JP2008246620A - Machine tool, control program for correcting thermal expansion, and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately position a tool of a spindle to a machining datum of a workpiece, and to enhance machining accuracy by correcting the difference of thermal expansion between the workpiece and the drive shaft even when there is significant difference in a coefficient of thermal expansion between the workpiece machined by a machine tool and the drive shaft of a drive system. <P>SOLUTION: Machining programs stored in a program memory are read line by line (S4), it is judged whether the read command is a move command to a Y-axis drive system or not (S5), when it is the move command to the Y-axis drive system (S5: Yes), it is judged whether displacement in the Y-axis direction from a machining reference position occurs or not (S6), when the displacement in the Y-axis direction from the reference position occurs (S6: Yes), a corrected feed amount obtained by correcting the feed amount of the move command with a scale magnification k is calculated (S7), and the drive of a Y-axis motor is controlled. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a machine tool, a thermal expansion correction control program, and a storage medium, and in particular, taking into account the difference between the thermal expansion of a drive shaft of an X, Y, Z axis drive system and the thermal expansion of a non-ferrous metal workpiece such as aluminum. It is related with what was constituted so that the feed amount which feeds and drives a work may be corrected.

  In general, a machine tool includes a program storage unit that stores a plurality of machining programs, reads a machining program from the program storage unit according to the type of machining, and based on position information set in the read machining program, X, The workpiece is processed while being fed and driven via the drive shafts of the Y and Z axis drive systems.

  Since each drive shaft of the X, Y, Z axis drive system is usually made of steel, when machining a non-ferrous metal (for example, aluminum, aluminum alloy, copper, copper alloy, etc.) workpiece, When the thermal expansion coefficients are significantly different, if the processing temperature is different from the standard temperature (usually 20 ° C) for measuring the dimensions of the workpiece after processing, the difference in thermal expansion between the workpiece and each drive shaft Since it becomes large, the processing accuracy of a workpiece | work will fall. In such a case, in order to increase the machining accuracy of the workpiece, it has been proposed to correct the feed amount for feeding and driving the workpiece via the drive shaft.

In the thermal deformation correction method and the thermal deformation correction device for an NC machine tool described in Patent Document 1, the difference between the thermal expansion amount of the workpiece and the drive shaft with respect to normal temperature (20 ° C.) per stroke length of the drive shaft is calculated. This calculation result is equally distributed from the start end to the end of the stroke of the drive shaft, which is a reference point for pitch error correction, and the correction value is increased according to the stroke length of the drive shaft.
JP 2006-116654 A

  By the way, when machining a workpiece, the workpiece is fixed in a state where it abuts against the reference surface of the abutting jig fixed on the table, and the position where the workpiece abuts against the abutting jig is set as the workpiece machining reference, and machining is started. Sometimes the machining is started after the tool attached to the spindle is aligned with the workpiece machining reference.

However, in the apparatus of Patent Document 1, the correction value is set to 0 at the start of the stroke of the drive shaft, and the correction value is increased according to the stroke length of the drive shaft. The amount of movement of the table up to the machining reference when aligning the workpiece with the machining reference is also corrected. Therefore, when the spindle tool is aligned with the workpiece machining reference, the spindle tool is displaced from the workpiece machining reference, so that the workpiece machining accuracy is lowered.
That is, the amount of thermal expansion of each part of the workpiece such as aluminum is proportional to the amount of displacement in the feed direction of each part of the workpiece from the machining reference, and therefore is proportional to the amount of displacement in the feed direction of each part of the workpiece from the machining reference. It is desirable to correct with a correction amount.

  The object of the present invention is to accurately align the spindle tool with the workpiece machining reference at the start of machining even when the workpiece and drive shaft have different thermal expansion coefficients in the machine tool, thermal expansion correction control program and storage medium. It is possible to accurately correct the feed amount during machining by taking into account the thermal expansion difference between the workpiece and the drive shaft.

