Numerical control device and computer-readable storage medium

Abstract

This numerical control device acquires a cutting trajectory of a processing head of a machine tool for processing a board material, acquires a positioning path of the processing head, determines that avoidance on the positioning path is necessary when the cutting trajectory and the positioning path intersect, and adds a retreat movement and a return movement of the processing head in the height direction to the positioning path.

Description

[Technical Field]

[0001] The present disclosure relates to a numerical control device and a computer-readable storage medium. [Background Art]

[0002] Conventionally, there are machine tools that process plate materials, such as laser processing machines, plasma processing machines, and gas processing machines. In such machine tools, energy such as laser, plasma, and gas is emitted from a processing head. When a plate material is cut into a closed shape, the cut portion may not fall, but may be partially caught, resulting in an inclined state and protruding from the plate material. If the processing head interferes with this protruding portion, it may cause a failure of the processing head.

[0003] As a conventional technique for avoiding this interference, there is a technique of automatically moving a preset retraction amount in a direction opposite to the plate material when the processing head performs positioning. See, for example, Patent Document 1. [Prior Art Literature] [Patent Literature]

[0004] [Patent Document 1] Japanese Utility Model Laid-Open No. 03-101380 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Generally, when avoiding interference, retraction is performed with a fixed retraction amount. However, an excessive retraction amount causes unnecessary processing time and required energy. For interference avoidance operations, a technique for obtaining an efficient retraction amount is desired. [Means for Solving the Problem]

[0006] A numerical control device according to one aspect of the present disclosure is a machine tool for processing a plate material Therefore, when cutting sheet metal into a closed shape, the cut portion falls or tilts.A trajectory acquisition unit that acquires the cutting trajectory of the machining head, a path acquisition unit that acquires the positioning path of the machining head, and the cutting trajectory and positioning path The path projected onto the processing surface and The system includes an avoidance unit that determines that avoidance is necessary in the positioning path when the paths intersect, and adds a retraction and return movement of the processing head in the height direction to the positioning path. [Brief explanation of the drawing]

[0007] [Figure 1] This is a block diagram of the numerical control device according to the first embodiment. [Figure 2] This is a schematic diagram showing an example of a cut section. [Figure 3] This is a schematic diagram showing an example of a closed shape. [Figure 4] This is a schematic diagram illustrating the method for calculating evacuation amounts. [Figure 5] This is a schematic diagram illustrating the method for calculating evacuation amounts. [Figure 6] This is a schematic diagram illustrating how to determine the need for avoidance. [Figure 7] This is a schematic diagram illustrating an example of dividing a circular arc into straight lines. [Figure 8] This is a flowchart explaining the operation of a numerical control device. [Figure 9] This is a schematic diagram showing an example of the path of the machining head. [Figure 10] This is a screen display diagram showing an example of a processing program. [Figure 11] This is a block diagram of the numerical control device according to the second embodiment. [Figure 12] This is a hardware configuration diagram of a numerical control device. [Modes for carrying out the invention]

[0008] The numerical control device 100 described below controls a machine tool that processes sheet metal. Examples of machine tools that process sheet metal include laser cutters, gas cutters, and plasma cutters. In the following embodiment, a laser cutter will be used as an example. It should be noted that the components of the numerical control device 100 are categorized by their functions, and do not need to be clearly distinguished in terms of physical configuration and program configuration.

[0009] (First Embodiment) The numerical control device 100 according to the first embodiment will be described below. FIG. 1 is a block diagram of the numerical control device 100. The numerical control device 100 includes a trajectory acquisition unit 11, a trajectory storage unit 12, a path acquisition unit 13, a closed shape detection unit 14, a closed shape storage unit 15, a retreat amount calculation unit 16, a retreat range storage unit 17, an avoidance unit 18, a machining program analysis unit 19, and a machining program execution unit 20.

[0010] The trajectory acquisition unit 11 acquires a cutting trajectory of a machining head of a laser processing machine. A machining path of the laser processing machine is commanded by a machining program. The machining path includes cutting a plate material Cutting path and a positioning path for moving to a next machining start point.

