JPH11188573A - Drilling control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stop drilling immediately before rupture when a material extendable against an external force is drilled by a rotating cutting tool. SOLUTION: A rotating blade 3 uses a square-cut end mill in order to make it difficult for an object to be drilled 11 to be projected from a drill hole end. When a material extendable against the external force is cut, a load current of a motor 5 for feeding varies at a gentle inclination. In a control circuit 9, drilling is made while the load current of the motor 5 for feeding is detected. Then, before the rotating blade 3 is projected from the drill hole end of the object to be drilled 11, a stop instruction is given to the motor for feeding 5 when a load current value corresponding to this case is detected so as to automatic perform a drilling stop control. Whether the rotating blade 3 is already projected or not can be judged by a comparison of a load current of the motor for feeding with a predetermined threshold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling control device, and more particularly to a drilling control device capable of stopping drilling immediately before breakage when drilling a material that can be extended by an external force by a rotary cutting tool.

[0002]

2. Description of the Related Art When drilling is performed using a rotary cutting tool represented by a drill, whether drilling or non-piercing is determined from the load current (main motor load current) of an electric motor that rotates the spindle of the tool. can do. Conventionally, a technique is known in which a main motor load current is monitored during drilling, and when this current value changes from drilling to non-piercing, the feed operation of the tool is stopped after drilling is completed to improve cutting efficiency. (Japanese Unexamined Patent Publication
-213246).

[0003]

By the way, the conventional drilling control method mainly aims at improving the cutting efficiency by stopping the feed motor when the drilling is completely completed. However, depending on the conditions of the drilling operation, it may not be preferable for the tool to protrude from the material.
Under such conditions, the conventional drilling control method cannot be applied as it is. The present invention has been made in view of such a conventional problem, and provides a drilling control device that can stop drilling immediately before breaking when drilling a material that is extended by an external force by a rotary cutting tool. The purpose is to do.

[0004]

SUMMARY OF THE INVENTION Therefore, the present invention (claim 1) provides a rotary cutting means having a cutting blade, and an object to be pierced, the material of which partially extends due to the pressing caused by the piercing by the rotary cutting means. A feed direction moving means for feeding and returning the rotary cutting means toward the object to be drilled; a load amount detecting means for detecting a load amount of the rotary cutting means or the feed direction moving means; Stop means is provided for stopping the feed direction moving means before the cutting blade projects from the piercing end of the pierced object based on the load amount detected by the detecting means.

[0005] The rotary cutting means performs drilling by pressing the object to be drilled by the feed operation of the feed direction moving means while rotating the cutting blade. The material of the object to be pierced partially extends due to the pressure accompanying the piercing. The load amount detecting means detects a load amount of the rotary cutting means or the feed direction moving means. The feed direction moving means is stopped by the stopping means before the cutting blade projects from the piercing end of the pierced object.
The determination as to whether or not the cutting blade is protruding is made based on the load detected by the load detector. This makes it possible to perform optimal cutting when it is not desirable for the cutting blade to protrude from the material.

According to the present invention (claim 2), the stopping of the stopping means is performed when at least one of the magnitude of the load detected by the load detecting means and the slope of the fluctuation calculated from the load. It is characterized in that it is performed by comparing a predetermined threshold value. There is a limit point before the cutting blade protrudes during the drilling of the object to be drilled by the rotary cutting means. This limit point can be found by monitoring the magnitude of the load and the slope of the change in the load.
A threshold value is determined in advance from these characteristics for each different material, and the stop position of the stopping means is determined by comparing the threshold value with the threshold value. This makes it possible to prevent the cutting blade from protruding from the material by a simple process of comparing with the threshold value.

