JP2019217560A - Machine tool, calculation method and calculation program - Google Patents

Abstract

To provide a machine tool that can accurately calculate a contact time during which a tool is in contact with a work-piece.SOLUTION: The machine tool comprises: a tool for processing a work-piece; a main spindle for rotating the tool or the work-piece; a detecting part for detecting loads acting on the tool or the main spindle; and a control device for controlling the machine tool. The control device specifies a first timing at which increase degrees of the loads become maximum in a period of time during which the tool contacts the work-piece and then separates from the work-piece, and specifies a second timing at which decrease degrees of the loads become maximum in the period of time during which the tool contacts the work-piece and then separates from the work-piece, and calculates a period of time from the first timing to a third timing being a timing after a predetermined time elapses after the second timing, as a contact time during which the tool is in contact with the work-piece.SELECTED DRAWING: Figure 5

Description

  The present disclosure relates to a technique for accurately calculating a contact time between a tool and a workpiece.

  Various problems occur when wear of the tool in the machine tool progresses. For example, a desired machining accuracy cannot be obtained, or a machine tool breaks down due to breakage of a tool. In order to address these problems, techniques for estimating the degree of tool wear have been developed.

  Japanese Patent Application Laid-Open Publication No. 2017-24112 (Patent Document 1) discloses a technique for estimating the degree of wear of a tool. "Discloses machine tools. Focusing on the fact that the load acting on the tool increases as the tool wears, the machine tool determines that the tool is worn when the average value of the load exceeds a predetermined threshold.

JP-A-2017-24112

  As another example, the degree of wear of the tool can be estimated from the contact time between the tool and the workpiece. More specifically, the machine tool identifies a timing at which the tool load exceeds a preset threshold during the processing of the workpiece as the first timing at the moment when the tool contacts the workpiece. Next, during machining of the workpiece, the machine tool identifies a timing at which the value falls below a preset threshold value as a second timing at the moment when the tool leaves the workpiece. Then, the machine tool calculates a period between the first timing and the second timing as a contact time between the workpiece and the tool. The longer the contact time, the more the degree of wear of the tool is advanced.

  However, the inventors have obtained a new finding that the moment when the tool separates from the workpiece is not the second timing. Therefore, if the contact time between the tool and the work is calculated based on the second timing, errors accumulate, and the machine tool cannot accurately estimate the wear and the life of the tool. Therefore, it is desired to more accurately calculate the contact time between the tool and the workpiece during the processing of the workpiece.

  The present disclosure has been made in order to solve the above-described problems, and an object of one aspect is to provide a machine tool capable of more accurately calculating a contact time between a tool and a workpiece during the processing of the workpiece. It is to provide. An object in another aspect is to provide a calculation method capable of more accurately calculating a contact time between a tool and a work during the processing of the work. Another object of the present invention is to provide a calculation program that can more accurately calculate the contact time between a tool and a workpiece during the processing of the workpiece.

  In an example of the present disclosure, a machine tool includes a tool for processing a work, a main shaft for rotating the tool or the work, a detection unit for detecting a load applied to the tool or the main shaft, A control device for controlling the machine tool. The control device specifies a first timing at which the degree of increase in the load is maximum between the time when the tool comes into contact with the work and the time when the tool comes into a non-contact state, and after the tool comes into contact with the work. A second timing at which the degree of reduction of the load is maximum before the non-contact state is specified, and a period from the first timing to a third timing that is a predetermined time after the second timing is defined as the second timing. It is calculated as the contact time between the tool and the work.

  Preferably, the control device calculates the predetermined time based on a radius of the tool and a moving speed of the tool.

  Preferably, when the cutting width of the workpiece by the tool is larger than the radius of the tool, the control device calculates the predetermined time based on the radius of the tool and a moving speed of the tool, When the cut width is smaller than the radius of the tool, the predetermined time is calculated based on the radius of the tool, the moving speed of the tool, and the cut width.

  Preferably, the control device estimates the degree of wear of the tool based on the accumulated value of the contact time.

  Preferably, the control device estimates a remaining machining time until the life of the tool is reached, based on the accumulated value of the contact time.

  Preferably, the control device calculates a moving average of the load sequentially detected by the detection unit, calculates a change amount of the sequentially calculated moving average per unit time, and calculates the change amount of the sequentially calculated change amount. The moving average is used as an index of the degree of increase and the degree of decrease.

  In another example of the present disclosure, a calculation method for calculating a contact time between a tool and a workpiece includes driving a spindle for rotating the tool or the workpiece, and the tool machining the workpiece; and Or a step of detecting a load applied to the spindle, and a step of specifying a first timing at which the degree of increase in the load is maximum between the time when the tool comes into contact with the workpiece and a time when the tool is brought into a non-contact state. A step of specifying a second timing at which the degree of reduction of the load is maximum between the time when the tool comes into contact with the workpiece and the time when the tool is brought into a non-contact state, and after a predetermined time from the first timing, after the second timing Calculating a period up to the third timing as a contact time between the tool and the work.

