JPH0453652A - Detection of tool breakdown for machine tool - Google Patents

Abstract

PURPOSE:To detect the breakdown of a cutting tool, by moving a finishing tool along a simulation tool path, and comparing the actual load current value with a reference current value of the tool feeding device at that time. CONSTITUTION:Simulation machining is performed with a finishing tool 7 with a simulation tool path 26 prior to the finishing cut with a tool path 13, after performing a rough cutting by a rough cutting tool 6 with a tool path 12. At this time in case the rough cutting tool 6 is broken, cutting is left remaining without the dimension after rough cutting being of a normal dimension tool. When simulation machining is performed by moving the finishing tool 7 following the simulation tool path 26, the load current value I2 of a Z axes motor 10 is increased by the cutting resistance and exceeds a reference current value I3, because of cutting being performed actually despite being a simulation work. Consequently, an abnormal signal is output from an abnormal signal output part 25 with the breakdown of the rough cutting tool 6 being detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a tool damage detection method for turning machine tools such as NC lathes.

Conventional technology For example, in an NC lathe for the purpose of polling,
By monitoring the load current value of the motor attached to the feeder in the direction of the tool's two-axis degrees of freedom, and comparing these current values with a preset reference current value. Methods of detecting tool damage are known.

For example, as shown in Fig. 5, the motor load current value 11 when the cutting tool is damaged is higher than the load current value i when the cutting tool is not damaged due to an increase in cutting resistance. From this, the load current value when the cutting tool is normal is 1. By setting in advance a reference current value 10 that is slightly higher than the reference current value 10, when the load current value exceeds the reference current value 10, an abnormal signal is output to the NC controller of the lathe, prompting, for example, to change the cutting tool. It is something.

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

Particularly in the case of NC lathes for machine programs, where rough cutting with a rough cutting tool is immediately followed by finishing cutting with a finishing tool, if damage to the rough cutting tool is not detected, the finish machining allowance will be removed due to uncut material due to damage to the rough cutting tool. There is a risk that even the finishing tool will be damaged due to fluctuations in the cutting speed.

The present invention was made in view of the above problems.
The purpose of this is to accurately detect damage to the rough cutting tool when performing finish cutting following rough cutting, as described above, without being affected by wear of the tool itself or variations in the cutting allowance of the material (rough material). The goal is to provide a method that makes it possible.

Means for Solving the Problems The present invention provides a turning machine tool in which a tool is moved along a preset tool path and, following rough cutting, finishing cutting is performed using a finishing tool different from the rough cutting tool.
Separately from the tool paths for roughing and finishing, a missing tool path for missing cutting is preset at a position slightly removed from the tool path for rough cutting, and the load current value of the tool feeder during this missing cutting is set in advance. A slightly higher reference current value is set in advance, and the finishing tool is moved in a missed tool pass after the rough cutting but before the finishing cut, and the actual load current value of the tool feeder at that time and the reference current are The feature is that damage to the rough cutting tool is detected by comparing the values.

Effect According to this method, if the rough cutting tool is damaged, the cutting allowance during finish cutting will become larger as a result, so the actual cutting is performed by the finishing tool during the blank machining prior to finishing cutting, while the rough cutting If the rebiting is appropriate, the cutting allowance during finish machining is also appropriate, so during blank machining, it is just blank machining and no actual cutting is performed.

As mentioned above, when cutting is actually performed during blank machining, the load current of the tool feeder becomes a value corresponding to the cutting load, whereas when actual machining is not performed during blank machining, is the no-load current value and there is a large difference between the two, so it becomes possible to accurately detect damage to the rough cutting tool by comparing it with the reference current value.

Embodiment FIGS. 1 and 2 are diagrams showing an embodiment of the present invention, and show an example of an NC lathe intended for poling processing.

As shown in the figure, the main spindle 1 is provided with a chuck 3 at its tip for gripping a workpiece 2, and is rotationally driven by a main spindle motor 4. On the other hand, the tool rest 5 is equipped with a rough cutting tool 6 and a finishing tool 7, and this tool rest 5 is equipped with an X-axis motor 8.
Feed in the X and Y directions is provided by an X-axis feed device 9 centered around the X-axis feed device 9 and a two-axis feed device 11 centered around the two-axis motor 10 .

The processing procedure is as shown in Figure 2.
After rough cutting the end faces 2a and 2b of the workpiece 2 with a rough cutting tool 6, the inner circumferential surface 2C of the workpiece 2 is rough cut using the same rough cutting tool 6. Furthermore, following the rough cutting of the inner circumferential surface 2C, the finishing cutter 7 similarly performs finish cutting on the inner circumferential surface 2c.

Here, the rough cutting tool 6 during rough cutting of the inner peripheral surface 2C
The locus of the tip of the tool, that is, the tool path of the rough cutting tool 6 is indicated by 12, and the tool path of the finishing tool 7 is indicated by 13. 14 shows the rough shape of the workpiece 2 before cutting.

The load current values Is, lx, Iz of each motor 4, 8.10 during cutting are monitored by the load current detection device 18 through the spindle controller 15 and the X-axis and Z-axis servo amplifiers 16.17. Current value 1s,
1. , 1□ are compared with reference current values II, L, I- in the current value comparison section 19°20.21. Reference current value! , ,I, ,1. is set in advance in the reference current value setting sections 22, 23, 24 provided independently for each motor 4, 8, 10.

