Numerical Control Device

Abstract

Provided is a numerical control device capable of reducing a cycle time by performing positioning while performing a positioning error elimination operation more appropriately. A numerical control device 1 provided with: a final positioning command determination unit 14 which, when block analysis is performed on a positioning command block including a positioning error elimination operation, reads the machining program in advance and thereby determines the final positioning command that should complete the positioning by finally eliminating the positioning error; a post-positioning movement direction determination unit 15 which determines the direction of movement indicated by the command following the final positioning command; and a positioning error elimination operation determination unit 16 which, on the basis of the results of the determination by the final positioning command determination unit 14 and the post-positioning movement direction determination unit 15, determines the axis on which a positioning error elimination operation should be performed, and determines an operation for eliminating the positioning error on the determined axis on which a positioning error elimination operation should be performed.

Description

[Technical field]

[0001] The present disclosure relates to a numerical control device. [Background technology]

[0002] Conventionally, numerical control devices capable of shortening cycle time by performing positioning at optimal timing have been proposed (see, for example, Patent Documents 1 and 2).

[0003] Incidentally, a function for final positioning from one direction is known to eliminate positioning errors in the reverse direction caused by, for example, backlash of a ball screw and perform positioning precisely. In this one-way positioning, positioning is performed only from one direction that has been set in advance. For example, when moving from the opposite direction to the set one direction, the robot passes the end point once, reverses direction, and moves toward the end point to perform positioning. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-210563 A [Patent Document 2] JP 2009-282829 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in reality, there are many cases where one-way positioning is not required. In such cases, if one-way positioning is set as a modal command, one-way positioning will be performed even though it is not required, which will lengthen the cycle time.

[0006] Furthermore, in the past, sufficient consideration was not given to the start timing of one-way positioning, and depending on the start timing, this could result in a longer cycle time.

[0007] Therefore, there is a demand for technology that can reduce cycle time by more appropriately performing a positioning error eliminating operation such as one-way positioning.

[0008] An object of the present disclosure is to provide a numerical control device capable of shortening cycle time by performing positioning while more appropriately eliminating positioning errors. [Means for solving the problem]

[0009] One aspect of the present disclosure is a numerical control device that drives axes of a machine tool based on a machining program to machine a workpiece, the numerical control device comprising: a final positioning command determination unit that determines a final positioning command that should ultimately eliminate the positioning error and complete positioning by reading ahead through the machining program during block analysis of a positioning command block with a positioning error eliminating operation; a post-positioning movement direction determination unit that determines the movement direction by a command after the final positioning command; and a positioning error eliminating operation determination unit that determines an axis on which a positioning error eliminating operation should be performed based on determination results of the final positioning command determination unit and the post-positioning movement direction determination unit, and determines an operation to eliminate the positioning error on the determined axis on which the positioning error eliminating operation should be performed.

[0010] Another aspect of the present disclosure is a numerical control device that drives an axis of a machine tool based on a machining program to machine a workpiece, the numerical control device comprising: a final positioning command determination unit that determines a final positioning command that should ultimately eliminate the positioning error and complete positioning by reading ahead the machining program during block analysis of a positioning command block with a positioning error eliminating operation; and a positioning error eliminating operation determination unit that determines a timing at which the positioning error eliminating operation can be started based on a determination result of the final positioning command determination unit, and determines an operation to eliminate the positioning error after the determined timing. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide a numerical control device that can reduce cycle time by performing positioning while more appropriately eliminating positioning errors. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram showing a configuration of a numerical control device according to an embodiment of the present disclosure. FIG. [Diagram 2] FIG. 1 is a diagram showing an example of a command path of a conventional numerical control program. [Diagram 3] FIG. 2 is a diagram illustrating an example of a command path of a numerical control program according to an embodiment of the present disclosure. [Figure 4] 4 is a flowchart showing a processing procedure of a numerical control device according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0014] The numerical control device 1 according to this embodiment drives the axis of a machine tool based on a machining program to machine a workpiece. The numerical control device 1 according to this embodiment also has a positioning function with a positioning error canceling operation for performing precise positioning by canceling positioning errors in the reverse direction caused by, for example, backlash of a ball screw. As a result, the numerical control device 1 according to this embodiment is a numerical control device that can shorten the cycle time by performing positioning while performing the minimum necessary positioning error canceling operation.