[0011] Cutting path are classified into linear interpolation and circular interpolation according to the command method for machining paths. Linear interpolation moves linearly from a start point to an end point specified by a machining program. Circular interpolation moves along a circular arc from the start point. In an NC program, the shape of a circle is set using information of any two or more of the end point of the circle, the center of the circular arc, and the rotation angle.

[0012] The path acquisition unit 13 acquires a positioning path. The positioning path is Cutting path different from that, and does not involve laser output. In positioning, the previous Cutting path from the end point to the next Cutting path moves the machining head to the start point of. When positioning the machining head, there is a risk that the machining head may interfere with an inclined cut portion (see FIG. 2).

[0013] The closed shape detection unit 14 detects a closed shape based on the cutting trajectory and stores the detected closed shape in the closed shape storage unit 15. Examples of the closed shape include a closed shape formed by a combination of straight lines, a closed shape formed by a circular arc, and a closed shape formed by a combination of straight lines and a circular arc. A circular arc can be regarded as a combination of straight lines. Referring to FIG. 3, detection of a closed shape formed by straight lines will be described. In the example of FIG. 3, it is assumed that five cutting trajectories (I) to (V) form a closed shape. The cutting trajectory acquired by the trajectory acquisition unit 11 holds information on intersection points formed between the own trajectory and other trajectories.

[0014] The information of intersection points is held by IDs, for example. If there is one cutting trajectory intersecting a given cutting trajectory, one ID is associated with this cutting trajectory. If there are two cutting trajectories intersecting a given cutting trajectory, two IDs are associated with this cutting trajectory. A cutting trajectory intersecting two or more cutting trajectories, that is, a cutting trajectory associated with two or more IDs is searched for. When intersecting a plurality of cutting trajectories, one of the plurality of cutting trajectories is selected. Then, if the selected cutting trajectory intersects another cutting trajectory, that cutting trajectory is selected. Then, if the selected cutting trajectory intersects another cutting trajectory, that cutting trajectory is selected. This is repeated, and if there exists a cutting trajectory having an intersection point selected in the past, it can be known that a closed shape is formed by cutting.

[0015] Closed shape detection will be specifically described with reference to the example of FIG. 3. 1. Cutting trajectory (I) is selected as the initial cutting trajectory. 2. Cutting trajectory (I) has two intersection points: intersection point A and intersection point B. Intersection point B is selected from the two intersection points. 3. Cutting trajectory (II) shares intersection point B with cutting trajectory (I). Cutting trajectory (II) has another intersection point C. 4. Cutting trajectory (III) shares intersection point C with cutting trajectory (II). Cutting trajectory (III) has another intersection point D. 5. Cutting trajectory (IV) shares intersection point D with cutting trajectory (III). Cutting trajectory (IV) has another intersection point E. 6. Cutting trajectory (V) shares intersection point E with cutting trajectory (IV). Cutting trajectory (V) shares intersection point A with cutting trajectory (I). Since cutting trajectory (V) shares intersection point A with cutting trajectory (I) selected in the past, it can be known that cutting trajectories (I) to (V) form a closed shape.

[0016] The retraction amount calculation unit 16 calculates the retraction amount of the machining head based on the closed shape and stores it in the closed shape storage unit 15. The retraction amount of the machining head is the retraction amount in the height direction. The retraction amount calculation unit 16 calculates a sufficient height so that the machining head does not interfere with the cutting portion when it is positioned.

[0017] Two methods for calculating the amount of evacuation are shown below. The first method involves identifying the two points at the cutting section that are furthest apart, and using the distance between these two points as the amount of retraction. Figure 4 is a plan view of the cutting section. In Figure 4, the distance between points A and B is the furthest apart at the cutting section. The retraction amount calculation unit 16 calculates the length of line segment AB as the amount of retraction. This calculation method is based on the fact that when the cutting section tilts and protrudes from the plate material, the height of the protruding portion will always be shorter than the length of line segment AB. Existing technology is used to calculate the furthest apart distance at the cutting section.