If any of the load current values 1-, lx, and Iz exceeds the corresponding reference current value, it is determined that the load current has increased due to an increase in cutting resistance due to tool breakage,
An abnormality signal is outputted from the abnormality signal output section 25 to an NC controller (not shown), and a predetermined alarm is issued, for example, to prompt the operator to replace the tool.

In this embodiment, as a machining mode using the Z transport device 11, as shown in FIGS. 2 and 3.4, after rough machining is completed and before proceeding to finish machining, after the missing tool pass 26, A cutting program is set in advance to move the finishing tool 7 to perform so-called missed machining. The tool path 26 during this blank machining is a position that is slightly missed from the tool path 12 during rough machining, and if the rough machining tool 6 with the regular cutting edge shape is rough-machined according to the regular dimensions, the workpiece 2 will be cut. It is set in such a position that there is nothing to do.

Correspondingly, the reference current value setting unit 23 stores the load current value I2.
(Fig. 4) at a value that slightly exceeds the reference current value I,
is set.

On the other hand, the switch 27 shown in FIG. 1 operates at the same time as the start of the blank machining in response to the above-mentioned blank machining start command, and changes the load current value I2 of the Z-axis motor 10 only while the blank machining is being performed.
is taken into the current value comparison section 21. As a result, the load current value I2 is the above reference current value! , compared to .

That is, as shown in FIGS. 2 and 3.4, after performing rough cutting with the rough cutting tool 6 under the tool path 12, before finishing cutting with the tool path 13, the rough cutting is performed under the missing tool path 26. Perform blank machining with finishing tool 7.

At this time, if the rough cutting tool 6 is damaged due to, for example, a chipping of the cutting edge of the rough cutting tool 6, the dimensions after rough cutting will not be the normal dimensions, and uncut parts will be left. Therefore, when the finishing tool 7 is moved under the missed retooling path 26 to perform missed machining, cutting is actually performed even though it is missed machining, and the load current value ■2 of the Z-axis motor 10 increases due to the cutting resistance. As shown in FIG. 4, the current becomes high and exceeds the reference current value I. As a result, damage to the rough cutting tool 6 is detected as described above, and an abnormal signal is output from the abnormal signal output section 25 in FIG.

On the other hand, if the cutting edge of the rough cutting tool 6 is normal and the dimensions after rough cutting are the normal dimensions, the workpiece 2 will not be cut even if the finishing tool 7 is used for machining. Load current value I2 is no-load current value 12
．． Therefore, it will never exceed the reference current value ■. Then, unless damage to the rough cutting tool 6 is detected, finish cutting is performed by the finishing tool 7 under the tool path 13 shown in FIG. 2 following the missed machining.

As described above, according to this embodiment, since there is a large difference in the load current value I2 during machining when the rough cutting tool 6 is damaged and when it is not, it is possible to ensure that the rough cutting tool 6 is not damaged. As a result, even if the finishing cutting tool 7 advances rapidly during finishing cutting, tool damage due to collision between the finishing cutting tool 7 and the uncut portion during rough cutting can be prevented.

Effects of the Invention As described above, according to the present invention, after rough cutting is completed and before finishing, the finishing tool is moved under a missing tool path that is slightly missed than the tool path during rough cutting to perform missing cutting. As a result, there is a large difference in the load current of the tool feeder between when there is uncut material due to breakage of the rough cutting tool and when there is no uncut material due to damage to the rough cutting tool. It is possible to accurately detect damage to rough cutting tools without being affected by steady wear, and the reliability of tool damage detection is improved. Furthermore, it is possible to prevent the finishing tool from being damaged due to damage to the rough cutting tool, which is the case in the past.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of the main parts of an NC lathe to which the method of the present invention is applied, Fig. 2 is an explanatory diagram showing the interrelationship of each tool path,
Fig. 3 is a flowchart for explaining the operation under the configuration shown in Fig. 1, Fig. 4 is an explanatory diagram showing changes in load current during cutting, and Fig. 5 is a flowchart for explaining the load current in the conventional tool breakage detection method. FIG. 3 is an explanatory diagram showing changes in current. 1...Spindle, 2...Workpiece, 4...Spindle motor,
6...Rough cutting tool (rough cutting tool), 7...Finishing tool (finishing tool), 8...X-axis motor, 9...X
Axis feed device, 10...Z-axis motor, 11...Z transport device, 12...Roughing tool path, 13...
Tool path for finish cutting, ]8...Load current detection device, 19°20.21...Current value comparison section, 22.23
, 241. . Reference current value setting section, 26... Missing tool path. 12: Tool path for milling 13: Tool path for sharpening 26: Tool path for blank machining

Claims (1)

[Claims] (1) In a turning machine tool that moves the tool along a preset tool path and performs rough cutting and then finish cutting using a finishing tool different from the rough cutting tool, the tool path for rough cutting and finishing cutting and Separately, a missing tool path for missing cutting is set in advance at a position slightly offset from the tool path for rough cutting, and a reference current value that is slightly higher than the load current value of the tool feeder during this missing cutting is set in advance. is set in advance, and after the rough cutting and before finish cutting, the finishing tool is moved with a missed tool pass, and the actual load current value of the tool feeder at that time is compared with the reference current value, and the rough cutting tool is adjusted. A tool damage detection method for a machine tool, characterized by detecting damage to a machine tool.