JP7683373B2 - CONTROL DEVICE, CONTROL METHOD, CONTROL PROGRAM, AND STORAGE MEDIUM - Google Patents

Description

The present invention relates to a control device, a control method, a control program, and a storage medium.

The machine tool has a table and a ball screw that moves the table in a first direction. A control device that controls the machine tool pre-stores the pitch error of the ball screw, and when the table is moved in the first direction, reads out the pitch error and corrects the pitch error of the ball screw. The control device measures the position of the table in the first direction at predetermined time intervals while moving the table over the entire length of the ball screw, thereby calculating the pitch error of the entire ball screw at each correction interval.

Patent No. 5915436

When in use, the table of the above-mentioned machine tool carries a load such as a workpiece, a workpiece fixing jig, etc. The machine tool supports the table so that it can move in a first direction, and is equipped with a support table that can move in a second direction. The support part supports the support table. Depending on the mass of the load, the support part deflects in the first direction. At that time, even if the control device corrects the position in the first direction using the pitch error, the positioning error in the first direction of the table increases due to the effect of the deflection generated in the support part.

The object of the present invention is to provide a control device, a control method, a control program, and a storage medium that reduce positioning errors compared to conventional methods.

The control device of claim 1 of the present invention is a control device for controlling a machine tool including a first table on which a load is placed, a second table that supports the first table movably in a first direction parallel to the horizontal direction, a first drive unit that moves the first table in the first direction, a table support unit that supports the second table movably in a second direction intersecting the first direction, and a second drive unit that moves the second table in the second direction. The control device includes a mass acquisition unit that acquires the mass of the load placed on the first table, a first command acquisition unit that acquires a first position command that commands the position of the first table in the first direction, and a correction unit that uses a coefficient based on the mass acquired by the mass acquisition unit and the position of the first position command to correct the amount corresponding to the deflection of the table support unit due to the load placed on the first table and the position of the first position command. Since the correction unit uses a coefficient based on the mass of the load and the position of the first position command to correct the position of the first position command, the control device can reduce the positioning error in the first direction of the first table compared to conventional devices, taking into account the amount corresponding to the deflection of the table support unit due to the load placed on the first table.

The position of the first position command of the control device of claim 2 of the present invention is expressed as a distance from a reference position, which is the position where the amount corresponding to the deflection of the platform support part due to the load placed on the first platform is the smallest. The position of the first position command of the control device is more likely to represent a value corresponding to the deflection of the platform support part due to the load placed on the first platform than the position of the first position command when the reference position is a position where the amount corresponding to the deflection of the platform support part is not the smallest. Therefore, the control device can more easily calculate the amount corresponding to the deflection of the platform support part than when the reference position is a position where the amount corresponding to the deflection of the platform support part is not the smallest.

The amount according to the deflection of the platform support part due to the load placed on the first platform of the control device of claim 3 of the present invention is the product of the coefficient and the distance. The control device can easily calculate the amount according to the deflection of the platform support part.

The coefficient of the control device of claim 4 of the present invention is a value based on a constant specific to the machine tool. By setting the coefficient used for correction to a value based on a constant specific to the machine tool, the control device can correct the position of the first position command without measuring all individual machine tools.

The reference of the control device of claim 5 of the present invention is the center of the movable range of the first unit. The control device can reduce the amount of deflection of the platform support part compared to when the reference is at the end of the movable range of the first unit.

The coefficient of the control device of claim 6 of the present invention is based on a value corresponding to the height of the load from a predetermined position between the lower end of the platform support part and the upper surface of the first platform. The control device can correct the position of the first position command taking into account the height of the load.

The predetermined position of the control device of claim 7 of the present invention is a position where the error in the position of the first platform in the first direction caused by the deflection of the platform support part due to the load placed on the first platform is minimized. The control device can correct the position of the first position command so that the error caused by the deflection of the platform support part due to the load placed on the first platform, depending on the height of the load from the predetermined position, is minimized.

The machine tool of the control device of claim 8 of the present invention includes a spindle on which a tool is attached, a spindle head that supports the spindle and can move up and down, a head support unit that supports the spindle head so that it can move in the vertical direction, and a third drive unit that moves the spindle head in the vertical direction. The machine tool includes a second command acquisition unit that acquires a second position command that commands the vertical position of the spindle head, and a height acquisition unit that acquires the height of the tip of the tool from the specified position based on a tool length correction amount corresponding to the tool attached to the spindle and the second position command, and the value corresponding to the height of the load is the height of the tip of the tool from the specified position acquired by the height acquisition unit. The control device can correct the position of the first position command by taking into account the vertical position of the spindle head indicated by the second position command.

The control device of claim 9 of the present invention further includes a type determination unit that determines whether the second position command is a positioning command or a cutting command, and the height acquisition unit acquires the height of the tip of the tool from the predetermined position in response to the type determination unit's determination that the second position command is the positioning command, and the correction unit updates the coefficient using the height of the tip of the tool from the predetermined position acquired by the height acquisition unit, and corrects the position of the first position command using the updated coefficient and the position of the first position command corresponding to the second position command. The control device can correct the position of the first position command corresponding to the second position command by taking into account the vertical position of the spindle head indicated by the second position command when the second position command is a positioning command. Therefore, the control device can appropriately correct the position of the first table in the first direction indicated by the first position command even when the height of the load placed on the first table from the predetermined position is relatively large.

The control device of claim 10 of the present invention further includes a storage device and a storage control unit that stores the coefficients updated by the correction unit in the storage device, and the correction unit corrects the position of the first position command using the coefficients stored in the storage device and the position of the first position command in response to the type determination unit determining that the second position command is the cutting command. The control device can correct the position of the first position command so as to suppress adverse effects such as making the size of the cutting portion larger than the size indicated by the first position command during cutting processing.

The correction unit of the control device of claim 11 of the present invention uses the coefficient and the position of the first position command corrected using the center of gravity of the load and the first platform to correct the amount corresponding to the deflection of the platform support part due to the load placed on the first platform and the position of the first position command. The control device can appropriately correct the amount corresponding to the deflection of the platform support part due to the load placed on the first platform and the position of the first position command, taking into account the position of the load in the first direction of the first platform.

