Machine tool

Abstract

A control device (20) of a machine tool (1) checks data relating to the inertia of rotating bodies (15, 16) when rotating the rotating bodies (15, 16) in accordance with a machining program, checks whether or not the rotational speed of the rotating bodies (15, 16) specified in the machining program is equal to or less than a limit rotational speed set in accordance with the inertia when the data relating to the inertia is set, and if the limit rotational speed is exceeded, determines that the rotating bodies (15, 16) rotate in accordance with the machining program. If so, the rotation speed is equal to or less than the limit rotation speed, and the rotation speed of the rotating bodies (15, 16) specified in the machining program is limited by the preset rotation speed as the permissible rotation speed.

Description

Technical Field

[0001] The present invention relates to a machine tool comprising: a motion mechanism including a rotating body; and a control device for controlling at least the rotating motion of the rotating body according to a machining program. Background Art

[0002] In the field of machine tools, a motor is used for rotating a workpiece or a tool as a rotating body. The motor is connected to the rotating body to drive the rotating body, and the operation of the motor is controlled by the control device.

[0003] However, such machine tools are conventionally provided with a circuit called a dynamic brake circuit, which is used to stop the motor urgently when the motor cannot be controlled due to a power failure or other reasons during its rotation. As an example of a device having such a dynamic brake circuit, a motor drive device disclosed in Japanese Patent No. 6285477 (hereinafter referred to as Patent Document 1) is conventionally known.

[0004] As disclosed in the publication, the motor drive device is composed of the following parts: an inverter that drives the motor; a rotation speed acquisition unit that acquires the rotation speed of the motor; an inertia information storage unit that stores information related to the inertia of the motor; a rotation energy calculation unit that calculates the rotation energy of the motor based on the rotation speed and inertia of the motor; a dynamic braking circuit that generates a deceleration torque using the motor's power generation braking during an emergency stop; a tolerance information storage unit that stores information related to the tolerance of the resistor in the dynamic braking circuit; a power element operation unit that turns on the power element of one of the upper arm and the lower arm and turns off the power element of the other arm during an emergency stop of the motor; a dynamic braking circuit operation unit that operates a switch of the dynamic braking circuit; and a tolerance comparison unit that compares the rotation energy of the motor with the tolerance of the dynamic braking circuit.

[0005] Furthermore, the dynamic brake circuit operating unit does not operate the dynamic brake circuit when the rotational energy of the motor exceeds the tolerance of the dynamic brake circuit, and operates the dynamic brake circuit when the rotational energy of the motor is below the tolerance. It should be noted that when the rotational energy of the motor exceeds the tolerance, the dynamic brake circuit operating unit reduces the rotational speed of the motor by idling the motor for a period of time, and operates the dynamic brake circuit after the rotational energy of the motor becomes below the tolerance.

[0006] Thus, in the conventional motor drive device, damage to the dynamic brake circuit is avoided by the dynamic brake circuit operation unit operating as described above. Prior art literature Patent Literature

[0007] Patent Document 1: Japanese Patent No. 6285477 Summary of the invention

[0008] As described above, the conventional motor drive device is constructed such that, when the motor cannot be controlled due to power failure or other reasons during operation, the emergency stop circuit is used to stop the motor if the rotational energy of the motor does not exceed the tolerance of the emergency stop circuit. If the rotational energy of the motor exceeds the tolerance, the motor is allowed to idle for a period of time, and after its rotational energy becomes below the tolerance, the emergency stop circuit is operated to stop the motor urgently.

[0009] However, when the motor rotation speed is set to a high speed, there is a concern that it may exceed the tolerance of the emergency stop circuit that operates during an emergency stop as described above. In addition, when the inertia of the rotating body is large, a large load is applied to the motor during its acceleration and deceleration, so it cannot be said to be in an optimal state.

[0010] In processing using NC machine tools, an NC program is used. The NC program is generated by an operator or automatically by an automatic programming device. The rotation speed of the tool spindle or the rotation speed of the motor for the workpiece spindle is determined based on many factors related to processing conditions such as the tool material, workpiece material or processing accuracy. In the past, there has been no research on the inertia of the rotating body including the motor.

