MACHINE TOOL, CONTROL METHOD, AND CONTROL PROGRAM

Abstract

A technique is provided for detecting faults in a pump for supplying coolant to a tool. [Solution] A machine tool capable of machining a workpiece using a tool having a first coolant passage formed therein is configured to be able to mount the tool and includes a spindle having a second passage connected to the first passage when the tool is mounted, a pump for pumping coolant to a main passage connected to the second passage, a pressure sensor for detecting the pressure of the coolant flowing through the main passage, and a controller. The controller executes a process of controlling the pump rotation speed so that the pressure detected by the pressure sensor becomes a predetermined pressure, a process of acquiring the pump rotation speed based on the pressure detected by the pressure sensor becoming the predetermined pressure, and a process of outputting a warning regarding a pump failure based on the rotation speed acquired in the acquisition process.

Description

[Technical field]

[0001] The present disclosure relates to a machine tool, a control method, and a control program. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2016-64462 (Patent Document 1) discloses a machine tool capable of machining a workpiece while discharging coolant from the tip of a tool. The machine tool supplies the coolant to the tool by pumping it with a pump. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-64462 A Summary of the Invention [Problem to be solved by the invention]

[0004] A pump for supplying coolant to a tool wears with use. When the pump wears, it may not be possible to control the discharge pressure and discharge amount of the coolant from the tool as intended. Therefore, a technology for detecting a fault in the pump for supplying coolant to the tool is desired. However, Patent Document 1 does not disclose any such technology. [Means for solving the problem]

[0005] In one example of the present disclosure, a machine tool capable of machining a workpiece using a tool having a first coolant passage formed therein is provided. The machine tool includes a spindle configured to be able to mount the tool and having a second passage connected to the first passage when the tool is mounted, a pump for pumping coolant to a main passage connected to the second passage, a pressure sensor for detecting the pressure of the coolant flowing through the main passage, and a controller. The controller executes a process of controlling the rotation speed of the pump so that the pressure detected by the pressure sensor becomes a predetermined pressure, a process of acquiring the rotation speed of the pump based on the pressure detected by the pressure sensor becoming the predetermined pressure, and a process of outputting a warning regarding a failure of the pump based on the rotation speed acquired in the acquiring process.

[0006] In one example of the present disclosure, the machine tool further includes a first valve provided in the main flow path, and a second valve provided in a first branch flow path branching off from the main flow path between the pump and the first valve. The control unit executes the controlling process and the acquiring process with the first valve closed and the second valve open.

[0007] In one example of the present disclosure, the machine tool further includes a third valve provided in a second branch passage branching off from a portion between the pump and the first valve in the main passage. The control unit further executes a drawback process in which, when stopping the discharge of coolant from the tool to the outside, the third valve is opened to return the coolant present at least from the first valve to an opening on the tip side of the tool to the second branch passage, and a filling process in which, after the drawback process is executed, the first valve and the third valve are closed and the second valve is opened to fill the main passage between the pump and the first valve with coolant, and the controlling process and the acquiring process are executed in parallel with the filling process.

[0008] In one example of the present disclosure, the output process includes a process of outputting a first warning indicating a sign of a failure of the pump when the acquired rotation speed is equal to or greater than a first threshold value and smaller than a second threshold value, and a process of outputting a second warning indicating a failure of the pump when the acquired rotation speed exceeds the second threshold value, the second threshold value being larger than the first threshold value.

[0009] In one example of the present disclosure, the machine tool further includes a flow sensor for detecting a flow rate of the coolant in the first branch passage. The control unit executes a process of acquiring a flow rate from the flow sensor based on the pressure detected by the pressure sensor reaching the predetermined pressure, and a process of outputting a warning regarding an abnormality in the second valve based on the acquired flow rate.

[0010] In another example of the present disclosure, a method for controlling a machine tool capable of machining a workpiece using a tool having a first coolant passage formed therein is provided. The machine tool includes a spindle configured to be able to mount the tool and having a second passage connected to the first passage when the tool is mounted, a pump for pumping coolant to a main passage connected to the second passage, and a pressure sensor for detecting a pressure of the coolant flowing through the main passage. The control method includes a step of controlling a rotation speed of the pump so that the pressure detected by the pressure sensor becomes a predetermined pressure, a step of acquiring the rotation speed of the pump based on the pressure detected by the pressure sensor becoming the predetermined pressure, and a step of outputting a warning regarding a failure of the pump based on the rotation speed acquired in the acquiring process.

[0011] In another example of the present disclosure, a control program for a machine tool capable of machining a workpiece using a tool having a first coolant passage formed therein is provided. The machine tool is configured to be able to mount the tool and includes a spindle having a second passage connected to the first passage when the tool is mounted, a pump for pumping coolant to a main passage connected to the second passage, and a pressure sensor for detecting the pressure of the coolant flowing through the main passage. The control program causes the machine tool to execute a process of controlling the rotation speed of the pump so that the pressure detected by the pressure sensor becomes a predetermined pressure, a process of acquiring the rotation speed of the pump based on the pressure detected by the pressure sensor becoming the predetermined pressure, and a process of outputting a warning regarding a failure of the pump based on the rotation speed acquired in the acquiring process.

[0012] The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing the appearance of a machine tool. [Diagram 2] FIG. 4 illustrates an example of a coolant supply mechanism. [Diagram 3] FIG. 11 is a diagram showing a flow of a pump failure detection process. [Figure 4] FIG. 13 is a diagram showing a warning WRA that indicates a sign of a pump failure. [Diagram 5] FIG. 13 shows a warning WRB indicating a pump failure. [Figure 6] FIG. 2 is a diagram illustrating an example of a hardware configuration of a CPU (Central Processing Unit). [Figure 7] 13A and 13B are diagrams showing a coolant supply mechanism according to a first modified example. [Figure 8] FIG. 13 is a diagram showing a flow of a failure detection process according to a first modified example. [Figure 9]It is a diagram showing a coolant supply mechanism according to a second modification example. [Figure 10] It is a diagram showing a control flow of a draw-back process. [Figure 11] It is a diagram showing a control flow of a coolant filling process. [Figure 12] It is a diagram showing a flow of a failure detection process according to a second modification example. [Figure 13] It is a diagram showing a coolant supply mechanism according to a third modification example. [Figure 14] It is a diagram showing a flow of a failure detection process according to a third modification example. [Figure 15] It is a diagram showing a coolant supply mechanism according to a fourth modification example.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, each embodiment according to 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 also the same. Therefore, detailed descriptions thereof will not be repeated. Note that each of the embodiments and each modification example described below may be selectively combined as appropriate.

