Work seating detection device

Abstract

Provided is a workpiece seating detection device in which piping length is reduced, the workpiece seating detection device having: a detection orifice through which air is discharged from a seating surface of a chuck for grasping a workpiece; an air supply flow path for sending air from an air supply source to the detection orifice; a pressure control valve provided to the air supply flow path; a seating sensor provided to the air supply flow path at a location on the secondary side of the pressure control valve; a relay device for transmitting measurement data measured by the seating sensor; and a control device for calculating a threshold value for assessing seating on the basis of display, on an operation display device, of the measurement data acquired via the relay device, and the operation of the operation display device.

Description

Technical Field

[0001] The present invention relates to a workpiece seating detection device for determining the seating of a workpiece gripped by a spindle chuck.

Background Art

[0002] In machine tools such as lathes, a workpiece is gripped by a spindle chuck, and machining is performed by applying a cutting tool to the workpiece by the rotation of the spindle. At that time, if the workpiece is not in exact contact with the seating surface of the spindle chuck, the quality of the finished product will deteriorate, such as the workpiece being cut excessively. Therefore, a workpiece seating detection device is provided in the machine tool so that it can be determined whether the workpiece is properly applied to the seating surface of the spindle chuck. Specifically, a detection hole is formed in the seating surface of the spindle chuck, and air is sent into it from an air supply source. The workpiece gripped by the spindle chuck is applied to the seating surface to block the detection hole, but since a slight gap is generated and a certain amount of air leaks, the seating determination is made according to the amount of leakage.

[0003] In the workpiece seating detection device described in Patent Document 1 below, when the workpiece is pressed against the seating surface with respect to the chuck of the unclamp, in the correct seating state, the seating sensor is turned on, and the clamp prohibition is released by the control device. In response to this release, a clamp command is output and the chuck performs a clamping operation. Even if the correct seating is achieved and the clamping operation is started, if a seating defect occurs later, the seating sensor is turned off, the clamp command stops, and the clamping operation of the chuck is interrupted.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When the workpiece machining is repeatedly performed by a machine tool, the seating surface is contaminated by the chips generated and the coolant scattered, the state of the detection hole deteriorates, and the leakage amount of the air ejected from the detection hole changes. It is essential for the workpiece seating detection device to periodically adjust the threshold value for seating determination so as to cope with the change. The threshold adjustment is performed with the master workpiece in close contact with the anvil of the spindle chuck. However, the seating sensor is attached at a position away from the spindle chuck, such as the front of the machine body, so that the operator can easily perform the work. Therefore, in the conventional workpiece seating detection device, since the pipe for flowing air from the seating sensor to the spindle chuck is long and it takes time to boost the pressure, the working time required for threshold adjustment has become long.

[0006] Therefore, an object of the present invention is to provide a workpiece seating detection device with a shortened pipe length in order to solve such problems.

Means for Solving the Problems

[0007] The workpiece seating detection device according to one aspect of the present invention includes a detection hole for discharging air from the seating surface of a chuck that holds a workpiece, an air supply flow path for sending air from an air supply source to the detection hole, a pressure control valve provided in the air supply flow path, a seating sensor provided in the air supply flow path on the secondary side of the pressure control valve, a relay device that transmits measurement data measured by the seating sensor, and the relay device transmitted by of the measurement data capable of performing display and measurement data acquisition operations operation display device and operation of the operation display device based on the measurement data acquired by calculate the threshold value for seating determination perform and a control device.

Effects of the Invention

[0008] According to the above configuration, air from the air supply source flows through the air supply passage and is sent to the detection holes formed on the seating surface of the chuck that grips the workpiece. The measurement data measured by the seating sensor provided on the secondary side of the pressure control valve is transmitted to the control device via the relay device. The measurement data is displayed on the operation display device, and based on the display, it is possible to calculate the threshold value for seating determination by operating the operation display device. Therefore, it is not necessary to arrange the seating sensor at a position far from the seating surface, the air supply passage of the workpiece seating detection device can be shortened, and the time from seating the workpiece until the pressure in the air supply passage rises to a state where seating determination is possible can be shortened.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0010] An embodiment of the workpiece seating detection device 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 equipped with the workpiece seating detection device of this embodiment. The machine tool 1 is assembled on a movable bed 2 equipped with wheels and is movable in the front-rear direction (Z-axis direction) along a rail laid on a base 3. The machine tool 1 has a tool post 11 equipped with a rotary tool such as an end mill or a drill, or a cutting tool such as a tool bit, and is provided with a turret device 4 capable of indexing the rotation of the tool post 11.