The control method of claim 12 of the present invention is a control method for a machine tool including a first table on which a load is placed, a second table supporting the first table so as to be movable in a first direction parallel to the horizontal direction, a first drive unit moving the first table in the first direction, a table support unit supporting the second table so as to be movable in a second direction intersecting the first direction, and a second drive unit moving the second table in the second direction, the control method includes a mass acquisition process for acquiring the mass of the load placed on the first table, a command acquisition process for acquiring a position command that commands the position of the first table in the first direction, and a correction process for correcting the position of the position command by an amount corresponding to the deflection of the table support unit due to the load placed on the first table, using a coefficient based on the mass acquired in the mass acquisition process and the position of the position command. The control device performs a control method, and the correction unit corrects the position of the position command using a coefficient based on the mass of the load and the position of the position command, so that the positioning error in the first direction of the first platform corresponding to the mass of the load placed on the first platform can be reduced more than ever before, taking into account the amount corresponding to the deflection of the platform support part due to the load placed on the first platform.

The control program of claim 13 of the present invention is a control program executable by a control unit of a control device that controls a machine tool including a first table on which a load is placed, a second table that supports the first table so that it can be moved in a first direction parallel to the horizontal direction, a first drive unit that moves the first table in the first direction, a table support unit that supports the second table so that it can be moved in a second direction intersecting the first direction, and a second drive unit that moves the second table in the second direction, and includes instructions to cause the control unit of the control device to execute a mass acquisition process that acquires the mass of the load placed on the first table, a command acquisition process that acquires a position command that commands the position of the first table in the first direction, and a correction process that corrects the position of the position command by an amount corresponding to the deflection of the table support unit due to the load placed on the first table, using a coefficient based on the mass acquired in the mass acquisition process and the position of the position command. In the control device that executes the control program, the correction unit corrects the position of the position command using a coefficient based on the mass of the load and the position of the position command, so that the positioning error in the first direction of the first platform corresponding to the mass of the load placed on the first platform can be reduced more than ever before, taking into account the amount corresponding to the deflection of the platform support part due to the load placed on the first platform.

The storage medium of claim 14 of the present invention is a storage medium that stores a control program executable by a control unit of a control device that controls a machine tool including a first table on which a load is placed, a second table that supports the first table movably in a first direction parallel to the horizontal direction, a first drive unit that moves the first table in the first direction, a table support unit that supports the second table movably in a second direction intersecting the first direction, and a second drive unit that moves the second table in the second direction, and the control program stores instructions to cause the control unit of the control device to execute a mass acquisition process that acquires the mass of the load placed on the first table, a command acquisition process that acquires a position command that commands the position of the first table in the first direction, and a correction process that corrects the position of the position command by an amount corresponding to the deflection of the table support unit due to the load placed on the first table, using a coefficient based on the mass acquired in the mass acquisition process and the position of the position command. The control device, which executes the control program stored in the storage medium, has a correction unit that uses a coefficient based on the mass of the load and the position of the position command to correct the position of the position command, so that the positioning error in the first direction of the first platform corresponding to the mass of the load placed on the first platform can be reduced more than ever before, taking into account the amount corresponding to the deflection of the platform support part due to the load placed on the first platform.

FIG. FIG. FIG. 2 is a block diagram of the electrical configuration of the control device 30 and the machine tool 1. FIG. 2 is a schematic front view of the table device 10. 1 is a flow diagram of the mass acquisition process. 4 is a flowchart of a main process according to the first embodiment. 13A is a graph showing the relationship between the error and the distance x from the reference R to the position of the first position command before position correction of the first position command, and FIG. 13B is a graph showing the relationship between the error and the distance x from the reference R to the position of the first position command after position correction of the first position command in the main processing of the first embodiment. 13 is a flowchart of a main process according to a second embodiment. 4 is a flow diagram of an axis operation command process. 13A is a graph showing the relationship between the error and the distance x from the reference R to the position of the first position command before position correction of the first position command, and FIG. 13B is a graph showing the relationship between the error and the distance x from the reference R to the position of the first position command after position correction of the first position command in the main processing of the second embodiment. FIG. 2 is a schematic front view of the table device 10. 13A is a graph showing the relationship between the error and the distance x from the reference R to the position of the first position command before position correction of the first position command, and FIG. 13B is a graph showing the relationship between the error and the distance x from the reference R to the position of the first position command after position correction of the first position command in the main processing of the modified example.

The configuration of the machine tool 1 will be explained. In the following explanation, the left/right, front/back, and up/down directions shown by arrows in the figure will be used. The left/right, front/back, and up/down directions of the machine tool 1 are the X-axis, Y-axis, and Z-axis directions of the machine tool 1, respectively. The X-axis direction is the first direction, and the Y-axis direction is the second direction. The configuration of the machine tool 1 will be explained using Figures 1 and 2. The machine tool 1 is a machine that rotates a tool 4 attached to a spindle 9 and performs cutting on a workpiece 3 held on the upper surface 11 of a first table 13. A control device 30 controls the operation of the machine tool 1.

The machine tool 1 includes a base 2, a column 5, a spindle head 7, a spindle 9, a table device 10, a tool changer 20, a control box 6, an operation panel 15 (see FIG. 3), etc. The base 2 is made of metal and is a substantially rectangular parallelepiped base. The column 5 is substantially prismatic and is fixed to the rear of the upper part of the base 2. The spindle head 7 moves in the Z-axis direction along the front surface of the column 5. The spindle head 7 rotatably supports the spindle 9 inside. The spindle 9 is rotated by the drive of a spindle motor 52 (see FIG. 3). The spindle motor 52 is provided on the spindle head 7. The spindle head 7 moves in the Z-axis direction by a Z-axis movement mechanism (not shown) provided on the front surface of the column 5. The control device 30 controls the drive of the Z-axis motor 51 (see FIG. 3) to control the movement of the spindle head 7 in the Z-axis direction.

The table device 10 is a ball screw drive mechanism. The table device 10 includes a Y-axis moving mechanism 18, a second table 12, an X-axis moving mechanism 17, a first table 13, etc. The Y-axis moving mechanism 18 is provided on the front side of the upper surface of the base 2, and includes a Y-axis track 61, a Y-axis ball screw 62, a Y-axis motor 54, etc. The Y-axis track 61 and the Y-axis ball screw 62 extend in the Y-axis direction. The second table 12 is formed in a substantially rectangular parallelepiped shape, and includes a nut (not shown) on the outer surface of the bottom. The nut is screwed into the Y-axis ball screw 62. When the Y-axis motor 54 rotates the Y-axis ball screw 62, the second table 12 moves along the Y-axis track 61 together with the nut. Therefore, the Y-axis moving mechanism 18 supports the second table 12 so that it can move in the Y-axis direction.