[0015] <A. Machine Tool 100> First, with reference to FIG. 1, a machine tool 100 according to an embodiment will be described. FIG. 1 is a diagram showing the appearance of the machine tool 100.

[0016] As used herein, the "machine tool" is a concept encompassing various devices having a function of processing a workpiece. The machine tool 100 may be a horizontal machining center, or may be a vertical machining center. Alternatively, the machine tool 100 may be a lathe, or may be other cutting machines, grinding machines, multi-tasking machines, 5-axis machining centers, etc. Further, the machine tool 100 is not limited to performing only removal machining. The machine tool 100 may perform additional machining in addition to removal machining.

[0017] The machine tool 100 has a tool storage unit 40A and a processing machine main body 40B. Each of the tool storage unit 40A and the processing machine main body 40B is partitioned by a cover.

[0018] The tool storage unit 40A is provided with a magazine 150 and an ATC (Automatic Tool Changer) 160. The processing machine main body 40B is provided with a spindle head 170.

[0019] The spindle head 170 includes a spindle barrel 175 and a spindle 180. The spindle 180 is rotatably supported by the spindle barrel 175 about its axial direction as the rotation center. The rotation of the spindle 180 is realized by a drive mechanism such as a motor, for example.

[0020] One tool selected from the magazine 150 is mounted on the spindle 180. More specifically, the machine tool 100 drives the magazine 150 to move one tool (hereinafter also referred to as "processing tool") corresponding to the processing step to the first tool change position. Also, the machine tool 100 drives the spindle head 170 to move the tool (hereinafter also referred to as "used tool") mounted on the spindle 180 to the second tool change position. Thereafter, the ATC 160 exchanges the processing tool waiting at the first tool change position with the used tool waiting at the second tool change position. The tool exchange is performed through a door D provided in the partition between the processing machine main body 40B and the tool storage unit 40A. The door D is a slide-type door and is opened and closed by a drive source such as a motor. Thereafter, the machine tool 100 processes the workpiece using the processing tool mounted on the spindle 180.

[0021] The machine tool 100 is also provided with an operation panel 400. The operation panel 400 includes a display 405 for displaying various information related to processing and operation keys 406 for receiving various operations on the machine tool 100.

[0022] <B. Coolant Supply Mechanism> Next, a coolant supply mechanism in machine tool 100 will be described with reference to Fig. 2. Fig. 2 is a diagram showing an example of the coolant supply mechanism.

[0023] The machine tool 100 has a control unit 50, a coolant tank 52, a motor driver 54, a motor 55, a pump 56, a pressure sensor 59, and a spindle 180.

[0024] For ease of explanation, the pump 56 side in the coolant flow passage is also referred to as the "upstream side," and the spindle 180 side in the coolant flow passage is also referred to as the "downstream side."

[0025] A main coolant flow path F1 is provided inside machine tool 100. One end of main flow path F1 is connected to coolant tank 52. The other end of main flow path F1 is connected to a communication path L2 (second path) formed in spindle 180. Communication path L2 passes through the inside of spindle 180 along the axial direction of spindle 180.

[0026] Various kinds of tools can be attached to the spindle 180. In the example of Fig. 2, a tool T having a through passage L1 (first passage) for coolant formed therein is attached to the spindle 180. The through passage L1 extends from a connection surface between the tool T and the spindle 180 to the tip of the tool T, and penetrates the tool T along the axial direction of the spindle 180.

[0027] The discharge port of the through passage L1 formed in the tool T is not limited to being formed on the base end surface or the tip end surface of the tool T, and may be formed, for example, on the side surface of the tool T. In addition, although the example of Fig. 2 shows the tool T having one discharge port, the tool T may have multiple discharge ports. The diameter of the discharge port of the tool T is, for example, 5 mm or less.

[0028] When the tool T is attached to the spindle 180, the through passage L1 is connected to a communication passage L2 inside the spindle 180. That is, one end of the communication passage L2 is connected to the through passage L1. The other end of the communication passage L2 can be connected to the main flow path F1.

[0029] The control unit 50 controls various devices within the machine tool 100. The device configuration of the control unit 50 is arbitrary. The control unit 50 may be composed of a single control unit or a plurality of control units. As an example, the control unit 50 includes at least one of a PLC (Programmable Logic Controller), a CNC, and the above-described operation panel 400.

[0030] The pump 56 is provided in the main flow path F1 and pumps coolant from the coolant tank 52 to the main flow path F1. The rotation speed of the pump 56 is controlled by the control unit 50. The coolant pumped by the pump 56 flows in the order of the main flow path F1, the communication path L2, and the through path L1, and is discharged from the tip of the tool T to the workpiece to be machined. The spindle 180 having such a coolant discharge function is also called a coolant through spindle.

[0031] More specifically, a motor 55 is connected to the pump 56. The motor 55 is driven by a motor driver 54. The motor driver 54 is composed of a control circuit, an inverter, etc. The motor driver 54 receives an input of a control signal from the control unit 50 and outputs an alternating current with a frequency corresponding to the control signal to the motor 55. Thereby, the rotation speed of the motor 55 changes, and the flow rate of the coolant pumped into the main flow path F1 is controlled.

[0032] The pressure sensor 59 detects the coolant pressure applied to the coolant flowing through the main flow path F1. In the example of FIG. 2, the pressure sensor 59 is provided on the downstream side of the branch point P2 and on the upstream side of the spindle 180. The coolant pressure detected by the pressure sensor 59 is output to the control unit 50.

[0033] <C. Fault Detection Function> The above-described pump 56 wears out as it is used. In particular, when fine chips are contained in the coolant, the pump 56 tends to wear out.