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

[0012] In addition to the machine body cover 15 that constitutes the machining chamber 10, the machine tool 1 is provided with an openable front cover 16 on the front part of the machine body. The machine tool 1 is modularized like other working machines that constitute a machining machine line, and a plurality of front covers 16 are arranged in the machine body width direction to form a workpiece transfer space 20. And a workpiece automatic transfer machine for delivering the workpiece W to each working machine is incorporated in the workpiece transfer space 20.

[0013] When the spindle chuck 12 of the machine tool 1 receives the workpiece W, a workpiece seating detection device is provided to determine whether the workpiece W is properly gripped. FIG. 2 is a diagram showing a simplified configuration of the workpiece seating detection device 17 provided in the machine tool 1. In the workpiece seating detection device 17, three detection holes 22 are formed in the seating surface 21 of the spindle chuck 12 (see FIG. 3). An air supply source 24 such as a compressor is connected to the detection holes 22 via an air pipe 23, and an electromagnetic on-off valve 25, a pressure control valve 26, and a seating sensor 27 are connected in order toward the downstream side of the air pipe 23.

[0014] In the workpiece seating detection device 17, the air sent from the air supply source 24 to the air pipe 23 flows to the spindle chuck 12 at a predetermined pressure, and in the unclamped state, the air is discharged from the detection holes 22. On the other hand, when the workpiece W is transferred to the spindle chuck 12 by the workpiece transfer robot, the detection holes 22 are blocked and the air flow is interrupted. However, the workpiece W does not adhere tightly to the seating surface 21 so that the detection holes 22 are completely blocked, and a small amount of air leaks from the slightly generated gap. The seating sensor 27 of the present embodiment is a flow sensor that measures the flow rate of the air flowing out from the detection holes 22, and will be described as the flow sensor 27 in the following explanation.

[0015] In the workpiece seating detection device 17, the measured value by the flow sensor 27 is transmitted to the control device 9, and the seating determination is made by comparing with a preset threshold value. For setting such a threshold value, a master workpiece MW that creates a predetermined gap in the seating surface 21 of the spindle chuck 12 is used. FIG. 3 is a diagram showing the seating surface of the spindle chuck 12. As shown by the dashed-dotted line on the seating surface 21, the master workpiece MW is gripped by the chuck jaws in a centered state. The master workpiece MW has a hole 31 formed in the central portion of the disk shape, and a first adjustment groove 33 and a second adjustment groove 34 extending from the central hole 31 to the outer diameter end in the radial direction are formed at positions 180 degrees apart on one end surface in the axial direction.

[0016] The first adjustment groove 33 is a shallow OK groove that creates a tolerable gap when the workpiece is seated, and the second adjustment groove 34 is a deep NG groove that creates a gap determined as a seating error. There are three detection holes 22 on the seating surface 21 of the spindle chuck 12 on the same circumference at intervals of 120 degrees. In the threshold setting operation, the master workpiece MW is positioned so that the first adjustment groove 33 and the second adjustment groove 34 are successively overlapped with respect to each detection hole 22.

[0017] The threshold value serving as the criterion for seating determination is not only set initially but also periodically. When the machining of the workpiece is repeated in the machine tool 1, chips and coolant scattered in the machining chamber adhere to the detection holes 22 of the spindle chuck 12, and the leakage amount of air changes by obstructing the air flow. Even in such a situation, it is necessary to perform stable and accurate seating determination, and it is necessary to periodically reset the threshold value according to the change in the leakage amount.

[0018] The machine tool 1 has a short dimension in the machine body width direction, but the turret device 4 and the spindle device 5 are arranged in the front-rear direction of the machine body, so the distance in the same direction becomes long. The workpiece seating detection device 17 is provided on the rear side of such a spindle device 5. On the other hand, when setting the threshold value in the workpiece seating detection device 17, it is necessary to check the measured value of the flow sensor 27, but it is extremely difficult to work if the flow sensor 27 is arranged deep inside the machine body.

[0019] Therefore, in the conventional workpiece seating detection device 100, as shown in FIG. 7, the flow sensor 105 was installed at the upper part of the front surface of the machine body of the machine tool 1. This is an arrangement that makes it easy for the operator to view the measured value of the flow sensor 105. However, in the conventional workpiece seating detection device 100, the air pipe 110 had to pass through the ceiling part of the cover from the rear part to the front part of the machine body, and the pipe length exceeded 6 m. Therefore, it took a long time for the pressure in the air pipe 110 to increase and the state to become stable, and it took a long time to obtain an appropriate measured value of the flow sensor 105 and set the threshold value.