[0015] 1 is a block diagram showing the configuration of a numerical control device 1 according to an embodiment of the present disclosure. The numerical control device 1 according to this embodiment has a hardware configuration including a CPU, a ROM, a RAM, a non-volatile memory, a bus, an axis control circuit, a servo amplifier, an interface, and the like, none of which are shown in the drawings. In addition, a servo motor, an input / output device, and the like, none of which are shown in the drawings, are connected to the numerical control device 1 according to this embodiment.

[0016] As shown in FIG. 1, a numerical control device 1 according to this embodiment includes a program prefetching unit 11, a program analysis unit 12, and a distribution processing unit .

[0017] In addition, the program analysis unit 12 of this embodiment includes a positioning determination unit 13 with positioning error eliminating operation, a final positioning command determination unit 14, a post-positioning movement direction determination unit 15, a positioning error eliminating operation decision unit 16, and a positioning error eliminating operation command generation unit 17.

[0018] Prior to actual machining by executing the machining program, the program pre-reading unit 11 pre-reads the machining program block by block. The pre-read machining program is analyzed by a program analysis unit 12, which will be described later, and the machining path of the workpiece is analyzed.

[0019] The program pre-fetching unit 11 of this embodiment starts pre-fetching the machining program when the program analysis unit 12 reads in one block at a time and the block is determined to be a positioning block with positioning error eliminating operation by the positioning determination unit with positioning error eliminating operation 13 described below. Moreover, the program pre-fetching unit 11 of this embodiment ends pre-fetching the machining program after the positioning error eliminating operation command generation unit 17 described below generates a positioning error eliminating operation command.

[0020] The positioning error eliminating operation-equipped positioning determination unit 13 determines whether or not a block is a positioning block with a positioning error eliminating operation when the program analysis unit 12 reads in the block one by one. Specifically, it determines whether or not the block is a one-way positioning operation command block defined by the G code (G60).

[0021] When program analysis unit 12 performs block analysis of a positioning command block with a positioning error eliminating operation, final positioning command determination unit 14 determines a final positioning command that should ultimately eliminate the positioning error and complete positioning by pre-reading the machining program using above-mentioned program pre-read unit 11. Specifically, when there are consecutive positioning blocks, final positioning command determination unit 14 determines the final positioning command block of the consecutive positioning blocks as the final positioning command that should ultimately eliminate the positioning error and complete positioning.

[0022] The post-positioning movement direction determination unit 15 determines the movement direction in accordance with a command after the final positioning command determined by the above-mentioned final positioning command determination unit 14. Specifically, the post-positioning movement direction determination unit 15 determines the movement direction in a machining operation command such as a linear interpolation operation command after the final positioning command.

[0023] The positioning error eliminating operation determination unit 16 determines the axis for which the positioning error eliminating operation should be performed based on the determination results of the above-mentioned final positioning command determination unit 14 and post-positioning movement direction determination unit 15. Specifically, the positioning error eliminating operation determination unit 16 determines the axis for which the positioning error eliminating operation should be performed based on the final positioning command that should finally eliminate the positioning error among the consecutive positioning blocks and complete positioning, and the movement direction of the command after the final positioning command.

[0024] For example, the positioning error eliminating operation determination unit 16 may determine an axis that has completed its axial movement as the axis on which the positioning error eliminating operation should be performed. More specifically, the positioning error eliminating operation determination unit 16 may determine an axis that is not in the subsequent moving direction but has been moved in the positioning operation up to that point and has completed its axial movement as the axis on which the positioning error eliminating operation should be performed.