  The machine tool according to claim 1 is a machine tool that processes a workpiece while controlling the X, Y, and Z axis drive systems based on position information included in the machining program, and detects the ambient temperature around the machine tool. The detection means, the input linear expansion coefficient α of the workpiece, the linear expansion coefficient β of the metal material constituting any of the drive axes of the X, Y, Z axis drive system of the machine tool, and the preset A storage means for storing a standard temperature; a temperature difference ΔT between a detected temperature detected by the temperature detection means and a standard temperature stored in the storage means; and the linear expansion coefficient α, stored in the storage means A displacement amount coefficient calculating means for calculating a displacement amount coefficient using β, and a feed amount for feeding and driving the workpiece via the drive shaft to a position set in a machining program during machining of the workpiece, Set on the machine table Feed amount correcting means for correcting using a correction value obtained by multiplying the current feed direction displacement amount from the workpiece machining reference by the displacement amount coefficient is provided.

  In this machine tool, the displacement coefficient calculating means uses the temperature difference ΔT between the detected temperature detected by the temperature detecting means and a preset standard temperature, and the linear expansion coefficients α, β described in the storage means, A displacement amount coefficient is calculated. For any one of the X, Y, and Z axis drive systems, for feeding and driving the workpiece to the position set in the machining program by the feed amount correction means during machining of the workpiece. The feed amount is corrected using a correction value obtained by multiplying the current feed direction displacement amount from the workpiece machining reference set on the table of the machine tool by a displacement amount coefficient.

  Thus, for any of the X, Y, and Z axis drive systems, the feed amount for feeding and driving the workpiece via the drive shaft is determined from the workpiece machining reference set on the machine tool table. Therefore, when aligning the spindle tool with the workpiece machining reference at the start of machining after fixing the workpiece to the table, the tool is The amount of displacement moved to the machining reference is not corrected. Therefore, when the thermal expansion coefficients of the workpiece and the drive shaft are greatly different, even if the spindle tool is aligned with the workpiece machining reference, the spindle tool does not deviate from the workpiece machining reference.

  The machine tool of claim 2 is obtained by repeating the measurement of the actual feed amount by the measuring means after the feed operation is executed by the drive shaft at the standard temperature a plurality of times. The feed error calculation means for calculating the feed error per unit length from the measured data, the ambient temperature when processing the workpiece, the displacement amount coefficient, and the feed error calculated by the feed error calculation means And a correction coefficient calculating means for calculating a correction coefficient for correcting the displacement amount coefficient.

  According to a third aspect of the present invention, there is provided a thermal expansion correction control program that detects temperature of an ambient atmosphere around a machine tool, drives a linear expansion coefficient α of a workpiece, and an X, Y, or Z axis drive system of a machine tool. It has a storage means for storing the linear expansion coefficient β and standard temperature of the metal material that constitutes the shaft, and is processed into a workpiece while controlling the X, Y, Z axis drive system based on position information included in the processing program The computer of the machine tool that performs the above processing is configured to calculate the temperature difference ΔT between the detected temperature detected by the temperature detecting means and the standard temperature stored in the storage means, and the linear expansion coefficients α and β stored in the storage means. A displacement amount coefficient calculating means for calculating a displacement amount coefficient, and a feed amount for feeding and driving the workpiece via the drive shaft to a position set in a machining program during machining of the workpiece. Set on the table It is made to function as a feed amount correcting means for correcting using a correction value obtained by multiplying the current feed direction displacement amount from the workpiece machining reference by the displacement amount coefficient.

  In this thermal expansion correction control program, the displacement coefficient calculating means calculates the temperature difference ΔT between the detected temperature detected by the temperature detecting means and the standard temperature stored in the storage means, and the linear expansion stored in the storage means. Using the coefficients α and β, the displacement amount coefficient is calculated, and the feed amount for feeding and driving the workpiece via the drive shaft to the position set in the machining program during machining of the workpiece by the feed amount correction means, It functions to be corrected using a correction value obtained by multiplying the current feed direction displacement amount from the machining reference of the workpiece set on the table of the machine tool by a displacement amount coefficient. Thus, the effect similar to that of the first aspect is achieved.

A storage medium according to claim 4 stores the thermal expansion correction control program according to claim 3.
As a storage medium, a ROM, a CD-ROM, a flexible disk, or the like is applicable. By causing the computer to execute the thermal expansion correction control program stored in the storage medium, the temperature difference ΔT between the detected temperature detected by the temperature detection means and the standard temperature stored in the storage means by the displacement amount coefficient calculation means The displacement coefficient is calculated using the linear expansion coefficients α and β stored in the storage means, and the workpiece is moved to the position set in the machining program during machining of the workpiece via the drive shaft by the feed amount correction means. The feed amount for feed driving functions to be corrected using a correction value obtained by multiplying the current feed direction displacement amount from the machining reference of the workpiece set on the table of the machine tool by a displacement amount coefficient. . Thereby, there exists an effect | action substantially the same as Claim 1 or 3.