The X-axis moving mechanism 17 is provided on the upper surface of the second table 12, and includes an X-axis track 63, an X-axis ball screw 64, an X-axis motor 53, etc. The X-axis track 63 and the X-axis ball screw 64 extend in the X-axis direction. The first table 13 is formed in a rectangular plate shape in a plan view, and is provided on the upper surface of the second table 12. The first table 13 includes a nut (not shown) at the bottom. The nut is screwed into the X-axis ball screw 64. When the X-axis motor 53 rotates the X-axis ball screw 64, the first table 13 moves along the X-axis track 63 together with the nut. The X-axis moving mechanism 17 supports the first table 13 so that it can move in the X-axis direction. Therefore, the first table 13 moves on the base 2 in the X-axis and Y-axis directions by the Y-axis moving mechanism 18, the second table 12, and the X-axis moving mechanism 17.

A pair of left and right covers 67 cover parts of the X-axis track 63 and the X-axis ball screw 64. The covers 67 expand and contract as the first base 13 moves in the X-axis direction. The front cover 69 and rear cover (not shown) cover parts of the Y-axis track 61 and the Y-axis ball screw 62. The front cover 69 and rear cover expand and contract as the second base 12 moves in the Y-axis direction.

The tool changer 20 is provided in front of the spindle head 7 and has a disk-shaped tool magazine 21. The tool magazine 21 has a frame 71 and multiple arms 73, and can store multiple tools 4 including tools 4A and 4B. The frame 71 is cylindrical. The multiple arms 73 are provided so as to be able to swing along the outer periphery of the frame 71. The tool changer 20 rotates the tool magazine 21 around the magazine axis J by the magazine motor 55 (see FIG. 3) and positions the tool 4 specified by the tool change command at the change position. The tool change command is commanded by an NC program. The change position is the lowest position of the tool magazine 21. The tool changer 20 replaces the used tool 4 attached to the spindle 9 with the tool 4 to be next attached to the spindle 9. The tool change is performed by a series of operations: raising the spindle head 7, rotating the tool magazine 21, and lowering the spindle head 7.

The control box 6 houses the control device 30 (see Figure 3). The control device 30 controls the Z-axis motor 51, spindle motor 52, X-axis motor 53, and Y-axis motor 54 provided on the machine tool 1, and moves the first table 13 and the tool 4 relatively along the X-axis, Y-axis, and Z-axis directions. At that time, the workpiece 3 fixed on the first table 13 and the tool 4 attached to the spindle 9 move relatively to each other, and various types of processing are performed on the workpiece 3. The various types of processing include hole drilling using a drill, tap, etc., and side processing using an end mill, milling cutter, etc. The control device 30 controls the magazine motor 55 to rotate the tool magazine 21.

The operation panel 15 (see FIG. 3) is provided on the outer wall of a cover (not shown) that covers the machine tool 1. The operation panel 15 includes an input unit 16 and a display unit 14 (see FIG. 3). The input unit 16 accepts input of various information, operation instructions, etc., and then outputs the operation instructions, etc. to the control device 30. The display unit 14 displays various screens in response to commands from the control device 30.

The electrical configuration will be described with reference to FIG. 3. The control device 30 and the machine tool 1 are equipped with a CPU 31, a ROM 32, a RAM 33, a storage device 34, an input/output unit 35, drive circuits 51A to 55A, etc. The CPU 31 controls the control device 30. The ROM 32 stores the main program, mass program, etc. The main program reads the NC program line by line and executes various operations. The NC program is composed of multiple lines including various control commands, and the CPU 31 controls various operations including the axis movement of the machine tool 1 and tool replacement on a line-by-line basis. The mass program is a program for executing the mass acquisition process (see FIG. 5). The RAM 33 temporarily stores various information. The storage device 34 is non-volatile and stores the NC program and various information. The CPU 31 can store in the storage device 34 the NC program input by the operator through the input unit 16 of the operation panel 15, as well as the NC program read by external input.

The drive circuit 51A is connected to the Z-axis motor 51 and the encoder 51B. The drive circuit 52A is connected to the spindle motor 52 and the encoder 52B. The drive circuit 53A is connected to the X-axis motor 53 and the encoder 53B. The drive circuit 54A is connected to the Y-axis motor 54 and the encoder 54B. The drive circuit 55A is connected to the magazine motor 55 and the encoder 55B. The Z-axis motor 51, the spindle motor 52, the X-axis motor 53, the Y-axis motor 54, and the magazine motor 55 are all servo motors. The drive circuits 51A to 55A receive commands from the CPU 31 and output drive currents based on the commands to the corresponding motors 51 to 55, respectively. The drive circuits 51A to 55A receive feedback signals from the encoders 51B to 55B and perform feedback control of the position and speed (angular velocity). The input/output unit 35 is connected to the input unit 16 and the display unit 14 of the operation panel 15, respectively.

With reference to FIG. 4, an outline of the correction process for correcting the effect of the deflection of the base 2 due to the load W placed on the first platform 13 will be described. It is assumed that the first platform 13 is located at a position Px described later, and the amount of deflection of the base 2 due to the load W placed on the first platform 13 is proportional to the distance x from the reference R in the X-axis direction of the first platform 13 to the position Px as shown in formula (1). The reference R in this embodiment is the X-axis position at which the amount of deflection of the base 2 due to the load W placed on the first platform 13 is minimized. In the example of FIG. 4, the reference R is the center of the movable range of the first platform 13, and is a position where the center of the X-axis direction of the first platform 13 coincides with the center of the X-axis direction of the second platform 12 and the center of the X-axis direction of the base 2. The distance x indicates the movement distance from the reference R. In FIG. 4, the first platform 13 is shown by a solid line when it is at the reference R, and the first platform 13 is shown by a dashed line when it is at the position Px. When the first platform 13 is at position Px, the load W is not shown. The distance when the first platform 13 is to the right of the reference R is a positive distance, and the distance when the first platform 13 is to the left of the reference R is a negative distance.