[0018] The second method involves calculating the center of gravity of the cut section and using the distance to the point furthest from the center of gravity as the amount of relocation. Figure 5 is a plan view of the cut section. In Figure 5, point C is furthest from the center of gravity. The relocation amount calculation unit 16 calculates the length of the line segment WC connecting the center of gravity W and point C as the amount of relocation. This calculation method is based on the idea that when the cut section tilts, one part of the cut section will get caught, and the section will tilt towards the center of gravity relative to the point that got caught. In this way of thinking, the longest height distance of the protruding part occurs when a point slightly offset from the center of gravity W in the direction of the line segment WC gets caught, so it is sufficient to relocate by the length of the line segment WC. Existing technology is used to calculate the center of gravity W and point C, which is furthest from the center of gravity W.

[0019] The retraction range storage unit 17 stores the upper or lower limit of the retraction amount. The retraction amount calculation unit 16 adjusts the retraction amount so that it falls within the upper or lower limit range if the calculated retraction amount exceeds the upper or lower limit range. Adjustment is necessary if the retraction amount is too large. Also, if the retraction amount is too small, there is a risk that the dross (molten metal attached in the form of spheres or ice columns) at the cutting portion will interfere with the processing head. Therefore, the retraction amount is adjusted using the lower limit.

[0020] When positioning the machining head, the avoidance unit 18 determines the need for avoidance in the positioning path, and if avoidance is necessary, adds a retraction and return operation of the machining head to the positioning path.

[0021] The need for avoidance is determined by whether or not the cutting trajectory forming a closed shape intersects with the positioning path. One example of a determination method is one that uses the cross product of vectors. Referring to Figure 6, a method for determining whether the cutting trajectory AB and the positioning path CD intersect will be explained. For the purpose of this explanation, the machining surface is defined as the XY plane, and the height direction from the machining surface is defined as the Z axis. Note that cutting trajectory AB is one of the cutting trajectories included in the closed shape. If one of the cutting trajectories included in the closed shape intersects with the positioning path, it is determined that the cutting portion of the closed shape and the positioning path intersect.

[0022] To determine the intersection of the cutting trajectory and the positioning path on the machining surface, the cutting trajectory and the positioning path are projected onto the machining surface (XY plane). In the projection, point ABCD is determined by ignoring the Z-axis components of the cutting trajectory AB and the positioning path CD. If the signs of the cross product of vector AB and vector AC do not match and the signs of the cross product of vector AB and vector AD do not match, and the signs of the cross product of vector CA and vector CB do not match and the signs of the cross product of vector CD and vector CB do not match, then it is determined that the cutting trajectory and the positioning path intersect. If the cutting trajectory and the positioning path intersect, the avoidance unit 18 determines that avoidance is necessary.

[0023] When processing a sheet material into an arc, the avoidance unit 18 divides the arc into multiple straight lines, as shown in Figure 7, and determines whether or not the divided line segments intersect with the positioning path.

[0024] The avoidance unit 18 determines that avoidance is necessary when the positioning path and the closed shape intersect, and adds retraction and return operations of the machining head to the positioning path. The height to which the machining head is retracted is calculated by the retraction amount calculation unit 16. Normally, the retraction operation starts at the starting point of the positioning path. The return operation starts when the remaining distance of the positioning path falls below a predetermined distance. The start timing of the retraction and return operations is not limited to this; it is sufficient if the machining head passes the cutting section at the retracted height. During the retraction and return operations, the movement speed in the XY axis direction does not change. The numerical control device 100 of this embodiment does not change the movement speed of the machining head in the XY axis direction during positioning, and moves it in a straight line on the XY plane, so positioning can be done more quickly than by bypassing the cutting area.

[0025] The avoidance unit 18 determines, in intersection determination, the intersection of the positioning path for one block and the cutting trajectory of a block executed before that block. A block refers to one line of the machining program. The avoidance unit 18 determines whether the cutting trajectory prior to a positioning block (for example, a block containing the command "G00") intersects with the positioning path of that block, if such a block exists in the machining program.