  According to the first aspect of the present invention, the temperature detection means, the storage means, the displacement amount coefficient calculation means, and the work for feeding and driving the work via the drive shaft to the position set in the machining program during the work of the work. Since there is provided a feed amount correcting means for correcting the feed amount using a correction value obtained by multiplying the current feed direction displacement amount from the workpiece machining reference set on the table of the machine tool by a displacement amount coefficient, When the spindle tool is aligned with the workpiece machining reference via the table movement at the start of machining after the workpiece is fixed to the table, the feed displacement amount up to the workpiece machining reference is not corrected. For example, if each drive shaft of the X, Y, Z axis drive system is made of steel and the workpiece is made of an aluminum alloy, the spindle tool can be used even when the thermal expansion coefficients of the drive shaft and the workpiece are greatly different. Accurate alignment with workpiece machining standards.

  In addition, the displacement coefficient is calculated using the linear expansion coefficient α of the workpiece, the linear expansion coefficient β of the drive shaft, and the temperature difference ΔT between the detected temperature and the standard temperature, and the position set in the machining program is set via the drive shaft. Since the feed amount for feeding and driving the workpiece is corrected using a correction value obtained by multiplying the current feed direction displacement from the workpiece machining reference set on the table of the machine tool by the displacement amount coefficient, The machining accuracy of the workpiece can be improved by correcting the feed amount in consideration of the difference in thermal expansion of the drive shaft.

  According to the invention of claim 2, a unit length is obtained from the measurement data obtained by repeating a plurality of times the measurement means measures the actual feed amount after the feed operation is executed by the drive shaft at the standard temperature. Based on the feed error calculation means that calculates the feed error per strike, the ambient temperature when machining the workpiece, the displacement amount coefficient, and the feed error calculated by the feed error calculation means, the displacement amount coefficient is corrected. Since the correction coefficient calculating means for calculating the correction coefficient is provided, the displacement coefficient can be corrected with high accuracy, and the workpiece machining accuracy when the workpiece and the drive shaft have different thermal expansion coefficients can be further improved. .

  According to the invention of claim 3, the displacement amount calculating means and the feed amount for feeding and driving the workpiece via the drive shaft to the position set in the machining program during machining of the workpiece are displayed on the table of the machine tool. Therefore, the present invention has the same effect as that of the first aspect of the present invention. .

  According to the invention of claim 4, since the thermal expansion correction control program according to claim 3 is stored, the computer is caused to execute the thermal expansion correction control program stored in the storage medium. Has almost the same effect.

  The present invention provides a machine tool, a thermal expansion correction control program, and a storage medium that can accurately cut a workpiece made of aluminum, aluminum alloy, copper, copper alloy, etc., taking into account the thermal expansion of the workpiece. The best mode for carrying out the present invention will be described below with reference to the drawings.

  As shown in FIGS. 1 and 2, the machine tool 1 includes a base 2, a column 3 standing on the base 2 and movable in a direction orthogonal to the paper surface (X direction), and a Y axis from the top of the column 3. Main shaft head 4 extending in the direction (rightward), main shaft 5 mounted on the right end of the main shaft head 4, a table 7 for mounting and fixing the work 10, and the main shaft 5 and the X, Y, Z axis drive system And a temperature sensor 21 (temperature detection means) for detecting the ambient temperature around the machine tool 1.

Inside the base 2 are an X-axis drive system that drives the column 3 to move in a direction orthogonal to the paper surface (X-axis direction), and a Y-axis drive system that drives the table 7 to move in the Y-axis direction (left-right direction). Is provided. The X axis drive system is driven by an X axis motor 31, and the Y axis drive system is driven by a Y axis motor 32.
Inside the column 3, a Z-axis drive system for moving the spindle head 4 in the Z-axis direction (vertical direction) is provided, and this Z-axis drive system is driven by a Z-axis motor 33. A temperature sensor 21 that detects the ambient temperature around the machine tool 1 is provided on the side of the column 3. A spindle motor 30 for rotating the tool 6 attached to the lower end of the spindle 5 together with the spindle 5 is provided on the outer peripheral member of the spindle 5.

