JP2002086330A - Method for cutting by numerically controlled machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cutting by a numerically controlled machine tool capable of preventing the misdetection of the abnormal loading caused by residual cutting chips in a bored hole and also using a cutting tool effectively over the life span of the cutting tool. SOLUTION: While the cutting tool moves at a specified cutting speed, the load acting on the cutting tool is always detected, and when this load reaches a preset load level or higher, the position of the cutting tool at this point of time is recorded as a cutting depth discontinuance position, and one is also added to a retry counter, and if the retry counter does not count up, the cutting tool is retracted to the preset retraction position once and then the cutting tool positioned at the retraction position is made to move to a position on this side of a specified distance from the cutting depth discontinuance position at a rapid feed rate, and then cutting is made by moving the cutting tool from this position to the position where the cutting finishes at a cutting speed. The above processes are continued until the cutting tool reaches the position where the cutting finishes or the retry counter counts up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for performing a predetermined cutting process on a workpiece using a numerically controlled machine tool, and more particularly, to a method in which a load acting on a cutting tool during cutting is equal to or higher than a preset load level. It relates to the processing method when it becomes.

[0002]

2. Description of the Related Art Generally, in a numerically controlled machine tool for performing a cutting process such as a drilling process, an abnormal load is detected in order to prevent breakage of a cutting tool during cutting. This focuses on the fact that the cutting resistance becomes larger than usual immediately before the cutting tool wears or breaks, and this effect increases the load on the tool spindle that rotates the cutting tool and moves the cutting tool in the cutting direction. This is to detect an increase in the load on the feed shaft to be moved. As a method of detecting the load at this time, for example, there is a method of detecting the load applied to the tool spindle by connecting a meter relay or the like to a load meter terminal or the like provided in the tool spindle control device, while the feed axis is connected to the feed spindle. For such a load, for example, there is a method using a function of monitoring the load state of the feed axis control device.

[0003] Incidentally, all of these methods relate to the detection of an abnormality for stopping the equipment, and the tool management itself such as the tool life is generally controlled by using a counter or the like. Specifically, a so-called tool change counter is provided in the numerically controlled machine tool, thereby managing all tools used in the numerically controlled machine tool. More specifically, the tool change counter is configured to accumulate a count value one by one for each cutting operation, and to output a tool life when the accumulated value reaches a preset count-up value. . If the numerically controlled machine tool is provided with an automatic tool changer with a tool magazine, the automatic tool changer is operated at the time when the tool change counter outputs the tool life described above, and the cutting that has reached the tool life is performed. The cutting process is interrupted by exchanging the tool with a non-expired cutting tool in the tool magazine and allowing the operator to exchange the expired cutting tool transferred to the tool magazine. It is possible to replace a cutting tool that has reached the end of its life without any trouble.

[0004]

However, the conventional numerically controlled machine tool described above has the following problems. The first point is the detection of an abnormal load due to the cutting chips remaining in the processing hole. For example, in the case of drilling with a drill, chips remain in the holes drilled during cutting,
An abnormal load may be detected due to the residual chips even though the cutting tool is not abnormal (breakage or wear). The second point is that the tool change counter counts up (outputs the tool life) before the actual tool life. Generally, the count-up value set in the tool change counter in advance is set based on the specifications of each cutting tool. On the other hand, the actual tool life depends on the material of the work material, cutting speed,
It has a certain width depending on the usage environment. Therefore, it is necessary to set the count-up value of the tool change counter in consideration of the fact that the actual tool life varies to some extent. A situation where the life is output may occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and prevents erroneous detection of an abnormal load due to residual chips in a machined hole and effectively prevents a cutting tool from reaching its tool life. An object of the present invention is to provide a cutting method of a numerically controlled machine tool that can be used.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, after the cutting tool is moved at a rapid traverse speed to the rapid traverse end position, the cutting tool is moved from the rapid traverse end position to the cutting ending position. In a cutting method of a numerically controlled machine tool that is configured to perform cutting by moving at a cutting speed, a load acting on the cutting tool is always detected while the cutting tool is moving at the cutting speed. When the load acting on the cutting tool is equal to or higher than a preset load level, the position of the cutting tool at that time is recorded as a cutting interruption position, and 1 is added to a retry counter. If the count value has not reached the preset count-up value, the cutting tool is temporarily evacuated to a preset evacuation position, and then the evacuation position is set. The cutting tool is in the up position a predetermined amount before the cut interruption position is moved at a rapid traverse speed,
Thereafter, cutting is performed by moving at a cutting speed from a position before the cutting interruption position by a predetermined amount to the cutting end position, and the above processing is performed when the cutting tool reaches the cutting end position or the retry. A method for cutting a numerically controlled machine tool is provided, wherein the method is continued until the count value of the counter reaches a count-up value.