  In another example of the present disclosure, a calculation program for calculating a contact time between a tool and a work includes: driving a main spindle for rotating the tool or the work on a machine tool; and the tool processing the work. Detecting the load applied to the tool or the spindle; and specifying a first timing at which the degree of increase in the load is maximum between the time when the tool comes into contact with the work and the time when the tool is not contacted. Determining a second timing at which the degree of reduction of the load is maximum between the time when the tool comes into contact with the workpiece and the time when the tool is brought into a non-contact state; and the second timing from the first timing. Calculating a contact time between the tool and the workpiece during a period up to a third timing after the predetermined time.

  In one aspect, the contact time between the tool and the workpiece during the processing of the workpiece can be calculated more accurately.

  The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the invention that is understood in connection with the accompanying drawings.

FIG. 2 is a diagram showing an example of a machine tool according to an embodiment. It is a figure showing an example of a processing mode of a work. FIG. 3 is a diagram illustrating a processing mode illustrated in FIG. 2 from a Z direction. FIG. 5 is a diagram illustrating an example of a processing mode from when a tool comes into contact with a work until the tool comes into a non-contact state. FIG. 5 is a diagram illustrating a temporal change of a tool load and a temporal change of a rate of change of a tool load in the machining process illustrated in FIG. 4. It is a figure showing the processing mode in case the cut width of a work is larger than the radius of a tool. It is a figure showing a processing mode in case a cut width of a work is smaller than a radius of a tool. FIG. 3 is a diagram showing an example of a functional configuration of the machine tool according to the embodiment. It is a figure showing an example of the data structure of processing history information. It is a flowchart showing the calculation processing of the machining time of a tool. FIG. 3 is a block diagram showing a main hardware configuration of the machine tool according to the embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are the same. Therefore, detailed description thereof will not be repeated. In addition, each embodiment and each modification described below may be appropriately selectively combined.

<A. Configuration of Machine Tool 100>
The configuration of the machine tool 100 will be described with reference to FIG. FIG. 1 is a diagram illustrating an example of a machine tool 100.

  FIG. 1 shows a machine tool 100 as a machining center. The following describes the machine tool 100 as a machining center, but the machine tool 100 is not limited to a machining center. For example, the machine tool 100 may be a lathe or another cutting machine or grinding machine. The machine tool 100 may be a horizontal machining center on which tools are mounted in a vertical direction, or may be a vertical machining center on which tools are mounted in a horizontal direction.

  As shown in FIG. 1, the machine tool 100 has a spindle head 21. The spindle head 21 includes a spindle 22 and a housing 23. The main shaft 22 is arranged inside the housing 23. A tool for processing a workpiece, which is a workpiece, is mounted on the spindle 22. In the example of FIG. 1, a tool 32 as an end mill is mounted on the main shaft 22.

  The spindle head 21 is configured to be drivable in the Z-axis direction along a ball screw 25. A drive mechanism such as a servomotor is connected to the ball screw 25. The drive mechanism moves the spindle head 21 by driving the ball screw 25, and moves the spindle head 21 to an arbitrary position in the Z-axis direction.

  A drive mechanism such as a servomotor is connected to the spindle 22. The drive mechanism drives the main shaft 22 to rotate about a center axis AX1 parallel to the Z-axis direction (vertical direction). As a result, the tool 32 mounted on the main shaft 22 rotates around the central axis AX1 in conjunction with the rotation of the main shaft 22. When the machine tool 100 is a lathe, a work is mounted on the spindle 22. In this case, the work mounted on the main shaft 22 rotates with the rotation of the main shaft 22.

  The machine tool 100 further includes an automatic tool changer (ATC: Automatic Tool Changer) 30. The automatic tool changer 30 includes a magazine 31, an extruding mechanism 33, and an arm 36. The magazine 31 is a device for accommodating various tools 32 for processing a work. The magazine 31 is composed of a plurality of tool holders 34 and sprockets 35.

  The tool holding unit 34 is configured to be able to hold various tools 32. The plurality of tool holders 34 are arranged annularly around the sprocket 35. The sprocket 35 is provided so as to be rotatable around a central axis AX2 parallel to the X axis by driving a motor. With the rotation of the sprocket 35, the plurality of tool holders 34 rotate around the central axis AX2.