Next, the Y axis drive system will be described.
A steel ball screw shaft 9 (which corresponds to a drive shaft) extending in the Y-axis direction is disposed inside the base 2, and a Y-axis motor 32 is coupled to the right end of the ball screw shaft 9. The ball screw nut 8 fixed to the lower surface of the table 7 is screwed to the ball screw shaft 9, and the ball screw shaft 9 is rotated by driving the Y-axis motor 32, so that the table 7 together with the ball screw nut 8 is moved in the left-right direction in FIG. It is supposed to move. Note that the X and Z axis drive systems have substantially the same configuration as the Y axis drive system, and a description thereof will be omitted.

  An abutting jig 11 extending in the X-axis direction is fixed to the central portion of the upper surface of the table 7 in FIG. 1 in the left-right direction. The workpiece 10 is fixed to the upper surface of the table 7 in the abutted state. The processing reference surface 11a of the abutting jig 11 is set as the processing reference position of the workpiece 10 in the Y-axis direction. At the start of processing, the table 7 is moved so that the axis of the tool 6 attached to the spindle 5 is aligned with the axis of the workpiece 10. The position is aligned with the processing reference position, and processing is started from that position.

  The abutting jig 11 can be fixed by changing the position according to the dimensions of the workpiece 10. If the abutting jig 11 is fixed to the left end of the upper surface of the table 7, the larger workpiece 10 is fixed to the table 7. can do. Also in this case, the right side surface of the abutting jig 11 is set as the processing reference position of the workpiece 10 in the Y-axis direction. The machining reference position is set in the X-axis direction as in the Y-axis direction, and the upper surface of the table 7 that receives the lower end of the workpiece 10 is set as the machining reference position in the Z-axis direction.

Next, the control system of the machine tool 1 will be described.
As shown in FIG. 2, the control device 23 includes a CPU 25, a ROM 26, a RAM 27, a program memory 28 (program storage means), an input interface 24, and an output interface 29. The input interface 24 of the control device 23 is electrically connected to the keyboard 20, the temperature sensor 21, and a touch probe 22 (measuring means) that can measure at least the actual movement amount of the table 7 in the Y-axis direction. A spindle motor 30, an X-axis motor 31, a Y-axis motor 32, a Z-axis motor 33, and a liquid crystal display 34 are electrically connected to the output interface 29 of the control device 23. The output interface 29 is also provided with a plurality of drive circuits.

  The ROM 26 has various control programs for driving and controlling the machine tool based on the machining program, a display control program for displaying various display information on the liquid crystal display 34, a feed amount correction control control program shown in the flowchart of FIG. A control program for correction coefficient calculation control shown in the flowchart of FIG.

  In the feed amount correction control, the feed amount for feeding and driving the workpiece 10 via the ball screw shaft 9 to the position set in the machining program during machining of the workpiece 10 is set on the table 7 of the machine tool 1. Correction is performed using a correction value obtained by multiplying the current feed direction displacement amount from the machining reference of the workpiece 10 by the scale magnification k (displacement amount coefficient). In the correction coefficient calculation control, the scale magnification k is corrected based on the ambient temperature when the workpiece 10 is processed, the scale magnification k, and a feed error calculated from movement command data and movement amount measurement data described later. Calculate the correction factor.

  In the RAM 27, the linear expansion coefficient α of the metal material constituting the workpiece 10 and the linear expansion of the steel material constituting the drive shaft of the X, Y, Z axis drive system of the machine tool 1, which are set in advance from the keyboard 20. A coefficient β, a preset standard temperature T0 (for example, 20 ° C.), and movement command data and movement amount measurement data shown in FIG. 5 are stored. However, this RAM 27 is always backed up by a secondary battery or the like. The program memory 28 stores a plurality of machining programs including position information and tool information for driving and controlling the motors 31 to 33.