[0011] Therefore, in conventional machine tools, the rotation speed of the motor set during machining may be set to exceed the tolerance of the emergency stop circuit for emergency stopping the motor, and thus a countermeasure like the conventional example described above is required.

[0012] The present invention has been completed in view of the above actual situation, and its purpose is to provide a machine tool that can perform processing at a rotation speed that does not exceed the allowable rotation speed even when the rotation speed of the motor instructed by the NC program exceeds the allowable rotation speed based on the inertia of the rotating body.

[0013] The present invention for solving the above-mentioned problems is directed to a machine tool comprising a motion mechanism including a rotating body as a control object, and a control device for controlling at least the rotational motion of the rotating body according to a machining program. The control device is configured to confirm data related to the inertia of the rotating body when the rotating body is rotated according to the processing program, and when the data related to the inertia is set, confirm whether the rotation speed of the rotating body specified in the processing program is below the limit rotation speed set according to the inertia, and if it exceeds the limit rotation speed, the rotation speed of the rotating body specified in the processing program is limited to a preset rotation speed as an allowable rotation speed.

[0014] According to the machine tool involved in the present invention, when the control device rotates the rotating body according to the processing program, the control device, for example, refers to a storage unit provided for storing data related to the inertia of the rotating body, confirms the data related to the inertia of the rotating body, and when the data related to the inertia is set, confirms whether the rotation speed of the rotating body specified in the processing program is below the limit rotation speed set according to the inertia. If it exceeds the limit rotation speed, the rotation speed of the rotating body specified in the processing program is limited to a preset rotation speed as the allowable rotation speed.

[0015] Thus, in the machine tool involved in the present invention, when the rotation speed specified in the machining program exceeds the limit rotation speed set according to the inertia of the rotating body, the rotation speed of the rotating body is limited to an allowable rotation speed below the limit rotation speed, so that even if the motor driving the rotating body cannot be controlled due to power failure or other reasons, the motor can be safely stopped by the appropriately provided emergency stop device. In addition, it is possible to avoid excessive load acting on the motor when driving or stopping the rotating body.

[0016] It should be noted that, in addition to the motor, the rotating body also includes a workpiece rotated by the motor and other fixtures.

[0017] In addition, the following method can be adopted in the above-mentioned machine tool: the control device is configured to confirm whether the operator allows the allowable rotational speed. If the operator allows, the rotational speed of the rotating body specified in the processing program is limited to the allowable rotational speed and processing is continued; if the operator does not allow, the processing is stopped.

[0018] When machining is performed at the allowable rotation speed, the required machining accuracy such as surface roughness may not be achieved. Therefore, by confirming with the operator whether machining is possible at the allowable rotation speed, it is possible to prevent the machined product from becoming a defective product.

[0019] In addition, the following method can be adopted in the above-mentioned machine tool: the control device is configured to limit the rotation speed of the rotating body specified in the machining program to a preset safe rotation speed when no data related to the inertia is set or when the data related to the set inertia is judged to be an abnormal value.

[0020] If the inertia of the rotating body is not set, or if the inertia is set but the data is judged to be an abnormal value, it is impossible to determine whether the rotation speed specified in the machining program is an appropriate rotation speed that can enable emergency stop because the limit rotation speed of the rotating body cannot be identified.

[0021] In this case, the rotating body can be safely stopped in an emergency by limiting the rotational speed of the rotating body to a safe rotational speed with sufficient margin. The safe rotational speed is a rotational speed at which, even if the motor driving the rotating body cannot be controlled due to a power outage or other reasons, the motor can be safely stopped by a properly provided emergency stop device. In addition, excessive load on the motor when driving or stopping the rotating body can be avoided.

[0022] Furthermore, in this case, the following method can be adopted: the control device is configured to confirm whether the operator allows the safe rotation speed, and if the operator allows, limit the rotation speed of the rotating body specified in the processing program to the safe rotation speed and continue processing; if the operator does not allow, stop processing.

[0023] As described above, the rotation speed is a factor that affects the processing accuracy such as surface roughness, etc. Therefore, by confirming with the operator whether processing can be performed at the safe rotation speed, it is possible to prevent the processed product from becoming a defective product.