[0026] The machining program analysis unit 19 calculates the cutting path and positioning path of the machining head based on the machining program.

[0027] The machining program execution unit 20 controls the movement of the machining head, the laser output, etc., according to the analysis results of the machining program analysis unit 19. The avoidance unit 18 outputs the starting position of the retraction operation, the starting position of the return operation, the amount of retraction, etc., to the machining program execution unit 20. The machining program execution unit 20 adds the retraction operation and the return operation to the positioning operation of the machining head.

[0028] The operation of the numerical control device 100 will be explained with reference to Figure 8. The numerical control device 100 analyzes the machining program (step S1). The numerical control device 100 determines whether the program path of the block is a cutting path or a positioning path. If the path is a cutting path (step S2; cutting), the numerical control device 100 determines whether the cutting path forms a closed shape. If the cutting path does not form a closed shape (step S3; No), the numerical control device 100 proceeds to step S8. If the cutting path forms a closed shape (Step S3; Yes), the numerical control device 100 calculates the amount of retraction of the machining head based on the closed shape (Step S4). The numerical control device 100 stores the closed shape and the amount of retraction (Step S5) and proceeds to Step S8.

[0029] If the program path is a positioning path (step S2; positioning), the numerical control device 100 reads out the already stored closed-shape cutting trajectory and determines whether the positioning path and the closed-shape cutting trajectory intersect. If the closed-shape cutting trajectory and the positioning path intersect (step S6; Yes), the numerical control device 100 adds a retraction operation and a return operation to the positioning operation of the machining head to avoid interference between the cutting portion and the machining head (step S7).

[0030] The numerical control device 100 determines whether the read block marks the end of the machining program. If it does not mark the end of the machining program (step S8; No), it proceeds to step S1 and reads the next block. If it marks the end of the machining program (step S8; Yes), it terminates the operation.

[0031] As described above, the numerical control device 100 of the first embodiment detects whether or not a closed-shaped cutting portion exists in the path (cutting trajectory) where cutting has already been performed, and if a closed-shaped cutting portion exists, it calculates the amount of retraction based on the shape of the closed-shaped portion. The numerical control device 100 performs a retraction operation and a return operation with the calculated amount of retraction to avoid interference between the closed-shaped cutting portion and the processing head.

[0032] The numerical control device 100 of the first embodiment determines whether or not the machining head needs to be avoided based on whether or not there is an intersection between the closed-shaped cutting portion and the positioning path. If avoidance is not required, machining time and energy can be saved.

[0033] Furthermore, in the first embodiment, the numerical control device 100 determines the retraction and return operations of the machining head based on the intersection of the closed-shaped cutting portion and the positioning path. Therefore, there is no need to pre-set information for generating avoidance paths or avoidance paths other than those in the machining program, making it highly versatile.

[0034] Furthermore, since the numerical control device 100 of the first embodiment has a closed shape memory unit 15, even when processing a single sheet of material by executing multiple processing programs, it can store the closed shapes of past processing programs and determine whether or not the cutting trajectory and the positioning path intersect across multiple processing programs.

[0035] Furthermore, information on the retraction and return operations may be stored in association with the machining program. When the avoidance unit 18 executes the same machining program, it can reduce the computational load by referring to the information on the retraction and return operations that have already been executed.

[0036] (Examples) Referring to Figure 9, the operation of the numerical control device 100 of the first embodiment will be described in detail. Figure 9 shows the path of the machining head. Figure 10 shows the machining program. The machining head path is appended with the block number of the machining program. The G code "G90" for block number "N1" specifies absolute coordinates. "E001" for block number "N2" calls the machining condition file "E001". The G-code "G00 X80.0 Y100.0" for block number "N3" is a positioning command. The machining head moves to coordinates (X,Y)=(80.0,100.0). No closed shape is generated in the block preceding block "N3". Therefore, no avoidance is performed.

