JP6237736B2 - Processing method and processing apparatus - Google Patents

Description

  The present invention relates to a processing method and a processing apparatus suitable for drilling.

  When machining such as drilling, a spindle, a tool mounted on the spindle, a rotation motor that rotates the tool together with the spindle, a spindle stock that accommodates the spindle and the rotation motor, and the spindle stock parallel to the spindle A processing apparatus having a feed motor that moves in a direction is generally used.

  In such a processing device, as a method of preventing tool breakage, chipping is performed by measuring the power waveform of the rotary motor that rotates the tool, using the waveform of the new blade as the reference waveform, and pattern recognition of the power waveform during processing. There is known a method for detecting (for example, Patent Document 1).

JP 2003-245846 A

  However, it is difficult to obtain a reference waveform when the gaps are distributed inside the workpiece, which is the work material, or when the reproducibility is uncertain because the machinability varies depending on the cutting location (for example, casting). It is. In addition, when the gap is distributed in a portion corresponding to the rotation axis of the tool, the presence or absence or the state of the gap is not reflected in the current waveform of the rotary motor of the main shaft. This is because in the vicinity of the center of the tool, the relative speed between the blade and the workpiece is reduced, and the contribution to the load of the rotary motor is reduced.

  FIG. 7 is a diagram illustrating the load (Z-axis load) of the feed motor when the gap is processed. The waveform was greatly oscillated from the beginning of machining, reflecting the influence of the air gap. At this stage, machining was interrupted and the cutting edge was confirmed, and no chipping or cutting edge wear occurred. However, this vibration continues, and the load on the cutting blade accumulates, or the screw to which the cutting blade is attached loosens, leading to chipping.

  In this way, chipping does not occur after the cutting edge has been worn to some extent, but chipping occurs suddenly due to factors on the workpiece side. Therefore, if machining is stopped after chipping occurs, an increase in tool cost is inevitable. . Further, once the machining is interrupted, it is necessary to make a setup such as checking the tool edge, resulting in a decrease in productivity. Furthermore, the method of stopping machining after chipping occurs is effective for machining methods that reduce the cutting amount by the amount of cutting edge loss, such as some milling and lathe machining, but drilling such as drilling. Then, since the disappearance of the cutting edge leads to breakage of the tool body, there are cases where the machining stop cannot be made in time.

  Therefore, the problem to be solved by the present invention is that even if the workpiece includes parts having different machinability, the signs can be detected before damage such as chipping occurs in the tool. It is an object of the present invention to provide a processing method and a processing apparatus that can minimize the above.

  In order to solve the above-described problems, the present invention provides a main shaft, a tool that is mounted on the main shaft and performs machining on a workpiece, a rotation motor that rotates the tool together with the main shaft, a main spindle and a main shaft base that accommodates the rotation motor, A machining method for machining a workpiece using a machining apparatus having a feed motor for moving a headstock in a direction parallel to the spindle, and measuring an electrical parameter corresponding to the load of the feed motor at the time of machining by a measuring means Then, the fluctuation value of the electrical parameter is obtained from the waveform of the electrical parameter, the number of times that the fluctuation value exceeds a preset threshold is counted as the number of times the threshold is exceeded, and the threshold excess count is set in advance. Provided is a machining method characterized in that when the number of times is exceeded, a machining speed is reduced at a predetermined rate during machining of a workpiece by the tool.

  The present invention also includes a main shaft, a tool mounted on the main shaft and machining the workpiece, a rotation motor that rotates the tool together with the main shaft, a main shaft base that accommodates the main shaft and the rotation motor, and the main shaft base as the main shaft. A feed motor that moves in a parallel direction; a measuring unit that measures an electrical parameter corresponding to a load of the feed motor at the time of machining; and a control unit that controls at least a machining speed of the workpiece by the tool. The unit obtains a variation value of the electrical parameter from the waveform of the electrical parameter measured by the measurement unit, counts the number of times that the variation value exceeds a preset threshold as the threshold excess number, Provided is a machining apparatus characterized by decelerating a machining speed at a predetermined rate during machining of a workpiece by the tool when a preset limit number of times is exceeded. .