[0024] In addition, the control device can be configured to set new data related to the inertia of the rotating body when no data related to the inertia of the rotating body is set or when the data related to the set inertia is determined to be an abnormal value. Furthermore, the control device can be configured to calculate and set the data related to the inertia of the rotating body by causing the rotating body to perform a rotation action and a stop action. In this way, the inertia of the rotating body can be set correctly and automatically.

[0025] As described above, according to the present invention, when the rotational speed specified in the machining program exceeds the limit rotational speed set according to the inertia of the rotating body, the rotational speed of the rotating body is limited to an allowable rotational speed below the limit rotational speed. Therefore, even if the motor driving the rotating body cannot be controlled due to power failure or other reasons, the motor can be safely stopped by a properly set emergency stop device. In addition, it is possible to avoid excessive load on the motor when driving or stopping the rotating body.

[0026] On the other hand, when data related to inertia is not set, or when data related to the set inertia is judged to be an abnormal value, the rotating body can be safely stopped in an emergency by limiting the rotation speed of the rotating body to a safe rotation speed with sufficient margin. The safe rotation speed is a rotation speed at which even if the motor driving the rotating body cannot be controlled due to a power outage or other reasons, the motor can be safely stopped by a properly set emergency stop device. In addition, excessive load on the motor when driving or stopping the rotating body can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is an explanatory diagram showing a schematic configuration of a machine tool according to an embodiment of the present invention. Figure 2 This is a block diagram showing a schematic configuration of a machine tool according to the present embodiment. Figure 3 : is a flowchart showing the processing in the control device according to the present embodiment. Figure 4 : is a flowchart showing the processing in the control device according to the present embodiment. Figure 5 1 is a circuit diagram showing a circuit of a motor including an emergency stop circuit provided in a rotation control unit according to the present embodiment. Figure 6 This is a graph showing the relationship between the inertia and the rotation speed when a rotating body is brought to an emergency stop within a predetermined time. DETAILED DESCRIPTION

[0028] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0029] like Figure 1 and Figure 2 As shown, the machine tool 1 of this example is a so-called horizontal machining center, which is composed of a bed 2, a column 3 erected on the bed 2, a worktable 4 set on the bed 2, a spindle head 5 held by the column 3, a spindle 6 rotatably supported by the spindle head 5, a control device 20, and an input / output device 30. It should be noted that, of course, the machine tool to which the present invention can be applied is not limited to such a structure, and in addition to a vertical machining center and a lathe, various machine tools can also be applied, such as a composite machining type machine tool having a turning function and a milling function.

[0030] The worktable 4 has a workpiece W placed on its upper surface, and is driven to move in the horizontal Y-axis direction by a Y-axis feed device 11, and is driven to move in the horizontal X-axis direction orthogonal to the Y-axis by an X-axis feed device 10. In addition, the worktable 4 is driven by a worktable motor 16 to rotate around a vertical rotation axis.

[0031] The spindle head 5 is driven by a Z-axis feed device 12 to move in a vertical Z-axis direction orthogonal to the X-axis and the Y-axis. A tool T is mounted on the front end of the spindle 6 and is driven by a spindle motor 15 to rotate around a horizontal rotation axis.

[0032] Furthermore, the operations of the X-axis feed device 10 , the Y-axis feed device 11 , the Z-axis feed device 12 , the spindle motor 15 , and the table motor 16 are controlled by the control device 20 .

[0033] Thus, in the machine tool 1, under the control of the control device 20, the spindle 6 and the tool T are rotated by the spindle motor 15 and the table 4 is stopped, the table 4 and the workpiece W are moved in the X-axis and Y-axis directions by the X-axis feed device 10 and the Y-axis feed device 11, and the spindle 6 and the tool T are moved in the Z-axis direction by the Z-axis feed device 12, so that the workpiece W is machined by the tool T. In addition, in the state where the spindle 6 is stopped and the table 4 is rotated, similarly, the table 4 and the workpiece W are moved in the X-axis and Y-axis directions by the X-axis feed device 10 and the Y-axis feed device 11, and the spindle 6 and the tool T are moved in the Z-axis direction by the Z-axis feed device 12, so that the workpiece W is turned by the tool T.