The estimated error E(x) in the X-axis direction caused by the deflection of the base 2 due to the load W placed on the first platform 13 is calculated by the formula (1). E(x) can be said to be an amount corresponding to the deflection of the base 2 due to the load W placed on the first platform 13.
E(x)=H×K×M×x ...Formula (1)
Here, K is a constant specific to the machine. M is the mass of the load W placed on the first table 13. The mass M of the load W is the sum of the mass of the jig provided on the first table 13 and the mass of the workpiece 3 held by the jig. H is a value (height) according to the upper end of the load W from the predetermined position. The predetermined position is a position between the upper end of the base 2 and the upper surface 11 of the first table 13, and is, for example, a position where the positioning error of the first table 13 due to the deflection of the base 2 by the load W placed on the first table 13 is minimized. H in the first embodiment is the height H2 from the predetermined position to the upper end of the load W, which is stored in advance in the storage device 34. H in the second embodiment is the height H1 from the predetermined position to the tip of the tool 4. The height H1 is calculated in advance by the CPU 31 and then stored in advance in the storage device 34. In the first and second embodiments, K×M×H in formula (1) is treated as a coefficient C.

The mass acquisition process will be described with reference to FIG. 5. When the machine tool 1 is started, the CPU 31 reads out the program stored in the ROM 32, and then starts the mass acquisition process. The CPU 31 determines whether or not the mass M of the load W placed on the first platform 13 has been acquired (S1). The mass M of the load W is used to set the coefficient C for determining the estimated error E(x). The method of acquiring the mass M of the load W may be set appropriately. When the worker operates the input unit 16 to input the mass of the load W, the CPU 31 may acquire the input value as the mass M of the load W. The CPU 31 may obtain the mass M of the load W from the acceleration of the first platform 13 by the table device 10 and the torque during acceleration.

When calculating the mass M of the load W, the CPU 31 executes the following procedure. As an example, a case where the X-axis motor 53 is used will be described. The CPU 31 drives the X-axis motor 53 and accelerates the first platform 13 from a stationary state to a constant speed V at a constant acceleration. After that, the CPU 31 moves the first platform 13 in the X-axis direction at the constant speed V for a constant distance. After that, the CPU 31 decelerates at a constant deceleration to stop the first platform 13. The estimated load weight during acceleration and the estimated load weight during deceleration are shown in the following two equations (2) and (3). In equation (2), the acceleration at an arbitrary speed V1 during acceleration is α, and the torque is T1. In equation (3), the acceleration at a speed V1 during deceleration is -α, and the torque is T2. k is a parameter that converts the total mass into the motor shaft converted inertia. The total mass is the sum of the load weight and the mass of the first platform 13 without a load.
Estimated amount of loaded material during acceleration=[(T1-viscosity resistance x V1+sliding resistance of first platform 13)/(α x k)]-mass of first platform 13 without loaded material ...Equation (2)
Estimated amount of loaded material during deceleration=-[(T2-viscosity resistance x V1+sliding resistance of the first platform 13)/(α x k)]-mass of the first platform 13 without a loaded material ...Equation (3)
The average of the estimated load mass during acceleration and the estimated load mass during deceleration based on equations (2) and (3) is given by equation (4).
Average of the estimated weight of the loaded material during acceleration and the estimated weight of the loaded material during deceleration=[(T1-T2)/(2×α×k)]−mass of the first vehicle 13 without a load (Equation (4))
The CPU 31 can estimate the mass M of the load W by using equation (4) to offset fluctuations caused by the environmental temperature of the machine and aging.

In another method for calculating the mass M of the load W, the CPU 31 estimates the load mass Q by substituting the acceleration α and torque T during the fast-forward operation of the machine tool 1 into equation (5). The fast-forward operation is an operation in which the spindle 9 is moved relative to the workpiece 3 at a speed faster than the cutting movement in order to move the tool 4 closer to or farther away from the workpiece 3.
Q=T/α...Formula (5)
The CPU 31 further estimates the mass M of the load W based on the formula (6).
Mass M of the load W=load mass Q−equivalent mass of the feed mechanism−mass of the first platform 13 Equation (6)
The equivalent mass of the feed mechanism is a value obtained by converting the sum of the inertias of the components of the Y-axis movement mechanism 18 into mass.

When the CPU 31 acquires the mass M of the load W (S1: YES), it assigns the acquired mass M to the formula (7) to update the coefficient C, and stores the updated coefficient C in the storage device 34 (S2). The CPU 31 obtains the coefficient C in the formula (8) using K and H as constants stored in the storage device 34.
Coefficient C=K×M×H (7)

When the mass M of the load W has not been acquired (S1: NO), or after S2, the CPU 31 determines whether an end command has been acquired (S3). The worker operates the input unit 16 to input an end command. When an end command has not been acquired (S3: NO), the CPU 31 returns the process to S1. When an end command has been acquired (S3: YES), the CPU 31 ends the mass acquisition process.

The main processing of the first embodiment will be described with reference to Figures 6 and 7. When the CPU 31 receives an instruction to execute an NC program, it starts the main processing by reading and executing the main program stored in the ROM 32.

The CPU 31 reads one block of the NC program (S11) and judges whether the read block is an end command or not (S12). When the read block is not an end command (S12: NO), the CPU 31 judges whether the read block is an axis operation command or not (S13). The axis operation is an operation to move the position of the spindle 9 relative to the first table 13. The axis operation command is a positioning command or a cutting command. The positioning command is an command to position the spindle 9 at a target position (target value) relative to the first table 13. The cutting command is an command to perform, for example, drilling a hole with a tool 4 such as a tap or drill, or side processing with a tool 4 such as a milling cutter or end mill. The axis operation command includes at least one of a first position command, a second position command, and a third position command. The first position command commands the position of the first table 13 in the X-axis direction. The second position command commands the position of the spindle head 7 in the up-down direction. The third position command commands the position of the first table 13 in the Y-axis direction.

When the block is "G0X200.Y250;", the CPU 31 judges that the read block is an axis movement command (S13: YES) and acquires the coefficient C by referring to the storage device 34 (S14). The CPU 31 acquires the first position command that commands the position of the first platform 13 in the X-axis direction from the block (S15). When the block is "G0X200.Y250;", the CPU 31 acquires the first position command "X200". The "200" of the first position command corresponds to the distance from the reference R. The CPU 31 uses the coefficient C based on the mass M acquired in S1 and the position of the first position command to calculate a correction value that corrects the deflection of the second platform 12 due to the load W placed on the first platform 13 (S16). The CPU 31 substitutes the value x of the X-coordinate of the first position command into the formula (1) to obtain the estimated error E(x). The CPU 31 uses the formula (8) to obtain the position x' of the corrected first position command.
x'=x-E(x)...Formula (8)

The CPU 31 performs axial movement according to the block read out in S11 (S17). For movement in the X-axis direction according to the first position command, the CPU 31 drives the X-axis motor 53 to move the first table 13 in the X-axis direction to the position x' corrected in S16. Since the positioning command "G0X200.Y250;" includes the third position command "Y250", for movement in the Y-axis direction, the CPU 31 drives the Y-axis motor 54 in accordance with the third position command to move the first table 13 in the Y-axis direction. The CPU 31 returns the process to S11.