[0034] As wear of pump 56 progresses, the number of revolutions per unit time of pump 56 required to pump a certain amount of coolant increases. In other words, the degree of wear of pump 56 correlates with the revolutions of pump 56. Taking note of this point, machine tool 100 detects a failure of pump 56 based on the revolutions of pump 56.

[0035] The function of detecting a fault in the pump 56 will be described below with reference to Fig. 3. Fig. 3 is a diagram showing a flowchart relating to a process of detecting a fault in the pump 56.

[0036] The processing shown in Fig. 3 is executed by control unit 50 of machine tool 100. In another aspect, a part or all of the processing shown in Fig. 3 may be executed by circuit elements or other hardware.

[0037] In step S110, the control unit 50 controls the pump 56 so that the pressure detected by the pressure sensor 59 (hereinafter also referred to as "coolant pressure") becomes a predetermined target pressure. This control is realized, for example, by feedback control. The feedback control may be realized by PID (Proportional-Integral-Differential) control, PI (Proportional-Integral) control, or PD (Proportional-Differential) control.

[0038] In step S120, the control unit 50 determines whether or not the coolant pressure detected by the above-mentioned pressure sensor 59 has stabilized. As an example, the control unit 50 determines that the coolant pressure has stabilized based on the fact that a predetermined time has elapsed since the start of driving the pump 56.

[0039] As another example, the control unit 50 determines that the coolant pressure has stabilized based on the fact that the time during which the coolant pressure detected by the pressure sensor 59 remains within the target range has elapsed for a predetermined time. The target range is defined, for example, by a lower threshold value obtained by subtracting a predetermined value from the target pressure, and an upper threshold value obtained by adding a predetermined value to the target pressure.

[0040] If the control unit 50 determines that the coolant pressure has stabilized by the pressure sensor 59 (YES in step S120), the control unit 50 switches the control to step S122. If not (NO in step S120), the control unit 50 executes the process of step S120 again.

[0041] In step S122 when the coolant pressure reaches the predetermined target pressure, the control unit 50 acquires the rotation speed of the pump 56. The rotation speed may be a command value (for example, the rotation speed of the motor 55 per unit time) output by the control unit 50 to the motor driver 54, or may be the output frequency of the AC current output from the inverter provided in the motor driver 54.

[0042] In step S130, the control unit 50 determines whether or not a failure condition of the pump 56 is satisfied. As the failure condition, various conditions can be set. As one example, the failure condition is satisfied when the rotation speed acquired in step S122 exceeds a predetermined threshold value.

[0043] In step S130, if the control unit 50 determines that the failure condition of the pump 56 is satisfied (YES in step S130), the control unit 50 switches the control to step S132. If not (NO in step S130), the control unit 50 determines that the pump 56 is normal, and ends the process shown in FIG.

[0044] In step S132, the control unit 50 outputs a warning regarding the failure of the pump 56. This allows the operator to notice the failure of the pump 56.

[0045] As an example, the pump 56 is a screw pump. The screw pump rotates a screw housed in the compression chamber to pump the coolant to the main flow path F1. The cutting edge of the screw is polished or ground by fine metal chips (such as sludge) flowing through the main flow path F1. As a result, the gap between the inner wall of the compression chamber of the screw pump and the cutting edge of the screw gradually widens, and the discharge pressure from the tool T decreases. Therefore, the control unit 50 needs to increase the rotation speed of the screw in order to maintain a constant discharge pressure. The control unit 50 can detect an abnormality in which the gap between the inner wall of the compression chamber of the screw pump and the cutting edge of the screw widens by monitoring the rotation speed of the pump 56.

[0046] Typically, the coolant discharged from tool T to the workpiece is returned to coolant tank 52 after cutting chips are removed, and circulates within machine tool 100. In this way, the circulation mechanism within machine tool 100 is an open circulation flow path into which cutting chips from the workpiece, other machine oils, and the like flow, and is not a closed circulation flow path like the hydraulic circuit of a power shovel or the like. Therefore, an abnormality such as wear of the cutting edge of the screw within pump 56 is a specific abnormality that occurs in the circulation mechanism of machine tool 100.

[0047] Preferably, the control unit 50 changes the level of the warning depending on the rotation speed acquired in step S122. As an example, when the rotation speed is equal to or greater than a first threshold value and smaller than a second threshold value, the control unit 50 outputs a warning (first warning) indicating a sign of a failure of the pump 56. On the other hand, when the rotation speed is equal to or greater than a second threshold value, the control unit 50 outputs a warning (second warning) indicating a failure of the pump 56. The second threshold value is larger than the first threshold value.

[0048] FIG. 4 is a diagram showing a warning WRA indicating a sign of failure of the pump 56. The warning WRA is displayed, for example, on the display 405 of the operation panel 400. The warning WRA includes, for example, a message prompting replacement of the pump 56, an identifier of the target machine tool 100, and the remaining time that the pump 56 can be used. The remaining time is estimated, for example, according to the past usage pattern of the pump 56.

[0049] FIG. 5 is a diagram showing a warning WRB indicating a failure of the pump 56. The warning WRB is displayed, for example, on the display 405 of the operation panel 400. The warning WRB includes, for example, a message indicating that the pump 56 should be replaced immediately and an identifier of the target machine tool 100.

[0050] As described above, the control unit 50 changes the warning level related to the failure of the pump 56 according to the rotational speed acquired in step S122. Thereby, the operator can secure time to prepare a new pump. As a result, the downtime of the machine tool 100 can be shortened.

[0051] Note that the warning level related to the failure of the pump 56 does not necessarily have to be changed in two steps, and may be changed in three or more steps.

[0052] <Hardware Configuration of the D.CPU Unit 20> Next, with reference to FIG. 6, the hardware configuration of the CPU unit 20, which is an example of the above-described control unit 50, will be described. FIG. 6 is a diagram showing an example of the hardware configuration of the CPU unit 20.

[0053] The CPU unit 20 includes a control circuit 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, communication interfaces 104 and 105, and an auxiliary storage device 120. These components are connected to an internal bus 109.

