WO2017221380A1

WO2017221380A1 - Numerical control device

Info

Publication number: WO2017221380A1
Application number: PCT/JP2016/068692
Authority: WO
Inventors: 駿萱島
Original assignee: 三菱電機株式会社
Priority date: 2016-06-23
Filing date: 2016-06-23
Publication date: 2017-12-28
Also published as: JP6147456B1; JPWO2017221380A1; CN107771305B; CN107771305A

Abstract

A numerical control device (100) for numerically controlling a machine tool (200), characterized in being provided with a lost motion correction unit (100-2) for: reading blocks constituting a machining program (1) in advance; estimating, on the basis of a command in a block read in advance, a first inversion position of the direction of movement of a feed shaft of the machine tool (200) and a second inversion position, which is an inversion position that comes after the first inversion position; and estimating the inter-inversion position distance between the first inversion position and the second inversion position and thereby determining whether or not lost motion correction is necessary.

Description

Numerical controller

The present invention relates to a numerical control device that numerically controls a machine tool.

There is a lost motion correction function as a function to improve the accuracy of the machined surface of the workpiece that is the workpiece. The lost motion refers to a response delay caused by friction, twisting, and backlash that occurs when the moving direction of the feed shaft provided in the machine tool is reversed. Lost motion correction function reduces the amount of uncut or overcutting caused by lost motion by giving the previously calculated lost motion correction amount to the axis movement direction after reversal when the feed axis movement direction is reversed. It is a function. Hereinafter, the “uncut material” described above is referred to as a “quadrant projection”. On the other hand, when a machining program is automatically generated by a CAM (Computer Aided Manufacturing) device in order to machine a complicated shape on a workpiece typified by a mold, a minute reversing operation of about 1 μm is performed in the machining program. There are many descriptions to be made. In conventional numerical control devices, lost motion correction is performed at all positions where the axis movement direction is reversed, regardless of the distance between the reverse positions from the position where the movement direction of the feed axis was reversed last time to the position where it was reversed this time. For this reason, there is a problem in that the uncut or excessive cutting becomes excessive and the machined surface accuracy is lowered.

With respect to such a problem, Patent Document 1 discloses that when the distance between the reversing positions from the position where the moving direction of the feed axis is reversed last time to the position where it is reversed this time is smaller than a preset value, A method has been proposed in which the lost motion correction amount is automatically adjusted according to the number of times of minute inversion.

JP 2009-301081 A

However, Patent Document 1 uses the reverse position measured in the past, that is, the distance between the reverse positions from the position where the moving direction of the feed axis was previously reversed to the position where the current position was reversed. The distance between the reversal positions from the position to the next reversal position cannot be obtained, and it is not possible to prevent a reduction in processing surface accuracy due to overcorrection of lost motion correction for minute reversal.

The present invention has been made in view of the above, and an object of the present invention is to obtain a numerical control device capable of improving machining surface accuracy.

In order to solve the above-described problems and achieve the object, a numerical control device of the present invention is a numerical control device for numerically controlling a machine tool, and pre-reads blocks constituting a machining program, By estimating the distance between the reverse positions between the first reverse position in the moving direction of the feed axis of the machine tool and the second reverse position, which is the reverse position after the first reverse position, based on the command Judge whether the lost motion correction is necessary, and when the lost motion correction is unnecessary, the lost motion correction unit that adjusts the lost motion correction amount is provided, and the setting of whether or not the lost motion correction unit performs the lost motion correction is set. It is possible to provide a display unit that can be used.

The numerical control device according to the present invention has an effect of improving the machining surface accuracy.

The figure which shows the structure of the numerical control apparatus which concerns on embodiment of this invention External view of the machine tool shown in FIG. The figure which shows the movement path on the work of the tool, the position where the moving direction of the feed axis is reversed, the distance between the reversed positions, and the position where the lost motion is corrected. The flowchart for demonstrating the inversion position estimation process of the axis movement direction by the inversion position estimation part shown in FIG. The figure which shows an example of the machining program shown in FIG. The figure for associating and explaining the block prefetched from the machining program and the reverse position estimation operation by the reverse position estimation unit The flowchart for demonstrating the necessity determination process of the lost motion correction by the correction necessity determination part shown in FIG. The figure for demonstrating the distance between inversion positions estimated by the correction necessity judgment part, and the reference value set by a correction necessity judgment part Flowchart for explaining operations of the communication unit and the drive unit shown in FIG. Diagram for explaining model position by drive unit The figure which shows an example of the timing which transmits a correction stop command to a drive unit The figure which shows the hardware constitutions of the numerical control apparatus which concerns on embodiment of this invention

Hereinafter, a numerical controller according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a diagram showing a configuration of a numerical control apparatus according to an embodiment of the present invention. FIG. 1 shows a numerical control device 100 and a machine tool 200 according to an embodiment of the present invention. Below, after explaining the outline | summary of the structure of the machine tool 200, the structure of the numerical control apparatus 100 is demonstrated.

