JPH03213249A - Monitoring method for tool utilizing heat flow measurement - Google Patents

Abstract

PURPOSE:To high accurately and efficiently detect a change of machining resistance force, wearing condition, defect of chipping, etc., of a tool by arranging a heat flow sensor in the tool or in the vicinity of the tool, and measuring a heat flow generated by machining heat of the tool. CONSTITUTION:When a heat flow sensor 2 is mounted on a surface of a tool holder, machining heat is diffused in the tool holder, to partly permeate through the heat flow sensor 2, and dispersed into the air when cutting is performed by a tool 1. A heat flow, detected by the heat flow sensor 2, is converted into a voltage signal, amplified by an amplifier 11 and recorded in a monitoring data recorder 12. A condition of the tool can be judged by detecting a maximum value of the heat flow from this record. On the other hand, the voltage signal is input to a computer 14 through an A/D converter 13 from the amplifier 11 to recognize a change pattern of the heat flow and its maximum value, and machining resistance force, wearing condition and a defective condition of the tool 1 are judged from these data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for monitoring tools using heat flow measurement, and more specifically, by monitoring heat flow caused by machining heat, chipping of tools This invention relates to a method for detecting defects, wear, entanglement of cutting chips, etc.

[Background technology] In recent years, in promoting automation and unmanned production as typified by FMS (flexible manufacturing systems), it is important to establish monitoring technology that can recognize cutting and tool conditions in-process. This is an extremely important issue in achieving greater sophistication and intelligence.

As a method for detecting defects such as chipping and wear of a tool, a method using an AB sensor is conventionally known. When an object breaks, minute cracks occur inside the object.
As the crack progresses, elastic energy is released, generating elastic waves (ultrasonic waves) inside the object. This elastic wave is called AE (acoustic emission) and can be detected by an AE sensor. In other words, the AE sensor detects the sound of an object being destroyed, and in the conventional method, the AE sensor attached to the table or tool of the processing machine detects AE and detects damage such as chipping and wear of the tool. Detected. To explain more specifically, the output from the monitoring system using the AE sensor is a continuous high-frequency wave with small amplitude.
This is a noise-like) AE signal, and if chipping or the like occurs in the tool, a pulse-like AE multiplied signal with a large amplitude is generated in the noise-like AE multiplied signal, so the AE sensor detects the signal with an amplitude exceeding the threshold value. When a large AE multiplied signal is detected, it is determined that a loss or the like has occurred.

[Problems to be Solved by the Invention] However, in the method of detecting tool breakage etc. using an AE sensor, since the AE sensor picks up external noise and surrounding vibrations, the signal of external noise etc. picked up by the AE sensor is There is a problem that it becomes a noise component and lowers the signal-to-noise ratio of the AB multiplied signal, and is vulnerable to external noise and surrounding vibrations. especially,
Various types of noise are generated inside factories, which is an important problem.

Additionally, if machining oil or the like is applied to the cutting point of the tool, the friction coefficient between the tool and the workpiece decreases, causing AE to no longer occur or the AE signal level to change, resulting in tool wear and damage. etc. may not be able to be measured correctly.

In addition, the AE sensor attached to tools etc.
With the method of detecting E (elastic waves), there are locations where AE cannot be detected due to vibration-specific causes (for example, interference between AE and reflected waves from the tool surface), so when installing the AE sensor, it is necessary to You need to find a location to install it.

Moreover, if the size or shape of the tool changes, the installation position of the AE sensor also changes, so if the type of tool changes, the installation position of the AE sensor also needs to be changed, which is troublesome.

Furthermore, if the type of processing machine such as a lathe, milling machine, or surface grinder changes, or if the type of tool or material to be cut changes, the frequency distribution of the generated AE may change. If the AE sensor changes, it is necessary to change the AE sensor to a different model, resulting in a problem of lack of versatility.

Furthermore, during light load machining, it was difficult to obtain a signal-to-noise ratio, making it difficult to evaluate the state of tool wear.

Furthermore, since the AE sensor has a large external dimension, when it is attached to a relatively small tool, etc., it is easy to limit the mounting position. Moreover, it is also expensive.

In addition, since the AE sensor is a method of detecting AE caused by chipping or the like, it is possible to detect the chipping that occurs, but it is difficult to predict the occurrence of chipping in advance.

The present invention was made in view of the drawbacks of the conventional examples described above, and its main purpose is to ensure tool wear even under light loads, without being affected by surrounding environmental conditions. It is an object of the present invention to provide a highly reliable and versatile tool monitoring method that can detect the following.

