JPH06312308A - Tool breakage detecting method and device in multishaft head finishing machine - Google Patents

Abstract

PURPOSE:To improve the detecting accuracy of the breakage of a tool by detecting the process resistance operating to the tools held by a multishaft head by a detector respectively, and deciding that a tool is broken when the detecting value exceeds a set value. CONSTITUTION:In a multishaft head 8, a rotary shaft 12 rotated by an NC motor is held rotatable by a pair of the front side and the rear side angular bearings 13, in plural holding tubes 11 formed integral in front of the multishaft head 8, and a reaction in the thrust direction as a process resistance operating to the rotary shaft 12 is transmitted to an inner lace 15 through a flange 12a on the rotary shaft 12. In this case, a step 11b is formed at the rear position of the bearing 13 inside the holding tube 11, and a thrust reaction detecting unit 20 is provided between the bearing 13 and an outer lace 14. And it is discriminated whether the detecting value of the detecting unit 20 exceeds a set value or not at a specific position after the process is started, and the breakage of the tool 9 is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool breakage detection method and apparatus for a multi-axis head processing machine, for example.

[0002]

2. Description of the Related Art As a conventional tool breakage detecting method, there is a method of contacting a drill mounted on a spindle with a contactor and detecting whether the drill is normal or broken based on the presence or absence of an energized state.

In addition, when a drilling operation is performed on a workpiece, a thrust force corresponding to a working resistance acting on a spindle that supports the drill is sensed by, for example, a piezoelectric element, and the cutting edge of the drill is damaged so that the reaction force is generated. There is also proposed a method of determining that the drill is broken when the current value output from the piezoelectric element decreases and does not exceed a preset set value.

[0004]

However, in the former detection method, since the contactor is brought into contact with the drill, durability of the contactor becomes a problem, and the contactor becomes an obstacle when exchanging the drill. There is a problem that the number of processed pieces cannot be increased. Further, during drilling work, a coolant is supplied to the drill for lubrication and cooling. However, even if the drill is broken due to the influence of this coolant, it may be judged to be normal. Furthermore, even if the drill is not damaged due to the energized state when the contactor contacts the drill, that is, the condition of the surface of the drill or the state of the ball bearing that supports the spindle, it is possible to judge that the drill is broken, and the detection accuracy There was a problem of low.

On the other hand, the latter tool damage detection method is a non-contact method, so that the former problem can be solved.
When a long time has passed since the piezoelectric element or the like was activated, the output voltage of the amplifier that amplifies the output voltage becomes saturated (overload). For this reason, the output voltage from the amplifier becomes constant regardless of whether the drill is normal or broken, which makes detection impossible.

Particularly, in the multi-axis head, when the detection element for each tool is reset at the same time as the machining feed start feed, for tools having different cutting points, a long time is set until the breakage detection point. As a result, the overload as described above occurs during this period, and the tool breakage may not be detected. That is, as indicated by the chain double-dashed line L in FIG. 2, the output voltage becomes constant whether it is damaged or not. The higher the sensitivity of the sensing element, the earlier this overload appears. Therefore, it is not possible to perform highly accurate detection using the more sensitive sensing element, and the detection accuracy is limited.

Further, in the conventional method of simultaneously resetting, the output signal fluctuates due to the influence of machining vibrations of other tools, which becomes larger with time and cannot be escaped from the influence of such drift. was there.

An object of the present invention is to provide a tool breakage detection method and device for a multi-axis head machining machine which can solve the problems existing in the above-mentioned conventional techniques and improve the accuracy of breakage detection. .

[0009]

In order to achieve the above object, the invention according to claim 1 feeds a multi-axis head holding a plurality of tools toward a workpiece to form a plurality of workpieces on the workpiece. In a multi-axis head processing machine that performs the above, a plurality of detectors that detect the machining resistance acting on each tool and output a signal proportional to the machining resistance are provided. Is reset, and it is determined whether or not the output signal exceeds a set value at a predetermined position after the start of processing, and the damage of each tool is determined.

Further, the invention according to claim 2 is a multi-axis head processing machine for performing a plurality of processings on a workpiece by feeding a multi-axis head holding a plurality of tools toward the workpiece. A sensing element that senses each machining resistance is housed between a supporting member that supports the spindle of the tool and the spindle, at a position that receives machining resistance during machining, and an output signal is output to the sensing element via a lead wire. An amplifier for amplification is connected to the amplifier, and a breakage judging circuit for judging the presence or absence of breakage by comparing the signal output from the detection element with a preset setting value is provided to the breaker judging circuit. Prior to the damage detecting operation at the damage detecting position corresponding to the tool, a reset circuit is provided to reset the output signal of each detecting element before the predetermined position.

Further, the invention according to claim 3 is based on claim 2.
In, a piezoelectric element is used as the detection element, and the output signal has a voltage value.