FIG. 2 is an external view of the machine tool shown in FIG. A machine tool 200 shown in FIG. 2 is an example of an orthogonal three-axis vertical machine tool. The machine tool 200 includes a gantry 21, a saddle 22 installed on the gantry 21 and driven in the y-axis direction, and a saddle 22 And a column 24 fixed to the gantry 21 and extending upward from the gantry 21. A column 25 is attached to the column 24, and a work 300 is installed on the work table 23.

The machine tool 200 shown in FIG. 2 includes an x-axis drive mechanism 26x that is an actuator that is attached to the saddle 22 and drives the work table 23 in the x-axis direction, and an actuator that is attached to the mount 21 and drives the saddle 22 in the y-axis direction. And a z-axis drive mechanism 26z that is an actuator that is attached to the column 24 and drives the column 25 in the z-axis direction.

The x-axis drive mechanism 26x includes an x-axis motor 27x, a feed shaft 28x driven by the x-axis motor 27x, and a rotation angle detector 29x that detects the rotation angle of the feed shaft 28x. The y-axis drive mechanism 26y includes a y-axis motor 27y, a feed shaft 28y driven by the y-axis motor 27y, and a rotation angle detector 29y that detects the rotation angle of the feed shaft 28y. The z-axis drive mechanism 26z includes a z-axis motor 27z, a feed shaft 28z driven by the z-axis motor 27z, and a rotation angle detector 29z that detects the rotation angle of the feed shaft 28z.

The work table 23 is driven by the x-axis drive mechanism 26x, and the saddle 22 and the x-axis drive mechanism 26x installed thereon are driven by the y-axis drive mechanism 26y. The column 25 and the main shaft 30 are driven by a z-axis drive mechanism 26z attached to the column 24, and the workpiece 300 is machined by a tool 31 attached to the tip of the main shaft 30. As a result, by combining the motion of two degrees of freedom in the xy plane of the workpiece 300 and the motion of one degree of freedom in the z-axis direction of the tool 31 in the three-dimensional space of xyz, that is, in the three degrees of freedom, The material on the surface of the workpiece 300, which is a portion where the workpiece 300 interferes, is removed. As a result, a three-dimensional shape is created. The motor rotation angle detected by each of the three

rotation angle detectors

29x, 29y, and 29z is fed back to the numerical controller 100 shown in FIG.

In the machine tool 200, the relative displacement between the tool 31 and the workpiece 300 is important. This is because if a relative displacement occurs between the tool 31 and the workpiece 300 during the machining of the tool 31, a machining error due to an uncut or excessive cutting of the material of the workpiece 300 occurs. In the numerical control device 100, feedback control is performed in order to prevent such a processing error from occurring. However, in the numerical control device 100, a relative displacement occurs between the tool 31 and the workpiece 300 by the above-described lost motion. There is a case.

The problem caused by lost motion correction will be described with reference to FIG. FIG. 3 is a diagram showing a movement path of the tool on the workpiece, a position where the moving direction of the feed axis is reversed, a distance between the reversed positions, and a position where the lost motion correction is performed. 3 shows a cross section obtained by cutting the workpiece 300 shown in FIG. 2 along the XZ plane, a movement path A that is the movement locus of the tool 31 on the XZ plane, and a first reversal that is the reversal position of the feed axis in the movement path A. A position P11 and a second inversion position P12 that is the next inversion position of the first inversion position P11 are shown. In FIG. 3, it is assumed that the workpiece 300 is moving from the right side to the left side with respect to the tool 31.