[0034] It should be noted that, in the machine tool 1 of this example, the table 4, the X-axis feed device 10, the Y-axis feed device 11, the table motor 16, the spindle head 5, the spindle 6, and the Z-axis feed device 12 constitute a motion mechanism. In addition, the tool T, the rotating part of the spindle 6, and the rotating part of the spindle motor 15 constitute a spindle-side rotating body, and the workpiece W, the rotating part of the table 4, and the rotating part of the table motor 16 constitute a table-side rotating body.

[0035] The input / output device 30 includes, for example, a display including a touch panel or an input / output interface for inputting and outputting data, etc. Of course, the display displays images or text information, etc., and input can be performed via the display unit.

[0036] like Figure 2 As shown, the control device 20 is composed of an NC program storage unit 21, a program execution unit 22, a feed control unit 23, a rotation control unit 24, a rotation speed storage unit 25, an inertia storage unit 26, and a rotation monitoring unit 27. It should be noted that the control device 20 is composed of a computer including a CPU, a RAM, a ROM, etc., and a properly constructed power circuit and an electronic circuit, etc. The functions of the program execution unit 22, the feed control unit 23, the rotation control unit 24, and the rotation monitoring unit 27 are realized by a computer program or the power circuit, the electronic circuit, etc., and the processing described later is performed. In addition, the NC program storage unit 21, the rotation speed storage unit 25, and the inertia storage unit 26 are composed of a suitable storage medium such as a RAM.

[0037] The NC program storage unit 21 is a functional unit that stores an NC program (machining program) for NC control, and stores, for example, an NC program input from the input / output device 30 .

[0038] For the NC program to be executed, the program execution unit 20 reads each block constituting the NC program from the NC program stored in the NC program storage unit 21 in sequence, and processes the NC code contained in the block. When processing the NC code related to feed control, a control signal related to the NC code is generated and sent to the feed control unit 23; when processing the NC code related to rotation control, a control signal related to the NC code is generated and sent to the rotation control unit 24.

[0039] The feed control unit 23 is a functional unit that controls the operation of the X-axis feed device 10, the Y-axis feed device 11, and the Z-axis feed device 12. It receives a control signal related to feed control from the program execution unit 20, and controls the X-axis feed device 10, the Y-axis feed device 11, and the Z-axis feed device 12 to operate at a speed corresponding to the received control signal.

[0040] The rotation control unit 24 is a functional unit that controls the rotation movement of the spindle motor 15 and the worktable motor 16, and receives a control signal related to the rotation control from the program execution unit 20, so that the spindle motor 15 and the worktable motor 16 rotate in a rotation direction and rotation speed corresponding to the received control signal, respectively.

[0041] In addition, the rotation control unit 24 is provided with an emergency stop circuit, which is used to stop the spindle motor 15 and the table motor 16 in an emergency when the power supplied to the spindle motor 15 and the table motor 16 is cut off due to a power outage or other reasons. The emergency stop circuits are respectively provided corresponding to the spindle motor 15 and the table motor 16. When the power supply is cut off, each emergency stop circuit is respectively connected to the spindle motor 15 and the table motor 16, forming a Figure 5 The short circuit shown.

[0042] According to the short circuit, for example, in the case of the spindle motor 15, the power supply is cut off, and the induced current generated in the spindle motor 15 due to the idling of the spindle-side rotating body including the spindle motor 15 flows through the coil, thereby converting the rotational energy of the rotating body including the spindle motor 15 into heat and consuming it (copper loss occurs), thereby stopping the spindle motor 15. Similarly, for the table motor 16, the power supply is cut off, and if the table-side rotating body including the table motor 16 is idling, the induced current generated in the table motor 16 flows through the coil, thereby converting the rotational energy of the rotating body including the table motor 16 into heat and consuming it (copper loss occurs), thereby stopping the table motor 16.

[0043] It should be noted that the emergency stop circuit is not limited to such a circuit, and can also be, for example, a short-circuit circuit constructed as follows: when the power supply is cut off, the power lines are short-circuited between the spindle motor 15 and the worktable motor 16 and the amplifiers that drive them, so that only the internal resistance of the spindle motor 15 and the worktable motor 16 is used to consume power.

[0044] The rotation speed storage unit 25 is a functional unit for storing the allowable rotation speed and the safe rotation speed set for the spindle side rotating body and the worktable side rotating body respectively. The spindle side rotating body is composed of the tool T, the rotating part of the spindle 6 and the rotating part of the spindle motor 15, and the worktable side rotating body is composed of the workpiece W, the rotating part of the worktable 4 and the rotating part of the worktable motor 16, which are input from the input-output device 30 and stored in the rotation speed storage unit 25.