[0012]

The present invention operates as follows by taking the above means. In each of the multiple tools, the output signal of the sensing element is reset immediately before processing the workpiece,
The output signal gradually increases. In the process of gradually increasing, the processing of the material to be processed is started, and when the processing tool is normal, the processing resistance becomes high immediately after the start of processing. Therefore, the signal output from the detection element also exceeds the set value in the process of gradually increasing and rapidly increases, and the work tool is determined to be normal.

On the contrary, if the processing tool is damaged,
Since the contact resistance between the material to be processed and the processing tool is small, the output signal from the detection element does not suddenly increase in the process of gradually increasing. Therefore, the output does not exceed the set value immediately after the start of processing, and it is determined that the processing tool is damaged.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a method for detecting a breakage of a drill and a device therefor will be described with reference to the drawings.

As shown in FIG. 3, a column 2 is fixedly mounted on the upper surface of the base 1, and a work clamp 3 for clamping the workpiece W is mounted on the column 2. A fixed guide support base 4 is horizontally mounted on the upper surface of the base 1, and a movable table 5 is supported on the support base 4 by an NC motor 6 so as to be capable of reciprocating in the front-rear direction (left and right in FIG. 3). A mounting block 7 is fixed to the upper surface of the movable table 5, a multi-axis head 8 is mounted on the block 7, and a plurality of drills 9 having different lengths are attached to the multi-axis head 8. ing. An NC motor 10 for rotating the drill 9 is attached to the attachment block 7.

As shown in FIG. 4, a plurality of horizontal cylindrical support cylinders 11 are integrally formed on the front surface of the multi-axis head 8, and each support cylinder 11 is rotationally driven by the NC motor 10. The rotating shaft 12 is rotatably supported by a pair of front and rear angular bearings 13. The angular bearing 13 is an inner peripheral surface 11a of the support cylinder 11.
The outer race 14 fitted in the front and rear so that it can be moved slightly.
And an inner race 15 fitted to the outer peripheral surface of the rotating shaft 12, and a plurality of balls 16 interposed between the races 14 and 15. The reaction force in the thrust direction, which acts on the rotating shaft 12 during the drilling work, is brought into contact with the front end surface of the inner race 15 and acts in the thrust direction.
It can be transmitted to the inner race 15 via a flange portion 12a formed integrally with the second race. Further, the sleeve 18 is fitted between the inner race 15 and the flange portion 12b provided in the middle of the rotary shaft 12, and the inner race 15
Is to be positioned.

A cover plate 19 is fixed to the front end surface of the support cylinder 11 with bolts. A step portion 11b is formed inside the support cylinder 11 so as to be located near the rear of the angular bearing 13, and a thrust reaction force detection unit 20 is interposed between the step portion 11b and the outer race 14. ing. The detection unit 20 includes a housing ring 21, a power transmission ring 22 that covers a piezoelectric element 23 as a sensing element housed inside the housing ring 21,
Further, it is constituted by a spring 24 which biases the rear side surface of the piezoelectric element 23 forward. A lead wire 25 is connected to the piezoelectric element 23. The housing ring 21
An O-ring 26 is interposed between the power transmission ring 22 and the power transmission ring 22.

As shown in FIG. 5, the piezoelectric element 23
An amplifier 28 is connected to the via the lead wire 25. A damage determination circuit 29 is connected to the amplifier 28,
A reset circuit 30 is connected to the damage determination circuit 29. Further, the damage determination circuit 29 has a central processing circuit 31 for performing a detecting operation, a read only memory 32 for storing a program for the detecting operation, a random access memory 33 for storing a set value, and the like. In this embodiment, the machining start point of each drill 9 is set as a reference reset time point based on NC control, a reset point is set at a point before a predetermined position, and a position sent by a predetermined amount from the start of machining is detected for presence or absence of damage. And the reset and detection operations are performed by automatic control.

Next, the operation of the drill breakage detecting device of the drill boring machine configured as described above will be described. As shown in FIG. 3, the workpiece W is fixed to the work clamp 3, the NC motor 10 is started, and the drill 9 is rotated.
Also, the NC motor 6 is operated to move the movable table 5 forward, and the drill 9 together with the mounting block 7 and the multi-axis head 8 is moved.
Are advanced toward the workpiece W. Head 8 at this time
Is fast-forwarded by the NC motor 6 until the tip of the longest drill 9 approaches the surface of the workpiece W.

When the fast feed operation is completed, the cutting feed operation is switched to, and reset signals are sequentially output from the reset circuit 30 to the breakage determination circuits 29 at the reset positions set by NC in synchronism with the cutting feed operation. In this state, the piezoelectric element 23 outputs a gradually increasing voltage, as shown in FIG. Further, at the time of starting the processing of the workpiece W, if the drill 9 is normal, the cutting resistance during the drilling work by the drill increases, and the voltage output from the piezoelectric element 23 is as shown by the solid line in FIG. Rapidly increases, and exceeds a preset value Vs when a predetermined time elapses. Here, it is time to detect the presence or absence of breakage of the drill 9, and therefore it is determined that the drill 9 is not damaged.
It is judged by. Further, after the output voltage reaches the maximum as shown by the solid line in FIG. 1, the cutting resistance by the drill 9 decreases again, so that the output voltage slightly decreases, and then increases due to the drift characteristic of the piezoelectric element 23 itself, and the amplifier 28 is overloaded. At the time of loading, the output voltage becomes maximum.