[0054] The control circuit 101 is configured, for example, by at least one integrated circuit. The integrated circuit may be configured, for example, by at least one CPU, at least one GPU (Graphics Processing Unit), at least one ASIC (Application Specific Integrated Circuit), at least one FPGA (Field Programmable Gate Array), or a combination thereof.

[0055] The control circuit 101 controls the operation of the CPU unit 20 by executing various programs such as a control program 122. The control program 122 is a program for implementing various processes described in this specification. Based on receiving an execution command for the control program 122, the control circuit 101 reads the control program 122 from the auxiliary storage device 120 or the ROM 102 to the RAM 103. The RAM 103 functions as a working memory and temporarily stores various data required for the execution of the control program 122.

[0056] The communication interface 104 is an interface for performing periodic communication with external devices using a field network. The external devices include, for example, the above-mentioned motor driver 54, the above-mentioned pump 56, a pressure-maintaining valve 58A described later, an orifice valve 58B described later, a drawback valve 58C described later, the above-mentioned pressure sensor 59, and flow rate sensors 60A and 60B described later. As the field network, for example, EtherCAT (registered trademark), EtherNet / IP (registered trademark), CC-Link (registered trademark), CompoNet (registered trademark), or the like is adopted.

[0057] A communication interface 105 has a LAN (Local Area Network), an antenna, etc. connected thereto. The CPU unit 20 is connected to a network via the communication interface 105. Thereby, the CPU unit 20 exchanges data with external devices connected to the network. The external devices include, for example, the above-described operation panel 400 and a server (not shown).

[0058] The auxiliary storage device 120 is a storage medium such as a hard disk or a flash memory, for example. The auxiliary storage device 120 stores a control program 122 and the like. Note that the storage location of the control program 122 is not limited to the auxiliary storage device 120, and it may be stored in a storage area of the control circuit 101 (for example, a cache memory), the ROM 102, the RAM 103, an external device (for example, a server), or the like.

[0059] In addition, the control program 122 may be provided not as a single program but incorporated into a part of an arbitrary program. In this case, various processes according to the present embodiment are realized in cooperation with an arbitrary program. Even a program that does not include such a part of the module does not deviate from the gist of the control program 122 according to the present embodiment. Furthermore, part or all of the functions provided by the control program 122 may be realized by dedicated hardware. Furthermore, the control unit 50 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 control program 122.

[0060] <E. First Modification>[

[0061] (E1. Coolant Supply Mechanism) Next, with reference to FIG. 7, a first modification of the coolant supply mechanism shown in FIG. 2 will be described. FIG. 7 is a diagram showing the coolant supply mechanism according to the first modification.

[0062] The coolant supply mechanism according to this modification differs from the coolant supply mechanism shown in Fig. 2 in that it further includes a branch flow path F2 (first branch flow path), a pressure maintaining valve 58A (first valve), and an orifice valve 58B (second valve). The other points are as described above, and therefore the description thereof will not be repeated.

[0063] The pressure maintaining valve 58A is provided in the main flow path F1. The pressure maintaining valve 58A is provided downstream of the pump 56 and upstream of the main shaft 180, for example.

[0064] The pressure maintaining valve 58A is configured to be switchable between at least two states, an open state and a closed state, in response to a control command from the control unit 50. The opening degree of the pressure maintaining valve 58A may be adjustable or may be constant.

[0065] When pressure-maintaining valve 58A is in a closed state, the flow of coolant from coolant tank 52 to spindle 180 is stopped. On the other hand, when pressure-maintaining valve 58A is in an open state, coolant flows from coolant tank 52 to spindle 180. In this case, the coolant pumped by pump 56 flows through main flow path F1, communication path L2, and through path L1 in that order, and is discharged from the tip of tool T to the workpiece to be machined.

[0066] The branch flow passage F2 is a flow passage branched from the main flow passage F1. The branch flow passage F2 is a path for returning a part of the coolant flowing from the main flow passage F1 to the spindle 180. The number of branch flow passages F2 branching from the main flow passage F1 may be one or more. In the example of Fig. 7, one branch flow passage F2 branches from the main flow passage F1.

[0067] The branch flow path F2 branches off from the main flow path F1 at a branch point P2. In other words, one end of the branch flow path F2 is connected to the main flow path F1. The other end of the branch flow path F2 may be connected to any other destination. In the example of FIG. 7, the other end of the branch flow path F2 is connected to the coolant tank 52. As another example, the other end of the branch flow path F2 may be connected to a coolant tank other than the coolant tank 52.

[0068] The orifice valve 58B is provided in the branch flow passage F2 and adjusts the flow of the coolant in the branch flow passage F2. The orifice valve 58B has an orifice FR. The orifice FR is provided, for example, downstream of the orifice valve 58B and functions as a fluid resistance for the coolant flowing through the branch flow passage F2. In other words, the orifice FR is configured to be able to switch whether or not to apply fluid resistance to the coolant flowing through the branch flow passage F2 by opening and closing the orifice valve 58B.

[0069] The orifice valve 58B is switched between opening and closing in response to a control command from the control unit 50. Thus, the orifice valve 58B is configured to at least be able to switch whether or not the coolant flows from the main flow path F1 to the branch flow path F2. When the orifice valve 58B is in a closed state, the flow of the coolant in the branch flow path F2 is stopped. On the other hand, when the orifice valve 58B is in an open state, the coolant is returned from the main flow path F1 to the branch flow path F2. The opening of the orifice valve 58B may be adjustable or may be constant.

[0070] (E2. Overview) Machine tool 100 according to this modified example executes the above-mentioned fault detection process for pump 56 with pressure-maintaining valve 58A closed and orifice valve 58B open. By executing the fault detection process for pump 56 with pressure-maintaining valve 58A closed, the coolant pumped up by pump 56 passes through main flow path F1 and branch flow path F2 in that order. That is, in this modified example, the fault detection process is executed without discharging coolant from tool T. This reduces external factors that affect the accuracy of the fault detection process for pump 56. As a result, the accuracy of the fault detection process for pump 56 is improved.

[0071] (E3. Flowchart) Next, a fault detection function in this modified example will be described with reference to Fig. 8. Fig. 8 is a diagram showing the flow of fault detection processing according to this modified example.