The first reverse position P11 corresponds to the position where the movement direction of the feed shaft 28z shown in FIG. That is, the position where the moving direction of the feed shaft 28z that moves from the lower side of the drawing to the upper side of the drawing in the Z-axis direction is set as the first turning position P11. The second reverse position P12 corresponds to a position where the moving direction of the feed shaft 28z shown in FIG. That is, the position where the moving direction of the feed shaft 28z that moves from the upper side to the lower side in the Z-axis direction is reversed is defined as the second reversed position P12. The reversing position P21 corresponds to a position where the moving direction of the feed shaft 28z is reversed last time in the X-axis direction. The reversal position P22 corresponds to a position where the moving direction of the feed shaft 28z is reversed this time in the X-axis direction.

In FIG. 3, the distance from the first reverse position P11 to the second reverse position P12 in the Z-axis direction is shown as the reverse position distance L1, and the lost motion correction amount L2 is also shown. The distance L1 between the reverse positions corresponds to the distance between the reverse positions from the position where the moving direction of the feed shaft 28z shown in FIG.

Since the lost motion causes the machining accuracy of the workpiece 300 to decrease, the distance between the reversal positions when the lost motion correction is performed with the movement amount corresponding to the lost motion correction amount L2 at all reversal positions in the movement path A. Even when L1 is smaller than the lost motion correction amount L2, the feed shaft 28z shown in FIG. 2 is driven with a movement amount corresponding to the lost motion correction amount L2 at the reverse position P22. As a result, the correction becomes excessive, and in the portion of the surface of the workpiece 300 on the right side of the paper surface from the reversal position P22, the uncut or excessively cut is excessive, and the machining surface accuracy may be lowered.

In order to solve such a problem, the numerical control apparatus 100 according to the present embodiment pre-reads blocks constituting the machining program 1 while the tool 31 is moving, and the first inversion position 4 and the first Lost motion correction is performed by estimating a second reverse position 5 that is a reverse position after the reverse position 4 and estimating a distance between the reverse positions by the first reverse position 4 and the second reverse position 5. It is configured to suppress an excessive amount. Hereinafter, the configuration of the numerical controller 100 will be described.

A numerical control device 100 shown in FIG. 1 outputs a command for driving and controlling the machine tool 200 according to the machining program 1, and obtains feedback information and sensor information output from the machine tool 200, The lost motion correction unit 100-2 for adjusting the lost motion correction amount, the communication unit 10, and the drive unit 11 are provided. The control unit 100-1 has a function of controlling the movement of the main shaft 30 and the

feed shafts

28x, 28y, 28z shown in FIG. The following description focuses on the configuration of the lost motion correction unit 100-2, which is a characteristic part of the numerical control device 100 according to the present embodiment.

The lost motion correction unit 100-2 sequentially reads the blocks constituting the machining program 1 while the tool 31 is moving, and the reverse position estimation unit 2 that estimates the reverse position of the moving direction of the feed axis, and the lost motion correction amount. A correction amount calculation unit 3 for calculating and a drive unit 11 for driving a motor of the machine tool 200 are provided. The lost motion correction unit 100-2 determines whether the lost motion correction is necessary based on the lost motion correction amount 6 set in advance in the numerical controller 100, the threshold 7 arbitrarily set by the user, and the distance between the reversal positions. A correction necessity determination unit 9 is provided.

The communication unit 10 transmits the command output from the control unit 100-1 to the drive unit 11, and receives the correction stop signal 9a output from the correction necessity determination unit 9, and stops the lost motion correction. A correction stop command 10 a is transmitted to the drive unit 11.

The drive unit 11 stops the lost motion correction while the correction stop command 10a is transmitted even if the feed axis is being reversed based on the command output from the control unit 100-1.

The correction necessity determination unit 9 determines whether the distance between the inversion positions is smaller than a reference value described later, and determines whether the lost motion correction is necessary. Here, an error occurs in the operation of the tool 31 depending on the material of the workpiece 300 or the machine element of the machine tool 200, and in the determination of necessity of correction using only the lost motion correction amount 6, there is a possibility that uncut or excessive cutting may occur. . In the numerical control device 100 according to the present embodiment, a reference value selection parameter that enables selection of either the lost motion correction amount 6 set in advance in the numerical control device 100 or the threshold value 7 arbitrarily set by the user. 8, the reference value for determining whether the lost motion correction is necessary can be adjusted.

Next, a method for estimating the position where the reversal position estimation unit 2 reverses the moving direction of the feed axis will be described.