The threshold value may be fixed. However, according to the present invention (claim 3), the threshold value may be a load amount at the time of non-perforation and a load amount at the time of perforation detected by the load amount detecting means. And calculating based on at least one of the elongation characteristics of the material of the object to be drilled. It is conceivable that the load amount at the time of non-perforation and at the time of perforation varies depending on the material and lot of the object to be perforated. It is also conceivable that the load varies depending on the relative positional relationship between the object to be drilled and the rotary cutting means. For this reason, when the threshold value is varied according to the load amount at the time of non-drilling, the load amount at the time of drilling, the elongation characteristic of the material of the object to be drilled, etc., the limit point before the cutting tool protrudes becomes more strict. Desirable in seeking.

Further, the present invention (Claim 4) is characterized in that the cutting blade of the rotary cutting means has a flat bottom surface in the perforation. If the drilling bottom surface is flat, the cutting blade is more difficult to protrude from the drilled target. Also, the setting of the threshold value becomes easy.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an overall configuration diagram of an embodiment of the present invention. The overall configuration diagram is common to the first embodiment and the second embodiment of the present invention. In FIG. 1, a rotary blade 3 is attached to the tip of the spindle of the spindle rotating mechanism 1.
For the rotary blade 3, a cutting tool whose bottom surface is flat is used. The rotary blade 3 is, for example, a square cut end mill. The spindle rotating mechanism 1 corresponds to a rotary cutting unit. The rotary blade 3 is driven to rotate while being pressed against the target object 11 to be pierced. The object 11 to be pierced is, for example, a cast iron pipe. The main shaft rotating mechanism 1 is hydraulically driven.

The feed motor 5 is composed of a servomotor, and corresponds to a feed direction moving means. The main body of the feed motor 5 is fixed to the table 13. And
When the screw shaft 15 attached to the tip of the feed motor 5 is rotated by the feed motor 5, the spindle rotating mechanism 1 is moved up and down in the height direction (the Z-axis direction in the figure). . A current detection unit 7 for detecting a load current is incorporated in the feed motor 5. The current detector 7 corresponds to a load amount detector. Current detector 7
Is sent to the control circuit 9. The object 11 to be pierced is placed directly below the table 13, and the table 13 can be moved also in the X-axis. Further, even along the outer periphery of the cast iron tube as the object 11 to be drilled, the distance from the cast iron tube is set to be equal to 3 mm.
It can be moved 60 degrees.

Next, the operation of the first embodiment of the present invention will be described. The rotary cutter 3 uses a square-cut end mill in order to make it difficult for the rotary cutter 3 to protrude from the drilling end of the drilling target 11. The load current of the feed motor 5 changes as shown in FIG. In FIG. 2, a waveform 21 is a case where the material of the object 11 to be drilled does not show much elongation with respect to an external force, while a waveform 23 indicates that the material of the object 11 to be drilled elongates with an external force. This is the case with a material having a texture. In the case where the material of the pierced object 11 does not significantly extend with respect to the external force as in the waveform 21, the pierced object 11 is easily broken by the external force. It is easier to protrude than the damaged part of the object 11.

FIG. 3 shows a state where the latter half of the waveform 23 is enlarged. In FIG. 3, the rotary blade 3
, The load current value of the feed motor 5 shows a constant value. When the end of the drilling is approaching, the remaining wall thickness is reduced, so that the cutting surface is not flat, and the contact area with the rotary blade 3 having a flat bottom surface is reduced, and the reaction force, that is, the load is reduced. I do. This tendency continues until just before the fracture. Here, the load current of the feed motor 5 decreases accordingly. As described above, when cutting a material that is elongated by an external force, the load current of the feed motor 5 changes with a gentle slope. Thereafter, a break occurs, and a no-load current flows through the feed motor 5.

According to the present invention, the rotary blade 3 is provided with an object 11 to be pierced.
From the viewpoint of not protruding more, the present invention is applied to the case where the material of the object to be drilled 11 is a material which is extended with respect to an external force as shown by the waveform 23. From the load current value of the feed motor 5, it is possible to determine whether or not to pierce or not. Utilizing this, the control circuit 9 performs perforation while detecting the load current of the feed motor 5. Then, the object to be pierced 11
Before the rotary blade 3 protrudes from the perforation end, when a load current value corresponding to this case is detected, a stop command is sent to the feed motor 5 and the perforation stop control is automatically performed. Whether or not the rotary blade 3 is protruding is determined by comparing the load current of the feed motor 5 with a predetermined threshold value.