[0072] The processing shown in Fig. 8 is realized by control unit 50 of machine tool 100 executing the above-mentioned control program 122. In another aspect, a part or all of the processing shown in Fig. 8 may be executed by circuit elements or other hardware.

[0073] The flowchart shown in Fig. 8 differs from the flowchart shown in Fig. 3 described above in that it includes step S108. As the other points are as described above, the description thereof will not be repeated.

[0074] In step S108, the control unit 50 closes the pressure maintaining valve 58A and opens the orifice valve 58B. Thereafter, the control unit 50 executes the processes of steps S110, S120, S122, S130, and S132 described above.

[0075] As described above, the control unit 50 according to this modification example executes the failure detection process of the pump 56 with the pressure holding valve 58A closed and the orifice valve 58B open. The processes executed with the pressure holding valve 58A closed include at least the process of controlling the rotation speed of the pump 56 so that the coolant pressure detected by the pressure sensor 59 becomes a predetermined pressure (steps S110, S120), and the process of obtaining the rotation speed of the pump 56 based on the discharge pressure reaching the predetermined pressure (step S122). The process of outputting a warning regarding the failure of the pump 56 (steps S130, S132) may be executed with the pressure holding valve 58A closed or with the pressure holding valve 58A open.

[0076] <F. Second Modification Example>

[0077] (F1. Coolant Supply Mechanism) Next, with reference to FIG. 9, a modification example of the coolant supply mechanism shown in FIG. 7 will be described. FIG. 9 is a diagram showing a coolant supply mechanism according to the second modification example.

[0078] The coolant supply mechanism according to this modification example is different from the coolant supply mechanism shown in FIG. 7 described above in that it further includes a branch flow path F3 (second branch flow path) and a draw-back valve 58C (third valve). Since the other points are as described above, the explanations thereof will not be repeated.

[0079] The branch flow path F3 branches from the main flow path F1 at the branch point P3. That is, one end of the branch flow path F3 is connected to the main flow path F1. The connection destination of the other end of the branch flow path F3 is arbitrary. In the example of FIG. 9, the other end of the branch flow path F3 is connected to the coolant tank 52. As another example, the other end of the branch flow path F3 may be connected to a coolant tank different from the coolant tank 52. The branch point P3 is located, for example, on the downstream side of the pump 56 and on the upstream side of the branch point P2.

[0080] The drawback valve 58C is configured to be switchable between at least two states, an open state and a closed state, in response to a control command from the control unit 50. The opening degree of the drawback valve 58C may be adjustable or may be constant.

[0081] When the drawback valve 58C is closed, the flow of the coolant in the branch passage F3 is stopped. On the other hand, when the drawback valve 58C is open, the coolant flows through the branch passage F3.

[0082] Typically, the drawback valve 58C is provided upstream of the pressure-retaining valve 58A. In other words, the length of the coolant flow passage between the pressure-retaining valve 58A and the spindle 180 is shorter than the length of the coolant flow passage between the drawback valve 58C and the spindle 180.

[0083] Although FIG. 9 shows an example in which the drawback valve 58C is provided in the branch flow path F3 and the orifice valve 58B is provided in the branch flow path F2, the drawback valve 58C may be provided in the branch flow path F2 and the orifice valve 58B may be provided in the branch flow path F3.

[0084] It is assumed that the control unit 50 receives a command to replace the tool T. In response to this, the control unit 50 stops driving the pump 56 and executes a drawback process.

[0085] More specifically, the control unit 50 switches the drawback valve 58C from a closed state to an open state. The control unit 50 also opens the pressure-maintaining valve 58A and closes the orifice valve 58B. This causes at least the amount of coolant present from the pressure-maintaining valve 58A to the opening on the tip side of the tool T to be returned to the branch flow path F3. Typically, the coolant remaining in the through passage L1, the communication passage L2, and the main flow path F1 is discharged from the branch flow path F3. This makes it possible to prevent the coolant from dripping from the tool T or the spindle 180 when the tool T is replaced.

[0086] Preferably, the coolant returned from the main flow path F1 to the branch flow path F3 is sent back to the main flow path F1. At this time, the coolant returned to the branch flow path F3 is sent to the main flow path F1 via one or more coolant tanks 52. As an example, the coolant is discharged from the branch flow path F3 to the coolant tank 52. Then, the coolant discharged to the coolant tank 52 is sucked up by the pump 56 and sent back to the main flow path F1. This reduces the consumption of coolant.

[0087] In addition, the pressure-retaining valve 58A, the orifice valve 58B, and the drawback valve 58C in this embodiment are normally closed type valves that are closed when no voltage is applied. In other words, each valve is always closed, but opens when a command signal from the control unit 50 is input. Needless to say, even if each valve is a normally open type valve that is open when no voltage is applied, it is possible to cause it to function similarly to this modified example by appropriately setting the control signal.

[0088] (F2. Control process of coolant mechanism) Next, the control process of the coolant mechanism shown in Fig. 9 will be described with reference to Fig. 10 and Fig. 11. Fig. 10 is a diagram showing a control flow of the drawback process. Fig. 11 is a diagram showing a control flow of the coolant filling process.

[0089] Step S1 shows the state of the coolant mechanism during machining of the workpiece. In step S1, the control unit 50 opens only the pressure-holding valve 58A. In other words, the drawback valve 58C and the orifice valve 58B are closed. Then, the control unit 50 controls the pump 56 to pump the coolant to the main flow path F1. The coolant pumped through the main flow path F1 is discharged from the tip of the tool T via the communication path L2 and the through path L1.

[0090] Thereafter, it is assumed that the control unit 50 receives a command to stop the coolant from being discharged from the tool T or a command to replace the tool T. In response to this, the control unit 50 stops driving the pump 56 and executes the drawback process shown in step S2.

[0091] More specifically, in step S2, the control unit 50 switches the drawback valve 58C from a closed state to an open state. The control unit 50 also maintains the pressure-retaining valve 58A in an open state and the orifice valve 58B in a closed state. The control unit 50 then returns at least the amount of coolant that is present from the pressure-retaining valve 58A to the opening on the tip side of the tool T to the branch flow path F3. Typically, the coolant remaining in the through passage L1, the communication passage L2, and the main flow path F1 is discharged from the branch flow path F3. This prevents the coolant from dripping from the tool T or the spindle 180.