The operation of the above configuration will be described. If the factor of the abnormal load, that is, the factor when the load acting on the cutting tool becomes equal to or higher than the preset load level, is caused by the residual cutting chips in the drilled hole, the cutting feed is temporarily interrupted and the cutting is stopped. By retreating the tool to the preset evacuation position to discharge the residual chips existing in the machined hole, and then starting cutting again, it is unlikely that abnormal load will occur again immediately. Also, even if an abnormal load occurs again, if it is also caused by residual chips in the machined hole, the same process is repeated again, and eventually the predetermined value is reached before the count value of the retry counter reaches the count-up value. Is completed. on the other hand,
If the cause of the abnormal load is due to a tool abnormality such as tool wear or tool breakage, the cutting feed is temporarily interrupted, and the cutting tool is retracted to a preset evacuation position. If cutting is started again, an abnormal load will occur again immediately, and in this case, the count value of the retry counter reaches the count-up value before the predetermined cutting process is completed, and eventually the cutting process Will not be completed. The retracted position may be set in advance to a position at which the tip of the cutting tool is far from the opening of the machining hole enough to discharge the residual chips from the machining hole.

Accordingly, even if an abnormal load is detected due to the residual chips in the machining hole, the cutting work is not stopped only by this fact. Also, by setting the count-up value of the preset retry counter in consideration of the frequency of occurrence of an abnormal load due to residual chips in the machining hole, the count value of the retry counter reaches the count-up value before the cutting operation is completed. If it is determined at this point that the tool life has expired, the cutting tool can be used effectively until the tool life expires.

Further, in the above configuration, when the load acting on the cutting tool becomes equal to or higher than a preset load level, the position of the cutting tool at that time is recorded as a cutting interruption position, and the cutting position is recorded again. When starting cutting, move the cutting tool at a rapid traverse speed to a position a predetermined amount before the cutting interruption position where cutting has already been completed, and cut from the position a predetermined amount before this cutting interruption position to the cutting end position. Since the cutting tool is moved at the speed, the cutting start position (the same position as the rapid traverse end position described above)
The cutting time can be reduced as compared with the case where the movement of the cutting tool is started again at the cutting speed. Regarding the position at which re-cutting is started, this point is not a cutting interruption position but a position a predetermined amount before the cutting interruption position, and the cutting interruption position itself may be a place where cutting has not yet been completely performed. Therefore, if the cutting tool is moved to this position at the rapid traverse speed, an excessive load may be applied near the cutting interruption position. In consideration of this point, a predetermined amount of the cutting interruption position (for example, 1 〜2 mm) The cutting tool was moved at a rapid traverse speed to a position in front, and the cutting tool was moved at a cutting speed from this position to a cutting end position.

According to the second aspect of the present invention, when the numerically controlled machine tool has an automatic tool changer with a tool magazine, when the count value of the retry counter reaches a preset count-up value. Compares the cutting tool mounted on the tool spindle with the cutting tool in the tool magazine at that time, and if the same cutting tool as the cutting tool mounted on the tool spindle exists in the tool magazine, The same cutting tool is mounted on the tool spindle by operating an automatic tool changer. This allows
Even if the cause of the abnormal load is caused by a tool abnormality such as tool wear or tool breakage, cutting can be restarted without stopping the numerically controlled machine tool by automatically changing the cutting tool. As a result, the operation rate of the numerically controlled machine tool can be increased.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. 1 to 3 are flowcharts for executing a cutting method for a numerically controlled machine tool according to the present invention, and FIG. 1 shows steps 1 to 4 and 11,
FIG. 2 shows steps 5, 6 and 10, and FIG.
To 9 are respectively shown. In these figures, the numerical value following S indicates a step number.