Next, the first embodiment of the present invention will be described with reference to a flowchart.
A detailed operation of the embodiment will be described. In FIG. 4, step 0 (abbreviated as S0 in the figure; the same applies hereinafter) is a standby state before drilling, and waits for a drilling command from the control circuit 9. In step 1, the feed motor 5 starts feeding based on a drilling command from the control circuit 9. In step 2,
The current detection unit 7 measures the load current value of the feed motor 5. In step 3, it is determined whether or not the measured load current value is equal to or greater than a preset drilling threshold value. If it is less than the perforation threshold, the measurement of the load current value in step 2 and the determination in step 3 are repeated.

The magnitude of the load current value slightly fluctuates due to the frictional state of the screw shaft 15, the moving position of the table 13, the installation state of the table 13, the influence of gravity, and the like. For this reason, in order to accurately detect the no-load current value, it is desirable that the current detection unit 7 monitors the load current value of the feed motor 5 every time the drilling operation is performed. On the other hand, if the load current value is equal to or greater than the drilling threshold value, it is confirmed in step 4 that the rotary blade 3 of the spindle rotating mechanism 1 has started drilling on the drilling target 11. The reason for confirming the state of the start of the perforation is to make a comparison with the stop threshold value performed later in step 6 after the perforation is once performed.

In step 5, the load current value of the feed motor 5 after the start of the drilling is measured. And step 6
Then, it is determined whether or not the measured load current value is smaller than a preset stop threshold value. At this time, in order to prevent the rotary blade 3 from protruding from the drilling end of the drilling target 11, a drilling experiment based on the load current characteristics of the feed motor 5 and the material used for the drilling target 11 in advance in FIG. The stop threshold value is determined after adding a predetermined margin from an example or the like. Setting a fixed stop threshold value in advance in this way is particularly effective when the cutting target, conditions, and the like are limited, such as when the same material is continuously drilled.

Since the rotary blade 3 does not protrude from the piercing end of the object 11 to be pierced, the measured load current value is larger than the no-load current value. When the measured load current value is equal to or larger than the preset stop threshold value, the measurement of the load current value in step 5 and the determination in step 6 are repeated. At this time, the drilling operation is still ongoing. When the measured load current value is less than a preset stop threshold,
Proceed to step 7. In step 7, a command to stop the feed motor 5 is issued from the control circuit 9. As a result, the feed motor 5 stops. Thereafter, in step 8, the feed motor 5 rotates in the reverse direction to that during the feed operation to perform the return operation of the main shaft rotating mechanism 1. Then, it is stopped at a predetermined position in step 9 and returns to the state of step 0. As described above, since the stop threshold value is fixed, the control by the control circuit 9 can be simplified.

Next, the operation of the second embodiment of the present invention will be described. In the second embodiment of the present invention, unlike the first embodiment of the present invention, the determination as to whether or not the drilling is completed is made while finding the optimum threshold value each time. Fixing the threshold value as in the first embodiment of the present invention facilitates control, but requires a considerable allowance for the current value during stoppage.
For this reason, a threshold value is calculated by calculation each time a drilling operation is performed so that the tolerance is suppressed as much as possible. Thus, optimal stop control with high cutting efficiency can be performed.

Next, the second embodiment of the present invention will be described with reference to a flowchart.
A detailed operation of the embodiment will be described. Note that the same elements as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 5, in step 101, the current detecting unit 7 measures a no-load current value after the start of the feed of the feed motor 5. Then, in step 102, the no-load current value is stored. In step 103, a stop threshold is calculated from the no-load current value obtained in step 102 and the load current value obtained in step 5. The reason why the no-load current value and the load current value are obtained is that these values are supposed to be different for each drilling depending on the material of the drilling target 11 and the installation condition of the spindle rotating mechanism 1.