[0092] Preferably, a suction mechanism such as an ejector (not shown) is provided at the branch point P3 or the branch flow path F3. During the drawback process, for example, coolant at a predetermined flow rate or pressure supplied from the pump 56 flows into the ejector, thereby exerting a suction effect on the downstream side of the branch point P3. As a result, the coolant downstream of the branch point P3 flows back from the main flow path F1 into the branch flow path F3.

[0093] After the execution of the drawback process, the control unit 50 executes the filling process shown in step S3. More specifically, in step S3, the control unit 50 changes the pressure-retaining valve 58A from an open state to a closed state. The control unit 50 also changes the orifice valve 58B from a closed state to an open state. Furthermore, the control unit 50 changes the drawback valve 58C from an open state to a closed state. Thereafter, the control unit 50 drives the pump 56 to fill the main flow path F1 between the pump 56 and the pressure-retaining valve 58A with coolant. This reduces the time it takes for the coolant to be discharged from the tip of the tool T when a new tool T having a through passage L1 is attached to the spindle 180.

[0094] During the coolant filling process in step S3, the orifice valve 58B may be in an open state or in a closed state. In the example of FIG. 11, the control unit 50 sets the orifice valve 58B in an open state. If the orifice valve 58B is in an open state, the pressure of the coolant in the flow path can be prevented from rising too much above a predetermined value even if the pump 56 is not completely stopped and is kept operating at the minimum driving frequency. Therefore, even if the discharge and stopping of the coolant are repeated, it is possible to prevent an increase in power consumption caused by the pump 56 being completely stopped and started repeatedly as in the conventional case.

[0095] Preferably, the pressure-retaining valve 58A is provided on the spindle 180 side on the main flow path F1. The spindle 180 side refers to the vicinity of the spindle 180 on the main flow path F1. As an example, the spindle 180 side refers to the flow path between the center of the main flow path F1 and the spindle 180. As another example, the spindle 180 side refers to the flow path between the branch point P2 or the branch point P3 and the spindle 180. By providing the pressure-retaining valve 58A on the spindle 180 side, the coolant is filled up to the vicinity of the spindle 180. As a result, the time until the coolant is discharged from the tip of the tool T can be further shortened. In addition, while realizing such a shortened time until the coolant starts to be discharged, repeated starting and stopping of the pump 56 can be eliminated, thereby realizing energy saving.

[0096] After the coolant filling process is performed, the control unit 50 performs the process shown in step S4. More specifically, in step S4, the control unit 50 changes the orifice valve 58B from an open state to a closed state. The control unit 50 also maintains the pressure-retaining valve 58A in a closed state and the drawback valve 58C in a closed state. After that, the control unit 50 stops the pump 56.

[0097] In the above, an example in which the pump 56 is stopped in step S4 has been described, but if the pump 56 is an inverter-driven variable displacement pump, the control unit 50 needs to continue driving the pump 56 at the minimum driving frequency. In this case, in step S4, the control unit 50 drives the pump 56 at the minimum driving frequency while maintaining the orifice valve 58B in an open state. The minimum driving frequency is lower than the driving frequency of the pump 56 in step S3.

[0098] (F3. Overview) Machine tool 100 according to this modification executes the fault detection process for pump 56 in parallel with the coolant filling process shown in step S3. This makes it possible to execute the fault detection process for pump 56 in conjunction with the coolant filling process, thereby making it possible to reduce the amount of coolant consumed.

[0099] (F4. Flowchart) Next, a fault detection function in this modified example will be described with reference to Fig. 12. Fig. 12 is a diagram showing the flow of fault detection processing according to this modified example.

[0100] The processing shown in Fig. 12 is realized by control unit 50 of machine tool 100 executing the above-mentioned control program 122. In another aspect, a part or all of the processing shown in Fig. 12 may be executed by circuit elements or other hardware.

[0101] The flowchart shown in Fig. 12 differs from the flowchart shown in Fig. 3 described above in that it includes steps S102 and S104. As the other points are as described above, the description thereof will not be repeated.

[0102] In step S102, the control unit 50 executes the drawback process described above with reference to Fig. 10. That is, when the control unit 50 stops the discharge of the coolant from the tool T to the outside, the control unit 50 opens the drawback valve 58C and returns at least the coolant present from the pressure-retaining valve 58A to the opening on the tip side of the tool T to the branch flow path F3.

[0103] Next, the control unit 50 starts executing the coolant filling process described in FIG. 11 above. That is, the control unit 50 closes the pressure holding valve 58A and the draw-back valve 58C, and opens the orifice valve 58B to fill the main flow path F1 between the pump 56 and the pressure holding valve 58A with coolant.

[0104] Thereafter, the control unit 50 executes the processes of steps S110, S120, S122, S130, and S132 described above.

[0105] As described above, the control unit 50 executes the failure detection process of the pump 56 in parallel with the coolant filling process. The processes executed in parallel with the filling process include at least the process of controlling the rotation speed of the pump 56 so that the discharge pressure detected by the pressure sensor 59 becomes a predetermined pressure (steps S110, S120), and the process of obtaining the rotation speed of the pump 56 based on the fact that the discharge pressure has reached the predetermined pressure (step S122). The process of outputting a warning regarding the failure of the pump 56 (steps S130, S132) may be executed in parallel with the filling process or may be executed after the completion of the filling process.

[0106] <G. Third Modification Example>

[0107] (G1. Coolant Supply Mechanism) Next, with reference to FIG. 13, a modification example of the coolant supply mechanism shown in FIG. 7 will be described. FIG. 13 is a diagram showing a coolant supply mechanism according to the third modification example.

[0108] The coolant supply mechanism according to this modification example is different from the coolant supply mechanism shown in FIG. 7 above in that it further includes a flow rate sensor 60A. Since the other points are as described above, the descriptions thereof will not be repeated.