When the read block is not an axis operation command (S13: NO), the CPU 31 executes other processing according to the control command indicated by the block (S20). A control command that is not an axis operation command is a coolant discharge command, etc. The CPU 31 returns the processing to S11. When the read block is an end command (S12: YES), the CPU 31 ends the main processing.

Figure 7 shows the evaluation results of the first embodiment. The error measurement value under condition 1, where the mass M of the load W is 200 kg, is shown by a white square, the error measurement value under condition 2, where the mass M of the load W is 300 kg, is shown by a white circle, and the error measurement value under condition 3, where the mass M of the load W is 400 kg, is shown by a black circle. The solid line 81 in Figure 7 (A) is the estimated error E(x) under condition 1, the dotted line 82 is the estimated error E(x) under condition 2, and the thick line 83 is the estimated error E(x) under condition 3. In the evaluation of the first embodiment, the CPU 31 sets the height H1 from a predetermined position of the tip of the tool 4 at the time of error measurement to H, and sets the predetermined position and constant K to a value obtained by applying the least squares method to the error measurement value. As shown in Figure 7 (A), when the position of the first position command is not corrected by the main processing, the larger the absolute value of the distance from the reference R, the larger the absolute value of the error in the X-axis direction position of the first platform 13. Hereinafter, the position error in the X-axis direction will simply be referred to as the error. Condition 2 has a larger absolute value of the error of the first platform 13 than condition 1. As shown in FIG. 7B, when the position of the first position command is corrected using the coefficient C based on the mass M of the load W and the position of the first position command, the absolute value of the error of the first platform 13 is smaller than before correction. The absolute value of the error of the first platform 13 is within 15 μm regardless of the distance from the reference R. Therefore, the control device 30 of the first embodiment can reduce the positioning error in the first direction of the first platform 13 by taking into account the amount corresponding to the deflection of the base 2 due to the load W placed on the first platform 13.

The main processing of the second embodiment will be described with reference to Figures 8 to 10. When the CPU 31 receives an instruction to execute an NC program, it starts the main processing by reading and executing a program stored in the ROM 32. In Figure 8, the same processes as those in the main processing of the first embodiment shown in Figure 6 are given the same reference numerals. The main processing in Figure 8 differs in that instead of steps S14 to S17, processing S21 is performed, and instead of step S20, processing S22 to S24 is performed. A description of the processes similar to those in Figure 6 will be omitted.

In S21, the CPU 31 performs the axis operation process shown in FIG. 9. As shown in FIG. 9, the CPU 31 judges whether the block read in S11 is a positioning command (S31). When the block read in S11 is a positioning command (S31: YES), the CPU 31 acquires the second position command from the block read in S11 (S32). The CPU 31 acquires the height H1 from the specified position to the tip of the tool 4 based on the tool length correction amount corresponding to the tool 4 attached to the spindle 9 and the second position command (S33). The tool length correction amount is stored in the storage device 34 after being acquired by the CPU 31 in S22 described later. The CPU 31 subtracts the tool length correction amount from the height of the spindle 9 from the specified position indicated by the second position command to obtain the height H1 from the specified position to the tip of the tool 4. The height H1 is a value corresponding to the height H2 of the load W from the specified position, and is higher by a predetermined amount than the height H2. The CPU 31 substitutes the height H1 obtained in S33 for the height H in formula (7) and updates the coefficient C (S34). In formula (7), the CPU 31 updates the coefficient C using the values stored in the storage device 34 for K and M. Through the processing of S34, the coefficient C becomes a value based on the height H1 obtained in S33. When the tool length compensation amount is not specified, the CPU 31 determines the coefficient C by setting the tool length compensation amount to 0.

The CPU 31 obtains the first position command from the block read in S11 (S35). The CPU 31 uses the coefficient C according to the mass M and height H obtained in S1 and the position of the first position command corresponding to the second position command of S31 to correct the X-axis direction position of the first table 13 indicated by the first position command in the same manner as in S16 (S36). The CPU 31 performs a positioning operation in accordance with the block read in S11 (S37). As in S17, the CPU 31 drives the X-axis motor 53 for the movement in the X-axis direction according to the first position command to move the first table 13 to the position x' corrected in S36. The CPU 31 drives the Y-axis motor 54 for the movement in the Y-axis direction, and drives the Z-axis motor 51 for the movement in the Z-axis direction to move the first table 13 and the tool 4 relatively. The CPU 31 stores the coefficient C updated in S34 in the storage device 34 (S42).

When the block read in S11 is a cutting command (S31: NO), the CPU 31 acquires the coefficient C from the storage device 34 (S38). When the block read in S11 has a first position command, the CPU 31 acquires the first position command (S39). The CPU 31 uses the coefficient C acquired from the storage device 34 in S38 and the position of the first position command acquired in S39 to correct the position of the first position command in the same manner as in S16 (S40). The CPU 31 performs a cutting operation according to the block read in S11 (S41). As in S17, the CPU 31 drives the X-axis motor 53 for movement in the X-axis direction to move the first table 13 to the position x' corrected in S40. The CPU 31 drives the Y-axis motor 54 for movement in the Y-axis direction and drives the Z-axis motor 51 for movement in the Z-axis direction to move the first table 13 and the tool 4 relatively. After S41 or S42, the CPU 31 returns the process to the main process of FIG. 8. After S21, the CPU 31 returns to S11.

When the read block is not an axis operation command (S13: NO), the CPU 31 judges whether the read block is a command specifying a tool length compensation amount (S22). When the read block is "G43 H01;", the CPU 31 judges that it is a command specifying a tool length compensation amount (S22: YES), and stores the tool length compensation amount corresponding to the tool length compensation number "01" specified by the block "G43 H01;" in the memory device 34 (S23). When the read block is not a command specifying a tool length compensation amount (S22: NO), the CPU 31 executes other processing corresponding to the control command indicated by the block, similar to S20 (S24). After S23 or S24, the CPU 31 returns the processing to S11.

