Threshold Setting System

Abstract

To provide a threshold setting system which automatically resets a threshold of seating determination.SOLUTION: A threshold setting system comprises: a machine tool having a seating determination device in which a detection hole is formed on a seating surface of a spindle chuck gripping a workpiece and which measures a leakage amount of air flowing out from the detection hole with a flow amount measuring instrument; a workpiece automatic conveyance machine which delivers the workpiece to the spindle chuck; a master workpiece which is formed with an adjustment groove that generates a prescribed gap on the seating surface by being gripped by the spindle chuck; and a control unit which executes phase deciding processing of aligning the detection hole with the adjustment groove with respect to the machine tool and the workpiece automatic conveyance machine, delivery processing of delivering the master workpiece to the spindle chuck, and threshold calculation processing of calculating a threshold for seating determination on the basis of the leakage amount measured by the flow amount measuring instrument.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a threshold setting system that automatically sets a threshold value used for seating determination. [Background technology]

[0002] In machine tools such as lathes, a workpiece is held in a spindle chuck, and a cutting tool is applied to the workpiece by rotating the spindle to perform cutting processing. If the workpiece does not come into accurate contact with the seating surface of the spindle chuck, the workpiece will be cut in excess, which will reduce the quality of the finished product. Therefore, machine tools are provided with a workpiece seating determination device to determine whether the workpiece is properly seated on the seating surface of the spindle chuck. Specifically, a detection hole is formed in the seating surface of the spindle chuck, and air is fed into the hole from an air supply source. The workpiece held by the spindle chuck is placed on the seating surface and blocks the detection hole, but a small gap is created, allowing a certain amount of air to leak, and seating determination is performed based on the amount of air leaked.

[0003] In the seating judgment, the amount of air leaking out from the gap between the workpiece and the seating surface is measured, and the seating judgment is performed by comparing it with a preset threshold value. To set such a threshold value, a master work for checking air pressure that creates a predetermined gap on the seating surface of the workpiece is used. The master work has an adjustment groove formed therein to create a certain amount of air leakage. For example, the following Patent Document 1 discloses a master work that focuses on the fact that the amount of air leaking from the gap changes depending on the roughness of the workpiece surface. The master work has a screw protruding from the bottom of the adjustment groove that creates air leakage, and is configured so that the size of the gap can be adjusted according to the amount of protrusion of the screw. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-024090 A Summary of the Invention [Problem to be solved by the invention]

[0005] When machine tools repeatedly process workpieces, the seating surface becomes dirty due to the generated cutting chips and scattered coolant, which deteriorates the condition of the detection hole. This can change the amount of air leaking from the detection hole, making it necessary to reset the threshold periodically. However, in the threshold setting process, the detection hole and the adjustment groove of the master work must be aligned, so the master work needs to be installed with a phase setting, which is troublesome for some workers. In addition, since the dirt on the seating surface varies depending on the processing content, the threshold resetting process is not performed frequently, but the work of checking for dirt is also troublesome, and it is a task that is easily forgotten if the time until the next reset is long.

[0006] Therefore, in order to solve the above problem, an object of the present invention is to provide a threshold setting system that automatically resets the threshold value for seating determination. [Means for solving the problem]

[0007] The threshold setting system of the present invention includes a machine tool having a detection hole formed in the seating surface of a spindle chuck that grips a workpiece, and a seating determination device that measures the amount of air leakage flowing out from the detection hole with a flow measuring instrument, an automatic work transport machine that transfers the workpiece to and from the spindle chuck, a master workpiece having an adjustment groove formed therein that creates a predetermined gap on the seating surface when gripped by the spindle chuck, and a control device that executes a phase determination process for aligning the detection hole with the adjustment groove, a transfer process for transferring the master workpiece to the spindle chuck, and a threshold calculation process for calculating a threshold for seating determination based on the amount of leakage measured by the flow measuring instrument, for the machine tool and the automatic work transport machine. Effect of the Invention