  The keyboard 20 is used to input and set various commands and data to the control device 23. The temperature sensor 21 detects the ambient temperature around the machine tool 1, and the detected temperature T is input to the control device 23. The touch probe 22 is attached to the machine tool. For example, the touch probe 22 can measure the actual movement amount after moving the table 7 a predetermined distance via the Y-axis drive system. Coordinate data measured via the touch probe 22 is input to the control device 23 as movement amount measurement data.

Next, movement command data and movement amount measurement data stored in the RAM 27 will be described with reference to FIG. The movement command data is a command (target value) for moving and driving the table 7, and movement command data for a plurality of points is stored in the RAM 27. Next, by adjusting the position of the Y-axis drive system under the standard temperature T0, the tool is set to the machining reference position, and then the movement command data is read one by one, and the Y-axis drive system is read with the movement command data. Drive. At this time, feed amount correction control, which will be described later, is executed, and the workpiece 10 is processed at a position moved based on the movement command data. When machining is completed at all the movement command data positions, the machining position of the machined workpiece 10 is measured by the touch probe 22 and the measurement data is stored in the RAM 27.
The measurement using the touch probe 22 may be performed using a dedicated measuring machine that may be measured by attaching the touch probe 22 to the machine tool 1.

  Next, the feed amount correction control executed by the control device 23 will be described based on the flowchart of FIG. However, in the flowchart of FIG. 3, the feed amount correction control of the Y-axis drive system will be described as an example. The feed amount correction control for the X and Z axis drive systems can be performed in substantially the same manner as for the Y axis drive system. In the figure, Si (i = 1, 2, 3...) Indicates each step.

  After the machining program is selected, when this feed amount correction control is started by inputting a machining start command, initial setting is first performed (S1). Next, various types of information such as the linear expansion coefficient α of the workpiece 10, the linear expansion coefficient β of the steel material constituting the ball screw shaft 9 of the Y-axis drive system of the machine tool 1, and the detected temperature T are read (S2). Based on the linear expansion coefficients α and β and the temperature difference ΔT between the detected temperature T and the standard temperature T0, the scale factor k is calculated by an equation of k = [1.0+ (α−β) ΔT] (S3). ). However, ΔT = (T−T0).

  Next, the machining program stored in the program memory 28 is read for each line (one block) (S4), and it is determined whether or not the read command is a movement command to the Y-axis drive system. In the case of a movement command to (S5; Yes), it is determined whether or not a displacement in the Y-axis direction from the machining reference position occurs. That is, it is determined whether or not the tool 6 is moved relative to the table 7 in the region on the right side in FIG.

  FIG. 4 shows that the feed amount is corrected using the correction value only when the displacement in the Y-axis direction from the machining reference position occurs. As shown in FIG. Only when the displacement in the Y-axis direction occurs (S6; Yes), the feed amount of the movement command is calculated using a correction value obtained by multiplying the current feed direction displacement amount from the machining reference position of the workpiece 10 by the scale factor k. Correction is performed (S7). In this case, in FIG. 1, the scale magnification k is multiplied only by the amount of displacement in the feed direction that moves the tool 6 relative to the table 7 relative to the table 7 in the region to the right of the machining reference surface 11a. Then, the correction value is calculated, and the movement command feed amount is corrected using the correction value.

  However, if the command read in S5 is not a move command to the Y-axis drive system, the process proceeds to S9. Even if a move command to the Y-axis drive system is generated, for example, the machining reference plane in FIG. When the relative movement in the Y-axis direction between the table 7 and the tool 6 in the region on the right side of 11a has not occurred, the determination in S6 is No and the process proceeds to S8. In S8, the Y-axis motor 32 is driven based on the corrected feed amount or the uncorrected feed amount. Next, in S9, it is determined whether or not the machining program is finished. If the machining program is finished, this process is finished. If the machining program is not finished (S9; No), the process proceeds to S4.

  Next, correction coefficient calculation control executed by the control device 23 will be described based on the flowchart of FIG. However, in the flowchart of FIG. 6, only the correction coefficient calculation control of the Y-axis drive system has been described, and correction coefficient calculation control of the X and Z-axis drive systems is performed in substantially the same manner as in the Y-axis drive system. be able to. In the figure, Si (i = 10, 11, 12,...) Indicates each step. This correction coefficient calculation control is control for obtaining and correcting a correction coefficient for correcting the scale magnification k using measurement data acquired and stored in advance as shown in FIG.

