JP2553227B2 - Tool damage detection method for machine tools - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tool damage detection method for a turning machine tool represented by an NC lathe.

Conventional technology For example, in an NC lathe intended for boring,
In addition to the spindle drive motor, the load current values of the motor attached to the two-degree-of-freedom feed device of the tool are monitored, and these current values are compared with the preset reference current value. There are known methods of detecting damage to the.

For example, as shown in Fig. 5, the load current value i ₁ of the motor when the cutting tool is damaged is higher than the load current value i ₂ when the cutting tool is not damaged due to an increase in cutting resistance. Therefore, by setting in advance a reference current value i ₀ that is slightly higher than the load current value i ₂ when the bite is normal, when the load current value exceeds the reference current value i ₀ It outputs an abnormal signal to the NC controller side of the lathe.

Problems to be Solved by the Invention In the conventional tool damage detection method, for example, in the case of cutting allowance and rough cutting with a large feed rate, the constant wear of the tool itself or the cutting allowance of the material (rough material) is more than the current increase due to the tool damage The variation of the current value due to the variation is larger, and it is difficult to distinguish it from the tool breakage. Even if the tool breaks, it is extremely difficult to detect it accurately.

Especially for NC lathes with a machining program that immediately shifts to roughing with a roughing tool and then finishes with a finishing tool, if damage to the roughing tool is not detected, the finishing allowance will be left due to the uncut portion of the roughing tool. There is a risk that even the finishing tool may be damaged due to fluctuations in.

The present invention has been made in view of the problems as described above, and the purpose thereof is to perform wear of the tool itself and a cutting allowance of a material (coarse material) when performing finish cutting following rough cutting as described above. Without being affected by the
An object of the present invention is to provide a method capable of accurately detecting breakage of a rough cutting tool.

Means for Solving the Problems The present invention is directed to a turning machine tool that performs a roughing and then a finishing tool using a finishing tool different from the roughing tool, by moving the tool along a preset tool path. In addition to the tool path for finishing and the tool path for rough cutting, the idle tool path for idle machining is set in advance at a position slightly away from the tool path for roughing. Set a slightly higher reference current value in advance, move the finishing tool with the idle tool path after the rough cutting and before the finish cutting, and the actual load current value and reference current value of the tool feeding device at that time It is characterized by detecting the damage of the tool for rough cutting by comparing with.

Action According to this method, if the rough cutting tool is damaged, the cutting allowance at the time of finish cutting will be large due to the influence, so the actual cutting is performed by the finishing tool during the idle machining before the finish cutting, while the rough cutting bite If the value is appropriate, the machining allowance at the time of finish cutting is also appropriate. Therefore, during the idle machining, the actual machining is not performed by the idle machining.

Then, as described above, when the actual cutting is performed during the idle machining, the load current of the tool feeding device becomes a value according to the cutting load, whereas when the actual machining is not performed during the idle machining, Indicates a no-load current value, and the difference between the two is large. Therefore, it is possible to accurately detect damage to the rough cutting tool by comparison with the reference current value.

Embodiment FIG. 1 and FIG. 2 are views showing an embodiment of the present invention.
The example of the N lathe for the purpose of boring processing is shown.

As shown in the figure, the spindle 1 is provided with a chuck 3 for gripping the workpiece 2 at its tip, and is driven to rotate by a spindle motor 4. On the other hand, the tool rest 5 includes a rough cutting tool 6 and a finishing tool 7, and the tool rest 5 has an X-axis feed device 9 centered on the X-axis motor 8 and a Z-axis feed device centered on the Z-axis motor 10. 11 gives the feed in the X and Y directions.

Then, as a machining procedure, as shown in FIG. 2, the end surfaces 2a, 2b of the work 2 are roughly machined by the rough cutting tool 6, and then the inner peripheral surface 2c of the work 2 is also roughly machined by the rough cutting tool 6. Furthermore, after finishing rough cutting of the inner peripheral surface 2c, finishing bit 7
By the same way, the inner peripheral surface 2c is also finish-ground. Here, the locus of the tip of the rough cutting tool 6, that is, the tool path of the rough cutting tool 6 during rough cutting of the inner peripheral surface 2c is indicated by reference numeral 12, and the tool path of the finishing cutting tool 7 is indicated by reference numeral 13.
Reference numeral 14 indicates a rough shape of the work 2 before cutting.

Load current value I _S , I of each motor 4,8,10 during cutting
_X and I _Z are monitored by the load current detecting device 18 through the spindle controller 15 and the X and Z axis servo amplifiers 16 and 17, and the load current values I _S , I _X and I _Z are the current value comparing units 19 respectively. , 20, 21 are compared with the reference current values I ₁ , I ₂ , I ₃ . Reference current value I ₁ , I
₂ and I ₃ are preset in the reference current value setting units 22, 23 and 24 independently provided for the motors 4, 8 and 10, respectively.

If any of the load current values I _S , I _X , and I _Z exceeds the corresponding reference current value, it is judged that the load current has increased due to an increase in cutting resistance due to the damage to the cutting tool, and an abnormal signal An abnormal signal is output from the output unit 25 to an NC controller (not shown), and a predetermined alarm is issued, for example, to prompt the operator to change the tool.