FIG. 4 is a flowchart for explaining the inversion position estimation process in the axis movement direction by the inversion position estimation unit shown in FIG. The reversal position estimation unit 2 reads the user-created machining program 1 in S1, analyzes the blocks after the block currently being executed in S2, one block at a time, and determines each movement path of the plurality of

feed axes

28x, 28y, 28z. presume. Further, in S3, the reversal position estimation unit 2 determines whether or not there is reversal of the moving direction of each of the plurality of

feed shafts

28x, 28y, and 28z in the estimated moving path.

When there is a reversal of the axial movement direction in S3 (S3, Yes), the reversal position estimation unit 2 counts the number of reversals in S4, thereby increasing the number of reversals that have occurred after starting the axial reversal position estimation process Count.

In S5, the inversion position estimation unit 2 confirms whether or not the number of inversions currently occurring is 2 or more. When the number of inversions is 2 or more (S5, Yes), the inversion position estimation unit 2 estimates the second inversion position 5 in S6.

When the number of inversions is not 2 or more (S5, No), the inversion position estimation unit 2 estimates the first inversion position 4 in S7 and until the second inversion operation is counted from the block currently being executed. That is, the processes after S2 are repeatedly executed until the number of inversions is 2 or more. When there is no reversal of the axis movement direction in S3 (S3, No), the reversal position estimation unit 2 repeatedly executes the processes after S2.

The inversion position estimation operation by the inversion position estimation unit 2 will be specifically described with reference to FIGS. FIG. 5 is a diagram showing an example of the machining program shown in FIG. FIG. 6 is a diagram for explaining the block prefetched from the machining program and the reverse position estimation operation by the reverse position estimation unit in association with each other.

As shown in FIG. 5, a plurality of block numbers and commands are associated with the machining program 1, and in FIG. 5, the block numbers are indicated by N101 to N111. In the numerical control apparatus 100, these block numbers described in the machining program 1 are read in ascending order, and a position command for driving the machine tool 200 is generated based on a command corresponding to each block number. The cross section of the workpiece 300 and the movement path A of the tool 31 are shown on the upper side of FIG. 6 as in FIG. 3, and the block of the machining program 1 read by the reverse position estimation unit 2 is shown on the lower side of the paper of FIG. A number and a command corresponding to the block number are shown. L <b> 1 is the distance between the inversion positions from the first inversion position 4 to the second inversion position 5 estimated by the inversion position estimation unit 2. L2 is the lost motion correction amount 6 or the threshold value 7 shown in FIG.

The reversal position estimation unit 2 sequentially reads commands corresponding to the block numbers described in the machining program 1, and commands to reverse the feed axis at the reversal position P22 before the tool 31 reaches the reversal position P22, that is, the block The “second inversion command” corresponding to the number “N2” is prefetched. Thereby, the inversion position estimation part 2 can estimate the inversion position P22 before the tool 31 reaches the inversion position P22.

FIG. 7 is a flowchart for explaining the necessity determination process for the lost motion correction by the correction necessity determination unit shown in FIG. FIG. 8 is a diagram for explaining the distance between inversion positions estimated by the correction necessity determination unit and the reference value set by the correction necessity determination unit. The vertical axis in FIG. 8 represents the position of the feed axis, and the horizontal axis represents time. FIG. 8 shows the estimation result of the moving route, and the inversion position distance L1 estimated by the correction necessity determination unit 9 and the reference value L3 set by the correction necessity determination unit 9. In FIG. 8, L1 and L3 have a relationship of L1 <L3.

In S11 of FIG. 7, the correction necessity determination unit 9 reads the first inversion position 4 and the second inversion position 5, and in S12, the correction necessity determination unit 9 reads the first inversion position 4 and the second inversion position. An inversion position distance L1 as shown in FIG. In S13, the correction necessity determination unit 9 reads the lost motion correction amount 6, the threshold value 7, and the reference value selection parameter 8.

In S14, the correction necessity determination unit 9 confirms the content of the reference value selection parameter 8, and determines whether or not the lost motion correction amount 6 is selected in the reference value selection parameter 8. When the lost motion correction amount 6 is selected (S14, Yes), in S15, the correction necessity determination unit 9 sets the lost motion correction amount 6 as a reference value, and executes the process of S17. When the lost motion correction amount 6 is not selected in S14, that is, when the threshold value 7 is selected (No in S14), the correction necessity determination unit 9 sets the threshold value 7 as a reference value in S16. , S17 is executed.

