Patent Application
20200368870
This application is based on and claims priority to Japanese Patent Application No. 2019-096755 filed on May 23, 2019, the content of which is incorporated herein by reference in its entirety.
The present invention relates to a spindle abnormity detection device.
Conventionally, there is known a machine tool that monitors changes in radial runout of an outer peripheral surface of a tool holder attached to a spindle. Such a machine tool is disclosed in PTL 1, for example.
Japanese Unexamined Patent Application Publication No. 2004-42208
A spindle abnormity detection device according to one aspect of the present disclosure includes a first sensor configured to measure oscillation of a spindle of a machine tool, a second sensor configured to measure radial runout of an axis of a tool unit attached to the spindle, and a control unit configured to perform abnormity determination of the spindle based on an oscillation comparison result and a runout comparison result, the oscillation comparison result being obtained by comparing a detection result obtained by the first sensor with an oscillation standard of the spindle, the runout comparison result being obtained by comparing a detection result obtained by the second sensor with a runout standard of the tool unit.
Hereinafter, a spindle abnormity detection device 50 and a machine tool 1 according to an embodiment will be described with reference to the drawings.
As shown in
The column portion 3 is provided with a plurality of guide rails 3a extending in a vertical direction (Z-axis direction), and the spindle head 4b is supported by the guide rails 3a so as to be movable in the vertical direction. Further, a Z-axis motor 3b such as a servo motor is fixed to the upper end of the column portion 3, and an output from an output shaft of the Z-axis motor 3b is transmitted to a ball screw 3d via a reducer 3c and the like. The ball screw 3d is disposed along the guide rails 3a, and threaded with a ball screw nut fixed to a back surface 4c of the spindle head 4b. With this configuration, the spindle unit 4 moves in the vertical direction by the rotation of the output shaft of the Z-axis motor 3b.
Further, the spindle 4a and the tool T rotate around the center axis line of the spindle 4a by a spindle motor 5a connected to an upper end of the spindle 4a.
The machine tool 1 relatively moves the workpiece W and the tool T by horizontal movement of the X-Y table 22, vertical movement of the spindle 4a, and the like, and thus performs machining to the workpiece W by the rotating tool T.
The base 2 is installed using a leveling bolt, an anchor bolt, or the like, for example, at a place where the machine tool 1 is used. The X-Y table 22 is positioned on the base 2, and the workpiece W is fixed on an upper surface of the X-Y table 22 via an additional axis unit AU, a jig J, or the like. The X-Y table 22 and the workpiece W are moved in a horizontal direction with respect to the spindle 4a by motors 13 and 23 provided on the base 2. The tool magazine 7 and the spindle head 4b are supported at an upper end of the column portion 3, and the tool magazine 7, the spindle 4a, and the spindle head 4b are arranged above the X-Y table 22.
As shown in
Further, as shown in
With the above configuration, the X-Y table 22 moves in the X-axis direction and the Y-axis direction with respect to the spindle 4a.
The machine tool 1 is provided with a controller 40 that controls the machine tool 1. As shown in
Further, the storage unit 43 stores a machining program 43b and a tool exchange program 43c. The controller 40 transmits control commands to the motor and the like based on the machining program 43b and the tool exchange program 43c, and with this, machining by the machine tool 1, exchange of the tool unit TU of the spindle 4a using the tool magazine 7, and the like are carried out.
In one example, the spindle abnormity detection device 50 is provided with a computer (control unit) 60 such as a desktop computer, a laptop computer, a tablet computer, or the like. As shown in
Further, the storage unit 63 stores an oscillation storage program 63b, a runout storage program 63c, and an abnormity determination program 63d.
As one example, the computer 60 is a management computer connected to the plurality of machine tools 1. In this case, the computer 60 receives various information from the controller 40 of the plurality of machine tools 1, and provides the plurality of machine tools 1 with information such as machining conditions. The computer 60 may be an ordinary computer other than a management computer.