  In the present invention, after the machining speed is decelerated at a predetermined rate during machining of the workpiece by the tool, an operation for further decelerating the machining speed at a predetermined rate when the threshold excess number exceeds the limit number. In addition, the number of times of deceleration can be counted, and when the number of times of deceleration exceeds a preset limit number of times of deceleration, the machining can be interrupted even if the machining is not completed to a predetermined machining depth. .

  In the present invention, after the machining speed of the workpiece by the tool is decelerated at a predetermined rate, if the variation value of the electrical parameter does not exceed the threshold value for a predetermined time, the machining speed is returned to the speed before deceleration. Can be.

  In addition, a plurality of control numerical values that set the threshold value and the limit number of times as a set are set, and the number of times that the threshold value is exceeded is counted individually. During processing of the workpiece, the processing speed may be reduced at a predetermined rate.

  As the electrical parameter, the load current of the feed motor can be suitably used. At this time, the fluctuation value can be defined as | maximum value−minimum value | of the load current value of the feed motor.

  According to the present invention, the variation value of the electric parameter of the feed motor is obtained as an index of the load exerted on the tool, and the threshold value and limit number of the variation value are set in advance according to the material of the workpiece, etc. It is possible to detect the signs before breakage such as chipping occurs. Further, by reducing the machining speed when the limit number of times is exceeded, it is possible to perform machining with minimal damage such as machining interruption and tool chipping.

It is a figure which shows the structure of the processing apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the load current waveform of a feed motor. It is a figure which shows the relationship between a load amplitude and feed rate. It is a flowchart which shows the outline of the control flow in the processing apparatus of one Embodiment of this invention. It is a figure which shows an example of the control logic in the processing apparatus of one Embodiment of this invention. It is a figure which shows the load current waveform (Z-axis load waveform) at the time of drilling in the Example of this invention. It is a figure which shows the load (Z-axis load) of the feed motor at the time of processing a space | gap part by the conventional method.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram showing a configuration of a processing apparatus according to an embodiment of the present invention. This processing apparatus is configured as a drilling apparatus that forms a rough hole in a workpiece. The rough hole is a hole that does not depend on the roughness of the inner wall of the hole or the accuracy of the processing diameter.

  The processing apparatus 1 includes a main shaft 2, a tool 3 mounted on the main shaft 2, a rotation motor 4 that rotates the tool 3 together with the main shaft, a main shaft base 5 that accommodates the main shaft 2 and the rotation motor 4, and the main shaft base 5 as the main shaft. 2, a feed motor 6 that moves in a direction parallel to 2 (Z-axis direction), a gantry 7 on which a workpiece 10 is set, a measurement device 8 that measures the load current of the feed motor 6, and a measurement value that is measured by the measurement device 8. And a control unit 9 for controlling the processing. The feed motor 6 is provided in the movement mechanism (feed mechanism) 11, and the feed of the feed motor 6 is transmitted to the head stock 5 by an appropriate transmission mechanism (not shown) in the movement mechanism 11. Although not shown, the machining apparatus 1 also has an alignment mechanism that aligns the tool 3 with the workpiece 10.

  The measuring device 8 measures a load (Z-axis load) applied to the feed motor 6 as a load current when drilling a workpiece 10 with the tool 3. This load current corresponds to the load in the feed direction applied to the tool 3.

  The control unit 9 receives the load current signal measured by the measuring device 8, obtains the fluctuation value (fluctuation ratio) of the load current, and determines the number of times that the fluctuation value (fluctuation ratio) exceeds a preset threshold value. Counting as the number of times of exceeding the threshold, and when the number of times of exceeding the threshold exceeds a preset limit number of times, the machining speed is reduced. The machining speed is a tool movement speed (tool feed speed) in the Z-axis direction. Further, the control unit 9 increases the machining speed to the original speed as the upper limit if the fluctuation value does not exceed the threshold value for a certain time after deceleration. This fixed time is defined as the determination time.