[0109] The flow sensor 60A is provided in the branch flow path F2 and detects the flow rate of the coolant flowing through the branch flow path F2 per unit time. In the example of Fig. 13, the flow sensor 60A is provided downstream of the branch point P2 and upstream of the orifice valve 58B. The flow rate detected by the flow sensor 60A is output to the control unit 50.

[0110] (G2. Overview) The orifice valve 58B wears with use, and is particularly susceptible to wear when fine chips are present in the coolant.

[0111] As the orifice valve 58B becomes worn, the coolant becomes more likely to flow from the main flow path F1 to the branch flow path F2. In other words, the degree of wear of the orifice valve 58B correlates with the flow rate of the coolant in the branch flow path F2. In light of this, the machine tool 100 according to this modification detects a failure of the orifice valve 58B based on the flow rate detected by the flow sensor 60A.

[0112] (G3. Flowchart) Next, a fault detection function in this modified example will be described with reference to Fig. 14. Fig. 14 is a diagram showing the flow of fault detection processing according to this modified example.

[0113] The processing shown in Fig. 14 is realized by control unit 50 of machine tool 100 executing the above-mentioned control program 122. In another aspect, a part or all of the processing shown in Fig. 14 may be executed by circuit elements or other hardware.

[0114] In the failure detection process according to this modification, not only a failure in the pump 56 but also a failure in the orifice valve 58B is detected.

[0115] More specifically, in step S110, the control unit 50 starts the process of discharging the coolant from the tool T with the pressure-retaining valve 58A and the orifice valve 58B open. At this time, the control unit 50 controls the pump 56 so that the coolant pressure detected by the above-mentioned pressure sensor 59 becomes a predetermined target pressure. This control is realized by feedback control. The feedback control may be realized by PID control, PI control, or PD control.

[0116] Next, control unit 50 executes the process of step S120. The process of step S120 is as described above with reference to FIG. 3, and therefore the description thereof will not be repeated.

[0117] Next, the control unit 50 executes the process of step S122. The process of step S122 is as described above with reference to FIG. 3, and therefore the description thereof will not be repeated.

[0118] In step S124 when the coolant pressure reaches the predetermined target pressure, the control unit 50 obtains the flow rate of the coolant in the branch flow path F2 from the flow rate sensor 60A described above.

[0119] In step S130, the control unit 50 determines whether or not a failure condition is satisfied for the pump 56. As one example, the failure condition for the pump 56 is satisfied based on the rotation speed acquired in step S122 exceeding a predetermined threshold value.

[0120] Preferably, the control unit 50 determines whether or not the failure condition of the pump 56 is satisfied by using the flow rate obtained in step S124 in addition to the rotation speed obtained in step S122. More specifically, when the pump 56 is worn, the rotation speed of the pump 56 increases, but the flow rate of the coolant in the branch flow path F2 does not increase. In view of this, the control unit 50 determines that the failure condition of the pump 56 is satisfied when the rotation speed obtained in step S122 exceeds a predetermined threshold and the flow rate obtained in step S124 is equal to or less than the predetermined threshold. Note that the predetermined threshold for the rotation speed is different from the predetermined threshold for the flow rate.

[0121] In step S130, if the control unit 50 determines that the failure condition of the pump 56 is satisfied (YES in step S130), the control unit 50 switches the control to step S132. If not (NO in step S130), the control unit 50 switches the control to step S140.

[0122] The process of step S132 is as described above with reference to FIG. 3, and therefore the description thereof will not be repeated.

[0123] In step S140, the control unit 50 determines whether or not a failure condition of the orifice valve 58B is satisfied. As an example, the failure condition of the orifice valve 58B is satisfied based on the flow rate acquired in step S124 exceeding a predetermined threshold value.

[0124] Preferably, the control unit 50 determines whether or not the failure condition of the orifice valve 58B is satisfied by further using the rotation speed obtained in step S122 in addition to the flow rate obtained in step S124. More specifically, when the orifice valve 58B is worn, not only the rotation speed of the pump 56 increases, but also the flow rate of the coolant in the branch flow path F2 increases. In view of this, the control unit 50 determines that the failure condition of the orifice valve 58B is satisfied when the rotation speed obtained in step S122 exceeds a predetermined threshold and the flow rate obtained in step S124 exceeds a predetermined threshold. Note that the predetermined threshold for the rotation speed is different from the predetermined threshold for the flow rate.

[0125] In step S140, when the control unit 50 determines that the failure condition of the orifice valve 58B is satisfied (YES in step S140), the control is switched to step S142. Otherwise (NO in step S140), the control unit 50 ends the process shown in FIG. 14.

[0126] In step S142, the control unit 50 outputs a warning regarding the failure of the orifice valve 58B. As a result, the operator can be aware of the failure of the orifice valve 58B.

[0127] Preferably, the control unit 50 changes the warning level according to the flow rate acquired in step S124. As an example, when the flow rate is equal to or greater than the third threshold value and less than the fourth threshold value, the control unit 50 outputs a warning indicating a sign of failure of the orifice valve 58B. On the other hand, when the flow rate is equal to or greater than the fourth threshold value, the control unit 50 outputs a warning indicating a failure of the orifice valve 58B. The fourth threshold value is greater than the third threshold value.

[0128] Note that the warning level regarding the failure of the orifice valve 58B does not necessarily have to be changed in two steps, and may be changed in three or more steps.

[0129] <H. Fourth Modification Example> Next, with reference to FIG. 15, a modification example of the coolant supply mechanism shown in FIG. 13 will be described. FIG. 15 is a diagram showing a coolant supply mechanism according to the fourth modification example.

[0130] The coolant supply mechanism according to this modification example is different from the coolant supply mechanism shown in FIG. 13 described above in that it further includes a flow rate sensor 60B. Since the other points are as described above, the descriptions thereof will not be repeated.

[0131] The flow rate sensor 60B is provided in the main flow path F1, and detects the amount of coolant discharged from the tool T per unit time. In the example of Fig. 15, the flow rate sensor 60B is provided downstream of the branch point P2 and upstream of the spindle 180. The discharge amount detected by the flow rate sensor 60B is output to the control unit 50.