  The automatic tool changer 30 extracts the tool 32 to be mounted from the magazine 31 and mounts the tool 32 on the spindle 22 based on receiving the tool replacement command. More specifically, the automatic tool changer 30 moves the tool holding unit 34 that holds the target tool 32 before the pushing mechanism 33. Next, the pushing mechanism 33 pushes out the target tool 32 toward the replacement position by the arm 36. Thereafter, the arm 36 removes the target tool 32 from the tool holder 34 and removes the currently mounted tool 32 from the spindle 22. Thereafter, the arm 36 makes a half turn while holding these tools 32, mounts the target tool 32 on the main shaft 22, and stores the original tool 32 in the tool holder 34. Thereby, the exchange of the tool 32 is performed.

  The machine tool 100 further includes a moving mechanism 50 for moving the work to be processed on the XY plane. The moving mechanism 50 includes guides 51 and 53, ball screws 52 and 54, and a table 55 (work holding unit) for holding a work.

  The guide 51 is installed parallel to the Y axis. The guide 53 is provided on the guide 51 and is installed parallel to the X axis. The guide 53 is configured to be drivable along the guide 51. The table 55 is provided on the guide 53, and is configured to be driven along the guide 53.

  A drive mechanism such as a servomotor is connected to the ball screw 52. The drive mechanism moves the guide 53 along the guide 51 by driving the ball screw 52, and moves the guide 53 to an arbitrary position in the Y-axis direction. Similarly, a drive mechanism such as a servomotor is connected to the ball screw 54. The drive mechanism moves the table 55 along the guide 53 by driving the ball screw 54, and moves the table 55 to an arbitrary position in the X-axis direction. That is, the machine tool 100 moves the table 55 to an arbitrary position on the XY plane by cooperatively controlling the drive mechanisms connected to the ball screws 52 and 54, respectively. Thereby, the machine tool 100 can perform the processing while moving the work held on the table 55 on the XY plane.

  A dynamometer 110 is provided at a portion where the work W is installed on the table 55. The dynamometer 110 indirectly detects a load applied to the main shaft 22 or the tool 32 by detecting a force exerted by the tool 32 on the work W. Although the details will be described later, the detected load is used for estimating the contact time between the tool 32 and the workpiece W.

<B. Work mode of work>
With reference to FIG. 2 and FIG. 3, a working mode of the work W by the tool 32 is described. FIG. 2 is a diagram illustrating an example of a processing mode of the workpiece W. FIG. 3 is a diagram showing the processing mode shown in FIG. 2 from the Z direction.

  2 and 3 show the tool 32 as an end mill. The tool 32 has a plurality of blades on its side surface, and processes the work W by rotating and contacting the work W.

In the examples of FIGS. 2 and 3, the tool 32 repeatedly cuts the workpiece W along the machining path L programmed in advance. An example of a processing parameter that can be set is a cutting width of the work W. The “cutting width” here is a direction perpendicular to the axial direction of the main shaft 22 and the width at which the tool 32 cuts the work W in the axial direction of the main spindle 22 (hereinafter, also referred to as “cutting width a _p ”). This is a concept including a width at which the tool 32 cuts the work W in a direction orthogonal to the moving direction of the tool 32 with respect to the work W (hereinafter, also referred to as “cutting width a _e ”).

In the examples of FIGS. 2 and 3, a radial cut width a _e and an axial cut width a _e are set as parameters. When processed in accordance with this parameter is started, the tool 32 is sequentially cut the working portion of the first-stage cut width a _p for each notch width a _e. Next, the tool 32 is sequentially cut the working portion of the second stage notch width a _p for each notch width a _e. Then, successively cutting the working portion of the third stage of the cut width a _p for each notch width a _e. Then, successively cutting the working portion of the fourth-stage cut width a _p for each notch width a _e. As described above, the tool 32 processes the work W into an arbitrary shape by sequentially cutting the work W along the processing path L programmed in advance.

<C. Calculation method of contact time between tool and workpiece>
Hereinafter, the process of calculating the contact time between the tool 32 and the workpiece W will be described with reference to FIGS. FIG. 4 is a diagram illustrating an example of a processing mode from when the tool 32 comes into contact with the workpiece W until the tool 32 comes into a non-contact state. FIG. 5 is a diagram showing a temporal transition of the tool load and a temporal transition of the rate of change of the tool load in the machining process shown in FIG.

  The “tool load” shown in FIG. 5 is represented, for example, by a force acting on the blade surface of the tool 32 when the work W is removed. The “rate of change in tool load” refers to the amount of change in the force acting on the spindle 22 or the tool 32 per unit time. The length of the unit time is arbitrary (for example, 1 second). The rate of change of the tool load corresponds to the time derivative (that is, the slope) of the tool load. The tool load is obtained, for example, from the above-mentioned dynamometer 110 (see FIG. 1).

