed with a preset change speed threshold; 2. A method for deriving a motion error in a machine tool according to claim 1, wherein: In a machine tool that processes a workpiece on the table by relatively moving a table that holds the workpiece and a spindle that holds the tool under the control of a numerical controller, a position measurement sensor mounted on the spindle A derivation method for deriving a motion error by measuring the position of an object to be measured placed on the table,
an error measuring step of measuring and calculating a motion error of the machine tool by measuring an accuracy master placed on the table with a position measuring sensor attached to the spindle;
The motion error measured and calculated in the error measuring step, the date and time when the error measuring step was performed, and the temperature of each component detected by a temperature sensor provided in each component of the machine tool are represented by the numerical values. a recording step of recording in the recording means of the control device;
The collision history of the machine tool recorded in the recording means and/or the temperature of each component recorded in the recording step, the motion error recorded in the recording step, and the motion error recorded in the recording step and an error determination step of determining validity of the measurement result of the motion error from the execution date and time of the error measurement step. The error determination step includes
Error comparison for calculating a difference between the measurement result of the motion error in the error measuring step and the previous motion error recorded in the recording step, and comparing the difference in motion error with a preset error difference threshold. a step;
a repair state determination step of determining a state of the machine tool based on an unrepaired collision history in the collision history;
performing an interval comparison step of comparing the time interval between the execution date and time of the error measurement step recorded in the recording step and the current date and time, and a preset time difference threshold value, so as to determine the motion error measured this time; 6. A method for deriving a motion error in a machine tool according to claim 5, characterized in that it determines effectiveness. The error determination step includes
An error comparison step of calculating a difference between the motion error measurement result in the error measuring step and the previous motion error recorded in the recording step, and comparing the motion error difference with a preset error difference threshold. When,
A temporal temperature difference comparison for calculating a difference between the temperature of each component previously recorded in the recording step and the current temperature of each component, and comparing the temperature difference with a preset temporal temperature difference threshold. a step;
6. The machine tool according to claim 5, wherein an interval comparison step of comparing a time interval between the execution date and time of the previous recording step and the current date and time with a preset time difference threshold value is performed. A method for deriving motion errors in machines. In a machine tool that processes a workpiece on the table by relatively moving a table that holds the workpiece and a spindle that holds the tool under the control of a numerical controller, a position measurement sensor mounted on the spindle A derivation device for deriving a motion error by measuring the position of an object to be measured installed on the table,
Machine state for determining the state of the machine tool from the collision history of the machine tool recorded in the recording means of the numerical control device and/or the temperature detected by temperature sensors provided in each component of the machine tool. determination means;
measurement execution determination means for determining whether or not to measure the position of the object to be measured by the position measurement sensor based on the determination result of the machine state determination means. Derivation device. The machine state determination means is
9. A device for deriving a motion error in a machine tool according to claim 8, wherein the state of the machine tool is determined based on an unrepaired collision history in the collision history recorded in the recording means. The machine state determination means is
a temperature acquiring means for acquiring the temperature of each of the constituent elements by the temperature sensor;
temperature comparing means for obtaining a difference in temperature between the constituent elements from the temperatures of the constituent elements acquired by the temperature acquiring means, and comparing the difference in temperature with a preset temperature difference threshold. 9. The device for deriving motion error in a machine tool according to claim 8, wherein: The machine state determination means is
temperature acquisition means for acquiring the temperature of each component by the temperature sensor;
change speed comparison means for calculating a temperature change speed in each component from the temperature of each component acquired by the temperature acquisition means, and comparing the temperature change speed with a preset change speed threshold; 9. The device for deriving motion error in a machine tool according to claim 8, wherein: Movement for identifying the motion error in a machine tool that processes a workpiece on a table by relatively moving a table that holds the workpiece and a spindle that holds the tool under the control of a numerical controller. An error derivation device,
error measuring means for measuring and calculating the motion error by measuring an accuracy master placed on the table with a position measuring sensor attached to the spindle;
Record the motion error measured and calculated by the error measuring means, the date and time when the motion error was measured and calculated, and the temperature of each component obtained by the temperature sensor provided in each component of the machine tool. a recording means for
Measurement and calculation of the collision history of the machine tool recorded in the recording means and/or the temperature of each component recorded in the recording means, the motion error recorded in the recording means, and the motion error and error determination means for determining the accuracy of the measurement result of the motion error based on the date and time of the measurement of the motion error in a machine tool. The error determination means is
Error comparison for calculating a difference between the measurement result of the motion error by the error measuring means and the previous motion error recorded in the recording means, and comparing the difference of the motion error with a preset error difference threshold. means and
Unrepaired collision history determination means for determining the state of the machine tool based on the unrepaired collision history in the collision history;
and interval comparing means for comparing a time interval between the date and time of motion error measurement/calculation by the error measuring means recorded in the error measuring means and the current date and time with a preset time difference threshold value. 13. The device for deriving a motion error in a machine tool according to claim 12. The error determination means is
Error comparison for calculating a difference between the measurement result of the motion error by the error measuring means and the previous motion error recorded in the recording means, and comparing the difference of the motion error with a preset error difference threshold. means and
a temperature comparison means for calculating a difference between the temperature of each component previously recorded in the recording means and the current temperature of each component, and comparing the temperature difference with a preset temperature difference threshold;
and interval comparing means for comparing a time interval between the date and time of motion error measurement/calculation by the error measuring means recorded in the error measuring means and the current date and time with a preset time difference threshold value. 13. The device for deriving a motion error in a machine tool according to claim 12.

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