[0025] Furthermore, the positioning error eliminating operation determination unit 16 determines the operation to eliminate the positioning error on the axis for which the determined positioning error eliminating operation should be performed. Specifically, for the positioning error eliminating operation such as the one-way positioning operation defined by G60, various parameters such as the axis to be operated, the direction, the pullback amount, etc. are set, and the positioning error eliminating operation determination unit 16 determines the operation to eliminate the positioning error based on, for example, these parameter settings.

[0026] The positioning error eliminating operation determination unit 16 may determine the timing to start the positioning error eliminating operation for the axis on which the positioning error eliminating operation should be performed, and determine the operation to eliminate the positioning error for the axis on which the positioning error eliminating operation should be performed after the determined timing. This makes it possible to execute the positioning error eliminating operation at an optimal timing.

[0027] Specifically, the positioning error eliminating operation determination unit 16 starts the positioning error eliminating operation so that the positioning error eliminating operation is completed before the command after the final positioning command is completed. Alternatively, the positioning error eliminating operation determination unit 16 may start the positioning error eliminating operation on the axis for which the positioning error eliminating operation should be performed simultaneously with the start of movement of the next positioning block in the successive positioning blocks.

[0028] The positioning error eliminating operation command generator 17 generates a positioning error eliminating operation command based on the positioning error eliminating operation determined by the above-mentioned positioning error eliminating operation determiner 16. The generated positioning error eliminating operation command is output to a distribution processor 18, which will be described later.

[0029] The distribution processing unit 18 generates an interpolation move command based on the machining program command. The distribution processing unit 18 also generates a distribution command for distributing the generated interpolation move command and the positioning error eliminating operation command generated by the above-mentioned positioning error eliminating operation command generating unit 17 to each drive axis. The generated distribution command is output by a move command output unit (not shown).

[0030] Next, the positioning function with positioning error eliminating operation of the numerical control device 1 according to this embodiment will be described in detail.

[0031] The numerical control device 1 according to this embodiment has a positioning function with a positioning error canceling operation for performing precise positioning by canceling a positioning error in a reverse direction caused by, for example, backlash of a ball screw. An example of a positioning operation with a positioning error canceling operation is a one-way positioning operation that finally performs positioning from one direction.

[0032] In the one-way positioning operation, the positioning operation is performed only from one preset direction. For example, when moving from the opposite direction to the preset one direction, the robot passes the end point once, reverses direction, and moves toward the end point to perform positioning.

[0033] The one-way positioning operation is specified by the G code (G60) in the machining program. This one-way positioning operation can be selected as one-shot or modal by parameter setting. In addition, the axis for one-way positioning, the direction of one-way positioning, the amount of pullback (overrun stroke) when reversing, etc. are also set in advance by parameters.

[0034] Here, Fig. 2 is a diagram showing an example of a command path of a conventional numerical control program. Fig. 2 shows a command path on the XZ plane. In Fig. 2, each block of sequence numbers N01, N02, N06, N07, and N08 indicated by dashed arrows represents a positioning (fast forward) operation and is defined by the G code (G00). In Fig. 2, each block of sequence numbers N03, N04, N05, and N09 indicated by solid arrows represents a linear interpolation operation for machining a workpiece and is defined by the G code (G01).

[0035] In the example shown in Fig. 2, the parameters of the one-way positioning operation are set so that the positioning is performed relative to the X axis in a direction from right to left in Fig. 2. Also, in the example shown in Fig. 2, the parameters of the one-way positioning operation are set so that the positioning is performed relative to the Z axis in a direction from bottom to top in Fig. 2. Therefore, for example, at the end of block N08 shown in an enlarged view in Fig. 2, the object is pulled back in the X axis direction by a pullback amount in the X axis direction preset by the parameters, and then pulled back in the Z axis direction by a pullback amount in the Z axis direction also preset by the parameters, thereby being positioned at the G00 end point.