  In the example of FIG. 4, a state is shown in which the tool 32 as an end mill processes the workpiece W by down-cut from the left side of the page to the right side of the page. It is assumed that the tool 32 comes into contact with the workpiece W at the timing T1 of this machining process. At this time, the cutting amount of the work W by the tool 32 changes, and the tool load increases rapidly (see FIG. 5). Focusing on this, the machine tool 100 determines the timing T1 (first timing) at which the degree of increase in the tool load is maximum between the time when the tool 32 comes into contact with the workpiece W and the time when the tool 32 is brought into the non-contact state. It is assumed that the contact point 32 contacts the workpiece W.

  Thereafter, the tool load stabilizes while repeating some increase and decrease. That is, the rate of change of the tool load becomes substantially zero.

  Thereafter, it is assumed that the tool 32 reaches the end of the workpiece W at timing T2. At this time, the cutting amount of the work W by the tool 32 changes, and the tool load sharply decreases. Thereafter, the tool load stabilizes while repeating some increase and decrease. That is, the rate of change of the tool load becomes substantially zero. Thereafter, at timing T3, the cutting amount of the work W by the tool 32 becomes zero, and the tool 32 and the work W are brought into a non-contact state.

  As described above, the tool 32 is still in contact with the workpiece W at the timing T2 when the degree of reduction of the tool load is maximized. Therefore, the machine tool 100 sets the timing T3, which is the predetermined time ΔT after the timing T2, as the moment when the tool 32 separates from the workpiece W.

  The machine tool 100 sets a period from the timing T1 to the timing T3 as a contact time between the tool 32 and the workpiece W (hereinafter, also referred to as a “machining time”). The machine tool 100 calculates the processing time based on the timings T1 and T3 instead of the timings T1 and T2, so that the time during which the tool 32 is actually processing the workpiece W can be calculated more accurately.

  In the above description, the description has been given on the assumption that cutting is performed with the tool 32 as an end mill. However, the tool 32 is not limited to an end mill. The tool 32 may be any cutting tool for performing plane machining, and may be, for example, a milling cutter.

<D. Calculation method of predetermined time ΔT>
As described with reference to FIGS. 4 and 5, the machine tool 100 sets the timing T3, which is a predetermined time ΔT after the timing T2 at which the degree of reduction of the tool load becomes maximum, as the moment when the tool 32 separates from the workpiece W. Hereinafter, a method of calculating the predetermined time ΔT will be described.

  As described above, the timing T2 is a moment when the cutting amount of the work W by the tool 32 starts to decrease. When the tool 32 further advances the distance of the radius from the timing T2, the tool 32 and the workpiece W are surely brought into a non-contact state. Focusing on this point, the machine tool 100 calculates the predetermined time ΔT based on the radius of the tool 32 and the moving speed of the tool 32.

Preferably, the machine tool 100 changes the method of calculating the predetermined time ΔT depending on whether the cutting width a _e of the work W by the tool 32 is larger than the radius of the tool 32. Figure 6 is a diagram cut width a _e of the workpiece W is shown a working embodiment when greater than the radius r of the tool 32.

As shown in FIG. 6, when the cut width a _e of the work W is larger than the radius r of the tool 32, the tool 32 moves out of the radius r from the timing T2, and the tool 32 and the work W do not contact each other. In this state, the cutting amount of the work W becomes zero. Therefore, in this case, the machine tool 100 calculates the predetermined time ΔT based on the radius r of the tool 32 and the moving speed v of the tool 32. More specifically, the machine tool 100 calculates the predetermined time ΔT based on the following calculation formula (1).

ΔT = r / v (1)
Figure 7 is a diagram cut width a _e of the workpiece W is shown a working embodiment when smaller than the radius r of the tool 32.

As shown in FIG. 7, when the cut width a _e of the workpiece W is smaller than the radius r of the tool 32, at the timing T2 where the cutting amount changes, the tool 32 is somewhat protruding from the end of the workpiece W. Therefore, in this case, the machine tool 100 calculates the radius r of the tool 32, the moving speed v of the tool 32, based on the notch width a _e, a predetermined time delta. More specifically, the machine tool 100 calculates the predetermined time ΔT based on the following calculation formula (2).

_{^{ΔT = √ {r 2 - (}} r-a e) 2} / v ··· (2)
As described above, the machine tool 100 changes the method of calculating the predetermined time ΔT depending on whether the cutting width a _e of the work W by the tool 32 is larger than the radius r of the tool 32. Thereby, the machine tool 100 can calculate the processing time of the tool 32 more accurately.

  The predetermined time ΔT does not necessarily need to be calculated based on the above equations (1) and (2), and may be determined in advance for each type of tool 32. The calculation timing of the predetermined time ΔT may be during the processing of the work W or before the start of the processing of the work W.