[0008] According to the above configuration, the master workpiece is handed over to the spindle chuck, which has been phased by the automatic workpiece transport machine to align the phase of the detection hole with the adjustment groove, and air is supplied toward the detection hole, causing air to be released and a predetermined amount of air leakage to occur. The amount of leakage is measured by the flow measuring device, and a threshold value for seating determination is automatically calculated and set based on the measured predetermined amount of leakage. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a side view showing the internal structure of the machine tool. [Diagram 2] FIG. 1 is a simplified diagram illustrating a state in which an automatic workpiece transport device transfers a workpiece to a machine tool. [Diagram 3] FIG. 2 is a diagram showing a simplified configuration of a seating determination device; [Figure 4] FIG. 4 is a diagram showing the seating surface of the spindle chuck. [Diagram 5] FIG. 2 is a perspective view showing a master work. [Figure 6] FIG. 2 is a perspective view showing a master placement stage for placing a master work. [Figure 7] FIG. 2 is a block diagram showing a control system of the machine tool. [Figure 8] FIG. 11 is a flowchart showing the execution of a threshold setting program. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of a threshold setting system according to the present invention will be described below with reference to the drawings. Fig. 1 is a side view showing the internal structure of a machine tool. Machine tool 1 is mounted on a movable bed 2 equipped with wheels, and is capable of moving in the front-rear direction (Z-axis direction) along rails laid on a base 3. Machine tool 1 has a tool table 11 equipped with rotating tools such as an end mill or drill, or cutting tools such as a cutting tool, and is provided with a turret device 4 capable of rotating and indexing the tool table 11.

[0011] Machine tool 1 has a configuration in which a spindle unit 5 is mounted on a movable bed 2 and a spindle chuck 12 that grips a workpiece is rotatable. Machine tool 1 is a two-axis lathe in which a turret unit 4 is moved by a Z-axis drive unit 6 that moves the turret unit 4 in the Z-axis direction parallel to the spindle, and an X-axis drive unit 7 that moves the turret unit 4 in the X-axis direction which is the vertical direction of the machine body. Z-axis drive unit 6 and X-axis drive unit 7 each have a slidable Z-axis slide 13 or X-axis slide 14, and are configured to convert the rotation output of a servo motor into linear motion by a ball screw mechanism.

[0012] The machine tool 1 is provided with an openable front cover 16 at the front of the machine body, in addition to a machine body cover 15 that constitutes the machining chamber 10. The machine tool 1 is modularized like other work machines that constitute the machining machine line, and a plurality of front covers 16 are arranged in the machine body width direction to form a work transport space 20. As shown in Fig. 2, an automatic work transport machine 8 that transfers the work W is incorporated in the work transport space 20. Fig. 2 is a simplified diagram showing the state when the automatic work transport machine 8 transfers a work to the machine tool 1.

[0013] The automatic work transporter 8 is composed of a traveling device 18 that moves a traveling platform 21, and a work transport robot 19 mounted on the traveling platform 21. The work transport robot 19 is configured so that the form of the upper arm member 23 and the forearm member 25 can be changed by driving a first joint mechanism 24 and a second joint mechanism 26. Specifically, the upper arm member 23 and the forearm member 25 can be transformed into a compact moving posture in which they are folded and stand up, and into a working posture in which they are extended and inclined forward as shown in the figure. In the automatic work transporter 8, a robot hand 27 equipped with a chuck mechanism is attached to the tip of the work transport robot 19, making it possible to grip and release the work W.

[0014] The workpiece transport robot 19 enters the machining chamber 10 by opening the slide door of the machine body cover 15, and transfers the workpiece W to the spindle chuck 12. The machine tool 1 is provided with a seating determination device that determines whether the received workpiece W is properly gripped by the spindle chuck 12. FIG. 3 is a simplified diagram showing the configuration of the seating determination device 17 provided in the machine tool 1, and FIG. 4 is a diagram showing the seating surface of the spindle chuck 12. The seating determination device 17 has detection holes 32 formed in three locations on the same circumference at intervals of 120 degrees on the seating surface 31 of the spindle chuck 12. An air supply source 34 such as a compressor is connected to the three detection holes 32 via an air supply pipe 33. An electromagnetic opening / closing valve 35, a pressure control valve 36, and a flow rate measuring device 37 are connected to the air pipe 33 in this order.