[0036] However, as described above, there are many cases in which unidirectional positioning is unnecessary in actual machining operations. In such cases, if unidirectional positioning is set as a modal command, the unidirectional positioning will be performed even though it is not necessary, which will lengthen the cycle time.

[0037] Specifically, there is no need to execute a unidirectional positioning operation at the end position of the positioning operation in G00, i.e., at the end point of G00 which does not affect positioning at the start position of the linear interpolation operation in the next G01. In the example shown in Fig. 2, this corresponds to the end of block N07. That is, as shown in Fig. 2, a unidirectional positioning operation is executed for the X-axis at the end of block N07, but there is further movement in the X-axis direction in the next block N08, and since the end of block N07 does not affect positioning at the start position of block N09, which is the start position of the linear interpolation operation in the next G01, it can be seen that there is no need to execute a unidirectional positioning operation for the X-axis at the end of block N07.

[0038] Furthermore, after the positioning operation in G00 is completed, there is no need to execute a unidirectional positioning operation for the axis that moves in the next block. In the example shown in Fig. 2, this applies to the end of block N02 and the end of block N08. That is, as shown in Fig. 2, the axis that moves in block N03, which is the block next to block N02, is the Z-axis, so there is no need to execute a unidirectional positioning operation for the Z-axis at the end of block N02. Similarly, the axis that moves in block N09, which is the block next to block N08, is the Z-axis, so there is no need to execute a unidirectional positioning operation for the Z-axis at the end of block N08.

[0039] Also, it is not necessary to execute a one-way positioning operation at the end of each block in the positioning operation of G00. In the example shown in Fig. 2, this corresponds to the end of block N01. That is, as shown in Fig. 2, a one-way positioning operation is executed for the X-axis at the end of block N01, but from the viewpoint of shortening the cycle time, it is sufficient to execute the X-axis positioning operation during the movement in the Z-axis direction (the direction from top to bottom in Fig. 2) of the next block, block N02, and it is not necessary to start the movement of N02 after completing the one-way positioning operation at the end of block N01.

[0040] As described above, since one-way positioning is often not required in actual machining operations, it is desirable to issue a one-way positioning command only for blocks that require a minimum of one-way positioning. However, even if a one-way positioning command is issued only for blocks that require a minimum of one-way positioning, there is still room for improvement in terms of shortening the cycle time, as described above. Also, creating a program taking into account the locations where one-way positioning is required is not easy and is troublesome.

[0041] In contrast, the numerical control device 1 according to this embodiment automatically determines the axis for which a positioning error eliminating operation such as a one-way positioning operation should be performed. Also, the numerical control device 1 according to this embodiment automatically determines the timing for starting the positioning error eliminating operation for the axis for which a positioning error eliminating operation should be performed. As a result, according to this embodiment, the minimum required one-way positioning can be performed at the optimal timing.

[0042] Here, FIG. 3 is a diagram showing an example of a command path of the numerical control program according to this embodiment. As in FIG. 2, FIG. 3 shows a command path on the XZ plane. Also, in FIG. 3, each block of sequence numbers N01, N02, N06, N07, and N08 shown by dashed arrows represents a positioning (fast forward) operation, and is specified by the G code (G00). Similarly, in FIG. 3, each block of sequence numbers N03, N04, N05, and N09 shown by solid arrows represents a linear interpolation operation for machining, and is specified by the G code (G01). The command paths of each block shown in FIG. 3 are the same as those in FIG. 2, except for the positioning error cancellation operation command.