[0045] The allowable rotational speed is a rotational speed pre-set in the following manner: the preset rotational speed is the upper limit rotational speed at which the motors 15 and 16 can be stopped (safely) before sintering through the corresponding emergency stop circuit when the motors 15 and 16 are idling, and the rotational speed below the limit rotational speed is set according to the inertia of each rotating body (the main spindle side rotating body and the worktable side rotating body).

[0046] For example, the spindle side rotating body including the spindle motor 15 is used as an example to explain that the time t that the spindle side rotating body can be safely stopped by the emergency stop circuit is s [s], the rotational energy of the main shaft side rotating body is taken as r e [J], taking the copper loss of the emergency stop circuit as P loss [J / s] and calculated by the following mathematical formula 1. (Mathematical formula 1) t s =r e / P loss

[0047] In addition, Figure 2 In the case of the emergency stop circuit shown in FIG. 1 , the copper loss P can be calculated by the following mathematical formula 2: loss [J / s]. (Mathematical formula 2) P loss =3RI 2 =R·(K·ω) 2 / (R 2 +(ω·p·L) 2 ) Where R is the resistance value of one phase [Ω], L is the inductance of one phase [H], K is the line-to-line induced voltage constant [Vrms / (rad / s)], ω is the angular velocity of rotation [rad / s] (since the angular velocity of rotation is equivalent to the rotation speed [m / s], they are collectively referred to as "rotation speed" below), and p is the number of pole pairs (number of poles / 2).

[0048] Furthermore, the rotational energy r can be expressed by the following mathematical formula 3: e Where, I is the inertia of the main shaft side rotating body [kgm 2 ]. (Mathematical formula 3) r e =(I·ω 2 ) / 2

[0049] Therefore, the time t is expressed by the following mathematical formula 4: s [s]. (Mathematical formula 4) t s =(I·ω 2 ) / (2·P loss )

[0050] Furthermore, after transforming the above-mentioned mathematical formula 4, it becomes the following mathematical formula 5, which is used to obtain the s The relationship between the inertia I of the main-spindle-side rotating body and the rotation speed (i.e., the limit rotation speed) ω at which the main-spindle-side rotating body is stopped. (Mathematical formula 5) I=2·t s ·P loss / ω 2

[0051] Depend on Figure 6 The limit curve shown shows the relationship between the inertia I of the spindle rotating body and the limit rotation speed ω. When the rotation speed ω is below the limit curve relative to the inertia I of the spindle-side rotating body, the rotation speed ω is a rotation speed at which the spindle-side rotating body can be safely stopped in an emergency, and when it is above the limit curve, the rotation angular velocity ω is a rotation speed at which the spindle-side rotating body cannot be safely stopped.

[0052] Thus, based on the limit rotation speed corresponding to the inertia I of the main spindle side rotating body thus obtained, the allowable rotation speed is pre-set according to the inertia I so as to be a rotation speed below the limit rotation speed. Furthermore, the inertia of the main spindle side rotating body thus set and the allowable rotation speed are correlated with each other and stored in the form of a data workbench in the rotation speed storage unit 25. In addition, the same setting is performed on the table side rotating body including the table motor 16, and the inertia of the table side rotating body and the allowable rotation speed are correlated with each other and stored in the form of a data workbench in the rotation speed storage unit 25.

[0053] It should be noted that if the acceleration time of each motor 15, 16 is set to t ac [s], the output of each motor 15, 16 during acceleration is set to P motor [w], let the rotation speed be ω [rad / s], then the inertia of each rotating body is I [kgm 2 ] can be calculated by the following mathematical formula 6 respectively. (Mathematical formula 6) I=(2P motor ·t ac ) / ω 2

[0054] In addition, the safe rotational speed is a rotational speed that has sufficient margin so that each motor 15 and 16 can be safely stopped in an emergency through the emergency stop circuit even if the inertia of the spindle side rotating body and the worktable side rotating body is unclear. The safety rotational speed is set for the spindle side rotating body and the worktable side rotating body respectively based on experience and stored in the rotational speed storage unit 25.

