Control device for machine tool and machine tool control method

Abstract

Provided are a control device for a machine tool and a machine tool control method that are capable of reducing the load on a tool caused when a workpiece and the tool come into contact with each other by devising oscillation operation start timing, thereby extending the life of the tool. The present invention provides a control device 1 for a machine tool that has a spindle S for rotating a workpiece W and a tool T relative to each other and a feed shaft J for feeding the workpiece W and the tool T relative to each other, and that performs machining on the workpiece W while oscillating the workpiece W and the tool T relative to each other by cooperative operation of the spindle S and the feed shaft J, the control device 1 comprising an oscillation command creation unit 3 that creates an oscillation command on the basis of machining conditions acquired from at least one of a machining program 2, signal information 10, and parameters. The oscillation command creation unit 3 includes an oscillation command start unit 4. The oscillation command start unit 4 does not perform an oscillation operation at the start of machining of the workpiece W, and starts the oscillation operation when predetermined oscillation operation start conditions are satisfied during machining of the workpiece W.

Description

Machine tool control device and machine tool control method

[0001] The present disclosure relates to a control device for a machine tool and a control method for a machine tool.

[0002] Conventionally, there has been known a method of performing machining while oscillating the tool and the workpiece relative to each other to prevent problems caused by chips continuously generated during machining of the workpiece becoming entangled in the workpiece or cutting tool. With this method, by setting the tool path, which is the locus of the tool, to partially overlap the previous tool path, an air cut is generated in which the tool separates from the surface of the workpiece, thereby shredding the chips. For example, Patent Document 1 describes a technique related to oscillating machining.

[0003] International Publication No. 2021 / 166974

[0004] In swing machining, the position where the workpiece and tool come into contact and machining begins depends on the program, the workpiece, and the shape of the tool. In other words, when swing machining is performed, the feed speed when the workpiece and tool come into contact can be faster than when there is no swing motion. If the workpiece and tool come into contact at this fast feed speed, the load on the tool increases, which can shorten the tool's life.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a machine tool control device and a machine tool control method that can reduce the load on the tool when the workpiece and the tool come into contact by devising the timing at which the swinging operation starts, thereby extending the life of the tool.

[0006] One aspect of the present disclosure is a control device (1) for a machine tool that has a main spindle (S) that rotates a workpiece (W) and a tool (T) relative to one another, and a feed axis (J) that feeds the workpiece (W) and the tool (T) relative to one another, and that processes the workpiece (W) while swinging the workpiece (W) and the tool (T) relative to one another through coordinated operation of the main spindle (S) and the feed axis (J), the control device (1) for a machine tool that includes a swing command creation unit (3) that creates a swing command based on machining conditions acquired from one or more of a machining program (2), signal information (10), and parameters, the swing command creation unit (3) including the swing command initiation unit (4), which does not perform the swing operation at the start of machining of the workpiece (W), and starts the swing operation when a predetermined swing operation start condition is satisfied during machining of the workpiece (W).

[0007] One aspect of the present disclosure is a control method for a machine tool having a main spindle (S) that rotates a workpiece (W) and a tool (T) relative to one another, and a feed axis (J) that feeds the workpiece (W) and the tool (T) relative to one another, and machining the workpiece (W) while swinging the workpiece (W) and the tool (T) relative to one another through coordinated operation of the main spindle (S) and the feed axis (J), the control method comprising: a swing command creating means that creates a swing command based on machining conditions acquired from one or more of a machining program (2), signal information (10), and parameters; the swing command creating means including the swing command initiating means that does not perform the swing operation at the start of machining of the workpiece (W), and starts the swing operation when a predetermined swing operation initiating condition is satisfied during machining of the workpiece (W).

[0008] FIG. 1 is a schematic diagram showing the concept of swing machining. FIG. 2 is a block diagram showing the configuration of a control device for a machine tool. FIG. 3 is a graph showing the relationship between the feed speed of a feed axis and time. FIG. 4 is a flowchart showing the procedure of swing operation start timing determination control according to the present embodiment. FIG. 5 is a graph showing the start timing of a swing operation. FIG. 6 is a conceptual diagram showing one example of a setting mode of the start timing of a swing operation. FIG. 7 is a conceptual diagram showing another example of a setting mode of the start timing of a swing operation.

[0009] An example of an embodiment of the present invention will be described below.