[0043] As described above in the description of FIG. 2, after the end of the N01 block, only the X-axis is required to perform a unidirectional positioning operation. This is because the operation of the X-axis in the positioning block ends in the N01 block, and the operation of the Z-axis is executed in the next N02 block. However, as described above, it is not necessary to execute a unidirectional positioning operation at the end of the N01 block. In contrast, in the numerical control device 1 according to this embodiment, after the operation of the N01 block is completed, it is determined that a unidirectional positioning operation can be executed for the X-axis. After the determination, a positioning error eliminating operation command is generated, and the generated positioning error eliminating operation command is superimposed on the operation command of the N02 block. As a result, as shown by the dashed arrow in FIG. 3, instead of executing the positioning operation of the X-axis at the end of the N01 block as in the conventional case, the positioning operation of the X-axis is executed during the movement in the Z-axis direction (the direction from top to bottom in FIG. 3) in the N02 block. That is, since the movement in the Z-axis direction (the direction from top to bottom in FIG. 3) is performed while performing the positioning operation of the X-axis, the cycle time is shortened compared to the conventional case.

[0044] 2, in block N03, which is G01 after final positioning, the operation is movement in the Z-axis direction, and since the positioning operations up to that point have involved movement along the X-axis and Z-axis, no unidirectional positioning operation is required for the Z-axis at the end of block N02. In contrast, in the numerical control device 1 according to this embodiment, after the operation of block N02 is completed, it is not determined that a unidirectional positioning operation needs to be performed, and no unidirectional positioning operation is performed, thereby shortening the cycle time compared to the conventional method.

[0045] 2, the end of block N07 is further moved in the X-axis and Z-axis directions in the next block N08, and does not affect positioning at the start position of block N09, which is the start position of the linear interpolation operation of the next G01, so no unidirectional positioning operation is necessary at the end of block N07. In contrast, in the numerical control device 1 according to this embodiment, after the operation of block N07 is completed, it is not determined that a unidirectional positioning operation can be performed and no unidirectional positioning operation is performed, thereby reducing the cycle time compared to the conventional method.

[0046] As described above in the explanation of FIG. 2, at the end of block N08, only the X-axis requires a unidirectional positioning operation. This is because the operation of the X-axis in the positioning block ends in block N08, and the axis that moves in the next block, block N09, is the Z-axis. In contrast, in the numerical control device 1 according to this embodiment, after the operation of block N08 is completed, it is determined that a unidirectional positioning operation can be performed for the X-axis. After this determination, a positioning error eliminating operation command is generated, and in accordance with the generated positioning error eliminating operation command, the positioning error eliminating operation is performed after the operation of block N08 is completed, as shown by the dashed arrow in FIG. 3. This allows the minimum necessary unidirectional positioning operation to be performed for the X-axis, and the cycle time is shortened compared to the conventional method.

[0047] Next, a process procedure of the numerical control device 1 according to this embodiment will be described. Fig. 4 is a flowchart showing the process procedure of the numerical control device 1 according to this embodiment. This process is repeatedly executed at a predetermined cycle when the numerical control device 1 analyzes a machining program.

[0048] In step S1, the program analysis unit 12 sets a positioning error eliminating operation completion flag to True. Then, the program proceeds to step S2. The positioning error eliminating operation completion flag is set for each axis.

[0049] In step S2, one of the command blocks of the machining program is read by the program analysis unit 12. After that, the process proceeds to step S3.

[0050] In step S3, the positioning error eliminating operation-equipped positioning determination unit 13 determines whether the one block read in step S2 is a positioning error eliminating operation-equipped positioning block. For example, it determines whether the one block read in step S2 is a one-way positioning operation command block defined by the G code (G60). If this determination is YES, the process proceeds to step S4, and if NO, the process proceeds to step S13.

[0051] In step S4, it is determined whether or not the positioning error eliminating operation completion flag is True by the program analysis unit 12. If this determination is YES, the process proceeds to step S5, and if this determination is NO, the process proceeds to step S13.

[0052] In step S5, pre-reading of the machining program is started by the program pre-reading unit 11. After that, the process proceeds to step S6.