[Means for Solving the Problems] Therefore, in the tool monitoring method using heat flow measurement of the present invention, a heat flow sensor is disposed at or near the tool, and the heat flow generated by machining heat of the tool is detected by the heat flow sensor. It is characterized by monitoring tool characteristics such as machining resistance, wear status, and chipping status of the tool through measurement.

[Function] The present invention monitors the wear of tools by detecting the heat flow generated by machining heat. and can be detected efficiently (details will be described in the Examples section).

In addition to detecting tool breakage, it is also possible to predict the occurrence of tool chipping in advance.

Furthermore, compared to a detection method using an AE sensor, this method is less susceptible to ambient disturbances and noise, and rapid changes in ambient temperature are extremely rare, allowing for stable monitoring. In addition, the output from the heat flow sensor has an extremely good signal-to-noise ratio, and the heat flow characteristic curve changes significantly, so tool wear during light load machining can be easily evaluated. It is possible to carry out highly accurate and reliable monitoring without any impact even if the

Furthermore, the monitoring method of the present invention does not detect vibrations like a monitoring method using an AE sensor, but instead detects heat flow, so there is no undetectable position, and the heat flow sensor is not detected by the AE sensor. Since it is relatively small, there are fewer restrictions on the position of the AE sensor when it is attached to tools, etc. In addition, even if the type of tool, workpiece material, processing machine, etc. changes, there is no need to replace the heat flow sensor with a different model or change the mounting position of the heat flow sensor, making it highly versatile and easy to handle. It's easy.

Furthermore, since the heat flow sensor is less expensive than the AE sensor, an inexpensive monitoring system can be constructed.

[Example] Hereinafter, one embodiment of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 shows a basic configuration for monitoring wear, damage, etc. of a cutting tool using heat flow measurement.

A heat flow sensor 2 for measuring heat flow is mounted on the surface (in the illustrated example, the side surface) of the tool holder 3 in the vicinity of the tool (chip) 1, as shown in FIG. 1 or FIG. 2 (a) (b:l). It is attached in close contact with the

Heat flow (heat flux) q generally represents the amount of heat that passes through a unit area of a target surface in a unit time, and is expressed as q=c (dT/d
t) is defined as: Here, C is the heat capacity of the target surface (in this case, the heat flow sensor 2), T is the temperature, and t is time, and the heat flow is the time differential of the temperature T multiplied by the constant C. As the heat flow sensor 2 for measuring the heat flow defined in this way, for example, a transmission heat flow sensor (Schmidt type heat flow sensor) having a thin plate structure as shown in FIG.
There is. This consists of a thermopile 6 formed spirally on the surface of a thermal resistor 5, which is covered with a cover material 7, and a temperature difference ΔT occurring between both surfaces of the thermal resistor 5 is detected by a thermomobile 6. The heat flow q passing through the heat flow sensor 2 is measured according to the relational expression =λ(ΔT/d). Note that d is the thickness of the thermal resistor 5, and λ is the thermal conductivity of the thermal resistor 5.

As shown in FIG. 1, when the heat flow sensor 2 is attached to the surface of the tool holder 3, when cutting is performed with the tool holder 1, the machining heat generated at the cutting point of the tool holder 3 is transferred to the tool holder 3. A part of it passes through the heat flow sensor 2 and is dissipated into the air. At this time, the value of the heat flow q that passes through the heat flow sensor 2 can be measured, so that the machining resistance of the cutting tool 1 can be evaluated and wear and damage of the cutting tool 1 can be monitored.

Note that, as shown in FIG. 3, the heat flow sensor 2 attached to the surface of the tool holder 3 may be covered with a heat insulating cover 4. The heat insulating cover 4 is made of a Bakelite square material, and is attached to the heat flow sensor 2 through a gap without being brought into close contact with the heat flow sensor 2 in order to enable heat dissipation from the heat flow sensor 2. thus,
When the heat flow sensor 2 is covered with a heat insulating cover 4,
Since the heat flow sensor 2 can be protected from thermal disturbances caused by cutting waste discharged from the workpiece and changes in the temperature of the outside air, tool wear etc. can be detected efficiently, and heat flow The reliability of tool monitoring using the sensor 2 can be increased.

Furthermore, the heat insulating cover 4 can protect the heat flow sensor 2 from damage caused by cutting debris and the like.