Moreover, the spindle abnormity detection device 50 includes: a first sensor 71 such as an acceleration sensor attached to the spindle unit 4 as shown in
As shown in
The computer 60 determines whether or not there is an abnormity in the spindle 4a, using the detection result obtained by the first sensor 71 and the detection result obtained by the second sensor 72. A process by the computer 60 for making the determination will be described with reference to a flowchart of
First, the computer 60 transmits a signal for causing the machine tool 1 to rotate the spindle 4a sequentially at a plurality of rotation speeds (Step S1-1). With this, the controller 40 of the machine tool 1 controls the spindle motor 5a to rotate the spindle 4a, and sequentially rotates the spindle 4a at five rotation speeds of 100 rpm, 500 rpm, 1000 rpm, 5000 rpm, and 10000 rpm, for example. Here, the spindle 4a may be sequentially rotated at six or more rotation speeds, or at two or more and four or smaller rotation speeds.
In this embodiment, before rotating the spindle 4a as described above, the controller 40 controls the Z-axis motor 3b, the Y-axis motor 13, and the X-axis motor 23, and the tool T of the tool unit TU attached to the spindle 4a is arranged at a position at which a laser beam L from the second sensor 72 attached to the X-Y table 22 is irradiated to the tool T. With this, radial runout of the axis of the tool unit TU when the spindle 4a is rotated may be detected by the second sensor 72. Here, a laser beam may be irradiated to a different portion of the tool unit TU exposed from the spindle 4a. In this case, similarly, the radial runout of the axis of the tool unit TU is detected by the second sensor 72.
The transmission of signals in Step S1-1 may be performed daily at predetermined timing or may be at other predetermined timings. For example, the transmission of signals may be performed at timing at which a tool T is newly attached to the tool magazine 7.
Next, based on the oscillation storage program 63b, the computer 60 receives an oscillation detection result obtained by the first sensor 71 for each of the rotation speeds, and stores the received oscillation detection result for each rotation speed in the storage unit 63 (Step S1-2). The oscillation detection result stored in this manner is used as a standard of oscillation of the spindle 4a.
Further, based on the runout storage program 63c, the computer 60 receives a runout detection result obtained by the second sensor 72 for each of the rotation speeds, and stores the received runout detection result for each rotation speed in the storage unit 63 (Step S1-3). The runout detection result stored in this manner is used as a standard of runout of the tool T.
The computer 60 performs Step S1-1 to Step S1-3 every time when the predetermined timing comes.
It should be noted that in Step S1-2, while the detection result obtained by the first sensor 71 as shown in
As an example of the above analysis, a frequency analysis such as an FFT analysis is performed, for example. If the frequency analysis is performed to the detection result obtained by the first sensor 71 for each rotation speed, a frequency whose amplitude, acceleration, and the like of oscillation are large can be found out in the detection result of each of the rotation speeds. Consequently, regarding the detection result of each rotation speed, one or a plurality of frequencies whose amplitude, acceleration, and the like of oscillation are large, and the amplitude, the acceleration, and the like of the above frequency/frequencies become a result after the analysis, and the result is stored in the storage unit 63 as the oscillation detection result. In this embodiment, as one example, as shown in
Further, in Step S1-3, in one example, for each rotation speed, a maximum value of the detection results obtained by the second sensor 72 is stored in the storage unit 63 as the runout detection result. For example, as shown in
Next, based on the abnormity determination program 63d, the computer 60 performs a process of abnormity determination. The computer 60 compares a new oscillation detection result obtained by the first sensor 71 with the past oscillation detection result stored in the storage unit 63, and obtains an oscillation comparison result Gn that will be later described (Step S1-4). As shown in
In this embodiment, similarly to the case of
In Step S1-4, the computer 60 obtains the oscillation comparison result Gn based on an expression (1), for example.
|Fn−Sn|=Gn (1)
Based on the expression (1), the oscillation comparison result Gn is obtained for each frequency of each rotation speed.