In S17, the correction necessity determination unit 9 determines whether or not the inversion position distance L1 is smaller than the reference value set in S15 or S16. When the distance L1 between the reversal positions is smaller than the reference value (S17, Yes), the correction necessity determination unit 9 does not need the lost motion correction in S18, and therefore gives a correction stop signal 9a for stopping the lost motion correction. Output. When the inversion position distance L1 is larger than the reference value (No in S17), the correction necessity determination unit 9 ends the lost motion correction necessity determination process without performing the process of S18.

FIG. 9 is a flowchart for explaining the operation of the communication unit and the drive unit shown in FIG. FIG. 10 is a diagram for explaining the model position by the drive unit. The vertical axis in FIG. 10 represents the position of the feed axis, and the horizontal axis represents time. The positions indicated by arrows B and C are lost motion correction execution positions, the position B corresponds to the first inversion position 4, and the position C corresponds to the second inversion position 5. The width of the arrow indicated by the symbol D corresponds to the response delay time for the gain set in the drive unit 11. FIG. 11 is a diagram illustrating an example of timing for transmitting a correction stop command to the drive unit. The vertical axis in FIG. 11 represents the position of the feed axis, and the horizontal axis represents time. In FIG. 11, the lost motion correction is stopped at the position indicated by the arrow B. The shaded area indicated by symbol E is an area where the lost motion correction determined by the position where the pre-reading of the machining program is started and the position where the model position of the drive is slightly inverted is stopped. The multiplying area is a user-set error width indicated by L4 and is an area where the lost motion correction is stopped.

In S21, the communication unit 10 reads the correction stop signal 9a transmitted from the correction necessity determination unit 9, and in S22, the communication unit 10 determines whether the correction stop signal 9a is transmitted, and the correction stop signal 9a. Is transmitted (S22, Yes), the first inversion position 4 is read in S23, and transmission of the correction stop command 10a is started in S24. When the correction stop signal 9a is not transmitted (S22, No), the communication unit 10 ends the transmission process of the correction stop command 10a.

Here, the lost motion correction is executed at the timing at which the moving direction of the feed axis is reversed at the model position indicated by the dotted line as shown in FIG. 10, that is, the model position generated inside the drive unit 11. The model position refers to an ideal feed shaft position that is sequentially generated by the drive unit 11 that has received the position command transmitted from the control unit 100-1 in accordance with the control method in the drive unit 11. The model position has a response delay corresponding to the gain set in the drive unit 11 as compared with the command position generated by the control unit 100-1. Therefore, it is necessary to synchronize the timing at which the correction stop command 10a is transmitted and the model position on the drive unit 11 side. Therefore, in the present embodiment, this is dealt with by artificially calculating the model position inside the drive unit 11.

In S25, the numerical control device 100 updates the model position in a pseudo manner by internal calculation of the numerical control device 100 in accordance with a control method similar to the control method of the drive unit 11.

In S26, the communication unit 10 determines whether or not the updated model position matches the first inversion position 4. Specifically, after the model position reaches the first inversion position 4, the communication unit 10 obtains a value obtained by subtracting the user-set error width from the first inversion position 4, or the model position is the first inversion position 4. Before reaching, it is determined whether or not the value obtained by subtracting the error width set by the user from the first inversion position 4 matches the updated model position. If the updated model position matches the first inversion position 4 (S26, Yes), the communication unit 10 stops transmitting the correction stop command 10a to the drive unit 11 in S27. In S28, the communication unit 10 requests the correction necessity determination unit 9 to stop transmission of the correction stop signal 9a, and ends the transmission process of the correction stop command 10a. If the updated model position does not coincide with the first inversion position 4 (No in S26), the communication unit 10 repeatedly executes the processes after S24. Note that, by default, the communication unit 10 starts transmitting the correction stop command 10a from the position where the block prefetching is started.

In the above method, it is assumed that the reversing operation of the machine and the transmission timing error of the correction stop command 10a become large due to factors such as hardware and machine environment. Therefore, the communication unit 10 adds the area of the code F, which is an error width set by the user, to the area of the code E shown in FIG. 11, that is, the area where the correction stop command 10a is transmitted. The transmission timing of the correction stop command 10a is adjusted according to such factors.