[0055] The inertia storage unit 26 is a functional unit that stores the inertia of the main spindle-side rotating body and the table-side rotating body. When these are identified, the values ​​are inputted via the input / output device 30 and stored in the inertia storage unit 26 .

[0056] When the program execution unit 20 starts processing, the rotation monitoring unit 27 starts processing accordingly. Figure 3 and Figure 4 Specifically, when the processing of the program execution unit 20 is started, the rotation monitoring unit 27 first receives the NC code to be processed from the program execution unit 20, and identifies (monitors) whether the received NC code is related to the rotation instruction (step S1). The rotation instruction contains instructions for the spindle motor 15 and the table motor 16. In the following, the spindle motor 15 is explained as a representative example, and the same processing is performed on the table motor 16. It should be noted that the table motor 16 is annotated with brackets.

[0057] Furthermore, in step S1, if a rotation instruction for the spindle motor 15 (worktable motor 16) is confirmed, the rotation monitoring unit 27 refers to the inertia storage unit 26 to confirm whether the inertia storage unit 26 stores data related to the inertia of the spindle side rotating body (worktable side rotating body) (step S2). If data related to the inertia is stored, the rotation monitoring unit 27 refers to the rotation speed storage unit 25 to confirm the allowable rotation speed set for the inertia, and determines whether the instructed rotation speed is below the allowable rotation speed (step S3).

[0058] On the other hand, in step S2, if it is confirmed that no data related to inertia is stored, the rotation monitoring unit 27 reads the safe rotation speed stored in the rotation speed storage unit 25, sends a control signal corresponding to the safe rotation speed to the rotation control unit 24, and transfers the rotation speed of the spindle motor 15 (worktable motor 16) to the safe rotation speed. At the same time, the NC program is processed, that is, the program execution unit 22 is instructed to temporarily stop processing (step S6), and transfer to the next step S7.

[0059] In addition, in step S3, when it is determined that the command rotation speed is not lower than the allowable rotation speed, the rotation monitoring unit 27 sends a control signal corresponding to the allowable rotation speed to the rotation control unit 24, so that the rotation speed of the spindle motor 15 (worktable motor 16) is transferred to the allowable rotation speed, and at the same time, the NC program is processed, that is, the program execution unit 22 is instructing to temporarily stop processing (step S10) and then transfer to the next step S7.

[0060] On the other hand, in the step S3, when it is determined that the commanded rotation speed is below the permissible rotation speed, the rotation monitoring unit 27 estimates the inertia of the spindle-side rotating body based on the actual driving power of the spindle motor 15 (table motor 16), and determines whether the inertia of the spindle-side rotating body (table-side rotating body) stored in the inertia storage unit 26 is correct based on the estimated inertia (step S4). If correct, the processing after step S1 is repeatedly performed until a signal to end the processing is received from the program execution unit 22 (step S5). That is, the rotation monitoring unit 27 executes the processing after step S1 every time it receives a rotation command from the program execution unit 22. On the other hand, when it is determined that the inertia is wrong, the rotation monitoring unit 27 transfers to the processing of the aforementioned step S6.

[0061] It should be noted that the inertia of the spindle side rotating body (table side rotating body) can be calculated (estimated) by the above-mentioned mathematical formula 6, and the rotation monitoring unit 27 obtains the actual acceleration time t of the spindle motor 15 (table motor 16) from the rotation control unit 24. ac [s] and output P during acceleration motor[w], and estimate the inertia.

[0062] In step S7, the rotation monitoring unit 27 performs the following processing: the limited rotation speed is displayed on the display of the input / output device 30, and the operator is asked to confirm whether to accept the limited rotation speed and restart the processing. And, in the case where the operator accepts the limited rotation speed and restarts the processing through the display (step S8), the program execution unit 22 is sent a restart processing signal in the state of limiting the rotation speed, and after the processing is restarted (step S9), the process is transferred to the step S5.

[0063] On the other hand, in step S8, when the operator does not accept the rotation speed restriction selected via the display, the display confirms with the operator whether to newly set the inertia of the spindle side rotating body (the worktable side rotating body) (step S11). When the operator selects to newly set the inertia via the display, the display further confirms with the operator whether to perform automatic measurement (step S12).