[0010] 1 is a schematic diagram showing the concept of swing machining. In swing machining, at least one spindle S that rotates a tool T and a workpiece W relative to each other and at least one feed axis J that moves the tool T relative to the workpiece W are operated in coordination to rotate the tool T and the workpiece W relative to each other and swing the tool T and the workpiece W relative to each other in the feed direction while machining is performed.

[0011] At this time, the tool path L, which is the trajectory of the tool T, is set so that the current path partially overlaps the previous path. In other words, the part that has already been machined by the previous path is partially included in the current path, causing an air cut in which the cutting edge of the tool T separates from the surface of the workpiece W, thereby shredding the chips C.

[0012] In the swing machining according to one aspect of the present disclosure, the shape of the workpiece is not limited. For example, multiple feed axes may be required to form a tapered portion or an arc-shaped portion on the machining surface of the workpiece, or the workpiece may be columnar or cylindrical and only one feed axis may be required.

[0013] 2 is a block diagram showing the configuration of a machine tool control device 1. The machine tool control device 1 includes a machining program 2, a swing command creation unit 3, and a control unit 5 that controls a motor M that rotates and drives a feed axis J. The swing command creation unit 3 includes a swing command initiation unit 4. A predetermined signal (signal information) 10 is input to the swing command creation unit 3 by an operator. The signal 10 is a numerical value or a program that is input using an application UI (user interface) or a jog mode that allows manual input using a handle.

[0014] The machine tool control device 1, which is a numerical control device, can be realized, for example, by loading a predetermined program into a computer having a CPU, memory, etc. A swing command creation unit 3 creates a swing command consisting of the interval, amplitude, period, etc. of the swing operation based on at least one of the machining program 2, signal 10, and feedback values ​​from the motor M. A control unit 5 controls the motor M by superimposing the swing command created by the swing command creation unit 3 on a movement command for the feed axis J from the machining program 2. The tool T is driven in the feed direction via a ball screw or the like that is rotationally driven by the motor M.

[0015] A control device 1 for a machine tool according to one embodiment of the present disclosure is characterized in that it does not perform a swinging motion of the tool T before machining begins, i.e., before the workpiece W and the tool T come into contact, but starts the swinging motion when it is determined that machining has stabilized after the workpiece W and the tool T come into contact and machining has begun.

[0016] 3 is a graph showing the relationship between the feed rate of the feed axis J and time. When the feed rate Vb is V1 when no swing motion is superimposed, the feed rate Va when a swing motion is superimposed fluctuates above and below V1 as a median. As shown in the range indicated by the dashed circle A, if the cutting tool T contacts the workpiece W (machining is initiated) when the feed rate Va is faster than V1, the tool load increases and the life of the tool T is likely to be shortened compared to when the two contact at the feed rate V1. In contrast, in this embodiment, the swing motion is not performed before the tool T contacts the workpiece W, and the swing motion is initiated when it is determined that machining has stabilized after the workpiece W and the cutting tool T come into contact.

[0017] 4 is a flowchart showing the procedure for swing operation start timing determination control according to this embodiment. In step S1, a processing block consisting of a series of processing programs for processing the workpiece W is executed. In the following step S2, it is determined whether or not the swing operation start conditions have been met, and if a negative determination is made, the process returns to the determination in step S2. Then, if a positive determination is made in step S2, that is, if it is determined that the swing operation start conditions have been met, the process proceeds to step S3, where swing operation is started to be superimposed on the feed operation of the feed axis J, thereby performing swing processing. When swing processing is started, the series of controls related to swing operation start timing determination is terminated.

[0018] 5 is a graph showing the timing at which the oscillation operation starts. Whether or not the machining has stabilized after the start of machining can be determined based on various parameters. In this graph, after machining starts at time t=0, the torque Qa of the motor M driving the feed axis J increases significantly due to the initial resistance of machining. Then, at time t1, the torque Qa, which has risen beyond its peak and is now decreasing, falls below a predetermined value Q1, and the control unit 5 determines that "the machining has stabilized" and starts the oscillation operation.

[0019] Whether or not machining has stabilized can be determined, for example, by checking whether the fluctuation range of cutting resistance index values ​​such as torque and position deviation generated in the spindle motor of the main shaft or the servo motor of the feed shaft falls within a threshold value, or by checking whether or not the distance, coordinate, or time at which oscillation can begin specified in the machining program or parameters has been reached.