  First, as shown in FIG. 5, a plurality of movement measurement data (s1, s2, s2) corresponding to a plurality of movement command data (y1, y2,... Yn) in the Y-axis direction stored in the RAM 27. ... Sn) is read from the RAM 27 (S10). From these data, the relationship between the movement error (si−yi), (i = 1, 2,...) And the distance (yi), (i = 1, 2,. Calculation is performed as shown in FIG. 7 using a square method or the like. The slope of the straight line in FIG. 7 is calculated as a movement error δ per unit length (S11).

  As shown in FIG. 8, the movement error δ is a movement error that occurs when the standard temperature T0, that is, the temperature difference ΔT = 0. The slope employed in the scale factor k is (α−β), and it is assumed that the movement error is 0 when the temperature difference ΔT = 0, but in reality, when the temperature difference ΔT = 0. A movement error δ has occurred. Therefore, the actual inclination I of the scale magnification k is set as shown by a two-dot chain line in FIG.

  Therefore, in S12, (α−β) × ΔT is calculated using the gradient (α−β) employed in the scale factor k and the temperature difference ΔT during the current processing (S12). At this time, ΔT = (T−T0) using the air temperature T detected by the temperature sensor 21. Next, in S13, the actual slope I of the scale magnification is calculated by the following equation: I = [(α−β) × ΔT + δ] / ΔT. Next, the scale magnification correction coefficient γ is calculated by an equation of γ = actual inclination I / (α−β) (S14). Next, a corrected scale magnification k ′ obtained by correcting the calculated scale magnification k with the correction coefficient γ is calculated by an equation of k ′ = γ × scale magnification k (S15), and this processing is terminated.

After the correction scale magnification k ′ is calculated by the correction coefficient calculation control, the correction scale magnification k ′ is employed instead of the scale magnification k in the feed amount correction control shown in FIG.
The scale magnification calculating means is composed of S3 and the control device 23 in the flowchart shown in FIG. 3, and the feed amount correcting means is composed of S4 to S7 and the control device 23 in the flowchart shown in FIG. Is configured by S11 of the flowchart shown in FIG. 6 and the control device 23, and the correction coefficient calculation means is configured by S12 to S14 of the flowchart shown in FIG.

Next, functions and effects of the machine tool 1 will be described.
Thus, the machine tool 1 includes the temperature sensor 21, the linear expansion coefficient α of the workpiece 10, and the linear expansion coefficient β of the steel material constituting each drive shaft of the X, Y, Z axis drive system of the machine tool 1. Is stored in the RAM 27, the temperature difference ΔT between the detected temperature T detected by the temperature sensor 21 and the standard temperature T0, and the linear expansion coefficients α and β are used to calculate the scale magnification k. The feed amount for feeding and driving the workpiece 10 via the drive shaft to the position set in the machining program is changed to the current feed direction displacement amount from the machining reference of the workpiece 10 set on the table 7 of the machine tool 1. Since the correction is performed using the correction value multiplied by the scale factor k, the displacement in the feed direction when the tool 6 of the spindle 5 is aligned with the machining reference of the workpiece 10 at the start of machining after the workpiece 10 is fixed to the table 7. Is not corrected.

Therefore, even when the thermal expansion coefficient of the workpiece 10 and each drive shaft is significantly different, the tool 6 of the spindle 5 can be accurately aligned with the machining reference of the workpiece 10, and the machining accuracy of the workpiece 10 can be improved. Is possible.
Moreover, the scale coefficient k is calculated as k = [1.0+ (α−β) ΔT] using the linear expansion coefficient α of the workpiece 10, the linear expansion coefficient β of the drive shaft, and the temperature difference ΔT between the detected temperature and the standard temperature. The feed amount for feeding and driving the workpiece to the position set in the machining program via the drive axis is the current feed direction displacement from the workpiece machining reference set on the machine tool table. Further, since correction is performed using a correction value obtained by multiplying the scale magnification k, the machining accuracy of the workpiece 10 can be improved by correcting the feed amount in consideration of the thermal expansion difference between the workpiece 10 and the drive shaft.