[0064] Furthermore, in step S12, when the operator selects a new automatic measurement of inertia via the display, the rotation monitoring unit 27 performs automatic measurement of inertia (step S13). Automatic measurement can be performed by, for example, sending a control signal to rotate the spindle motor 15 (table motor 16) at the safe rotation speed and causing it to rotate at the safe rotation speed after sending a stop signal to the rotation control unit 24 and temporarily stopping the rotation of the spindle motor 15 (table motor 16). Based on the actual acceleration time, output during acceleration, and the safe rotation speed of the spindle motor 15 (table motor 16) obtained from the rotation control unit 24 at this time, the inertia can be calculated by the mathematical formula 6. It should be noted that by repeatedly performing the automatic measurement multiple times and averaging the obtained data, a more accurate inertia can be obtained. Furthermore, the rotation monitoring unit 27 stores the data related to the calculated inertia in the inertia storage unit 26 (step S13).

[0065] Next, the rotation monitoring unit 27 performs the following processing with reference to the inertia storage unit 26: identifies the allowable rotation speed corresponding to the calculated inertia, displays the identified allowable rotation speed on the display, and confirms with the operator whether to accept the allowable rotation speed and restart the processing (step S14). And, in the case where the operator selects to accept the allowable rotation speed and restart the processing through the display, a control signal related to the allowable rotation speed is sent to the rotation control unit 24, and the spindle motor 15 is rotated at the allowable rotation speed (step S16), and then the process is transferred to step S9 to restart the processing.

[0066] On the other hand, in step S11, when the operator does not set the inertia via the display selection, and in step S15, when the operator does not accept the allowable rotation speed via the display selection, a signal to stop processing is sent to the program execution unit 22 (step S18) to end the processing.

[0067] In addition, in step S12, when the operator selects via the display not to automatically measure the new inertia, in other words, to input it manually, the input of inertia is accepted via the display, and the data related to the input inertia is stored in the inertia storage unit 26 (step S17), and the processing after step S3 is executed.

[0068] According to the machine tool 1 of this example constructed as described above, the NC program is executed by the program execution unit 22, and based on the control signal from the program execution unit 22, the X-axis feed device 10, the Y-axis feed device 11 and the Z-axis feed device 12 are controlled by the feed control unit 23, and the spindle motor 15 and the worktable motor 16 are controlled by the rotation control unit 24. Through the operation of these X-axis feed device 10, Y-axis feed device 11 and Z-axis feed device 12 and the spindle motor 15 and the worktable motor 16, the workpiece W is processed by the tool T.

[0069] Furthermore, the rotation monitoring unit 27 monitors the rotation control of the spindle motor 15 and the table motor 16 by the rotation control unit 24 based on the control signal from the program execution unit 22 .

[0070] That is, whenever the program execution unit 22 processes a rotation instruction, the rotation monitoring unit 27 confirms whether the inertia of the rotating body (spindle-side rotating body or table-side rotating body) corresponding to the rotation instruction is known (step S2). If the inertia is known, it is determined whether the rotation instruction is below the allowable rotation speed set for the inertia (step S3). If it is below the allowable rotation speed, the processing is continued. Therefore, even if the motor (spindle motor 15 or table motor 16) driving the rotating body cannot be controlled due to power failure or other reasons, the emergency stop circuit provided in the rotation control unit 24 can be used to stop the motor 15, 16 safely without causing sintering. In addition, when processing at such a rotation speed, when driving and stopping the rotating body, excessive load on the motor 15, 16 can be avoided.

[0071] In addition, the rotation monitoring unit 27 is configured to: even if the rotation command is below the permissible rotation speed set for the inertia, by comparing the known inertia stored in the inertia storage unit 26 with the inertia estimated by actually rotating the motor, determine whether the known inertia is correct (step S4), and continue processing at the original rotation speed only when the known inertia is correct. Therefore, it is possible to prevent the processing from being continued when the rotation speed of the motors 15 and 16 is at a dangerous speed due to erroneous input of inertia.

[0072] In addition, the rotation monitoring unit 27 is configured to limit the rotation speed of the motors 15 and 16 to a safe rotation speed (step S6) when the inertia is unknown, and limit the rotation speed of the motors to an allowable rotation speed (step S10) when the rotation command exceeds the allowable rotation speed set according to the inertia. Therefore, when the motor is stopped in an emergency, the emergency stop circuit can be used to stop the motor safely without causing seizure.