  The fluctuation value (fluctuation ratio) of the load current is defined as follows based on FIG. 2, for example. FIG. 2 is an example of a load current flowing through the feed motor 6 during workpiece machining. The vertical axis represents the current of the feed motor 6 that flows during machining, and is indicated by a value normalized with respect to a reference value. The reference value can be, for example, a current value when there is no load, that is, when the workpiece is not processed. Here, when the upper region in FIG. 2 is the region X and the lower region is the region Y, the peak of the current value in the region X is the maximum value (Imax), and the peak of the current value in the region Y is the minimum. The value (Imin) is defined, and the fluctuation value (fluctuation ratio) of the load current is defined as | Imax−Imin | (the absolute value of the difference between Imax and Imin).

  In the processing apparatus 1 configured as described above, first, the workpiece 10 is set on the gantry 7, and then the tool 3 is aligned with the workpiece 10 by the alignment mechanism. Next, the rotary motor 4 rotates the tool 3 together with the spindle 2, and the feed motor 6 moves the spindle stock 5 downward, and the workpiece 10 is drilled with the rotating tool 3.

  At this time, when there are portions having different machinability, for example, when voids are distributed inside the workpiece, or when machinability is not uniform depending on the cutting location (for example, in the case of a casting), the tool 3 is used. The applied load in the feed direction may fluctuate (vibrate). If such a state continues, the tool 3 will be damaged such as chipping.

  Therefore, in the present embodiment, the load current of the feed motor 6 is measured by the measuring device 8, and the control unit 9 controls the machining speed based on the measurement signal to prevent damage such as chipping of the tool 3 in advance. . For example, as shown in FIG. 3, when the fluctuation of the load current increases and the fluctuation value (fluctuation ratio) exceeds a predetermined value (when the load amplitude is large), the number of times the load current exceeds the predetermined value is measured. If it exceeds, the machining speed is reduced.

  The outline of the control flow of the control unit 9 in this case is as shown in FIG. Here, the case where the feed speed of the feed motor 6 is controlled as the machining speed is shown. First, a fluctuation value is calculated from the load current waveform (step 1). As the variation value, | Imax−Imin | described above is used. | Imax−Imin | continuously measures the current at a predetermined sampling time, and compares the measured current value In with Imax and Imin at that time. If In is larger than Imax, In is set as a new value of Imax, and a fluctuation value (fluctuation ratio) | Imax−Imin | is obtained. If In is smaller than Imin, the fluctuation value (fluctuation ratio) | Imax−Imin | is obtained by using In as the new value of Imin. At this time, initial values of Imax and Imin are set to 0, for example. Further, the fluctuation value of the load current may be set to a predetermined fixed value according to the material of the workpiece 10, the processing conditions, and the like. Alternatively, the average value of the waveform may be defined as Iave, and the fluctuation value may be defined as dimensionless as | Imax−Imin | / Iave.

  Next, it is determined whether or not the fluctuation value (fluctuation ratio) exceeds a threshold value (step 2). If the threshold value is exceeded, the number of times the threshold value is exceeded is counted (step 3). Next, it is determined whether or not the number of times the threshold is exceeded exceeds the limit number (step 4). If the number exceeds the limit number, the machining speed is reduced at a predetermined rate (step 5). Thereafter, similarly, the fluctuation value (fluctuation ratio) is calculated to determine whether or not the fluctuation value (fluctuation ratio) is equal to or less than the threshold value (step 6). If the fluctuation value is exceeded, the same operation is repeated from step 2. If it is equal to or less than the threshold, it is determined whether or not the processing time exceeds the determination time (step 7). If the determination time is exceeded, the machining speed is increased up to the original speed as an upper limit, and the machining is continued. Further, the machining is continued with the speed reduced below the determination time.

  Thus, by obtaining the fluctuation value (fluctuation ratio) of the load current as an index of the load exerted on the tool and setting the threshold value and limit number of fluctuation values (fluctuation ratio) in advance according to the material of the workpiece 10, It is possible to detect the sign before the tool 3 is damaged such as chipping. Further, by reducing the feed rate when the limit number of times is exceeded, it is possible to perform machining with minimal damage such as machining interruption and chipping of the tool 3.