<E. Functional Configuration of Machine Tool 100>
With reference to FIG. 8, functions of the machine tool 100 will be described. FIG. 8 is a diagram illustrating an example of a functional configuration of the machine tool 100.

  As shown in FIG. 8, the machine tool 100 includes a control device 101 and a storage device 120 as a hardware configuration. The control device 101 is, for example, an NC control device that can execute an NC (Numerical Control) program. The NC control device includes at least one integrated circuit. The integrated circuit includes, for example, at least one CPU (Central Processing Unit), at least one ASIC (Application Specific Integrated Circuit), at least one FPGA (Field Programmable Gate Array), or a combination thereof.

  The control device 101 includes a load acquisition unit 152, a moving average unit 154, a change rate calculation unit 156, a moving average unit 158, a machining time calculation unit 160, a wear estimation unit 162, and a life estimation unit 164. .

The load acquisition unit 152 acquires a tool load from a load detection unit such as the dynamometer 110 (see FIG. 1) at a predetermined sampling rate. The acquired tool load is output to the moving average unit 154 as the tool load m ₁ (t) after being associated with the time information.

  The load detecting unit for detecting the tool load is not limited to the dynamometer 110, and various detecting means (detecting units) may be employed. As an example, the command value to the servo motor that drives the spindle 22 is correlated with the tool load. Therefore, the machine tool 100 may use a command value to the servomotor as an index of a tool load.

The moving average unit 154 calculates a moving average of the time-series tool load m ₁ (t). More specifically, the moving average unit 154 repeats the processing of calculating the average value of the tool load m ₁ (t) in a certain section and the processing of shifting the section, so that the moving average unit 154 calculates the average value of the tool load m ₁ (t) from the tool load m ₁ (t). The moving average m ₂ (t) is calculated. The calculated moving average m ₂ (t) is sequentially output to the change rate calculation unit 156.

By calculating the moving average m ₂ (t), the periodic change of the tool load m ₁ (t) generated due to the interrupted cutting is smoothed. Also, sudden changes in tool load are absorbed.

The change rate calculation unit 156 calculates a change rate m ₃ (t) per unit time of the moving average m ₂ (t). As an example, the change rate calculating unit 156 calculates the time derivative of the moving average m ₂ (t) as the tool load change rate m ₃ (t). The calculated change rate m ₃ (t) is sequentially output to the moving average unit 158.

The moving average unit 154 calculates a moving average of the time-series change rate m ₃ (t). More specifically, the moving average unit 154 repeats the process of calculating the average value of the change rate m ₃ (t) in a certain section and the process of shifting the section, thereby obtaining the change rate m ₃ (t) from the change rate m ₃ (t). The moving average m ₄ (t) is calculated. The calculated moving average m ₄ (t) is output to the processing time calculation unit 160.

By calculating the moving average m ₄ (t), the rate of change m ₃ (t) is smoothed. As a result, the moving average unit 154 can absorb sudden changes in the tool load, and is less likely to be affected by noise when calculating the machining time of the tool 32.

The processing time calculation unit 160 calculates the time during which the tool 32 is actually processing the workpiece W (that is, the processing time). More specifically, the processing time calculation unit 160 specifies the timing T1 at which the degree of increase of the moving average m ₄ (t) is maximum, and sets the timing T1 as the moment when the tool 32 contacts the workpiece W. Further, the processing time calculation unit 160 specifies the timing T2 at which the degree of decrease of the moving average m ₄ (t) is maximum, and sets the timing T3 that is a predetermined time ΔT after the timing T2 to the position where the tool 32 separates from the workpiece W. Moment. Then, the processing time calculation unit 160 sets the period from the timing T1 to T3 as the processing time of the tool 32.

  As described above, the predetermined time ΔT is calculated based on the radius of the tool 32 and the moving speed of the tool 32. The radius of the tool 32 can be obtained in various ways. As an example, the radius of the tool 32 is acquired from the below-described tool information 124 (see FIG. 11) that defines various information of the tool 32. Alternatively, the radius of the tool 32 may be set in advance by the user.

  Further, the moving speed of the tool 32 is specified by various methods. As an example, the moving speed of the tool 32 is specified by analyzing a machining program being executed. Alternatively, the moving speed of the tool 32 is specified from command values output to servo motors 112A to 112D (see FIG. 11) described later. Alternatively, the moving speed of the tool 32 is specified based on feedback signals output from encoders 113A to 113D (see FIG. 11) described later.

  The calculated processing time is written in the processing history information 126 stored in the storage device 120. FIG. 9 is a diagram illustrating an example of the data structure of the processing history information 126.