[0020] Therefore, the work seating detection device 17 of the present embodiment is configured such that its measurement data can be acquired by the control device 9 without directly checking the flow sensor 27. Here, FIG. 4 is a block diagram showing the control system of the machine tool 1. The control device 9 mainly consists of 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 device 4, the spindle device 5, the Z-axis drive device 6, the X-axis drive device 7, and the work seating detection device 17 via an I / 0 55.

[0021] In addition to the display of work information and operation screens, etc., the machine tool 1 is equipped with a touch panel type operation display device 18 on the front of the machine body that enables the operator to input set values, etc., and it is connected to the control device 9. In the present embodiment, the measurement data of the flow sensor 27 is displayed on the operation display device 18 via the control device 9, and in addition, the threshold value can be set from the operation display device 18. That is, the flow sensor 27 of the work seating detection device 17 is connected to the control device 9 via the relay device 28.

[0022] The flow sensor 27 is, for example, a Karman vortex flowmeter, and is configured to output an analog signal in response to the vibration transmitted from the pressure receiving part acting on the Karman vortex to the piezoelectric element, convert it into a digital signal by the sensor board, detect the frequency of the digital signal, and digitize the flow rate. As a communication means for capturing the measurement data of such a flow sensor 27, for example, IO-Link (registered trademark) is used, and the relay device 28 is an IO-Link master that performs point-to-point communication with the IO-Link device.

[0023] The threshold setting for seating determination is performed by gripping the master workpiece MW with the spindle chuck 12, and the threshold setting program stored in the control device 9 enables the input of threshold setting from the operation display device 18 based on the flow rate data displayed on the operation display device 18. In the threshold setting, first, the master workpiece MW is gripped by the spindle chuck 12 while changing the phase so as to sequentially overlap each of the first adjustment groove 33 and the second adjustment groove 34 with the three detection holes 22. In the detection hole 22 into which air is constantly fed, air leaks from one detection hole 22 through the first adjustment groove 33 or the second adjustment groove 34, and the openings of the remaining two detection holes 22 are blocked. In such a state, the amount of air leakage flowing out from one detection hole 22 is measured by the flow rate sensor 27, and the measurement data is sent to the control device 9 via the relay device 28.

[0024] The measured value of the flow rate sensor 27 taken into the control device 9 is stored in the storage unit of the control device 9 as the measured flow rate data at the time of measurement and is also displayed on the operation display device 18 installed on the front surface of the machine body. For example, as shown in FIG. 5, the change in the flow rate is represented as a graph on the operation screen 37 of the operation display device 18. This graph is the flow rate value measured by the flow rate sensor 27 and moves to the right as the measurement time elapses. The flow rate is displayed on the vertical axis, and the horizontal axis indicating the measurement time is switched and displayed as the time points of T1 - T6 as the graph moves with the passage of time. Then, at the upper part of the graph display area 41, the measured value at the current time of T6 is displayed in the flow rate display box 42.

[0025] The first adjustment groove 33 and the second adjustment groove 34 are sequentially overlapped with respect to the three detection holes 22, and the respective leakage amounts are taken into the storage unit as measurement values OK1, OK2, OK3 by the first adjustment groove 33 and as measurement values NG1, NG2, NG3 by the second adjustment groove 34. Specifically, the operator checks the flow rate while looking at the graph shown in FIG. 5, and when the value is stable, the operator presses the measurement value capture button displayed on the operation screen 37 to acquire the measurement value. There are an OK measurement button 43 and an NG measurement button 44 for the measurement value capture button, and the average flow rate measurement value at the time when each button is pressed or in the few seconds immediately before that is stored as, for example, the measurement value OK1 by the first adjustment groove 33.

[0026] The measurement values acquired by the operator are sequentially displayed in the measurement value box 46 provided on the operation screen 37 in accordance with the operations of the OK measurement button 43 and the NG measurement button 44. After each measurement value is obtained, the operator presses the threshold setting button 45 to automatically calculate the threshold based on the following formula. The threshold TH is obtained by TH = OKa+(NGa + OKa) / 2 when the average values of the leakage amounts in the OK groove and the NG groove of the three detection holes 22 are set as OKa=(OK1 + OK2 + OK3) / 3 and NGa=(NG1 + NG2 + NG3) / 3. That is, the intermediate value of the leakage amounts in the NG groove and the OK groove is set as the threshold TH.