[0073] In addition, the rotation monitoring unit 27 is configured to temporarily stop processing (steps S6 and S10) when the inertia is unknown and when the rotation instruction exceeds the allowable rotation speed set according to the inertia, and restart processing at the limited rotation speed when the operator accepts the limited rotation speed (steps S7-S9). When the rotation speed is limited, the target processing accuracy such as surface roughness may not be achieved, but by the operator confirming whether the processing can be performed at the limited rotation speed, it is possible to prevent the processed product from becoming a defective product.

[0074] The rotation monitoring unit 27 is configured to automatically measure the inertia of the rotating body or to allow manual input (steps S11 to S13 and S17). This allows the inertia to be set flexibly.

[0075] According to the machine tool 1 of this embodiment, the above-mentioned effects are achieved, but the monitoring by the processing monitoring unit 27 of this embodiment is particularly useful when the NC program is executed for the first time. When the NC program is executed for the first time, it is sometimes unclear whether the inertia of the rotating body is set appropriately, and the command rotation speed is set to meet the processing time or processing accuracy because it may exceed the limit rotation speed corresponding to the inertia.

[0076] An embodiment of the present invention has been described above, but specific forms that can be adopted by the present invention are not limited to the above examples.

[0077] For example, the machine tool 1 in the above example includes both a spindle side rotating body including a spindle motor 15 and a table side rotating body including a table motor 16 as rotating bodies, but is not limited to such a structure, and may include any one rotating body, or may include completely different rotating bodies.

[0078] It is to be repeated that the description of the above-mentioned embodiments is illustrative in all aspects and is not restrictive. For those skilled in the art, deformation and changes can be appropriately made. The scope of the present invention is not represented by the above-mentioned embodiments, but by the claims. In addition, the scope of the present invention includes changes made to the embodiments within the scope equivalent to the claims. Description of Reference Numerals

[0079] 1Machine Tools 2 Bed 3 columns 4 Workbench 5 spindle head 6 spindles 10 X-axis feeding device 11 Y-axis feeding device 12 Z-axis feed device 15 Spindle motor 16 Table motor 20 Control device 21 NC program storage unit 22 Program execution unit 23 Feed control unit 24 Rotation control unit 25 Rotation speed storage unit 26 Inertia storage unit 27 Rotation monitoring unit 30 Input and output devices

Claims

1. A machine tool comprising a motion mechanism including a rotating body as a control object, and a control device for controlling at least the rotational motion of the rotating body according to a machining program, characterized in that: The control device is configured to confirm data related to the inertia of the rotating body when the rotating body is rotated according to the processing program. When the data related to the inertia is set, it is confirmed whether the rotation speed of the rotating body specified in the processing program is below the limit rotation speed set according to the inertia. If it exceeds the limit rotation speed, the rotation speed of the rotating body specified in the processing program is limited to a preset rotation speed as an allowable rotation speed.

2. The machine tool according to claim 1, characterized in that: The control device is configured to confirm whether the operator permits the allowable rotational speed, and if the operator permits, limit the rotational speed of the rotating body specified in the machining program to the allowable rotational speed and continue machining, and if the operator does not permit, stop machining.

3. The machine tool according to claim 1 or 2, characterized in that: The control device is configured to limit the rotation speed of the rotating body specified in the machining program to a preset safe rotation speed when the data related to the inertia is not set or when it is determined that the data related to the set inertia is an abnormal value.

4. The machine tool according to claim 3, characterized in that: The control device is configured to confirm whether the operator permits the safe rotation speed, and if the operator permits, limit the rotation speed of the rotating body specified in the machining program to the safe rotation speed and continue machining, and if the operator does not permit, stop machining.

5. The machine tool according to claim 3 or 4, characterized in that: The control device is configured to be able to newly set data on the inertia of the rotating body when data on the inertia of the rotating body is not set or when it is determined that the set data on the inertia is an abnormal value.

6. The machine tool according to claim 5, characterized in that: The control device is configured to calculate and set data related to the inertia of the rotating body by causing the rotating body to perform a rotating operation and a stopping operation.

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