  As shown in FIG. 9, in the machining history information 126, the time information and the machining time of the tool 32 are associated with each other. The time information may be, for example, the time at which the tool 32 contacts the workpiece W, or the time at which the tool 32 separates from the workpiece W. In the machining history information 126, the accumulated value of the machining time of the tool 32 is managed as the total machining time. Preferably, a plurality of machining history information 126 are prepared for each tool 32, and the total machining time is managed for each tool 32.

  The wear estimating unit 162 refers to the processing history information 126 to obtain the total processing time of the tool 32 whose wear is to be estimated, and estimates the degree of wear of the tool 32 based on the total processing time. Typically, the longer the total machining time is, the greater the degree of wear of the tool 32 is. In other words, the shorter the total machining time, the smaller the degree of wear of the tool 32.

  As an example, the wear degree of the tool 32 is calculated based on a predetermined correlation between the total machining time and the wear degree. In a certain aspect, the correlation is defined by a correlation formula using the total machining time as an explanatory variable and the tool wear of the tool 32 as an objective variable. In another aspect, the correlation is defined in a table format in which the tool wear of the tool 32 is associated with each total machining time.

  The life estimation unit 164 refers to the processing history information 126 to obtain the total processing time of the tool 32 whose life is to be estimated, and based on the total processing time, the remaining processing time until the tool 32 reaches the life ( Hereinafter, this is also referred to as “tool life”.) Here, the “tool life” means the length of a period until the recommended replacement timing of the tool 32 or the failure timing comes.

  Typically, the longer the total machining time, the shorter the tool life. Stated differently, the shorter the total machining time, the longer the tool life.

  As an example, the tool life is calculated based on a predetermined correlation between the total machining time and the tool life. In a certain aspect, the correlation is defined by a correlation formula using the total machining time as an explanatory variable and the tool life as an objective variable. In another aspect, the correlation is defined in a table format in which the tool life is associated with each total machining time.

<F. Control structure of machine tool 100>
The control structure of the machine tool 100 will be described with reference to FIG. FIG. 10 is a flowchart illustrating a process of calculating the machining time of the tool 32. The processing in FIG. 10 is realized by the control device 101 of the machine tool 100 executing a program. In other aspects, some or all of the processing may be performed by circuit elements or other hardware.

  In step S110, control device 101 determines whether or not processing has been started. As an example, the control device 101 determines that the machining has been started based on the execution of the machining program. When determining that the processing of the workpiece W has been started (YES in step S110), the control device 101 switches the control to step S112. Otherwise (NO in step S110), control device 101 executes the process of step S110 again.

  In step S112, the control device 101 acquires the tool load at a predetermined sampling rate as the above-described load acquisition unit 152 (see FIG. 8). As an example, the tool load is obtained from a load detection unit such as the dynamometer 110 (see FIG. 1).

  In step S114, the moving average of the time-series tool loads acquired in step S112 is calculated as the moving average unit 154 (see FIG. 8).

  In step S120, the control device 101 determines whether the tool 32 has contacted the workpiece W. As an example, the control device 101 determines that the tool 32 has contacted the workpiece W based on the fact that the moving average of the tool load calculated in step S114 has exceeded a predetermined value. When determining that the tool 32 has contacted the workpiece W (YES in step S120), the control device 101 switches the control to step S122. Otherwise (NO in step S120), control device 101 returns the control to step S112.

  In step S122, the control device 101 calculates the tool load change rate as the above-described change rate calculation unit 156 (see FIG. 8). As an example, the change rate of the tool load is calculated by the time derivative of the moving average of the tool load calculated in step S114.

  In step S124, the control device 101 stores the change rate of the tool load calculated in step S122 in the storage device 120 in association with the current time information.

  In step S130, the control device 101 determines whether or not the tool 32 and the workpiece W have definitely come into a non-contact state. As an example, the control device 101 determines that the tool 32 and the workpiece W have certainly come into a non-contact state based on the fact that the moving average of the tool load has fallen below a predetermined value. If the control device 101 determines that the tool 32 and the workpiece W have definitely come into a non-contact state (YES in step S130), the control device 101 switches the control to step S132. Otherwise (NO in step S130), control device 101 returns the control to step S122.

  In step S132, the control device 101 determines the contact time between the workpiece W and the tool 32 based on the time-series change rate of the tool load stored in step S124 as the above-described machining time calculation unit 160 (see FIG. 8). (Ie, processing time) is calculated. The method of calculating the processing time is as described with reference to FIGS. 4 to 7, and thus the description thereof will not be repeated.

  In step S134, the control device 101 writes the processing time calculated in step S132 in the processing history information 126 (see FIG. 9).

  In step S140, the control device 101 determines whether the processing of the work W has been completed. If control device 101 determines that machining of work W has been completed (YES in step S140), control device 101 ends the process illustrated in FIG. Otherwise (NO in step S140), control device 101 returns the control to step S112.