[0015] In the seating determination device 17, air sent from an air supply source 34 to an air pipe 33 flows to the spindle chuck 12 at a predetermined pressure, and in the unclamped state, the air is released from a detection hole 32. When the workpiece W is delivered from the workpiece transport robot 19 to the spindle chuck 12, the detection hole 32 is blocked and the flow of air is cut off. However, if a small gap occurs, air leakage will occur. In the seating determination device 17, the amount of leakage is measured by a flow rate measuring device 37, and the measured value is sent to the control device 9, and seating determination is made by comparing it with a preset threshold value.

[0016] When workpiece machining is repeated in the machine tool 1, chips and coolant scattered in the machining chamber also adhere to the detection hole 32 of the spindle chuck 12, obstructing the air flow and causing changes in the amount of air leakage. Even in such cases, it is necessary to perform stable and accurate seating determination, and it is necessary to periodically reset the threshold value according to changes in the amount of leakage. Therefore, in this embodiment, a threshold setting system is configured that enables the resetting of the threshold value by controlling the machine tool 1 and the automatic workpiece transporter 8.

[0017] To set the threshold value, a master workpiece MW is used that creates a predetermined gap on the seating surface 31 of the spindle chuck 12. The master workpiece MW is gripped by the chuck jaws with its center aligned on the seating surface 31 as shown by the dashed line in FIG. 4. FIG. 5 is a perspective view showing the master workpiece MW. The master workpiece MW has a positioning hole 41 formed at the center of a cylindrical member, and a first adjustment groove 43 and a second adjustment groove 44 formed at positions 180 degrees apart on the axial end face, which extend radially from the positioning hole 41 to the outer diameter end. Furthermore, a phase determination hole 42 is formed at a position away from the positioning hole 41 to keep the phase constant when the master workpiece MW is handled.

[0018] The first adjustment groove 43 and the second adjustment groove 44 virtually create a gap when the workpiece is held by the spindle chuck 12 and placed against the seating surface 31. The two grooves have different depths, and the first adjustment groove 43 is a shallow OK groove that creates an allowable gap when the workpiece is seated, and has a depth of, for example, about 0.03 mm. The second adjustment groove 44 is a deep NG groove that creates a gap that is determined to be a seating error, and has a depth of, for example, about 0.05 mm. The first adjustment groove 43 and the second adjustment groove 44 are stacked in order with respect to the three detection holes 32 in the seating surface 31 when determining the leakage amount (threshold value) that is determined to be appropriate seating. Therefore, the master workpiece MW needs to be held in a constant phase state with respect to the spindle chuck 12.

[0019] 6 is a perspective view showing a master mounting table 45 on which the master work MW is placed. The master mounting table 45 has a positioning pin 47 and a phasing pin 48 stuck onto a flat plate 46. The positioning pin 47 is a cylindrical member having a diameter corresponding to the positioning hole 41 of the master work MW, and the phasing pin 48 is a cylindrical member having a diameter corresponding to the phasing hole 42. The positioning pin 47 and the phasing pin 48 are formed so that the positional relationship between the positioning hole 41 and the phasing hole 42 of the master work MW coincides.

[0020] 6, the master work MW is placed on the master stage 45 so that the positioning hole 41 fits onto the positioning pin 47 and the phasing hole 42 fits onto the phasing pin 48. The master stage 45 is provided within the movement range of the work transport robot 19, for example, midway through the work transport space 20 in which the work transport robot 19 moves, or at the work input or output section of the line. Therefore, by having the work transport robot 19 take out the master work MW at any timing, it is possible to automatically set a threshold value for the seating determination device 17 of the machine tool 1 or the like.

[0021] The processing machine line is provided with a plurality of working machines such as a machine tool 1, and an automatic work transporter 8 that transports workpieces to each working machine, and a control communication network is constructed that enables the exchange of command signals between a control device on the working machine side, such as the control device 9 of the machine tool 1 shown in Fig. 1, and a control device provided on the automatic work transporter. In the threshold setting system of this embodiment, a threshold setting program is stored in the control device 9 of the machine tool 1, and the threshold setting is executed by driving and controlling the machine tool 1 and the automatic work transporter 8.