For the each of the obtained oscillation comparison result Gn, a score is determined based on a predetermined determination standard as shown in
It should be noted that when frequencies of Fn and Sn applied to the expression (1) are different, a score of the oscillation comparison result Gn of this rotation speed is 0. As shown in
Further, the computer 60 compares a new runout detection result obtained by the second sensor 72 with the past runout detection result stored in the storage unit 63, and obtains a runout comparison result D that will be later described (Step S1-5). As shown in
The computer 60 calculates a difference between the new runout detection result and the past runout detection result as the runout comparison result D for each rotation speed, based on an expression (2), for example.
|new runout detection result−past runout detection result|=D (2)
The computer 60 may determine that there is an abnormity in the runout of the tool unit TU when the runout comparison result D of any of the rotation speeds is over a predetermined standard. Here, the computer 60 may calculate a difference between the new runout detection result and a predetermined runout standard as the runout comparison result D. The predetermined runout standard may be 0 μm. In this manner, the computer 60 obtains the runout comparison result D that can be obtained by comparing the new runout detection result with the runout standard.
In this embodiment, the computer 60 determines a score for the runout comparison result D for each rotation speed. For example, a score when the runout comparison result D is smaller than a value a is assumed to be 100, a score when the runout comparison result D is equal to or greater than the value a and smaller than value b is assumed to be 80, a score when the runout comparison result D is equal to or greater than the value b and smaller than a value c is assumed to be 40, and a score when the runout comparison result D is equal to or greater than the value c is assumed to be 0.
Further, the computer 60 evaluates, as the abnormity determination of the spindle 4a, a state of oscillation of the spindle 4a including the tool unit TU, using the oscillation comparison result Gn and the runout comparison result D (Step S1-6). For example, the computer 60 may evaluate the state of oscillation of the spindle 4a, using an average value of the scores of the oscillation comparison results Gn for all rotation speeds, and an average value of the scores of the runout comparison results D for all rotation speeds.
Then, the computer 60 outputs an evaluation result in Step S1-6 (Step S1-7). As one example of the output, the computer 60 displays the evaluation result in the display unit 62 of the computer 60. As a different example, the computer 60 may transmit the evaluation result to a user's computer, or may transmit the evaluation result to the controller 40 of the machine tool 1. The controller 40 may display the received evaluation result in the display unit 42. Based on the received evaluation result, the controller 40 may restrict or stop an operation of the machine tool 1.
It should be noted that while the computer 60 is provided separately from the controller 40 of the machine tool 1 in this embodiment, the computer 60 may be provided within the controller 40. In this case, a part or all of a configuration of the computer 60 such as the processor 61 and the storage unit 63 may be common to a configuration of the controller 40 such as the processor 41 and the storage unit 43.
As described above, the spindle abnormity detection device 50 according to this embodiment includes: the first sensor 71 for measuring oscillation of the spindle 4a of the machine tool 1; and the second sensor 72 for measuring radial runout of the axis of the tool unit TU attached to the spindle 4a. Further, the spindle abnormity detection device 50 obtains the oscillation comparison result Gn by comparing the detection result obtained by the first sensor 71 with the oscillation standard of the spindle 4a. Moreover, the spindle abnormity detection device 50 obtains the runout comparison result D by comparing the detection result obtained by the second sensor 72 with the runout standard of the tool unit TU. Then, the spindle abnormity detection device 50 performs abnormity determination of the spindle 4a based on the oscillation comparison result Gn and the runout comparison result D.
In this embodiment, the abnormity determination of the spindle 4a is performed, for example, based on oscillation which is based on an abnormity of the bearing B of the spindle 4a and that the user may not easily notice, runout of the tool unit TU that the user may not easily notice, and the like. Accordingly, it is possible to prevent deterioration of manufacturing efficiency and an increase of manufacturing costs due to machining performed to the workpiece W without noticing an abnormity of the spindle 4a.
Further, in this embodiment, the plurality of oscillation detection results obtained by the first sensor 71 when the spindle 4a is sequentially rotated at the plurality of rotation speeds are stored in the storage unit 43 for the respective rotation speeds. Moreover, the plurality of runout detection results obtained by the second sensor 72 when the spindle 4a is sequentially rotated at the plurality of rotation speeds are stored in the storage unit 43 for the respective rotation speeds.
Finally, in this embodiment, the abnormity determination of the spindle 4a is performed using the oscillation detection result of each of the plurality of rotation speeds and the runout detection result of each of the plurality of rotation speeds.