Step 1: Move the cutting tool at a rapid traverse speed. In cutting of a machine tool including a numerically controlled machine tool, in order to shorten the machining time, generally, the cutting tool is moved at a rapid traverse speed higher than the cutting speed to a position near the workpiece and then cut. The cutting tool is moved at the cutting speed until the end position. Therefore, also in the present embodiment, the cutting tool is moved at the rapid traverse speed to a position near the workpiece, that is, the rapid traverse end position, and the movement is started in this step. Note that the rapid traverse end position and the rapid traverse speed are set in a machining program or the like.

Step 2: The movement of the cutting tool is started at the cutting speed. In this step, the cutting tool moved to the rapid ending end position by the processing of the previous step 1 is started to move at the cutting speed toward the cutting end position. At this time, the movement of the cutting tool from the rapid feed end position to the cutting end position uses a skip feed function of the numerically controlled machine tool. In general, the skip feed function is such that when a skip signal is turned on during the skip feed, a predetermined process such as changing the feed speed or completing the processing can be performed during the skip feed. That is the function. As will be described in detail in a later step, in this embodiment, when an abnormal load is detected, a skip signal is turned on, and during the movement in this step, a predetermined process described in the following step is performed. ing. The cutting end position and the cutting speed are set in a machining program or the like.

Step 3: A load acting on the cutting tool is detected. In this step, the load acting on the cutting tool is always detected during the movement at the cutting speed. This focuses on the fact that the cutting resistance becomes larger than usual immediately before the cutting tool wears or breaks, and this effect increases the load on the tool spindle that rotates the cutting tool and moves the cutting tool in the cutting direction. This is to detect an increase in the load on the feed shaft to be moved. The load applied to the tool spindle and the load applied to the feed axis may be detected by using a function of monitoring the load state such as the torque and the current value of each control device of the tool spindle and the feed axis. But,
Alternatively, a meter relay may be connected to a load meter terminal provided in each control device, or a load sensor or the like may be used.

Step 4: The load acting on the cutting tool is compared with a threshold value. In this step, the load (load detection value) acting on the cutting tool detected in the previous step 3 is compared with a preset load level as a threshold.
In the present embodiment, since both the load applied to the tool spindle and the load applied to the feed axis are detected as loads acting on the cutting tool, the load level for the tool spindle and the load level for the feed axis are also detected. Are set in advance. Thus, if the load on the tool spindle is greater than the load level for the tool spindle, or the load on the feed axis is greater than the load level for the feed axis, it acts on the cutting tool. It is determined that the load has become larger than the preset load level. In this step, if the load acting on the cutting tool has become larger than the preset load level, the process proceeds to step 5 (step 4Y). On the other hand, if the load acting on the cutting tool is equal to or less than the preset load level, the process proceeds to Step 11 (Step 4N).

Step 5: Store various data for retry (recutting). In this step, the previous step 4
When the load acting on the cutting tool is equal to or higher than the preset load level (step 4Y), the skip signal is turned ON, the position of the cutting tool at that time is recorded as a cutting interruption position, and a retry counter is further provided. 1 in
Is added. The retry counter used here is capable of setting a count-up value, and when the count value of the retry counter reaches the count-up value, outputs a count-up signal indicating that. The counter used as the retry counter may be a so-called soft counter built in the numerical controller, but a counter as hardware may be provided on the operation panel or the like.

Step 6: It is determined whether or not the retry counter has counted up. In this step, it is determined whether or not the retry counter has counted up. If the count value of the retry counter has not reached the preset count up value, the process proceeds to step 7 (step 6N). If the count value has reached the preset count-up value, the process proceeds to step 10 (step 6Y). Note that the count-up value of the retry counter is set in consideration of the frequency of occurrence of an abnormal load due to the chip remaining in the machined hole. The frequency of occurrence of the abnormal load due to the residual chips from the machining hole differs depending on various conditions such as the depth of the machining hole, the shape of the cutting tool, the cutting speed, and the material of the workpiece. For example, if the depth of the drilled hole is deeper than the shallow one, the frequency of occurrence of abnormal load due to the residual cutting chips in the drilled hole is higher, so for this one, the count up value of the retry counter must be increased. An abnormal load caused by the residual cutting chips in the machining hole is erroneously detected as a tool abnormality such as breakage of the cutting tool. Therefore, it can be said that it is preferable to set the count-up value of the retry counter for each hole drilling process.