  In such control, the threshold value and the limit number are set as a set of control numerical values, and a plurality of the control numerical values are stored in the control unit 9 according to the material of the workpiece 10 and the like. You may set a some control numerical value at the time of one process.

  Further, in the control unit 9, even when the machining speed is reduced by a predetermined rate, if the variation value (variation rate) exceeds the threshold value, the number of times the threshold value is exceeded again is counted as the threshold excess number. When exceeding, the operation of decelerating the machining speed at a predetermined rate may be repeated, and the machining may be interrupted when the number of times of deceleration exceeds a preset number of deceleration limits. Thereby, damage, such as chipping of the tool 3, can be suppressed more effectively.

  Next, refer to FIG. 5 for an example of the control logic when the control value is set such that the above threshold value and the limit number of times are set as two sets, and further, the processing is interrupted when the deceleration limit number is exceeded. And will be described in detail. Here, a case where the feed rate of the moving mechanism is controlled is shown. Note that the number of sets of control numerical values may be one or three or more.

  Here, after the machining is started, the fluctuation value (fluctuation ratio) of the load current from the load current value of the feed motor 6 measured by the measuring device 8 is defined as | Imax−Imin | described with reference to FIG. (Step 11).

  Next, it is determined whether or not | Imax−Imin | exceeds a first threshold AA (for example, 15) (step 12), and if it exceeds, the number of times that the first threshold is exceeded (exceeding the first threshold) (Count) Na count (count Na) is started (step 13).

  On the other hand, if | Imax−Imin | does not exceed the first threshold AA in step 12, it is determined whether | Imax−Imin | exceeds a second threshold BB (for example, 9) (step 15). When it exceeds, the count (count Nb) of the number of times of exceeding the second threshold (second threshold excess number) Nb is started (step 16). Na and Nb are reset to 0 at the start of processing, and Imax and Imin are counted to Nb.

  Whether or not the first threshold excess count exceeds the limit count aa (for example, 5 times) (step 14), or whether the second threshold excess count exceeds the limit count bb (for example, 10) (step 14) 17) is judged, and if any of them is satisfied, the feed speed is decelerated (machining conditions are changed) (step 18). At this time, the count of the number of times of deceleration Nc (count Nc) is started. Nc is reset to 0 at the start of machining. Further, after the feed speed is decelerated, Na and Nb are reset to zero.

  Steps 12 to 18 are repeated, and it is determined whether or not the count Nc exceeds the limit number cc times (for example, 3 times) (step 19).

  In step 15, if | Imax−Imin | does not exceed the second threshold BB, it is determined whether or not the feed rate is decelerated (step 20). The time Tc (for example, the specified number of counts / rotation period of the tool) is measured (step 21), and if the threshold value is not counted for a certain time in step 22 (the time Tc exceeds the certain time (time Tb)) The feed speed is increased (step 23), and the original speed is restored.

  If the feed speed is not decelerated in step 20 and if Tc does not exceed Tb in step 22, the machining is continued under the original conditions.

  As described above, when the limit number is exceeded using the two thresholds, the feed speed is decelerated, and when the number of decelerations exceeds the limit deceleration number, the machining is interrupted, so that the tool 3 can be reliably damaged such as chipping. Can be prevented.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the above embodiment, the load current is used as an electrical parameter corresponding to the load in the axial direction of the feed motor. However, the present invention is not limited to this, and a load voltage or load power may be used. Further, when the gap is not distributed in the portion corresponding to the rotation axis of the tool, the load of the rotary motor may be used as a parameter. In the above embodiment, the feed speed is decelerated when the threshold excess count exceeds the limit count. However, the present invention is not limited to this, and the rotation speed of the rotary motor may be decelerated. Furthermore, in the above-described embodiment, the fluctuation ratio is calculated from the load current value by performing an operation such as | Imax−Imin |, and the threshold is set to the fluctuation ratio. However, the upper limit threshold is set to the maximum value, A predetermined value may be used as the fluctuation value, such as setting a lower limit threshold value for the minimum value. Furthermore, the present invention is not limited to drilling but can be applied to other processes such as cutting.