[0027] In the work seating detection device 17 of the present embodiment, the flow rate value measured by the flow rate sensor 27 is sent to the control device 9 via the relay device 28 and is displayed on the operation display device 18 attached to the front surface of the machine body. Therefore, it is not necessary to attach the flow rate sensor 27 to the front surface of the machine tool 1 so that the operator can easily check it, and it can be arranged behind the spindle device 5. Therefore, the air pipe 23 of the work seating detection device 17 can be shortened, and the time from when the master work MW is seated until the inside of the air pipe 23 is pressurized and the seating determination becomes possible can be shortened.

[0028] The workpiece seating detection device 17 displays the current value measured by the flow sensor 27 on the operation display device 18, and particularly as shown in FIG. 5, the temporal change in the flow rate is graphically shown. Therefore, the operator can also grasp the workpiece seating state during workpiece machining in the machine tool 1 from such information. Thus, as shown in FIG. 6 for example, the workpiece seating detection device 17 of the present embodiment is configured such that a first threshold value S1 and a second threshold value S2 for detecting a seating state that may occur during machining are set, and a situation determination is made as to whether the workpiece W is being gripped by the spindle chuck 12.

[0029] The first threshold value S1 is for detecting an increase in the air leakage flow rate when the workpiece W slightly moves in the spindle chuck 12. The second threshold value S2 is for detecting an increase in the air leakage flow rate when the workpiece W comes off the spindle chuck 12. Therefore, during the machining of the workpiece W started at time T7, the measured value of the flow sensor 27 should originally be a value near the flow rate R1. However, when displacement or dropping of the workpiece W occurs, the measured value rises to the flow rates R2 and R3. Therefore, when the measured value of the flow sensor 27 exceeds the first or second threshold value S1, S2 during workpiece clamping while workpiece machining is being executed, the drive of the machine tool 1 is stopped by the control device 9, and a warning display or alarm is issued on the operation display device 18.

[0030] Therefore, according to the present embodiment, a threshold value can be arbitrarily set, and predetermined drive control for the machine tool 1 can be performed based on that value. And as described above, the clamping state during machining can be discriminated by the first and second threshold values S1, S2. Also, the workpiece seating detection device 17 can store the flow rate value for each time measured by the flow sensor 27 in the storage unit of the control device 9 as workpiece chuck information. Therefore, a graph as shown in FIG. 5 can be reproduced retroactively, and when a defect occurs in the workpiece machining, it can be used as one piece of information for investigating the cause.

[0031] Although one embodiment of the present invention has been described, the present invention is not limited thereto, and various modifications can be made without departing from the spirit thereof. For example, a flow sensor is used as the seating sensor, and IO-Link (registered trademark) is cited as an example of the communication means for capturing the measurement data of the seating sensor. However, the workpiece seating detection device of the present invention is not limited thereto. Further, in the above embodiment, the measured value of the flow rate over time is displayed on the operation screen of the operation display device 18 in the form of a graph. However, the flow rate may be simply displayed as a numerical value together with the measurement time.

Description of Reference Numerals

[0032] 1... Machine tool 5... Spindle device 9... Control device 12... Spindle chuck 17... Workpiece seating detection device 18... Operation display device 21... Seating surface 22... Detection hole 23... Air pipe 24... Air supply source 25... Electromagnetic on-off valve 26... Pressure control valve 27... Seating sensor (flow sensor) 28... Relay device

Claims

1. A detection hole for discharging air from the seating surface of a chuck that holds a workpiece, an air supply flow path for sending air from an air supply source to the detection hole, a pressure control valve provided in the air supply flow path, a seating sensor provided in the air supply flow path on the secondary side of the pressure control valve, a relay device that transmits measurement data measured by the seating sensor, an operation display device capable of displaying the measurement data transmitted by the relay device and acquiring the measurement data, a control device that calculates a threshold value for seating determination based on the measurement data acquired by operating the operation display device; A workpiece seating detection device having the above.

2. The seating sensor is a flow rate sensor that measures the flow rate of air flowing out of the detection hole, and the control device displays a graph showing the relationship between the flow rate value and the measurement time on the screen of the operation display device from the measurement value measured by the seating sensor. The workpiece seating detection device according to Claim 1.

3. The operation display device displays the measurement value by the seating sensor, and the measurement value is arbitrarily taken into the control device by operating a measurement value capture button. The control device calculates the threshold value based on the captured measurement value. The workpiece seating detection device according to Claim 1 or Claim 2.

4. The control device stores the measurement value measured by the seating sensor as workpiece chuck information together with the measurement time in a storage unit. The workpiece seating detection device according to any one of Claims 1 to 3.

5. The control device has a processing threshold value set for detecting the seating state during workpiece processing, and executes predetermined control when the measurement value of the seating sensor exceeds the processing threshold value. The workpiece seating detection device according to any one of Claims 1 to 4.

Images