Step 7: The cutting tool is retracted, and the residual chips in the machining hole are discharged. In this step, if the count value of the retry counter has not reached the preset count-up value in the previous step 6 (step 6N), the cutting tool at the cutting interruption position is moved to the preset evacuation position. It is once retracted, and the residual chips in the machined holes are discharged by this operation. For the evacuation position,
This is enough to remove the residual chips from the holes
The position where the tip of the cutting tool is separated from the opening of the processing hole may be set in advance.

Step 8: The cutting tool is started to move at the rapid traverse speed toward the re-cutting start position. In this step, the cutting tool that has been evacuated to discharge the residual chips in the previous step 7 is moved to the re-cutting start position stored in the previous step 5, that is, a position that is a predetermined amount before the cutting interruption position. Start moving at the rapid traverse speed. Regarding the point where the re-cutting start position is not the cut stop position but a position before the cut stop position by a predetermined amount, it is highly likely that the cut stop position itself is a place where cutting has not yet been completely performed. If the robot is moved to the position at the rapid traverse speed, an excessive load may be applied near the cutting interruption position, and this point is taken into consideration. The position before the predetermined amount is 1-2 m
It is sufficient to set about m.

Step 9: The cutting tool is started to move at the cutting speed toward the cutting end position. In this step,
The cutting tool that has reached the position before the re-cutting start position, that is, the cutting interruption position by a predetermined amount in step 8 above,
The movement is started at the cutting speed toward the cutting end position.
Note that the cutting end position in this step is the same as the cutting end position in the previous step 2. After the movement of the cutting tool is started in this step, the skip signal is turned off, and the process returns to the previous step 3. This is for detecting the abnormal load continuously after the re-cutting is started. Therefore, if the abnormal load due to the remaining chip in the machined hole is detected again after the re-cutting is started, the evacuation and the re-cutting for discharging the remaining chip are repeated until the retry counter counts up.

Step 10: Processing is interrupted as a tool abnormality. In this step, if the count value of the retry counter reaches the preset count-up value in step 6 (step 6Y), it is determined that the tool is abnormal, and the machining is interrupted. As described above, the count-up value of the retry counter is set in consideration of the frequency of occurrence of an abnormal load due to residual chips in the machining hole, so if the retry counter counts up before the end of machining, The cause of the abnormal load is not due to the residual cutting chips in the machined holes, but it can be said that there is a high possibility of a so-called tool abnormality such as wear or breakage of the cutting tool. Therefore, when the retry counter has counted up, it is determined in this step that the tool is abnormal. By the determination of the tool abnormality, the numerically controlled machine tool interrupts the machining and retracts the cutting tool during the cutting from the machining hole. The retreat position of the cutting tool at this time is not particularly limited as long as it is a position distant from the machining hole, but may be, for example, a machining origin on a machining program or a so-called return position.

Step 11: It is determined whether the cutting tool has reached the cutting end position. In this step, if the load acting on the cutting tool is equal to or lower than the preset load level in step 4 (step 4N), it is determined whether the cutting tool has reached the cutting end position. If the cutting tool has not reached the cutting end position (step 11
N), the processing after step 3 is performed again. On the other hand, if the cutting tool has reached the cutting end position (step 11).
Y), a series of cutting steps are completed.

In step 10 described above, when the count value of the retry counter reaches a preset count-up value, it is determined that the tool is abnormal and the machining is interrupted. The cutting tool mounted on the tool spindle and determined to be abnormal at the time may be automatically replaced. Specifically, when the numerically controlled machine tool has a tool magazine capable of being equipped with a plurality of cutting tools, and includes an automatic tool changer, the count value of the retry counter is a preset count-up value. Is reached, the cutting tool currently mounted on the tool spindle and the plurality of cutting tools present in the tool magazine are compared, and the same cutting tool as the cutting tool mounted on the tool spindle is compared. Is present in the tool magazine, the same cutting tool is mounted on the tool spindle by operating the automatic tool changer. In addition,
As a matter of course, the condition is that the cutting tool existing in the tool magazine to be replaced at this time is not determined to be a tool abnormality. In this way, even if the cause of the abnormal load is caused by a tool abnormality such as tool wear or tool breakage, the automatic tool changer is operated to automatically change the cutting tool, thereby enabling numerical control. Cutting can be restarted without stopping the machine tool, and as a result, the operating rate of the numerically controlled machine tool can be increased.