(First embodiment)
In the present embodiment, an embodiment in which the above-described processing apparatus is actually applied and a work having a gap is drilled will be described.
FIG. 6 is a diagram illustrating a load current waveform (Z-axis load waveform) of the feed motor and a load current waveform (spindle rotational load waveform) of the spindle motor when the drilling process of the present embodiment is performed. As shown in this figure, the spindle rotation load varies in proportion to the tool feed speed, but the Z-axis load waveform shows different behavior. The Z-axis load waveform after the start of machining is confirmed to have a relatively small minimum value and maximum value of the peak value of the load current waveform, that is, a waveform with a small amplitude. Thereafter, a waveform with a large amplitude and | Imax−Imin | exceeding the threshold of 18 appeared, and counting of the number of times the threshold was exceeded was started. Thereafter, since the number of times of exceeding the threshold exceeded the limit number of times, the feed speed was decelerated (first deceleration). After the first deceleration, the vibration did not stop and the number of times the threshold was exceeded exceeded the limit number again, so the feed rate was further decelerated (second deceleration). Since the vibration did not stop at the second deceleration, the feed rate was further reduced (third deceleration). As a result, in the third deceleration, the load current amplitude was reduced and the threshold value was not exceeded. Therefore, the machining was continued and the drilling could be carried out to the planned machining depth.

(Second embodiment)
In this example, a carbide drill equivalent to P10 of JIS standard is used as a cutting tool, machining is performed under the abnormality detection conditions shown in Table 1 (control logic shown in FIG. 5), and vibration occurrence status and abnormality detection are performed. The accuracy and reduction effect were evaluated. The drill diameter was Φ20 mm, and the drill length was 200 mm. Cutting conditions were a peripheral speed of 100 m / min, a rotational feed of 1.0 mm / rev, and a machining length of 150 mm. The work material was FC300. The evaluation results are also shown in Table 1.

  In Table 1, the current value difference threshold AA, the current value difference threshold BB, the count threshold aa, the count threshold bb, and the number of decelerations cc are the values described in FIG. The “deceleration rate” is the rate at which the feed rate is reduced during machining. The deceleration includes a case where the cutting speed is decelerated and a case where the cutting speed is alternately decelerated such that the cutting speed is equal to the feed speed.

  “Successful detection” in Table 1 means that a load current value exceeding the threshold is detected a predetermined number of times. The result of “successful detection” was defined as “machining interruption” in which machining was interrupted without machining to a predetermined depth (150 mm), or “machining completed” in which machining was completed in a state where deceleration was suppressed and abnormality was suppressed. Further, “detection failure” in Table 1 means a state in which machining is continued with an abnormality occurring, and the result of “detection failure” is completed while chipping is not generated or abnormality is not suppressed during machining. “Chipping / processing completed”.

  For each of the conditions in Table 1, data for 100 holes was acquired for the state where an abnormality occurred, and “detection success × processing interruption”, “detection success × processing completion”, and “detection failure × chipping / processing completion” 3 The pattern was evaluated as a percentage. Among these, the most desirable result is “successful detection × processing completed”.

  As shown in Table 1, if the detection is successful under a condition where the threshold value AA of the load current value is as large as 70% or more, the ratio of “successful detection × processing completed” is large, but on the other hand, the ratio of failure in detection also increases. Further, when the threshold value AA of the load current value is as small as 40% or less, the ratio of the detection success itself increases, but the number of cases where the processing is interrupted due to overdetection increases. It can also be seen that “detection success × processing completion” increases by setting the count thresholds aa and bb to aa> bb.

  In this embodiment, the deceleration rate and the number of decelerations are fixed, but further improvements can be expected by adjusting them.

