JPS59187439A - Tool damage detecting device - Google Patents

Abstract

PURPOSE:To extract wave forms accompanying abrupt rise of characteristic wave form and fall due to working heat included in the variation of level value when a tool is damaged, catch and calculate the time width and raised value of this wave form for automatically judging the damage of the tool. CONSTITUTION:A machine tool controlling circuit 3 is connected to the rear stage of a detecting section 1 through a tool damage detecting section 2 which is connected to the input sides of a CR circuit 4, a raised value comparator 5 and a maximum level value comparator 6. The detecting section 1 shapes the detected signal to convert it to voltage and send it to the detecting section 2. Also, the circuit 4 of the detecting section 2 figures out the differential value in the rise and fall of the output signal wave form of the detecting section 1. Further, the comparators 5, 6 compare respectively voltage generated from a reference voltage source with voltage from the detecting section 1. By this constitution can be automatically judged the damage of tool.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tool chipping detection device that can automatically detect when a tool is chipped during cutting or the like.

Numerical control and tracing control are performed in milling machines and the like to save labor in LD and machining.

In automatic machine tools that perform numerical control or tracing control, in order to improve the machining accuracy of the workpiece, they detect when a tool breaks, stop the machine tool using this detection signal, and It is necessary to generate an alarm.

Many proposals have been made to date for this purpose. Particularly in recent years, with the development of various detectors and signal processing techniques, there has been increasing interest in detection during milling, that is, in-process detection methods and devices.

In conventional tool chipping detection, cutting resistance, cutting temperature, vibration, spindle motor current,
A method has been used in which tool damage is indirectly detected by measuring and processing these signals, paying attention to changes in acoustic emissions and the like.

However, in such an indirect detection method, the detected signal and cutting force are , cutting temperature, vibration, spindle motor current, acoustic emission, and other signals are constant, and if there is a signal change when a tool breaks, it can be clearly distinguished, making it possible to detect it.

However, in numerical control or profile control machining, the shape of the workpiece usually changes in a complex manner, and this results in uneven cutting depth and width, making normal cutting difficult. There was a problem in that the detection signal fluctuated greatly even when the tool was damaged, making it difficult to distinguish it from when the tool was missing. That is, the conventional tool defect detection device is not suitable for practical use in the above-mentioned machining, and requires a person to monitor the cutting state during machining, which is a major obstacle to unmanned machining.

This invention eliminates such obstacles, can be applied to a wide variety of machine tools, can handle different cutting conditions depending on the shape of the workpiece, and enables indirect tool breakage detection during machining. It is an object of the present invention to provide a tool defect detection device.

The tool chipping detection device of the present invention utilizes the power or current (power consumption or current consumption) of the spindle motor of a machine tool during cutting, and detects the characteristics included in the level value fluctuation when a tool is chipped. By extracting the targeted waveform, that is, the waveform that accompanies the sudden rise when the tool breaks and the waveform that falls due to machining heat, capture the time width (period) and rise value of this waveform, and perform the modulation process, This allows automatic determination of tool damage.

Next, this invention will be explained using figures. - Figure 1 shows the relationship between the cutting time and the power or current value of the spindle motor in a cutting machine.

In numerical control or profile control machining, the power or current of the spindle motor during the cutting process under normal conditions fluctuates and is unstable, but when a defect occurs, it exhibits characteristic behavior.

Figure 1 shows this state, and as shown in this figure,
The level during normal cutting (the part to the left of a in the figure) fluctuates and is unstable when the shape of the workpiece changes complexly and when the depth of cut is uneven.

However, the part beyond a in Figure 1 (the right part) shows the state when the tool is missing, and since the power or current consumed by the spindle motor further increases or decreases, it can be distinguished from the previous situation. . When a tool breaks, the electric power or current changes characteristically because the broken part is caught between the workpiece and the tool, or because of an overload condition that is temporarily applied to the tool during the cutting process. This causes the 'C force or current to rise sharply, and then - due to the associated decreasing cutting forces with the resulting increase in cutting heat - to drop rapidly.

The present invention was made based on such a theory.
The object of the present invention is to provide a detection device that detects that point in time as the time when a tool becomes defective.

Next, one embodiment of this invention will be explained with reference to FIG.
1 is a power or current detection unit, and t7 (not shown)
JV4 [1] It is connected to the main shaft motor of the processing machine and constantly detects the level of sleepiness or current. A machine tool control circuit 3 is connected downstream of the detection section 1' through a tool loss detection section 2, which will be described in detail next.

The tool missing detection section 2, CR circuit section 4, rise (tit comparator 5, machining maximum level 11u comparator 6)
.