[0037] A closed shape is formed in blocks "N4" through "N7". The coordinates of the vertices of the closed shape are (X,Y)=(80.0,100.0), (130.0,100.0), (130.0,70.0), and (80.0,70.0). The closed shape detection unit 14 determines that the cutting trajectories from "N4" to "N7" form a closed shape. Specifically, the cutting trajectory of "N4" has an intersection with the cutting trajectory of "N5", the cutting trajectory of "N5" has an intersection with the cutting trajectory of "N6", the cutting trajectory of "N6" has an intersection with "N7", the cutting trajectory of "N7" has an intersection with the cutting trajectory of "N4", and the cutting trajectory of "N4" has an intersection with the previously selected intersection, so it can be determined that it forms a closed shape.

[0038] The retraction amount calculation unit 16 calculates the retraction amount based on the vertices of the closed shape. The retraction amount is the longest distance at the vertices of the closed shape. The retraction amount of the closed shape formed from "N4" to "N7" is "58.3".

[0039] The G-code "G00 X20.0 Y50.0" for block number "N8" is a positioning command. The machining head moves from the endpoint of "N7" (80.0, 70.0) to the commanded destination of "N8" (20.0, 50.0). Here, the cutting paths of blocks "N4" to "N7" that form the closed shape do not intersect with the positioning path of "N8". It is determined that the path of "N8" does not pass over the closed shape formed by "N4" to "N8".

[0040] A closed shape is formed in blocks "N9" through "N12". The coordinates of the vertices of the closed shape are (X,Y)=(20.0,50.0), (50.0,50.0), (50.0,30.0), and (20.0,30.0).

[0041] The retraction amount calculation unit 16 calculates the retraction amount based on the coordinates of the vertices of the closed shape. The retraction amount is the longest distance at the vertices of the closed shape. The retraction amount for the closed shape formed by block numbers "N9" to "N12" is "36.1".

[0042] The G-code "G00 X200.0 Y120.0" for block number "N13" is a positioning command. The machining head moves from the endpoint of "N12" (20.0, 50.0) to the commanded destination of "N13" (200.0, 120.0). The avoidance unit 18 determines that the positioning path of "N13" intersects with the cutting portion from "N4" to "N7". Since the longest distance of the closed shape formed by block numbers "N4" to "N7" is "58.3", the retraction amount is set to "58.3", and the retraction and return operation of the processing head is added to "G00 (positioning operation)" of "N13".

[0043] (Second embodiment) Figure 11 is a block diagram of the numerical control device 100 according to the second embodiment. The numerical control device 100 of the second embodiment includes a pre-analysis unit 21. The pre-analysis unit 21 analyzes the machining program in advance. The trajectory storage unit 12 stores the machining path calculated by the pre-analysis unit 21. The machining path calculated by the pre-analysis unit 21 includes a cutting path and a positioning path.

[0044] When the laser processing machine is running, the trajectory acquisition unit 11 acquires execution data from the processing program execution unit 20. Based on the execution data from the processing program execution unit 20, the trajectory acquisition unit 11 adds completed information to the pre-calculated cutting path. Once the completed information is added, the cutting path becomes a cutting trajectory.

[0045] For example, the start and end points of a path are used to associate execution data with disconnected paths. When the trajectory acquisition unit 11 acquires execution data, it searches for disconnected paths that have the same start and end points as the execution data. The trajectory acquisition unit 11 adds completed information to disconnected paths that have the same start and end points as the execution data. Alternatively, the line number of the processing program may be added to both the execution data and the cutting path to associate the execution data with the cutting path.

[0046] The numerical control device 100 of the second embodiment can reduce the computational load during machining because it calculates the machining path in advance. In addition, it can predict whether there are other obstacles in the area to be avoided. Furthermore, before starting machining, the pre-calculated escape amount and machining path can be displayed on the display unit 70, and user settings (for example, escape amount, whether or not to perform the escape process) can be accepted via the input unit 30.

[0047] The hardware configuration of the numerical control unit 100 will be described below in accordance with this disclosure. Figure 12 is a hardware configuration diagram of the numerical control unit 100. As shown in Figure 12, the numerical control unit 100 includes a CPU 111 that controls the numerical control unit 100 as a whole, a ROM 112 that stores programs and data, and a RAM 113 for temporarily expanding data. The CPU 111 reads the system program stored in the ROM 112 via the bus and executes the workaround according to the system program.