At this time, the stop threshold value may be calculated by multiplying the difference between the no-load current value and the load current value by a predetermined ratio (for example, 20%), or from the load current value. It may be uniformly determined at a predetermined ratio. Further, the stop threshold value may be obtained by multiplying a predetermined ratio based on the gradient of the current change between the no-load current value and the load current value. However, at this time, the comparison process in step 6 needs to be changed to “the gradient of the current change of the load current value <the stop threshold value”.

The predetermined ratio or the predetermined ratio to be multiplied when the stop threshold value for the gradient of the current change of the load current value is multiplied is determined in advance so that the rotary blade 3 does not protrude from the piercing end of the object 11 to be pierced. It is determined after adding a predetermined margin based on a load current characteristic of the feed motor 5 in FIG. 2 and a drilling experiment example based on a material used for the drilled object 11.
As a result, the state of the rotary blade 3 and the target 1
Regardless of the cutting conditions such as the material of No. 1, it is possible to control with an optimum stop threshold value for each drilling. For this reason, the accuracy of the stop control is improved, and stop control with even higher cutting efficiency can be performed.

Incidentally, regarding steps 2 and 3,
Since the drilling search (movement distance of the rotary blade 3) is proportional to time, the distance between the movement start point of the rotary blade 3 and the surface of the drilled object 11 is measured in advance, and the start of drilling is determined based on the elapsed time. May be. As described above, the object to be pierced 1
Drilling can be stopped at a desired timing, such as immediately before the breaking of 1. In this embodiment, the hydraulic drive is used for the main shaft rotating mechanism 1. However, the present invention is not limited to this, and the present invention can be applied to a pneumatic drive or an electric motor. Also,
The present invention can also be applied to a case where an electric motor is employed for the spindle rotating mechanism 1 and the drilling stop control is performed based on the load current detected on the spindle rotating mechanism 1 side.

[0023]

As described above, according to the present invention, an object to be pierced, whose material is partially extended by the pressure accompanying the piercing, is fed before the cutting blade projects from the piercing end of the pierced object. As we decided to stop the direction moving means,
When it is not preferable that the cutting blade protrudes from the material due to the conditions of the drilling operation, it is possible to perform high-precision processing with high cutting efficiency.

[0024]

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a change in load current of a feed motor.

FIG. 3 is a diagram showing a state when the latter half of a change in load current in FIG. 2 is enlarged;

FIG. 4 is a flowchart illustrating a detailed operation of the first embodiment of the present invention.

FIG. 5 is a flowchart illustrating a detailed operation of the second embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 spindle rotating mechanism 3 rotary blade 5 feed motor 7 current detection unit 9 control circuit 11 drilled object 13 table 15 screw shaft 21 feed when the material to be drilled does not show much extension against external force Current of the feed motor 23 Load current of the feed motor when the material of the object to be drilled is a material that is elongated with respect to external force

Claims (4)

[Claims] 1. A rotary cutting means having a cutting blade, an object to be pierced, the material of which partially extends due to the pressure caused by the drilling by the rotary cutting means, and the rotary cutting means being fed toward the object to be pierced. And a feed direction moving means for performing a return operation, a load amount detecting means for detecting a load amount of the rotary cutting means or the feed direction moving means, and a load amount detecting means for detecting a load amount of the drilling target object based on the load amount detected by the load amount detecting means. A perforation control device comprising: a stopping means for stopping the feed direction moving means before the cutting blade projects from a perforation end. 2. The method according to claim 1, wherein the stopping of the stopping means compares a predetermined threshold value with at least one of a magnitude of the load detected by the load detecting means and a slope of a change calculated from the load. 2. The method according to claim 1, wherein
The perforation control device according to any one of the preceding claims. 3. The threshold value is based on at least one of a load amount at the time of non-perforation, a load amount at the time of drilling, and an elongation characteristic of a material of the object to be drilled detected by the load amount detecting means. The drilling control device according to claim 2, wherein the calculation is performed. 4. The drilling control device according to claim 1, wherein the cutting blade of the rotary cutting means has a flat bottom surface.