[0053] In step S6, the final positioning command determination unit 14 determines the command that should eliminate the positioning error and complete the positioning. Specifically, when the positioning blocks are consecutive, the final positioning command determination unit 14 determines the final positioning command block among the consecutive positioning blocks as the final positioning command that should finally eliminate the positioning error and complete the positioning. Then, the process proceeds to step S7.

[0054] In step S7, the post-positioning movement direction determination unit 15 determines the movement direction in accordance with the command after the final positioning command. Specifically, the post-positioning movement direction determination unit 15 determines the movement direction in the machining operation command, such as the linear interpolation operation command, after the final positioning command. Then, the process proceeds to step S8.

[0055] In step S8, the axis for which the positioning error eliminating operation should be performed is determined by the positioning error eliminating operation determination unit 16. Specifically, the positioning error eliminating operation determination unit 16 determines the axis for which the positioning error eliminating operation should be performed based on a final positioning command for finally eliminating the positioning error in the consecutive positioning blocks and completing positioning, the axis that moves to the final positioning command, and the moving direction of the command after the final positioning command. Then, the process proceeds to step S9.

[0056] In step S9, the timing at which the positioning error eliminating operation can be started for each axis for which the positioning error eliminating operation should be performed is determined by the positioning error eliminating operation decision unit 16. Then, the process proceeds to step S10.

[0057] In step S10, a positioning error eliminating operation command is generated by positioning error eliminating operation command generator 17. Specifically, the positioning error eliminating operation command is generated based on the positioning error eliminating operation determined by positioning error eliminating operation determiner 16. Then, the process proceeds to step S11.

[0058] In step S11, the program analysis unit 12 sets a positioning error eliminating operation completion flag to False. More specifically, the program analysis unit 12 sets a positioning error eliminating operation completion flag to False for the axis determined in step S8 as the axis for which the positioning error eliminating operation should be performed. Then, the program proceeds to step S12.

[0059] In step S12, the pre-reading of the machining program by the program pre-reading unit 11 is completed. After that, the process proceeds to step S13.

[0060] In step S13, the program analysis unit 12 executes normal analysis processing of the command block, and then the process proceeds to step S14.

[0061] In step S14, the program analysis unit 12 determines whether or not the positioning error eliminating operation is completed. If the determination is YES, the process proceeds to step S15, and if the determination is NO, the process proceeds to step S16.

[0062] In step S15, the program analysis unit 12 sets a positioning error eliminating operation completion flag to True. More specifically, the program analysis unit 12 sets a positioning error eliminating operation completion flag to True for the axis for which it is determined in step S14 that the positioning error eliminating operation has been completed. Then, the program proceeds to step S16.

[0063] In step S16, the distribution processing unit 18 executes the distribution processing. Specifically, the distribution processing unit 18 generates a distribution command for distributing the interpolation movement command generated from the machining program and the positioning error eliminating operation command generated in step S10 to each drive axis. Then, the process returns to step S2.

[0064] The numerical control device 1 according to this embodiment provides the following effects.

[0065] (1) The numerical control device 1 according to this embodiment is equipped with a final positioning command determination unit 14 which determines a final positioning command that should ultimately eliminate the positioning error and complete positioning by reading ahead the machining program during block analysis of a positioning command block with a positioning error eliminating operation, a post-positioning move direction determination unit 15 which determines the move direction due to a command after the final positioning command, and a positioning error eliminating operation decision unit 16 which determines an axis for which a positioning error eliminating operation should be performed based on the determination results of the final positioning command determination unit 14 and the post-positioning move direction determination unit 15, and decides an operation to eliminate the positioning error on the axis for which the determined positioning error eliminating operation should be performed.

[0066] This allows the minimum necessary unidirectional positioning to be performed, and the cycle time can be shortened compared to conventional operations. In addition, while it is troublesome to create a program while considering the locations where unidirectional positioning is required, the numerical control device 1 according to this embodiment can automatically determine the axis that should be subjected to the positioning error cancellation operation, making it easier to create a program.