[0020] Furthermore, whether or not machining has stabilized can also be determined by setting a position at which the cutting tool can start swinging in advance and detecting that the tool has reached this set position with a position sensor, etc. Furthermore, the distance, coordinates, time, position, etc. at which swinging can start may be set as values ​​at which the torque and position deviation of the spindle motor of the main shaft, the servo motor of the feed shaft, etc., obtained in advance, fall within predetermined threshold values.

[0021] 6 is a conceptual diagram showing one embodiment of a setting mode for the start timing of the swing operation. In this embodiment, the swing operation is set to start when the travel distance D of the tool T from the start of the machining block reaches a predetermined value. This makes it possible to easily determine the start timing of the swing operation based on the travel distance D of the tool T estimated and detected by the machining program, etc.

[0022] 7 is a conceptual diagram showing another embodiment of the setting mode of the start timing of the swing operation. In this embodiment, the swing operation is set to start when the tool T passes through a predetermined position P after the start of a machining block. This makes it possible to easily determine the start timing of the swing operation based on the position of the tool T detected by a position sensor or the like.

[0023] That is, the swing command initiation unit 4 can set the predetermined swing operation start condition when the fluctuation range of a cutting resistance index value, such as torque, position deviation, or speed deviation, related to the feed of the spindle S or the feed axis J, falls within a threshold value. The swing command initiation unit 4 can also set the predetermined swing operation start condition when the movement distance D of the tool T driven by the feed axis J reaches a predetermined value. The swing command initiation unit 4 can also set the predetermined swing operation start condition when the position of the tool T driven by the feed axis J reaches a predetermined position P. The swing command initiation unit 4 can also set the predetermined swing operation start condition when the movement time of the tool T driven by the feed axis J reaches a predetermined value.

[0024] In addition, the swing command initiation unit 4 can set the above-mentioned movement distance D, predetermined position P, and movement time as values ​​that will allow the fluctuation range of the cutting resistance index value, such as torque, position deviation, or speed deviation, related to the feed of the main spindle S or feed axis J, which has been previously acquired, to fall within a threshold value.

[0025] As described above, according to the control device for the machine tool of this embodiment, the swing command initiation unit does not perform a swing operation when machining of the workpiece begins, but starts the swing operation when a predetermined swing operation start condition is satisfied during machining of the workpiece, thereby reducing the load on the tool when machining begins and making it possible to extend the life of the tool.

[0026] A machine tool control device can be composed of one or more control units and memory units. Here, the control unit is a processor such as a CPU (Central Processing Unit) that realizes various functions by executing programs stored in the memory unit. The memory unit is composed of a storage device such as a ROM (Read Only Memory) or RAM (Random Access Memory) that stores an OS (Operating System) and application programs, and a hard disk drive or SSD (Solid State Drive) that stores various other information.

[0027] According to the above-described machine tool control device, a machine tool control method can be obtained in which the swing command creation unit 3 serves as a swing command creation means, the swing command initiation unit 4 serves as a swing command initiation means, and the control unit 5 serves as a control means.

[0028] The above-described machine tool control device and machine tool control method can be realized by hardware, software, or a combination of these. Here, "realized by software" means that the computer reads and executes a program.

[0029] The program can be stored and supplied to a computer using various types of non-transitory computer-readable media. Non-transitory computer-readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (e.g., hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / Ws, and semiconductor memories (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, and RAMs (Random Access Memory)).

[0030] Furthermore, although the above-described embodiments are preferred embodiments of the present invention, the scope of the present invention is not limited to only the above-described embodiments, and the present invention can be implemented in various modified forms within the scope that does not deviate from the gist of the present invention.

[0031] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these.

[0032] The machine tool control device and machine tool control method according to the present disclosure can be applied to various machine tools and industrial machines.

[0033] The following supplementary notes are further disclosed regarding the above-described embodiments and modifications: (Supplementary Note 1) A control device (1) for a machine tool having a main spindle (S) that rotates a workpiece (W) and a tool (T) relative to one another, and a feed axis (J) that feeds the workpiece (W) and the tool (T) relative to one another, wherein the control device (1) machines the workpiece (W) while swinging the workpiece (W) and the tool (T) relative to one another through coordinated operation of the main spindle (S) and the feed axis (J), the control device comprising: a swing command creation unit (3) that creates a swing command based on machining conditions acquired from one or more of a machining program (2), signal information (10), and parameters, the swing command creation unit (3) including the swing command initiation unit (4), the swing command initiation unit (4) not performing the swing operation at the start of machining of the workpiece (W), and starting the swing operation when a predetermined swing operation start condition is satisfied during machining of the workpiece (W).