The rotation speed of the spindle 4a when machining to the workpiece W is performed varies according to a type of machining, a request level of machining accuracy, a material of the workpiece W, and the like, and the rotation speed is determined arbitrarily by the user of the machine tool 1. In this embodiment, the abnormity determination of the spindle 4a is performed using the oscillation detection result and the runout detection result of each of the plurality of rotation speeds. Accordingly, it is possible to appropriately determine whether or not there is an abnormity in the spindle 4a, even when machining to the workpiece W is performed at an arbitrary rotation speed by the user.
It should be noted that in Step S1-6, the state of oscillation of the spindle 4a may be evaluated based on at least one oscillation comparison result Gn at a rotation speed equal to or smaller than 500 rpm, and at least one runout comparison result D at a rotation speed equal to or greater than 1000 rpm. When an abnormity such as a dent is produced within the bearing B supporting the spindle 4a, oscillation detected by the first sensor 71 when the spindle 4a is rotated at a low speed tends to become larger. Further, even when an abnormity such as a dent is produced within the bearing B, there is a case in which this abnormity does not give a large influence to oscillation of the spindle 4a rotating at a high speed. As a rotation speed equal to or smaller than 500 rpm is rarely used in usual machining, there is a case in which an operator on site may not notice the above phenomenon.
As described above, evaluating the oscillation comparison result Gn at a rotation speed equal to or smaller than 500 rpm leads to early detection of an abnormity of the bearing B of the spindle 4a. Here, it is more preferable to evaluate the oscillation comparison result Gn at a rotation speed equal to or smaller than 300 rpm.
On the other hand, there is a case in which runout of the tool unit TU increases at a rotation speed equal to or greater than 1000 rpm that is often used in machining. For example, when there is an abnormity in a fixation mechanism FM for fixing the tool unit TU of the spindle 4a (
In this case, in Step S1-2, a detection result obtained by the first sensor 71 for at least one rotation speed equal to or greater than 1000 rpm may be stored in the storage unit 63.
It should be noted that in Step S1-4, the above oscillation comparison result Gn may be obtained using one or a part of the plurality of oscillation detection results whose oscillation level is high, respectively corresponding to the plurality of rotation speeds. An example of the one oscillation detection result whose oscillation level is high is an oscillation detection result whose oscillation level is the highest among the plurality of oscillation detection results. As one example, the oscillation detection result whose oscillation level is high each exceed a predetermined oscillation level.
Further, in Step S1-5, the above runout comparison result D may be obtained using one or a part of the plurality of runout detection results whose runout level is high, respectively corresponding to the plurality of rotation speeds. An example of the one runout detection result whose runout level is high is a runout detection result whose runout level is the highest among the plurality of runout detection results. As one example, the runout detection result whose runout level is high each exceed a predetermined runout level.
Using only a part of the oscillation detection results and the runout detection results in this manner leads to an increased processing speed. On the other hand, as an oscillation detection result whose oscillation level is high and a runout detection result whose runout level is high are used, the evaluation in Step S1-6 is accurate.
It should be noted that while the oscillation detection results stored in the storage unit 63 for the respective rotation speeds are used as the oscillation standard in the above embodiments, an oscillation standard for each rotation speed may be determined in advance. Similarly, while the runout detection results stored in the storage unit 63 for the respective rotation speeds are used as the runout standard in the above embodiments, a runout standard for each rotation speed may be determined in advance.
It should be noted that in the above embodiments, it is also possible to perform abnormity determination of the spindle 4a by obtaining an oscillation detection result and a runout detection result at a certain rotation speed, and by comparing these results respectively with the oscillation standard and the runout standard. In this case, the same effects as described above may also be achieved.
It should be noted that in the above embodiments, the first sensor 71 and the second sensor 72 are provided in the spindle abnormity detection device 50. However, one or both of the first sensor 71 and the second sensor 72 may be provided in the machine tool 1. In this case, the computer 60 is also able to perform Step S1-2 to S1-7 described above based on the detection results obtained by the first sensor 71 and the second sensor 72, and to obtain the results as described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2019-096755 | May 2019 | JP | national |