[0048] The non-volatile memory 114 retains its stored state even when the power to the numerical control device 100 is turned off, for example, by being backed up by a battery (not shown). The non-volatile memory 114 stores various data, such as programs read from external devices 120 via interfaces 115, 118, and 119, and user operations input via the input unit 30. The non-volatile memory 114 may also store programs and data for executing the numerical control device 100 of this embodiment. In addition, the display unit 70 displays various data, measurement results, factors causing incorrect data, etc.

[0049] Interface 115 is an interface for connecting the numerical control unit 100 to an external device 120 such as an adapter. Programs and various parameters are read from the external device 120. Interface 118 is an interface for connecting the numerical control device 100 to a display unit 70 such as a liquid crystal display. The display unit 70 displays data loaded into memory, data obtained as a result of executing programs, etc. Interface 119 is an interface for connecting the numerical control unit 100 with input units 30 such as a keyboard and pointing device. The input units 30 transmit commands, data, etc., based on operations by the operator to the CPU 111 via interface 119.

[0050] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto.

[0051] The following additional information is disclosed regarding the above embodiments and modifications. (Note 1) The numerical control device (100) includes a trajectory acquisition unit (11) for acquiring the cutting trajectory of the processing head of a machine tool for processing sheet material, a path acquisition unit (13) for acquiring the positioning path of the processing head, a closed shape detection unit (14) for detecting the cutting trajectory that forms a closed shape, a retraction amount calculation unit (16) for calculating the amount of retraction of the processing head in the height direction based on the closed shape, and an avoidance unit (18) for determining that avoidance is necessary in the positioning path when the closed shape and the positioning path intersect, and for adding a retraction operation to the positioning path that retracts the processing head in the height direction by the retraction amount and a return operation that restores the height of the processing head. (Note 2) The amount of retraction is the distance between the two points on the outer circumference of the closed shape that are furthest apart. (Note 3) The amount of retraction is the distance between the point on the outer circumference of the closed shape that is furthest from the center of gravity of the closed shape and the center of gravity. (Note 4) The avoidance unit (18) performs the retraction and return operations of the machining head only when it determines that avoidance is necessary in the positioning path. (Note 5) The numerical control device (100) includes a machining program analysis unit (19) that analyzes the numerically controlled machining program and calculates a machining path including a cutting path and a positioning path, and a machining program execution unit (20) that drives the machine tool based on the analysis results of the machining program. The trajectory acquisition unit (11) acquires the machining path executed by the machining program execution unit (20) as a cutting trajectory, and the path acquisition unit (13) acquires the positioning path from the machining program analysis unit (19). (Note 6) The numerical control device (100) includes a pre-analysis unit (21) that analyzes the machining program in advance and calculates the machining path of the machining head, a machining program analysis unit (19) that analyzes the machining program and calculates the machining path of the machining head, and a machining program execution unit (20) that drives the machine tool based on the analysis results of the machining program. The machining path includes a cutting path and a positioning path, and the trajectory acquisition unit (11) adds the executed information of the machining program execution unit to the cutting path and acquires it as the cutting trajectory. (Note 7) The numerical control device (100) includes a trajectory storage unit (12) that stores the cutting trajectories of multiple machining programs, and the avoidance unit (18) determines that avoidance is necessary in the positioning path when the closed shape formed by the multiple machining programs intersects with the positioning path. (Note 8) The trajectory memory unit (12) stores information on the retraction operation and the return operation in association with the machining program, and refers to the information on the retraction operation and the return operation when executing the machining program. (Note 9) The storage medium (112, 113, 114) stores a computer-readable instruction for one or more processors (111) to execute a process that involves acquiring the cutting trajectory of the processing head of a machine tool that processes sheet metal, acquiring the positioning path of the processing head, detecting the cutting trajectory that forms a closed shape, calculating the amount of retraction of the processing head in the height direction based on the closed shape, determining that avoidance is necessary in the positioning path when the closed shape and the positioning path intersect, and adding a retraction operation to the positioning path that retracts the processing head in the height direction by the amount of retraction, and a return operation that restores the height of the processing head. [Explanation of Symbols]