[0022] FIG. 7 is a block diagram showing the control system of the machine tool 1. The control device 9 is mainly a computer equipped with storage devices such as a ROM 52, a RAM 53, and a non-volatile memory 54 in addition to a CPU 51, and is connected to each drive unit such as the turret unit 4, the spindle unit 5, the Z-axis drive unit 6, the X-axis drive unit 7, and the seating determination unit 17 via an I / O 55. In addition, the machine tool 1 has an operation display unit 58 attached to the front of the machine body, which displays work information and an operation screen, and allows the operator to input setting values, and the like, and is connected to the control device 9. The control device 9 stores machining programs related to various types of machining, workpiece types, workpiece machining information related to tools and jigs, and the like in a memory unit. In particular, in this embodiment, a threshold setting program is stored.

[0023] 8 is a diagram showing a flowchart for executing the threshold setting program. The threshold resetting is programmed to be automatically started on a set date in conjunction with a calendar function so that it is performed, for example, once a month. In addition, since the degree of dirt on the spindle chuck 12 varies depending on the machining contents, the operator can press the start button on the operation display device 58 to start the threshold setting program at any timing.

[0024] By starting the threshold setting program, first, in the automatic workpiece transport machine 8, the master workpiece MW is taken out from the master table 45 by the workpiece transport robot 19 (S101). In the machine tool 1, the phase of the detection hole 32 of the spindle chuck 12 is determined (S102). The master workpiece MW on the master table 45 is in a fixed state, and the spindle chuck 12 performs phase determination for the master workpiece MW transported in that state. Then, when the master workpiece MW is transferred between the workpiece transport robot 19 and the spindle chuck 12, the first adjustment groove 43 and the second adjustment groove 44 are positioned as shown in FIG. 4, and one of the three detection holes 32 is overlapped with the second adjustment groove 44, which is an NG groove (S103).

[0025] Air is constantly blowing out of the three detection holes 32, but air leaks from the first detection hole 32 overlapping the second adjustment groove 33 while the other detection holes 32 are blocked. The amount of leakage in this situation is measured by the flow rate measuring device 37 and stored in the memory of the control device 9 as the measured value NG1 at the first detection hole 32 (S104). Thereafter, the master workpiece MW is removed from the spindle chuck 12 by the work transport robot 19 (S105), and it is confirmed whether the measurement and storage of the amount of leakage from the three detection holes 32 has been completed (S106). Since it is still the first detection hole 32 (S106: NO), the process returns to step S102, the spindle chuck 12 is rotated 120 degrees, and phase determination is performed so that the second detection hole 32 is overlapped with the second adjustment groove 44, which is the NG groove.

[0026] Then, steps S103-S106 are repeated. That is, the master workpiece MW is transferred to the spindle chuck 12, the amount of air leakage blowing out from the second detection hole 32 overlapping the second adjustment groove 33 is measured, and the measured value NG2 is stored in the memory unit. Thereafter, the master workpiece MW is removed from the spindle chuck 12, it is confirmed that the processing is for the second detection hole 32, and the process returns to step S102 (S106: NO). Next, steps S103-S106 are repeated for the third detection hole 32, and the measured value NG3 of the leakage amount is measured and stored in the memory unit. When the processing of the third detection hole 32 for the NG groove is completed (S106: YES), the process moves to the processing for the OK groove.

[0027] Next, the processing for the OK slot is performed in the same manner as for the NG slot. First, the spindle chuck 12 is phased so that the first detection hole 32 is overlapped with the first adjustment groove 43 of the OG slot shown in Fig. 4 (S107), and the master workpiece MW is delivered there from the workpiece transport robot 19 (S108). Since air is blowing out from the detection hole 32 through the first adjustment groove 43, the leakage amount is measured for the first detection hole 32, and the value is stored in the memory unit as the measurement value OK1 (S109). After that, the master workpiece MW is removed from the spindle chuck 12 (S110), and it is confirmed whether the measurement and storage of the leakage amount for the three detection holes 32 is completed (S111).