[0132] An operator can switch the discharge mode in machine tool 100 according to this modified example. Examples of the settable discharge modes include a discharge pressure control mode that prioritizes keeping the discharge pressure from the tool T constant, and a discharge amount control mode that prioritizes keeping the discharge amount from the tool T constant.

[0133] When the discharge mode is the discharge pressure control mode, the control unit 50 controls the pump 56 so that the coolant pressure detected by the pressure sensor 59 becomes the target pressure. On the other hand, when the discharge mode is the discharge amount control mode, the control unit 50 controls the pump 56 so that the amount of coolant detected by the flow rate sensor 60B becomes the target flow rate.

[0134] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0135] 20 CPU unit, 40A tool storage section, 40B machine body, 50 control section, 52 coolant tank, 54 motor driver, 55 motor, 56 pump, 58A pressure retention valve, 58B orifice valve, 58C drawback valve, 59 pressure sensor, 60A flow sensor, 60B flow sensor, 100 machine tool, 101 control circuit, 102 ROM, 103 RAM, 104 communication interface, 105 communication interface, 109 internal bus, 120 auxiliary storage device, 122 control program, 150 magazine, 170 spindle head, 175 spindle tube, 180 spindle, 400 operation panel, 405 display, 406 operation key, D door, F1 main flow path, F2 branch flow path, F3 branch flow path, FR orifice, L1 through passage, L2 connecting passage, P2 Junction, P3 junction, T tool, WRA warning, WRB warning.

Claims

1. A machine tool capable of machining a workpiece using a tool having a first coolant passage formed therein, a spindle configured to be able to mount the tool and having a second passage connected to the first passage when the tool is mounted; a pump for pumping coolant to a main passage connected to the second passage; a pressure sensor for detecting a pressure applied to the coolant flowing through the main flow passage; A first valve provided in the main flow path; a second valve provided in a first branch flow path that branches off from the main flow path between the pump and the first valve; A control unit. The control unit is A process of controlling a rotation speed of the pump so that the pressure detected by the pressure sensor becomes a predetermined pressure; A process of acquiring a rotation speed of the pump based on the pressure detected by the pressure sensor reaching the predetermined pressure; and outputting a warning regarding a failure of the pump based on the rotation speed acquired in the acquiring process. The machine tool, wherein the controlling process and the acquiring process are executed in a state in which the first valve is closed and the second valve is open.

2. The machine tool further comprises: a third valve provided in a second branch flow path that branches off from the main flow path between the pump and the first valve; The control unit further includes: a drawback process in which the third valve is opened when the discharge of the coolant from the tool to the outside is stopped, and the coolant present at least between the first valve and an opening on the tip side of the tool is returned to the second branch flow path; After the execution of the drawback process, a filling process is executed in which the first valve and the third valve are closed and the second valve is opened to fill the main flow path between the pump and the first valve with coolant; The machine tool according to claim 1 , wherein the controlling process and the obtaining process are executed in parallel with the filling process.

3. The machine tool further comprises: a flow rate sensor for detecting a flow rate of the coolant in the first branch flow path, The control unit is A process of acquiring a flow rate from the flow rate sensor based on the pressure detected by the pressure sensor reaching the predetermined pressure; The machine tool according to claim 1 or 2, further comprising a process of outputting a warning regarding an abnormality in the second valve based on the acquired flow rate.

4. A machine tool capable of machining a workpiece using a tool having a first coolant passage formed therein, a spindle configured to be able to mount the tool and having a second passage connected to the first passage when the tool is mounted; a pump for pumping coolant to a main passage connected to the second passage; a pressure sensor for detecting a pressure applied to the coolant flowing through the main flow passage; A control unit. The control unit is A process of controlling a rotation speed of the pump so that the pressure detected by the pressure sensor becomes a predetermined pressure; A process of acquiring a rotation speed of the pump based on the pressure detected by the pressure sensor reaching the predetermined pressure; and outputting a warning regarding a failure of the pump based on the rotation speed acquired in the acquiring process. The output process includes: a process of outputting a first warning indicating a sign of a failure of the pump when the acquired rotation speed is equal to or greater than a first threshold value and smaller than a second threshold value; and outputting a second warning indicating a failure of the pump when the acquired rotation speed exceeds the second threshold value. The second threshold value is greater than the first threshold value.

5. A method for controlling a machine tool capable of machining a workpiece using a tool having a first coolant passage formed therein, comprising the steps of: The machine tool comprises: a spindle configured to be able to mount the tool and having a second passage connected to the first passage when the tool is mounted; a pump for pumping coolant to a main passage connected to the second passage; a pressure sensor for detecting a pressure applied to the coolant flowing through the main flow passage; A first valve provided in the main flow path; a second valve provided in a first branch flow path that branches off from the main flow path between the pump and the first valve, The control method includes: controlling the rotation speed of the pump so that the pressure detected by the pressure sensor becomes a predetermined pressure; acquiring a rotation speed of the pump based on the pressure detected by the pressure sensor reaching the predetermined pressure; and outputting a warning regarding a failure of the pump based on the rotation speed acquired in the acquiring process. The control method, wherein the controlling step and the obtaining step are performed in a state where the first valve is closed and the second valve is open.

6. A control program for a machine tool capable of machining a workpiece using a tool having a first coolant passage formed therein, comprising: The machine tool comprises: a spindle configured to be able to mount the tool and having a second passage connected to the first passage when the tool is mounted; a pump for pumping coolant to a main passage connected to the second passage; a pressure sensor for detecting a pressure applied to the coolant flowing through the main flow passage; A first valve provided in the main flow path; a second valve provided in a first branch flow path that branches off from the main flow path between the pump and the first valve, The control program causes the machine tool to A process of controlling a rotation speed of the pump so that the pressure detected by the pressure sensor becomes a predetermined pressure; A process of acquiring a rotation speed of the pump based on the pressure detected by the pressure sensor reaching the predetermined pressure; and outputting a warning regarding a failure of the pump based on the rotation speed acquired in the acquiring process. the control program, wherein the controlling process and the acquiring process are executed in a state in which the first valve is closed and the second valve is open.

Images