In the present embodiment, using the Z-axis feed device 11, as shown in FIGS. 2 and 3 and 4 as a machining mode, after the rough machining is completed and before the finish machining is performed, the blanking tool path 26 is used. A machining program is set in advance to move the finishing bit 7 to perform so-called idle machining. The tool path 26 at the time of idle machining is a position slightly escaped from the tool path 12 at the time of rough cutting, and the rough cutting is performed by the rough cutting tool 6 having the regular cutting edge shape to cut the workpiece 2. The position is set so that it will not occur.

Correspondingly to this, the reference current value setting unit 23 sets the load current value I _Z1 of the Z-axis motor 10 ( _Z The reference current value I ₃ is set to a value slightly higher than the figure).

On the other hand, the switch 27 of FIG. 1 operates at the same time when the idling machining start command is received, and the load current value I _Z of the Z-axis motor 10 is set to the current value only while the idling machining is being performed. Captured in the comparison unit 21. As a result, the load current value I _Z is compared with the above reference current value I ₃ .

That is, as shown in FIG. 2 and FIGS. 3 and 4, after performing rough cutting with the rough cutting tool 6 under the tool path 12,
Prior to the finish cutting in the tool path 13, the blanking tool 7 is used to perform the blanking work under the blanking tool path 26.

At this time, for example, when the rough cutting tool 6 is damaged due to a breakage of the cutting edge of the rough cutting tool 6 or the like, the dimension after the rough cutting is not a regular dimension, and uncut portions are left. Therefore, when the finishing bit 7 is moved under the idling tool path 26 to perform the idling, the cutting current causes the actual cutting to be performed. Therefore, the cutting resistance causes the load current value I _Z of the Z-axis motor 10 to be changed. As shown in FIG. 4, it becomes higher and exceeds the reference current value I ₃ . As a result, as described above, the breakage of the rough cutting tool 6 is detected, and the abnormal signal output section 25 of FIG. 1 outputs an abnormal signal.

On the other hand, if the cutting edge of the rough cutting tool 6 is normal and the dimension after rough cutting is a normal dimension, the workpiece 2 will not be cut even if idle machining is performed with the finishing tool 7, so that the Z-axis motor 10 The load current value I _Z becomes the no-load current value I _Z1 and does not exceed the reference current value I ₃ . Then, unless breakage of the rough cutting tool 6 is detected, finish machining is performed by the finishing tool 7 under the tool path 13 of FIG.

As described above, according to the present embodiment, a large difference in the load current value I _Z appears during the idling machining between when the rough cutting tool 6 is damaged and when the rough cutting tool 6 is not damaged. As a result, even if the finishing bit 7 advances rapidly during the finishing, it is possible to prevent the tool from being damaged due to the collision between the uncut portion and the finishing bit 7 during the rough cutting.

EFFECTS OF THE INVENTION As described above, according to the present invention, after finishing roughing and before finishing, the finishing tool is moved under the blanking tool path slightly released from the tool path at the time of roughing to perform the blanking machining. By doing so, there is a large difference in the load current of the tool feeder between when there is uncut material due to damage to the rough cutting tool and when there is no uncut material. The damage of the rough cutting tool can be accurately detected without being affected by the steady wear of, and the reliability of the tool damage detection is improved.
Further, there is an effect that it is possible to prevent the finish tool from being damaged due to the damage of the rough cutting tool as in the conventional case.

[Brief description of drawings]

FIG. 1 is an explanatory view of the structure of the main part of an NC lathe to which the method of the present invention is applied, FIG. 2 is an explanatory view showing the mutual relation of each tool path, and FIG. 3 is an operation under the structure of FIG. FIG. 4 is an explanatory diagram showing a change in load current during cutting, and FIG. 5 is an explanatory diagram showing a change in load current in a conventional tool breakage detection method. 1 ... spindle, 2 ... work, 4 ... spindle motor, 6 ...
Roughing tool (roughing tool), 7 ... Finishing tool (finishing tool), 8 ... X-axis motor, 9 ... X-axis feed device,
10 …… Z-axis motor, 11 …… Z-axis feed device, 12 …… Rough cutting tool path, 13 …… Finishing tool path, 18
...... Load current detection device, 19,20,21 …… Current value comparison unit, 2
2, 23, 24 …… Reference current value setting part, 26 …… Missing tool path.

Claims (1)

(57) [Claims] 1. A turning machine tool for moving a tool along a preset tool path, performing roughing, and then finishing using a finishing tool different from the roughing tool, the tool for roughing and finishing. Separately from the path, the idle tool path for idle machining is set in advance at a position slightly away from the tool path for rough cutting, while the standard of a value slightly higher than the load current value of the tool feed device during this idle machining. The current value is set in advance, the finishing tool is moved by the idle tool path after the rough cutting but before the finish cutting, and the actual load current value of the tool feeding device at that time is compared with the reference current value to perform the rough cutting. A tool damage detection method for a machine tool, which is characterized by detecting damage to a tool.