On the other hand, when the drill 9 is damaged, the cutting resistance does not increase even after the start of cutting,
The voltage output from the piezoelectric element 23 only gradually increases as shown in the lower part of FIG. 1, and the output voltage does not exceed the set value at the thrust reaction force detection timing and the initial stage of the start of drilling. The circuit 29 determines that the drill 9 is damaged.

If the drill 9 is damaged at the initial stage of the start of drilling, the cutting thrust reaction force drops sharply.
The voltage output from the piezoelectric element 23 suddenly decreases, and therefore the detection voltage of the piezoelectric element 23 does not exceed the set value Vs at the detection time, and the damage determination circuit 29 detects the damage state of the drill 9. More specifically, each piezoelectric element 23 resets the signal at a position before the damage detection position by a predetermined amount, and outputs a signal for damage detection about 2 to 3 mm after the start of cutting. As a result, the piezoelectric element 2
3. The breakage of each drill 9 can be reliably detected without any influence of the overload of the amplifier 28.

The higher the sensitivity of the piezoelectric element 23, the faster the overload time of the amplifier 28. In this embodiment, however, the piezoelectric element 23 is reset immediately before the start of machining, and the drill 9 is checked for damage during the process of gradually increasing the detection voltage. Since the determination is made, the detection accuracy can be improved. In addition, the high-sensitivity piezoelectric element 23
Can also be used.

As shown in FIG. 2, in a multi-spindle drilling machine in which the lengths of the plurality of drills 9, 9 are greatly different, when both drills are not damaged, accurate output is shown as a solid line and they are damaged. In this case, a curve without an increase in voltage is obtained, and it is possible to accurately determine whether the curve is normal or abnormal with high sensitivity.

The present invention can be embodied as follows. (1) As the detection element for detecting the processing resistance, a sensor such as a semiconductor strain gauge may be used.

(2) It is possible to set a time from the reset time to detect the presence or absence of damage by a timer.

[0027]

As described above in detail, the present invention resets the signal for tool breakage detection for each tool of the multi-axis head immediately before the start of each processing, so that the detector can be used even for tools with greatly different detection positions. Accurate output can be obtained without being affected by peculiar overload and drift, and highly accurate detection is possible. In addition, the present invention also enables the use of a highly sensitive detection element, which has the effect of significantly improving the accuracy of tool damage detection.

[Brief description of drawings]

FIG. 1 is a graph showing an embodiment embodying a tool breakage detection method of the present invention.

FIG. 2 is a graph illustrating a tool breakage detection method.

FIG. 3 is a schematic front view showing a multi-axis drilling machine.

FIG. 4 is a cross-sectional view near a main shaft that supports a drill.

FIG. 5 is a block circuit diagram of a tool breakage detection device.

[Explanation of symbols]

9 ... Drill as tool, 12 ... Rotary shaft, 20 ... Thrust reaction force detection unit, 21 ... Piezoelectric element housing ring, 2
2 ... Power transmission ring, 23 ... Piezoelectric element as detection element, 28 ... Amplifier, 29 ... Damage determination circuit, 30 ... Reset circuit.

Claims (3)

[Claims] 1. A multi-axis head processing machine for performing a plurality of processes on a workpiece by feeding a multi-axis head holding a plurality of tools toward the workpiece, and detecting a machining resistance acting on each tool. Then, a plurality of detectors that output a signal proportional to the machining resistance are provided.These detectors are reset immediately before the start of machining with each tool, and the output signal shows the set value at a predetermined position after the start of machining. A method for detecting tool breakage in a multi-axis head machine, characterized by judging whether or not the tool is exceeded, and judging the breakage of each tool. 2. A multi-axis head processing machine for performing a plurality of processes on a workpiece by feeding a multi-axis head holding a plurality of tools toward the workpiece, and a supporting member for supporting a spindle of each tool. A sensing element for sensing the respective machining resistance is received between the spindle and the spindle at a location where the machining resistance during machining is received, and an amplifier for amplifying an output signal is connected to the sensing element via a lead wire, The amplifier is equipped with a damage determination circuit that compares the signal output from the detection element with a preset value to determine the presence or absence of damage, and the damage determination circuit is provided with a damage detection position corresponding to each tool. A tool breakage detection device in a multi-axis head processing machine, wherein a reset circuit for resetting the output signal of each detection element is provided before a predetermined position prior to the damage detection operation. 3. The tool breakage detection device according to claim 2, wherein the detection element is a piezoelectric element, and the output signal is a voltage value.