[0052] 100 Numerical control device 11 Trajectory acquisition part 12 Trajectory memory section 13 Route acquisition unit 14. Closed shape detection unit 15 Closed shape memory section 16. Evacuation Amount Calculation Unit 17 Evacuation Range Memory Unit 18 Avoidance part 19 Machining Program Analysis Department 20 Processing program execution unit 21 Preliminary Analysis Department 111 CPU 112 ROM 113 RAM 114 Non-volatile memory

Claims

1. A machine tool for processing sheet metal, comprising a trajectory acquisition unit that acquires the cutting trajectory of the machining head of the machine tool, where the cutting portion falls or tilts when the sheet metal is cut into a closed shape, A path acquisition unit that acquires the positioning path of the processing head, A closed shape detection unit that detects the cutting trajectory that forms a closed shape, A retraction amount calculation unit that calculates the amount of retraction in the height direction of the processing head based on the closed shape, When the cutting trajectory included in the closed shape and the path obtained by projecting the positioning path onto the machining surface intersect, it is determined that avoidance is necessary in the positioning path, and an avoidance unit is provided that adds a retraction operation to the positioning path by retracting the machining head by the amount of retraction and a return operation to restore the height of the machining head. A numerical control device equipped with the following features.

2. The numerical control device according to claim 1, wherein the amount of retraction is the distance between the two points on the outer circumference of the closed shape that are furthest apart.

3. The numerical control device according to claim 1, wherein the amount of retraction is the distance between the point on the outer circumference of the closed shape that is furthest from the center of gravity of the closed shape and the center of gravity.

4. The numerical control device according to claim 1, wherein the avoidance unit performs a retraction operation and a return operation of the processing head only when it determines that avoidance is necessary in the positioning path.

5. A machining program analysis unit analyzes the machining program and calculates the machining path including the cutting path and the positioning path, The system includes a machining program execution unit that drives the machine tool based on the analysis results of the machining program, The trajectory acquisition unit acquires the machining path executed by the machining program execution unit as a cutting trajectory. The numerical control device according to claim 1, wherein the path acquisition unit acquires a positioning path from the machining program analysis unit.

6. A pre-analysis unit analyzes the machining program in advance and calculates the machining path of the machining head, The system comprises a machining program analysis unit that analyzes the machining program and calculates the machining path of the machining head, and a machining program execution unit that drives the machine tool based on the analysis results of the machining program. The aforementioned processing path includes a cutting path and a positioning path. The numerical control device according to claim 1, wherein the trajectory acquisition unit adds the executed information of the processing program execution unit to the cutting path and acquires it as the cutting trajectory.

7. It is equipped with a trajectory storage unit that stores the cutting trajectories of multiple machining programs, The numerical control device according to claim 1, wherein the avoidance unit determines that avoidance is necessary in the positioning path when the closed shape formed by the plurality of processing programs intersects with the positioning path.

8. The numerical control device according to claim 7, wherein the trajectory memory unit stores information on the retraction operation and the return operation in association with the machining program, and refers to the information on the retraction operation and the return operation when executing the machining program.

9. One or more processors, A machine tool for processing sheet metal, which acquires the cutting trajectory of the machining head of the machine tool when the sheet metal is cut into a closed shape, and the cutting part falls or tilts. The positioning path of the machining head is obtained, Detect the cutting trajectory that forms a closed shape, Based on the closed shape, the amount of retraction of the processing head in the height direction is calculated. When the cutting trajectory included in the closed shape intersects with the path obtained by projecting the positioning path onto the machining surface, it is determined that avoidance is necessary in the positioning path, and a retraction operation to move the machining head back in the height direction by the amount of retraction, and a return operation to restore the height of the machining head are added to the positioning path. A storage medium that stores instructions that can be read by the computer executing the process.

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