[0067] (2) Furthermore, the positioning error eliminating operation determination unit 16 of the numerical control device 1 according to this embodiment determines the timing to start the positioning error eliminating operation for an axis that should perform the positioning error eliminating operation, and determines the operation to eliminate the positioning error for the axis that should perform the positioning error eliminating operation after the determined timing. This makes it possible to execute the positioning error eliminating operation at an optimal timing, in addition to the effect of (1) above.

[0068] (3) Furthermore, the positioning error eliminating operation determination unit 16 of the numerical control device 1 according to this embodiment determines that an axis that has completed its axial movement is an axis for which a positioning error eliminating operation should be performed, thereby more reliably achieving the effects of (1) and (2) described above.

[0069] The present disclosure is not limited to the above-described embodiment, and various modifications and variations are possible.

[0070] For example, in the above embodiment, the one-way positioning operation has been described as an example of the positioning error eliminating operation, but the present invention is not limited to this and can be applied to other positioning error eliminating operations besides the one-way positioning operation.

[0071] As another embodiment in which only the configuration of the positioning error eliminating operation determiner is changed from the above embodiment, a configuration may be adopted in which the timing at which the positioning error eliminating operation can be started is determined without determining which axis should undergo the positioning error eliminating operation. In this case, the positioning error eliminating operation determiner determines the timing at which the positioning error eliminating operation can be started based on the determination result of the final positioning command determiner, and determines the operation to eliminate the positioning error after the determined timing. This allows the positioning error eliminating operation to be performed at the optimal timing, thereby shortening the cycle time. [Explanation of symbols]

[0072] 1 Numerical control device 11 Program look-ahead section 12 Program Analysis Section 13 Positioning judgment unit with positioning error cancellation operation 14 Final positioning command judgement unit 15 Post-positioning movement direction determination section 16 Positioning error elimination action decision unit 17 Positioning error elimination operation command generation unit 18 Distribution processing section

Claims

1. A numerical control device that drives an axis of a machine tool based on a machining program to machine a workpiece, a final positioning command determination unit which determines a final positioning command for finally completing positioning by eliminating the positioning error by reading ahead the machining program during block analysis of a positioning command block with a positioning error eliminating operation, the positioning command block being a one-way positioning operation for performing positioning only from one preset direction; a post-positioning movement direction determination unit that determines a movement direction according to a command after the final positioning command; a positioning error eliminating operation determination unit that determines an axis for which the positioning error eliminating operation should be performed based on determination results of the final positioning command determination unit and the post-positioning movement direction determination unit, and determines an operation to eliminate the positioning error by the one-directional positioning operation on the determined axis for which the positioning error eliminating operation should be performed.

2. 2. The numerical control device according to claim 1, wherein the positioning error eliminating operation determination unit determines a timing at which the positioning error eliminating operation can be started for an axis for which the positioning error eliminating operation should be performed, and determines an operation to eliminate the positioning error for the axis for which the positioning error eliminating operation should be performed after the determined timing.

3. 3. The numerical control device according to claim 1, wherein the positioning error eliminating operation determination unit determines an axis that has completed its axial movement as an axis for which the positioning error eliminating operation should be performed.

4. A numerical control device that drives an axis of a machine tool based on a machining program to machine a workpiece, a final positioning command determination unit which determines a final positioning command for finally completing positioning by eliminating the positioning error by reading ahead the machining program during block analysis of a positioning command block with a positioning error eliminating operation, the positioning command block being a one-way positioning operation for performing positioning only from one preset direction; a positioning error eliminating operation determination unit that determines a timing at which the positioning error eliminating operation can be started based on a determination result of the final positioning command determination unit, and determines an operation to eliminate the positioning error by the one-directional positioning operation after the determined timing.

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