  In the example of FIG. 10, an example in which the processing time is calculated during the processing of the workpiece W has been described. However, the calculation of the processing time may be calculated after the processing is completed. As an example, the control device 101 accumulates the rate of change of the tool load calculated in step S122 in the storage device 120, and refers to the database at any time after the end of the processing, and The processing time may be calculated.

<G. Hardware configuration of machine tool 100>
An example of a hardware configuration of the machine tool 100 will be described with reference to FIG. FIG. 11 is a block diagram illustrating a main hardware configuration of the machine tool 100.

  The machine tool 100 includes a spindle 22, ball screws 25, 52, and 54, a control device 101, a ROM 102, a RAM 103, a communication interface 104, a display interface 105, an input interface 109, a dynamometer 110, a servo Drivers 111A to 111D, servo motors 112A to 112D, encoders 113A to 113D, and a storage device 120 are included.

  The control device 101 controls the operation of the machine tool 100 by executing various programs such as a machining program 122 (NC program) of the machine tool 100. The control device 101 reads the processing program 122 from the storage device 120 to the ROM 102 based on the reception of the execution instruction of the processing program 122. The RAM 103 functions as a working memory and temporarily stores various data necessary for executing the machining program 122.

  The communication interface 104 is connected to a LAN, an antenna, or the like. The machine tool 100 exchanges data with an external communication device via the communication interface 104. External communication devices include, for example, a server and other communication terminals. The machine tool 100 may be configured to be able to download the machining program 122 from the communication terminal.

  The display interface 105 is connected to a display device such as the display 130, and transmits an image signal for displaying an image to the display 130 according to a command from the control device 101 or the like. The display 130 is, for example, a liquid crystal display, an organic EL display, or another display device. As an example, the display 130 displays the degree of wear of the tool 32, the life of the tool 32, a warning when the degree of wear of the tool 32 exceeds a limit value, and the like.

  The input interface 109 can be connected to the input device 131. The input device 131 is, for example, a mouse, a keyboard, a touch panel, or another input device that can receive a user operation.

  The servo driver 111A sequentially receives an input of a target rotation speed (or a target position) from the control device 101, and controls the servo motor 112A so that the servo motor 112A rotates at the target rotation speed. More specifically, the servo driver 111A calculates the actual rotation speed (or actual position) of the servo motor 112A from the feedback signal of the encoder 113A, and when the actual rotation speed is smaller than the target rotation speed, the servo driver 112A. Is increased, and when the actual rotation speed is larger than the target rotation speed, the rotation speed of the servomotor 112A is decreased. As described above, the servo driver 111A approaches the rotation speed of the servo motor 112A to the target rotation speed while sequentially receiving the feedback of the rotation speed of the servo motor 112A. The servo driver 111A moves the table 55 (see FIG. 1) connected to the ball screw 54 along the X-axis direction, and moves the table 55 to an arbitrary position in the X-axis direction.

  With the same motor control, the servo driver 111B moves the guide 53 (see FIG. 1) connected to the ball screw 52 along the Y-axis direction, and moves the table 55 (see FIG. 1) on the guide 53 in the Y-axis direction. Move to any position. By performing the same motor control, the servo driver 111C moves the spindle head 21 (see FIG. 1) connected to the ball screw 25 to an arbitrary position in the Z-axis direction. By performing the same motor control, the servo driver 111D controls the rotation speed of the main shaft 22.

  The control signal (current value) output from the servo driver 111D to the servomotor 112D correlates with the magnitude of the tool load. Therefore, control device 101 may detect the tool load from the control signal output from servo driver 111D instead of the output value of dynamometer 110. Typically, the control device 101 calculates a result obtained by dividing the current value output from the servo driver 111D by the rotation speed of the servomotor 112D as a tool load. As described above, various detection units such as the dynamometer 110 and the servo driver 111D can be employed in the configuration for detecting the tool load.

  The storage device 120 is, for example, a storage medium such as a hard disk or a flash memory. The storage device 120 stores a machining program 122 according to the present embodiment, tool information 124 defining the radius of the tool 32 and the like, the above-described machining history information 126 (see FIG. 9), and the like. The storage locations of the machining program 122, the tool information 124, and the machining history information 126 are not limited to the storage device 120, but include a storage area (for example, a cache area) of the control device 101, the ROM 102, the RAM 103, and an external device (for example, a server). And so on.

  The machining program 122 may be provided as a part of an arbitrary program, not as a single program. In this case, the control processing according to the present embodiment is realized in cooperation with an arbitrary program. Even a program that does not include such some modules does not depart from the gist of the machining program 122 according to the present embodiment. Further, some or all of the functions provided by the machining program 122 may be realized by dedicated hardware. Further, the machine tool 100 may be configured in a form such as a so-called cloud service in which at least one server executes a part of the processing of the machining program 122.