[0034] (Supplementary Note 2) The control device for a machine tool according to Supplementary Note 1, wherein the predetermined condition for starting the swing operation is at least one of the following: a fluctuation range of a cutting resistance index value, such as torque, position deviation, or speed deviation, related to the feed of the main spindle (S) or the feed axis (J), falls within a threshold value; or a moving distance (D) of the tool (T) by driving the feed axis (J) reaches a predetermined value; or a moving time of the tool (T) by driving the feed axis (J) reaches a predetermined value.

[0035] (Supplementary Note 3) The control device of a machine tool according to Supplementary Note 2, wherein the movement distance, the predetermined position, and the time are set as values ​​such that a fluctuation range of a cutting resistance index value, such as torque, position deviation, or speed deviation, related to the feed of the main spindle (S) or the feed axis (J) obtained in advance falls within a threshold value.

[0036] (Supplementary Note 4) A method for controlling a machine tool having a main spindle (S) that rotates a workpiece (W) and a tool (T) relative to one another, and a feed axis (J) that feeds the workpiece (W) and the tool (T) relative to one another, wherein the main spindle (S) and the feed axis (J) cooperate to perform a coordinated operation of the main spindle (S) and the feed axis (J) while swinging the workpiece (W) and the tool (T) relative to one another, the method comprising: a swing command creating means that creates a swing command based on machining conditions acquired from one or more of a machining program (2), signal information (10), and parameters; the swing command creating means including the swing command initiating means; and the swing command initiating means that does not perform the swing operation at the start of machining of the workpiece (W), and starts the swing operation when a predetermined swing operation initiating condition is satisfied during machining of the workpiece (W).

[0037] REFERENCE SIGNS LIST 1 Machine tool control device 2 Machining program 3 Swing command creation unit 4 Swing command start unit 5 Control unit 10 Signal information S Spindle J Feed axis W Workpiece T Tool D Travel distance P Predetermined position

Claims

1. A control device for a machine tool having a main spindle that rotates a workpiece and a tool relative to one another, and a feed axis that feeds the workpiece and the tool relative to one another, wherein the main spindle and the feed axis operate in coordination to machine the workpiece while swinging the workpiece and the tool relative to one another, the control device for a machine tool comprising: a swing command creation unit that creates a swing command based on machining conditions obtained from one or more of a machining program, signal information, and parameters, the swing command creation unit including the swing command initiation unit that does not perform the swing operation when machining of the workpiece begins, and starts the swing operation when a predetermined swing operation start condition is met during machining of the workpiece.

2. A control device for a machine tool as described in claim 1, wherein the predetermined condition for starting the swing operation is at least one of the following: when the fluctuation range of a cutting resistance index value, such as torque, position deviation, or speed deviation, related to the feed of the main spindle or the feed axis, falls within a threshold value; when the movement distance of the tool due to the drive of the feed axis reaches a predetermined value; when the tool reaches a predetermined position due to the drive of the feed axis; or when the movement time of the tool due to the drive of the feed axis reaches a predetermined value.

3. A control device for a machine tool as described in claim 2, wherein the travel distance, the predetermined position, and the time are set to values ​​such that the fluctuation range of cutting resistance index values, such as torque, position deviation, or speed deviation, related to the feed of the main spindle or feed axis, which have been previously acquired, falls within a threshold value.

4. A method for controlling a machine tool having a main spindle that rotates a workpiece and a tool relatively, and a feed axis that feeds the workpiece and the tool relatively, and which processes the workpiece while swinging the workpiece and the tool relatively through coordinated operation of the main spindle and the feed axis, the method comprising: a swing command creating means that creates a swing command based on machining conditions obtained from one or more of a machining program, signal information, and parameters, the swing command creating means including a swing command initiating means that does not perform the swing operation when machining of the workpiece begins, and starts the swing operation when a predetermined swing operation initiating condition is satisfied during machining of the workpiece.

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