Connected to the input side. The detection section 1 shapes the detected signal, converts it into a voltage, and sends it to the tool loss detection section 2. The CR circuit section 4 of the tool loss detection section 2 calculates differential values when the output signal waveform of the detection section 1 rises and falls. The rising value comparator 5 and the highest level value comparator 6 are connected to a voltage generated by a reference voltage source (not shown) and a voltage from the detection unit 1, respectively. It is for comparison.

A slip-flop circuit 7 and a waveform calculation circuit 8 are connected to the rear stage of the CR circuit section 4, and the rear stage of the waveform calculation circuit 8 is
One input terminal of the AND circuit 9 is connected. /-1 at the other input terminal of the AND circuit 9, the above-mentioned rising value comparator 5
The output side of is connected. The output side of the AND circuit 9 is
It is connected to the input end of the machine tool control circuit 3 together with the maximum level value comparator 6 mentioned above. 1.degree. is for applying a signal from the waveform time width threshold setting circuit section 1o to the flip-flop circuit 7 as a control signal for the flip-flop circuit 7.

Next, to explain the operation of this cage configured in this way, first, the rise value comparator 5 and the highest level value comparator 6
Through experiments conducted in advance, we determined that the above-mentioned power and I
``Set it so that it responds to changes in the OiOi current.

This can be done by monitoring the waveform time width 11 rise value V, rise and fall differential value dV/dt, and M high level T in Figure @1.

The current of the machine tool spindle motor is detected by the detection unit 1, shaped there, and converted into pressure. The CR circuit section 4id of the tool missing detection section 2 calculates the differential voltage (dV/dt) when the output signal waveform of the detection section 1 rises and falls, and provides this to the slip-flop circuit 7 for storage. The waveform calculation circuit 8 at the next stage measures the waveform time width t, and identifies whether or not the coefficient waveform stored in the flip-flop circuit 7 is unique to the time of a loss.

As a result, if the waveform is compatible, the waveform time width threshold setting circuit section 10, the waveform time width signal circuit section 11, and the waveform calculation circuit 8 measure the waveform time width t, and calculate the time characteristic at the time of loss. If it is determined whether or not the waveform has a width, and if both the rise value V of the waveform conforms to the initial setting threshold,
The machine tool control circuit 3 is activated through the AND circuit 9 to effect an emergency stop of the machine tool. As in the missing embodiment, the level T is detected and the highest level value comparator 6
If the tool defect signal is obtained by comparing it with the highest level value, more reliable detection can be achieved.

As an example of the difference when a tool breaks, the differential value when ascending and descending when cutting steel is +5. OIcp・nl/sec~±4
．． 0 to 9 m/sec, and the waveform time width t is 0.5 seconds to 1.5 seconds. On the other hand, silk iron has +2.0 kg・m
/See~±4.0 to 7m/see, and the time is 05 seconds to 15 seconds as in the case of steel. To further explain this in the case of gASKDll as a specific example, the differential value at the time of rising and falling is +5.71 mark -m/H and -4,
0 kg m/g<, and the waveform time width t is 09 seconds. Id +3.6 k4- m / with rolled cast iron FC20
Tatsumi c and -5,0kg・m 15pr, waveform 1)
5i paper width t is 1.3 seconds.

As described above in detail along with the embodiments, according to the present invention, tool damage is detected by analyzing the behavior of each signal during the cutting process. In addition,
In the above embodiment, each block has been described as a separate unit, but some of these 1/'1 can be replaced as a whole with a microcomputer, a minicomputer, or the like.

Since this invention is configured as explained above, there is a result that the tool operation can be stopped by determining whether the tool is damaged or not.

[Brief explanation of drawings]

Figure 11 is a graph showing the relationship between electric power or commercial power consumption and cutting time; 1...Detection part 2...Engineer shortage inspection 1i-
Part 3 6...Machine tool control circuit 4...CR circuit section 5...Rise (++1.+
i4 comparator 7'・°Frinopfrosov circuit

Claims (1)

[Claims] A detection unit that detects changes in power or current of the machine tool spindle motor when a tool is missing, a CR circuit unit that calculates differential values with respect to time when the output signal of the detection unit rises and falls, and an output of the CR circuit unit. A flip-flop circuit that stores a signal, a waveform calculation circuit that determines whether the signal stored in the flip-flop circuit is unique to a pre-stored loss, and detects an increase value of the output signal of the detection section. A tool chipping device comprising: a rise value comparator; an AND path for inputting output signals of the rise value comparator and the waveform calculation circuit; and a machine tool control circuit connected to the AND circuit. Detection device.