FIG. 12 is a diagram showing a hardware configuration of the numerical control apparatus according to the embodiment of the present invention. As illustrated in FIG. 12, the numerical control device 100 includes a processor 51 that performs arithmetic processing, a memory 52 that the processor 51 uses as a work area, a storage device 53 that stores the machining program 1, and an input interface between users. , An input device 54, a display device 55 for displaying information to the user, and a communication device 56 having a communication function with the machine tool 200. The processor 51, the memory 52, the storage device 53, the input device 54, the display device 55, and the communication device 56 are connected by a data bus 50.

As described above, according to the numerical control apparatus 100 according to the present embodiment, the machining program 1 is prefetched to estimate the distance between the reverse positions of each feed axis, and the distance between the reverse positions and the reference value are compared. Then, it is determined whether or not the lost motion correction is necessary. In the conventional numerical control device, the reverse position measured in the past, that is, the distance between the reverse positions from the position where the moving direction of the feed axis was reversed last time to the position where the current position was reversed is used. Therefore, it is impossible to obtain the distance between the reversal positions until the next reversal position, and it is impossible to prevent the processing surface accuracy from being lowered due to the over-correction of the lost motion correction for the minute reversal. According to the numerical control device 100 according to the present embodiment, the machining program 1 can be pre-read and it can be determined whether or not the lost motion correction is necessary, so that it is possible to suppress uncut or excessive cutting and to improve the machining surface accuracy. Obtainable.

Furthermore, according to the numerical control device 100 according to the present embodiment, when the distance between the inversion positions is smaller than the reference value, the lost motion correction can be automatically stopped, and the processing surface accuracy can be further improved. it can.

Note that the numerical control device 100 according to the present embodiment may include the display device 55 that is a display unit capable of setting whether or not to cause the lost motion correction unit 100-2 to perform the lost motion correction. On the screen of the display device 55, various parameters by the numerical control device 100 are displayed, and a display capable of selecting whether or not the lost motion correction unit 100-2 performs the lost motion correction is performed. In the numerical control device 100, the “lost motion correction adjustment mode” for causing the lost motion correction unit 100-2 to perform the lost motion correction is set, and the “lost motion correction adjustment mode” is normally OFF. When the operation of turning on the “lost motion correction adjustment mode” is performed on the screen of the display device 55, the “lost motion correction adjustment mode” becomes effective, and the lost motion correction unit 100-2 performs the above-described lost motion correction. Is executed. The screen of the display device 55 has a parameter “0” indicating that the “lost motion correction adjustment mode” is OFF and a parameter “1” indicating that the “lost motion correction adjustment mode” is ON. It shall be displayed so that selection is possible. The user performs an operation of changing the parameter “0” displayed in this way to “1”, thereby turning on the “lost motion correction adjustment mode”.

The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

1 machining program, 2 reversal position estimation unit, 3 correction amount calculation unit, 4 1st reversal position, 5 second reversal position, 6 lost motion correction amount, 7 threshold value, 8 reference value selection parameter, 9 correction required Non-determination unit, 9a correction stop signal, 10 communication unit, 10a correction stop command, 11 drive unit, 21 mount, 22 saddles, 23 worktables, 24, 25 columns, 26x x-axis drive mechanism, 26y y-axis drive mechanism, 26z z Axis drive mechanism, 27x x-axis motor, 27y y-axis motor, 27z z-axis motor, 28x, 28y, 28z feed axis, 29x, 29y, 29z rotation angle detector, 30 spindles, 31 tools, 50 data bus, 51 processor, 52 memory, 53 storage device, 54 input device, 55 display device, 56 communication device , 100 numerical controller 100-1 controller, 100-2 lost motion correction unit, 200 a machine tool, 300 work.

Claims

A numerical control device for numerically controlling a machine tool,
The block constituting the machining program is prefetched, and the first reversal position in the moving direction of the feed axis of the machine tool and the reversal position after the first reversal position are based on the prefetched block command. A lost motion correction unit that determines whether or not the lost motion correction is necessary by estimating the distance between the inverted positions of the two inverted positions and adjusts the lost motion correction amount when the lost motion correction is unnecessary. ,
A numerical control apparatus comprising a display unit capable of setting whether or not to cause the lost motion correction unit to perform lost motion correction.
The lost motion correction unit selects either the lost motion correction amount or a threshold set by a user as a reference value, and when the distance between the inversion positions is smaller than the reference value, the second motion correction unit The numerical control apparatus according to claim 1, wherein the lost motion correction amount at the reverse position is adjusted.