Figure 10 shows the evaluation results of the second embodiment. The error measurement values under condition 4, where height H1 is 200 mm, are shown as white squares, and the error measurement values under condition 5, where height H1 is 300 mm, are shown as white circles. The error measurement values under condition 6, where height H1 is 400 mm, are shown as black circles. The masses M of the loads W are all 300 kg. The solid line 84 in Figure 10 (A) is the estimated error E(x) under condition 4, the dotted line 85 is the estimated error E(x) under condition 5, and the thick line 86 is the estimated error E(x) under condition 6. As shown in Figure 10 (A), when the position of the first position command is not corrected by the main processing, the larger the absolute value of the distance from the reference R, the larger the absolute value of the error in the position of the first platform 13 in the X-axis direction. As shown in FIG. 10B, when the position of the first position command is corrected using the coefficient C based on the mass M of the load W and the position of the first position command according to the main processing of the second embodiment, the absolute value of the position error in the X-axis direction of the first platform 13 is smaller than before correction. According to the main processing of the second embodiment, the absolute value of the position error in the X-axis direction of the first platform 13 is within 15 μm regardless of the distance from the reference R and the height H1.

11 , when the center of gravity of the load W is located away from the center of the first platform 13 in the first direction, the position of the first position command may be corrected using the centers of gravity of the load W and the first platform 13. The control device 30 of the modified example may use the estimated error E(x) calculated by equation (9) instead of equation (2) and perform S36 and S40 of the main processing of the second embodiment.
E(x)=C×(x-xc)
=K×M×H×(x-xc)...Formula (9)
xc is expressed by equation (10).
xc=M×xw/(Mt+M)...Formula (10)
Mt is the mass of the first platform 13 when unloaded, and xw is the distance between the center of gravity of the load W and the center of the first direction of the first platform 13. The method of acquiring xw may be set appropriately. When the worker operates the input unit 16 to input xw, the CPU 31 may acquire the input value as xw. The control device 30 may estimate xw based on an image captured of the load W placed on the first platform 13. The control device 30 of the modified example can correct the position of the first position command by taking into account the deviation of the center of gravity of the load W on the first platform 13.

Figure 12 shows the evaluation results of the modified example. In Figure 12 (A), the error measurement value under condition 7, where the mass M of the load W is 200 kg and the center of gravity of the load W is located 250 mm to the right of the center in the first direction of the first platform 13, is shown by a black circle. In Figure 12 (A), the estimated error E(x) using equation (2) is the straight line 87 shown by the dotted line, and the estimated error E(x) using equation (9) is the straight line 87 shown by the solid line. The error measurement value under condition 7 is 0 when the distance from the reference R is -150 mm. For the error measurement value under condition 7, the rate of change in error with respect to the distance from the reference R was greater under the condition where the distance was less than -150 mm from the reference R than under the condition where the distance was greater than -150 mm from the reference R. In Figure 12 (B), the error measurement value when the position of the first position command is corrected with the estimated error E(x) using equation (2) is shown by a white circle, and the error measurement value when the position of the first position command is corrected with the estimated error E(x) using equation (9) is shown by a black circle. As shown in Figure 12 (B), in the range of distances from the reference R from -150 mm to 100 mm, the error was smaller when the position of the first position command was corrected with the estimated error E(x) using equation (2) than when the position of the first position command was corrected with the estimated error E(x) using equation (2).

In the control device 30 of the first and second embodiments and modified examples, the first table 13, the second table 12, the X-axis motor 53, the base 2, the Y-axis motor 54, the machine tool 1, and the control device 30 are examples of the first table, the second table, the first drive unit, the table support unit, the second drive unit, the machine tool, and the control device of the present invention, respectively. The CPU 31 that performs S1 is an example of the mass acquisition unit, the mass acquisition process, and the mass acquisition step of the present invention. The CPU 31 that performs S15, S35, and S39 is an example of the first command acquisition unit, the command acquisition process, and the command acquisition step of the present invention. The CPU 31 that performs S16, S36, and S40 is an example of the correction unit, the correction process, and the correction step of the present invention. The tool 4, the spindle 9, the spindle head 7, the column 5, the Z-axis motor 51, and the storage device 34 are examples of the tool, the spindle, the spindle head, the head support unit, the third drive unit, and the storage device of the present invention, respectively. The CPU 31 that performs S32 is an example of the second command acquisition unit of the present invention. The CPU 31 that performs S33 is an example of the height acquisition unit of the present invention. The CPU 31 that performs S31 is an example of a type determination unit of the present invention. The CPU 31 that performs S42 is an example of a memory control unit of the present invention. The X-axis direction and the Y-axis direction are examples of a first direction and a second direction of the present invention, respectively.

The control device 30 controls the machine tool 1, which includes a first table 13, a second table 12, an X-axis motor 53, a base 2, and a Y-axis motor 54. The first table 13 carries a load W. The second table 12 supports the first table 13 so that it can move in a first direction parallel to the horizontal direction. The X-axis motor 53 moves the first table 13 in the first direction. The base 2 supports the second table 12 so that it can move in a second direction intersecting the first direction. The Y-axis motor 54 moves the second table 12 in the second direction. The CPU 31 acquires the mass M of the load W placed on the first table 13 (S1). The CPU 31 acquires a first position command that commands the position of the first table 13 in the first direction (S15; S35, S39). The CPU 31 uses the coefficient C based on the acquired mass M and the position of the first position command to correct the position of the first position command by an amount corresponding to the deflection of the base 2 due to the load W placed on the first platform 13 (S16; S36, S40). The control device 30 corrects the position of the first position command using the coefficient C based on the mass M of the load W and the position of the first position command, so that the positioning error in the first direction of the first platform 13 can be reduced more than before by taking into account the amount corresponding to the deflection of the base 2 due to the load W placed on the first platform 13.

The position of the first position command of the control device 30 is represented by the distance from the reference R, which is the position where the amount corresponding to the deflection of the base 2 due to the load W placed on the first platform 13 is the smallest. The position of the first position command of the control device 30 is more likely to represent a value corresponding to the deflection of the base 2 due to the load W placed on the first platform 13 than the position of the first position command when the reference is a position where the amount corresponding to the deflection of the base 2 is not the smallest. Therefore, the control device 30 can more easily calculate the amount corresponding to the deflection of the base 2 than when the reference is a position where the amount corresponding to the deflection of the base 2 is not the smallest.