FIG. 4 shows an example of a screen displayed on a display device provided in the numerically controlled machine tool according to the present invention. The load acting on the cutting tool with respect to the tool spindle and the feed shaft is constantly read by a control device (generally, a sequencer with a built-in NC or an external sequencer), and a graph meter display 1 or a numerical meter display 2 is performed. In the case of FIG. 4, a combined display of the graph meter display 1 and the numerical meter display 2 is performed. The set value 3 is the above-described load level, and is set as a variable on the NC machining program or parameter data of the control device. A plurality of these setting values can be set for each cutting tool or the same tool. In addition, these set values are displayed on the graph meter display 4 and the numerical meter display 3 as well as the load acting on the cutting tool, so that both the set value and the load acting on the cutting tool can be easily visually checked during machining. It has become something.

Hereinabove, one embodiment of the present invention has been described. In the present embodiment, as the load acting on the cutting tool, both the load on the tool spindle and the load on the feed shaft are detected. However, the present invention is not necessarily limited to this, and only one of the axes is used. An abnormal load may be detected as a load acting on the cutting tool as a load acting on the cutting tool.

[0026]

According to the present invention, even if an abnormal load is detected due to a residual hole in a machined hole, the cutting operation is not stopped only by this fact. By setting the count-up value in consideration of the frequency of occurrence of abnormal load due to residual chips in the machining hole, if the count value of the retry counter reaches the count-up value before cutting is completed, the tool life and Since it can be determined that the cutting tool has expired, the cutting tool can be used effectively until the end of the tool life, and a tool change counter is not required. Further, when the load acting on the cutting tool becomes equal to or higher than a preset load level, the position of the cutting tool at that time is recorded as a cutting interruption position, and when cutting is started again, the cutting interruption is performed. Since the cutting feed is started from a position a predetermined amount before the position, the cutting time can be shortened as compared with the case where cutting feed is started again from the cutting start position.

[Brief description of the drawings]

FIG. 1 is a flowchart for executing a cutting method for a numerically controlled machine tool according to the present invention;
4 and 11 are shown.

FIG. 2 is a flowchart for executing a cutting method for a numerically controlled machine tool according to the present invention,
6 and 10 are shown.

FIG. 3 is a flowchart for executing a cutting method of the numerically controlled machine tool according to the present invention, and includes steps 7 to 7;
9 is shown.

FIG. 4 shows an example of a screen displayed on a display device included in the numerically controlled machine tool according to the present invention.

Claims (2)

[Claims] 1. A numerically controlled machine tool wherein a cutting tool is moved at a rapid traverse speed from a rapid traverse end position to a rapid traverse end position and then moved at a cutting speed from the rapid traverse end position to a cutting end position. In the cutting method, the load acting on the cutting tool is always detected while the cutting tool is moving at the cutting speed, and the load acting on the cutting tool becomes equal to or higher than a preset load level. Records the position of the cutting tool at that time as the cutting interruption position and adds 1 to the retry counter. If the count value of the retry counter has not reached the preset count-up value, the cutting tool is stopped. After temporarily retreating to a previously set retreat position, the cutting tool at the retreat position is rapidly traversed to a position a predetermined amount before the cutting interruption position. After that, cutting is performed by moving at a cutting speed from a position a predetermined amount before the cutting interruption position to the cutting end position, and the above processing reaches the cutting end position by the cutting tool. Alternatively, the cutting is continued until the count value of the retry counter reaches a count-up value. 2. When the numerically controlled machine tool includes an automatic tool changer with a tool magazine, when the count value of the retry counter reaches a preset count-up value, Compare the cutting tool mounted on the tool spindle with the cutting tool in the tool magazine, and if the same cutting tool as the cutting tool mounted on the tool spindle at that time exists in the tool magazine, 2. The method according to claim 1, wherein the same cutting tool is mounted on a tool spindle by operating the automatic tool changer.