<H. Summary>
As described above, the machine tool 100 specifies the timing T1 at which the degree of increase in the tool load is maximum between the time when the tool 32 comes into contact with the workpiece W and the time when the tool 32 comes into a non-contact state, and sets the timing T1 to the tool T It is assumed that the contact point 32 contacts the workpiece W. Thereafter, the machine tool 100 specifies the timing T2 at which the degree of reduction of the tool load is maximum between the time when the tool 32 comes into contact with the workpiece W and the time when the tool 32 comes into non-contact, and after a predetermined time ΔT of the timing T2. Is the moment when the tool 32 is separated from the workpiece W. Then, the machine tool 100 calculates a period from the timing T1 to the timing T3 as an actual machining time. Thereby, the machine tool 100 can calculate the actual machining time more accurately.

  The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  21 spindle head, 22 spindle, 23 housing, 25, 52, 54 ball screw, 30 automatic tool changer, 31 magazine, 32 tools, 33 extrusion mechanism, 34 tool holder, 35 sprocket, 36 arm, 50 moving mechanism, 51 , 53 guide, 55 table, 100 machine tool, 101 controller, 102 ROM, 103 RAM, 104 communication interface, 105 display interface, 109 input interface, 110 dynamometer, 111A, 111B, 111C, 111D servo driver, 112A, 112B , 112C, 112D servo motor, 113A, 113B, 113C, 113D encoder, 120 storage device, 122 machining program, 124 tool information, 126 machining history information, 130 display 131 input device 152 load acquisition unit, 154 and 158 moving average unit, 156 change rate calculating section, 160 processing time calculation unit, 162 the wear estimation unit, 164 life estimator.

Claims (8)

A machine tool,
A tool for processing the work,
A spindle for rotating the tool or the work;
A detection unit for detecting a load applied to the tool or the spindle,
A control device for controlling the machine tool,
The control device includes:
The first timing at which the degree of increase in the load is maximum between the time when the tool comes into contact with the work and the time when the tool becomes non-contact is specified,
A second timing at which the degree of decrease in the load is maximum during a period from when the tool comes into contact with the workpiece to when the tool is in a non-contact state,
A machine tool for calculating a period from the first timing to a third timing that is a predetermined time after the second timing as a contact time between the tool and the work.   The machine tool according to claim 1, wherein the control device calculates the predetermined time based on a radius of the tool and a moving speed of the tool. The control device includes:
When the cutting width of the workpiece by the tool is larger than the radius of the tool, the predetermined time is calculated based on the radius of the tool and the moving speed of the tool,
The machine tool according to claim 2, wherein when the cut width is smaller than a radius of the tool, the predetermined time is calculated based on the radius of the tool, a moving speed of the tool, and the cut width.   The machine tool according to any one of claims 1 to 3, wherein the control device estimates the degree of wear of the tool based on the accumulated value of the contact time.   The machine tool according to any one of claims 1 to 4, wherein the control device estimates a remaining machining time until a life of the tool is reached, based on the accumulated value of the contact time. The control device includes:
Calculating a moving average of the loads sequentially detected by the detection unit,
Calculating the amount of change per unit time of the moving average, which is calculated sequentially,
The machine tool according to any one of claims 1 to 5, wherein a moving average of the sequentially calculated change amounts is used as an index of the increase degree and the decrease degree. A calculation method for calculating a contact time between a tool and a work,
Driving a spindle for rotating the tool or the work, and the tool processing the work;
Detecting a load on the tool or the spindle;
A step of specifying a first timing at which the degree of increase in the load is maximum between the time when the tool comes into contact with the workpiece and the time when the tool is brought into a non-contact state,
A step of specifying a second timing at which the degree of decrease in the load is maximum between the time when the tool comes into contact with the work and the time when the tool comes into a non-contact state,
Calculating a period from the first timing to a third timing that is a predetermined time after the second timing as a contact time between the tool and the workpiece. A calculation program for calculating a contact time between a tool and a work,
The calculation program is provided for a machine tool,
Driving a spindle for rotating the tool or the work, and the tool processing the work;
Detecting a load on the tool or the spindle;
A step of specifying a first timing at which the degree of increase in the load is maximum between the time when the tool comes into contact with the workpiece and the time when the tool is brought into a non-contact state,
A step of specifying a second timing at which the degree of decrease in the load is maximum between the time when the tool comes into contact with the work and the time when the tool comes into a non-contact state,
Calculating a period from the first timing to a third timing that is a predetermined time after the second timing as a contact time between the tool and the work.

Images