The amount of deflection of the base 2 caused by the load W placed on the first platform 13 of the control device 30 is the product of the coefficient C and the distance. The control device 30 can easily calculate the amount of deflection of the base 2.

The coefficient C of the control device 30 is a value based on a constant specific to the machine tool 1. By setting the coefficient C used for correction to a value based on a constant specific to the machine tool 1, the control device 30 can correct the position of the first position command without measuring all individual machine tools 1.

The reference R of the control device 30 is the center of the movable range of the first table 13. The control device 30 can make the maximum value of the amount corresponding to the deflection of the base 2 smaller than when the reference R is at the end of the movable range of the first table 13.

The coefficient C of the control device 30 is based on a value corresponding to the height H2 of the load W from a predetermined position between the lower end of the base 2 and the upper surface 11 of the first table 13. The control device 30 can correct the position of the first position command taking into account the height H2 of the load W from the predetermined position.

The predetermined position of the control device 30 is a position where the error in the position of the first platform 13 in the first direction caused by the deflection of the base 2 due to the load W placed on the first platform 13 is minimized. The control device 30 can correct the position of the first position command so that the error caused by the deflection of the base 2 due to the load W placed on the first platform 13, which is in accordance with the height H1 of the load W from the predetermined position, is minimized.

The machine tool 1 of the control device 30 includes a spindle 9 on which the tool 4 is attached, a spindle head 7 that supports the spindle 9 and can move up and down, a column 5 that supports the spindle head 7 so that it can move in the vertical direction, and a Z-axis motor 51 that moves the spindle head 7 in the vertical direction. The CPU 31 acquires a second position command that commands the vertical position of the spindle head 7 (S35). The CPU 31 acquires the height H1 of the tip of the tool 4 from a predetermined position based on the tool length correction amount corresponding to the tool 4 attached to the spindle 9 and the second position command (S33). The value corresponding to the height H2 of the load W is the acquired height H1 of the tip of the tool 4 from a predetermined position. The control device 30 can correct the position of the first position command by taking into account the vertical position of the spindle head 7 indicated by the second position command by setting the coefficient C used for correction to a value based on the height H1 of the tip of the tool 4 from the predetermined position.

The CPU 31 of the control device 30 judges whether the second position command is a positioning command or a cutting command (S31). In response to judging that the second position command is a positioning command (S31: YES), the CPU 31 acquires the height H1 of the tip of the tool 4 from a predetermined position (S33). The CPU 31 updates the coefficient C using the acquired height of the tip of the tool 4 from a predetermined position (S34), and corrects the position of the first position command using the updated coefficient C and the position of the first position command corresponding to the second position command (S36). The control device 30 can correct the position of the first position command corresponding to the second position command by taking into account the vertical position of the spindle head 7 indicated by the second position command when the second position command is a positioning command. Therefore, the control device 30 can appropriately correct the position of the first position command even when the height H2 of the load W placed on the first table 13 from the predetermined position is relatively large.

The control device 30 includes a storage device 34, and stores the coefficient C updated in S34 in the storage device 34 (S42). In response to determining that the second position command is a cutting command (S31: NO), the CPU 31 corrects the position of the first position command using the coefficient C stored in the storage device 34 and the position of the first position command. The control device 30 can correct the position of the first position command so as to suppress adverse effects during cutting, such as making the size of the cutting portion larger than the size indicated by the first position command.

The CPU 31 of the control device 30 uses the coefficient C and the position of the first position command corrected using the center of gravity of the load W and the first platform 13 to correct the position of the first position command by an amount corresponding to the deflection of the base 2 due to the load W placed on the first platform 13 (S36, S40). The control device 30 can appropriately correct the position of the first position command by an amount corresponding to the deflection of the base 2 due to the load W placed on the first platform 13, taking into account the position of the load W in the first direction of the first platform 13.

The control device, control method, control program, and storage medium of the present invention can be modified in various ways in addition to the above-mentioned embodiments. The control device 30 may be a device separate from the machine tool 1. The tool 4, spindle 9, spindle head 7, column 5, Z-axis motor 51, and storage device 34 may be omitted or modified as appropriate. The machine tool 1 may be capable of mounting only one type of tool 4, and the tip height H1 of the tool 4 may be the same regardless of the type of tool 4. The first and second directions may be modified as appropriate, and the front-back direction (Y-axis direction) and the left-right direction (X-axis direction) may be the first and second directions. The first and second directions may be parallel to the horizontal direction and intersect with each other, and do not have to be perpendicular to each other.

The program for the control device 30 to perform control processing may be stored in the storage device 34 of the control device 30 before the CPU 31 executes the program. Therefore, the program acquisition method, acquisition path, and device that stores the program may each be changed as appropriate. The program executed by the CPU 31 may be received from another device via a cable or wireless communication and stored in a storage device such as a flash memory. The other device may include, for example, a PC and a server connected via a network.

A part or all of the processing performed by the control device 30 may be performed by an electronic device (e.g., an ASIC) other than the CPU 31. The processing performed by the control device 30 may be distributed among multiple electronic devices (e.g., multiple CPUs). The order of each step of the processing performed by the control device 30 may be changed, steps may be omitted, or steps may be added as necessary. The scope of the present invention also includes an embodiment in which an operating system (OS) running on the control device 30 performs a part or all of each process at the command of the CPU 31. For example, the following modifications may be made to the above embodiment as appropriate.

The position of the reference R may be changed as appropriate. The calculation formula for the amount corresponding to the deflection of the base 2 may be changed as appropriate. The method of setting the coefficient C may be changed as appropriate, and the coefficient C may not be a value corresponding to a constant specific to the machine tool 1. The predetermined position may be the position of the upper surface 11 of the first table 13, and the value corresponding to the height of the load W from the predetermined position may be the height of the tip of the tool 4 from the upper surface 11 of the first table 13, or the height of the load W from the upper surface 11 of the first table 13. The axis operation command may include other control commands such as a fast-forward command. At this time, the CPU 31 may determine whether the axis operation command is a cutting command separately from S31. When the axis operation command is a cutting command, the CPU 31 may obtain the height H2 of the tip of the tool 4 from the predetermined position, and correct the position of the first position command using the coefficient C updated according to the height H2. When the center of gravity of the load W is located away from the center of the first platform 13 in the first direction, the control device 30 may use the coefficient C and the position of the first position command corrected using the center of gravity of the load W and the first platform 13, and correct the position of the first position command by an amount corresponding to the deflection of the base 2 due to the load W placed on the first platform 13, provided that the position of the first position command is within a predetermined range. The above modified examples may be combined within a range that does not cause inconsistencies.