  Further, a feed error δ per unit length is calculated using the measurement data shown in FIG. 5 prepared in advance, and based on the detected temperature T, the slope of the scale magnification k (α−β), and the feed error δ, A correction coefficient γ for correcting the scale magnification k is calculated and the current feed direction displacement from the machining reference of the work 10 is corrected using the scale magnification k ′ corrected by the correction coefficient γ. Therefore, the accuracy of feeding amount correction is improved, and the machining accuracy of the workpiece 10 when the workpiece 10 and the drive shaft have different thermal expansion coefficients is further improved.

Next, a modified example in which the above embodiment is partially modified will be described.
1] Only the feed amount correction control may be performed without performing the correction coefficient calculation control, and the workpiece 10 may be fed and driven based on the corrected feed amount obtained by multiplying the scale factor k.
2] Instead of providing the temperature sensor 21, a temperature difference ΔT from the standard temperature T0 may be calculated by inputting the temperature from the keyboard 20. In this case, it is possible to improve the machining accuracy of the workpiece 10 while reducing the cost of the machine tool 1.
3] The control program for the feed amount correction control and the control program for the correction coefficient calculation control may be stored in an external storage medium such as a CD-ROM or a flexible disk instead of being stored in the ROM 26.

1 is a schematic configuration diagram of a machine tool according to an embodiment of the present invention. It is a block diagram of the control system of a machine tool. It is a flowchart of feed amount correction control. It is a characteristic diagram which shows the correction value in the displacement amount of a Y-axis direction. It is explanatory drawing which shows movement command data and movement amount measurement data. It is a flowchart of correction coefficient calculation control. It is a correlation diagram of the distance (target value) from a processing reference position, and a movement error. It is a diagram which shows the inclination of scale magnification, and the actual inclination of scale magnification.

Explanation of symbols

1 Machine Tool 7 Table 9 Ball Screw Shaft 10 Work 11a Processing Reference Surface 21 Temperature Sensor 22 Touch Probe 23 Controller 27 RAM

Claims (4)

In a machine tool that processes a workpiece while controlling the X, Y, Z axis drive system based on position information included in the machining program,
Temperature detection means for detecting the ambient temperature around the machine tool;
The linear expansion coefficient α of the workpiece, the linear expansion coefficient β of the metal material constituting one of the drive axes of the X, Y, and Z axis drive systems of the machine tool, and a preset standard temperature are set. Storage means for storing;
Using the temperature difference ΔT between the detected temperature detected by the temperature detecting means and the standard temperature stored in the storage means, and the linear expansion coefficients α, β stored in the storage means, the displacement amount coefficient is calculated. Displacement amount coefficient calculating means to perform,
The current feed direction from the workpiece machining reference set on the table of the machine tool, the feed amount for feeding and driving the workpiece via the drive shaft to the position set in the machining program during machining of the workpiece A feed amount correcting means for correcting using a correction value obtained by multiplying the displacement amount by the displacement amount coefficient;
A machine tool characterized by comprising A feed error per unit length is calculated from measurement data obtained by repeating a plurality of times the measurement means measures the actual feed amount after the feed operation is executed by the drive shaft at the standard temperature. Feed error calculation means;
Correction coefficient calculation means for calculating a correction coefficient for correcting the displacement amount coefficient based on the ambient temperature when processing the workpiece, the displacement amount coefficient, and the feed error calculated by the feed error calculation means; The machine tool according to claim 1, wherein the machine tool is provided. Temperature detecting means for detecting the ambient temperature around the machine tool, the linear expansion coefficient α of the workpiece, and the linear expansion coefficient β of the metal material constituting one of the drive axes of the X, Y, Z axis drive system of the machine tool, A computer of a machine tool that has a storage means for storing a standard temperature and performs processing on the workpiece while controlling the X, Y, Z axis drive system based on position information included in the processing program,
Using the temperature difference ΔT between the detected temperature detected by the temperature detecting means and the standard temperature stored in the storage means, and the linear expansion coefficients α, β stored in the storage means, the displacement amount coefficient is calculated. Displacement amount coefficient calculating means to perform,
The current feed direction from the workpiece machining reference set on the table of the machine tool, the feed amount for feeding and driving the workpiece via the drive shaft to the position set in the machining program during machining of the workpiece A thermal expansion correction control program that causes a displacement amount to be corrected using a correction value obtained by multiplying the displacement amount by the displacement amount coefficient. A storage medium storing the thermal expansion correction control program according to claim 3.