[0028] Until the processing for the third detection hole 32 is performed (S111: NO), steps S107-S111 are repeated for the second and third detection holes 32 in order, and the respective leakage amounts are stored in the memory as the measured values ​​OK2 and OK3. Then, when the processing for the third detection hole 32 for the OK groove is completed (S111: YES), the threshold value is calculated based on the following formula (S112). The threshold value TH is calculated by TH=OKa+(NGa+OKa) / 2, assuming that the average values ​​of the leakage amounts in the NG groove and the OK groove of the three detection holes 32 are NGa=(NG1+NG2+NG3) / 3 and OKa=(OK1+OK2+OK3) / 3. In other words, the intermediate value of the leakage amounts in the NG groove and the OK groove is set as the threshold value TH.

[0029] After completing the threshold setting process, the master work MW is returned to the master table 41. The master work MW held by the robot hand 27 is in the same state as when it is attached to the spindle chuck 12, that is, the positions of the first adjustment groove 43 and the second adjustment groove 44 are the same. Therefore, by returning the master work MW to the master table 45 as is, the positioning hole 41 of the master work MW is always aligned with the position of the positioning pin 47, and the phase determination hole 42 is always aligned with the position of the phase determination pin 48, as shown in FIG.

[0030] Therefore, according to this embodiment, it is possible to automatically set the threshold value for the seating determination device 17 by controlling the machine tool 1 and the automatic workpiece transporter 8 in accordance with the threshold value setting program stored in the control device. This eliminates the need for a troublesome operation by the operator, and by inputting the execution time, the threshold value is periodically reset, so that seating determination is always performed using a stable threshold value.

[0031] Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications are possible without departing from the spirit of the present invention. In the above embodiment, the resetting of the threshold value is described. However, for example, the initial setting performed after cleaning the detection hole 32 can be executed by an operator pressing the start button on the operation display device 58 to start up the threshold setting program. [Explanation of symbols]

[0032] 1...machine tool 8...automatic workpiece transporter 12...spindle chuck 17...seating determination device 31...seating surface 32...detection hole 37...flow rate measuring device 41...positioning hole 42...phase determination hole 43...first adjustment groove 44...second adjustment groove 45...master stand 47...positioning pin 48...phase determination pin MW...master workpiece

Claims

1. a machine tool having a seating determination device in which a detection hole is formed in a seating surface of a spindle chuck that grips a workpiece, the machine tool being equipped with a seating determination device that measures an amount of air leakage flowing out from the detection hole with a flow rate measuring device; an automatic workpiece conveyor that delivers the workpiece to and from the spindle chuck; a master workpiece having an adjustment groove formed therein for generating a predetermined gap on the seating surface when the master workpiece is gripped by the spindle chuck; a control device that executes, for the machine tool and the automatic workpiece transporter, a phase determination process for aligning the detection hole with the adjustment groove, a transfer process for transferring the master workpiece to the spindle chuck, and a threshold calculation process for calculating a threshold for seating determination based on the amount of leakage measured by the flow rate measuring device; A threshold setting system having:

2. 2. The threshold setting system according to claim 1, wherein the detection holes are formed in a plurality on the same circumference of the seating surface, and the master work is formed with a shallow first adjustment groove that creates an acceptable gap when the work is seated, and a second adjustment groove that is deeper than the first adjustment groove and creates a gap that is determined to be a seating error.

3. The threshold setting system according to claim 2, wherein the control device phases the plurality of detection holes in sequence with respect to the first adjustment groove and the second adjustment groove, and calculates the threshold based on the respective leakage rates measured by the flow measuring device.

4. The threshold calculation process calculates a first average value of the leakage amount occurring at each of the multiple detection holes phased to the first adjustment groove and a second average value of the leakage amount occurring at each of the multiple detection holes phased to the second adjustment groove, and sets the threshold value to the first average value plus the average of the first average value and the second average value.

5. 5. The threshold setting system according to claim 1, wherein the master work has a positioning hole formed at the center of a cylindrical member, and a phase determination hole formed at a position away from the positioning hole.

6. The threshold setting system according to claim 5 , wherein the first adjustment groove and the second adjustment groove of the master work are formed at positions 180 degrees apart on the axial end face from the positioning hole to the outer diameter end in the radial direction.

7. 7. The threshold setting system according to claim 5, wherein the master work is placed so as to fit onto a master stage having positioning pins and phase determination pins corresponding to the positioning holes and the phase determination holes, and the master stage is disposed at any position from which the master work can be removed by the automatic work transport machine.

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