1: Machine tool 2: Base 4: Tool 5: Column 7: Spindle head 9: Spindle 12: Second table 13: First table 30: Control device 31: CPU
34: Storage device 51: Z-axis motor 53: X-axis motor 54: Y-axis motor

Claims (12)

A control device for controlling a machine tool including a first table on which a load is placed, a second table supporting the first table so as to be movable in a first direction parallel to a horizontal direction, a first drive unit for moving the first table in the first direction, a table support unit supporting the second table so as to be movable in a second direction intersecting the first direction, and a second drive unit for moving the second table in the second direction,
a mass acquisition unit that acquires a mass of the load placed on the first platform;
a first command acquisition unit that acquires a first position command that commands a position of the first unit in the first direction;
a correction unit that uses the mass acquired by the mass acquisition unit and a coefficient based on a constant specific to the machine tool , and the position of the first position command to obtain an estimate of an error in the first direction of the position of the first position command caused by bending of the table support unit, and corrects the position of the first position command by subtracting the estimate from the position of the first position command ,
A control device, wherein the position of the first position command is expressed as a distance from a reference, which is a position where the estimated value is minimum . 2. The control device according to claim 1 , wherein the estimate is a product of the coefficient and the distance. 3. The control device according to claim 1 , wherein the reference is the center of a movable range of the first unit. The control device according to any one of claims 1 to 3 , characterized in that the coefficient is based on a value corresponding to the height of the load from a predetermined position between the lower end of the platform support portion and the upper surface of the first platform. The control device described in claim 4, characterized in that the specified position is a position obtained by applying the least squares method so as to minimize the difference between the measured value of the position error in the first direction of the first table due to the deflection of the table support part by the load placed on the first table and the estimated value when correcting the position of the first position command . The machine tool includes a spindle on which a tool is attached, a spindle head supporting the spindle and movable up and down, a head support unit supporting the spindle head so as to be movable in the up and down direction, and a third drive unit moving the spindle head in the up and down direction,
a second command acquisition unit that acquires a second position command that commands a position of the spindle head in the vertical direction;
a height acquisition unit that acquires a height of a tip end of the tool from the predetermined position based on a tool length correction amount corresponding to the tool attached to the spindle and the second position command,
6. The control device according to claim 4 , wherein the value according to the height of the loaded object is a height of the tip of the tool from the predetermined position acquired by the height acquisition unit. A type determination unit that determines whether the second position command is a positioning command or a cutting command,
the height acquisition unit acquires a height of the tip of the tool from the predetermined position in response to a determination by the type determination unit that the second position command is the positioning command,
The correction unit is
updating the coefficient using the height of the tip of the tool from the predetermined position acquired by the height acquisition unit;
correcting the position of the first position command using the updated coefficient and the position of the first position command;
7. The control device according to claim 6 . A storage device;
a storage control unit that stores the coefficient updated by the correction unit in the storage device,
The control device according to claim 7, characterized in that, in response to the type determination unit determining that the second position command is the cutting command, the correction unit corrects the position of the first position command by using the coefficient stored in the memory device and the position of the first position command. The control device according to any one of claims 1 to 8, characterized in that the correction unit uses the coefficient and the position of the first position command corrected using the center of gravity of the load and the first unit to obtain the estimated value , and corrects the position of the first position command by subtracting the estimated value from the position of the first position command. A method for controlling a machine tool including a first table on which a load is placed, a second table supporting the first table so as to be movable in a first direction parallel to a horizontal direction, a first drive unit which moves the first table in the first direction, a table support unit which supports the second table so as to be movable in a second direction intersecting the first direction, and a second drive unit which moves the second table in the second direction, comprising:
a mass acquisition step of acquiring a mass of the load placed on the first platform;
a command acquisition step of acquiring a position command for instructing a position of the first unit in the first direction;
a correction step of calculating an estimate of an error in the position of the position command in the first direction caused by bending of the platform support part by using the mass acquired in the mass acquisition step, a coefficient based on a constant specific to the machine tool, and the position of the position command, and correcting the position of the position command by subtracting the estimate from the position of the position command ,
A control method, wherein the position of the position command is expressed as a distance from a reference, which is a position where the estimated value is minimum . A control program executable by a control unit of a control device for controlling a machine tool including a first table on which a load is placed, a second table supporting the first table so as to be movable in a first direction parallel to a horizontal direction, a first drive unit for moving the first table in the first direction, a table support unit supporting the second table so as to be movable in a second direction intersecting the first direction, and a second drive unit for moving the second table in the second direction,
a mass acquisition process for acquiring a mass of the load placed on the first platform;
a command acquisition process for acquiring a position command for instructing a position of the first device in the first direction;
a correction process for calculating an estimated value of an error in the position of the position command in the first direction caused by bending of the platform support part by using the mass acquired in the mass acquisition process and a coefficient based on a constant specific to the machine tool, and the position of the position command, and correcting the position of the position command by subtracting the estimated value from the position of the position command ,
A control program, wherein the position of the position command is expressed as a distance from a reference, which is a position where the estimated value is minimum . A storage medium storing a control program executable by a control unit of a control device for controlling a machine tool including a first table on which a load is placed, a second table supporting the first table so as to be movable in a first direction parallel to a horizontal direction, a first drive unit moving the first table in the first direction, a table support unit supporting the second table so as to be movable in a second direction intersecting the first direction, and a second drive unit moving the second table in the second direction,
a mass acquisition process for acquiring a mass of the load placed on the first platform;
a command acquisition process for acquiring a position command for instructing a position of the first device in the first direction;
a correction process for correcting the position of the position command by using the mass acquired in the mass acquisition process and a coefficient based on a constant specific to the machine tool , and the position of the position command, to obtain an estimated value of an error in the position of the position command in the first direction caused by bending of the platform support part, and subtracting the estimated value from the position of the position command;
A storage medium , wherein the position of the position command is represented by a distance from a reference, which is a position where the estimated value is minimum .

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