DESCRIPTION OF SYMBOLS 1 Processing apparatus 2 Spindle 3 Tool 4 Rotation motor 5 Shaft base 6 Feed motor 7 Mounting base 8 Measuring apparatus 9 Control part 10 Work 11 Feed mechanism

Claims (12)

A spindle, a tool mounted on the spindle and machining the workpiece, a rotation motor that rotates the tool together with the spindle, a spindle stock that houses the spindle and the rotation motor, and the spindle stock in a direction parallel to the spindle A machining method for machining a workpiece using a machining apparatus having a feed motor,
Set the threshold value and the limit number of fluctuation values in advance according to the material of the workpiece,
Measure the electrical parameter corresponding to the load of the feed motor at the time of processing with the measuring means,
Obtain the fluctuation value of the electrical parameter from the waveform of the electrical parameter,
Count the number of times the fluctuation value exceeded the preset threshold as the number of times the threshold was exceeded,
A machining method comprising: decelerating a machining speed at a predetermined rate during machining of a workpiece by the tool when the number of times of exceeding a threshold exceeds the preset limit number of times.   After the machining speed is reduced at a predetermined rate during machining of the workpiece by the tool, when the number of times the threshold is exceeded exceeds the limit number, an operation for further reducing the machining speed at a predetermined rate is performed. The processing method according to claim 1, wherein the number of times of deceleration is counted, and the processing is interrupted when the number of times of deceleration exceeds a preset limit number of times of deceleration.   After reducing the machining speed of the workpiece by the tool at a predetermined rate, if the fluctuation value of the electrical parameter does not exceed the threshold for a predetermined time, the machining speed is returned to the speed before deceleration. The processing method according to claim 1 or 2.   A plurality of control numerical values with the threshold value and the limit number of times set as a set, the number of times that the threshold value is exceeded are counted individually, and if any of the threshold value exceeds the corresponding limit number, The processing method according to any one of claims 1 to 3, wherein the processing speed is reduced at a predetermined rate during the processing.   The processing method according to claim 1, wherein the electrical parameter is a load current of the feed motor. The processing method according to claim 5, wherein the fluctuation value is defined as | maximum value−minimum value | of the load current value of the feed motor at a predetermined sampling time . The spindle,
A tool mounted on the spindle and machining the workpiece;
A rotary motor that rotates the tool together with the spindle;
A headstock for housing the spindle and rotary motor;
A feed motor that moves the headstock in a direction parallel to the spindle;
Measuring means for measuring an electrical parameter corresponding to the load of the feed motor during processing;
A control unit that controls at least the machining speed of the workpiece by the tool,
The controller is
Set the threshold value and the limit number of fluctuation values in advance according to the material of the workpiece,
From the waveform of the electrical parameter measured by the measurement means to obtain the fluctuation value of the electrical parameter,
Count the number of times the fluctuation value exceeded a preset threshold as the number of times the threshold was exceeded,
A machining apparatus, wherein when the number of times of exceeding a threshold exceeds a preset limit number of times, the machining speed is reduced at a predetermined rate during machining of a workpiece by the tool.   The controller is configured to further reduce the machining speed by a predetermined rate when the number of times the threshold is exceeded exceeds the limit number after the machining speed is reduced by a predetermined rate during machining of the workpiece by the tool. 8. The processing apparatus according to claim 7, wherein the number of decelerations is counted, and the processing is interrupted when the number of decelerations exceeds a preset limit number of decelerations.   The control unit reduces the machining speed to the speed before deceleration when the variation value of the electrical parameter does not exceed the threshold value for a predetermined time after decelerating the machining speed of the workpiece by the tool at a predetermined rate. The processing apparatus according to claim 7, wherein the processing apparatus is returned.   The control unit sets a plurality of control numerical values with the threshold and the limit number as a set, individually counts the number of times the threshold is exceeded, and when any of the threshold exceeds the corresponding limit number The processing apparatus according to any one of claims 7 to 9, wherein a processing speed is reduced at a predetermined rate during processing of the workpiece by the tool.   The processing apparatus according to claim 7, wherein the electrical parameter is a load current of the feed motor. 12. The processing apparatus according to claim 11, wherein the fluctuation value is defined as | maximum value−minimum value | of the load current value of the feed motor at a predetermined sampling time .

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