Next, the principle of the tool monitoring method using heat flow measurement will be explained. FIG. 5 is a characteristic curve showing the temperature rise T of the heat flow sensor during the cutting process, and FIG. 6 is a characteristic curve showing the change in the heat flow q passing through the heat flow sensor during the cutting process. That is, although the characteristic curve in FIG. 8 is directly measured using a heat flow sensor, it can also be obtained by time-differentiating the characteristic curve in FIG. 5 and multiplying it by a constant. In FIGS. 5 and 6, t is the processing start time.

is machining end time, Δ1 (=1.-1.) is machining time, t
1 is the delay time from the start of processing until the temperature starts to rise. Moreover, qo indicates the maximum value of the heat flow q in the characteristic curve of FIG.

As is clear from FIG. 5, the temperature of the heat flow sensor gradually increases smoothly during the machining process, and the temperature continues to rise even after the machining is completed. Then, as the wear and chipping of the tool progresses and the machining resistance increases, the overall temperature rise increases and the characteristic curve in FIG. 5 moves upward. Therefore, it is conceivable to detect wear and tear of the cutting tool based on temperature rise, but in addition to the small amount of temperature change, it is also difficult to set the timing and threshold value for evaluating tool wear, etc.

On the other hand, as a result of experiments, if we pay attention to the slope of the characteristic curve in Fig. 5, that is, the characteristic curve representing the heat flow in Fig. 8, we find that
It became clear that changes in machining resistance of tools can be accurately evaluated. In other words, it has been found that as the tool wear progresses and the machining resistance increases, the maximum value of the slope of the characteristic curve shown in FIG. 5 gradually changes and becomes larger. In FIG. 6, as the wear of the tool progresses, the maximum value qc of the heat flow in the characteristic curve gradually increases, and the characteristic curve in FIG. 6 gradually becomes a vertically elongated pattern.

Therefore, the maximum slope of the characteristic curve (FIG. 5) representing the temperature rise or the maximum value q of the characteristic curve (FIG. 6) representing the heat flow. It is possible to easily determine the magnitude of cutting resistance from the magnitude of , and the wear state of the tool can be accurately detected. Furthermore, if the tool becomes entangled with cutting chips or damage such as chipping occurs, the slope or the maximum value of heat flow q
. Since this increases, tool abnormalities can be quickly detected. In addition, the gradient or the maximum value qc of heat flow is
When a preset threshold value is exceeded, it can be determined that it is time to replace the tool.

However, it is clear that it is easier to read the maximum value of the characteristic curve of FIG. 6 than to read the slope from the characteristic curve of FIG. Moreover, the characteristic curve in Fig. 6 has a larger amount of change than that in Fig. 5, and the evaluation position (maximum point)
is also clear. Furthermore, the characteristic curve shown in FIG. 6 rises faster than the characteristic curve shown in FIG. 5, and the machining state can be grasped more sensitively. Therefore, it is clear that a method of directly monitoring heat flow is superior to using a gradient of temperature rise.

Note that it is also possible to detect the temperature rise and monitor it by, for example, processing it with a computer to determine the slope (time differential) of the temperature rise curve, but if the heat flow is directly detected by a heat flow sensor as in the present invention, , the device becomes simpler and more compact, and the price of the device can also be lowered. Furthermore, since calculation errors are not introduced, monitoring accuracy is also improved.

FIG. 7 shows a schematic configuration diagram of an example of an in-process monitoring system for tools. This shows a monitoring system when cutting a workpiece 9 held by a chuck 8 with a cutting tool l. A cutting tool l with a heat flow sensor 2 attached to its side is held on a tool post lO, and the heat flow detected by the heat flow sensor 2 is converted into a voltage signal, and after being amplified by an amplifier 11, its analog output is It is recorded on a data recorder 12 for monitoring. Therefore, the system administrator can know the maximum value of heat flow by looking at this data recorder 12. On the other hand, the analog output from the amplifier 11 is converted into a digital signal by the A/D converter 13 and then input to the computer 14 for computer processing.

That is, the computer 14 recognizes the change pattern or maximum value of the heat flow, and evaluates the machining resistance, wear state, and defect state of (b) 1 based on these data.

Furthermore, if it is determined that the wear of the tool bit 1 has progressed and it is time to replace the tool tool 1, or if damage such as chipping of the tool tool l is detected, or if it is predicted that the tool tool l will be damaged, the computer A control signal is outputted from 14 to the production system, and the exhausted byte l is automatically replaced with a new byte l. The exchange of bytes l is, for example,
This can be done by attaching a plurality of cutting tool holders 3 to which heat flow sensors are attached to the tool post 10 and rotating the tool post to move another cutting tool to the cutting location.

Therefore, by incorporating an in-process monitoring system as described above into such an FMS, automation and unmanned production can be further promoted.

In addition, although the above embodiment has been explained by taking cutting processing using a cutting tool as an example, there is no reason why the field of application of the present invention is limited to cutting processing. It can also be used to monitor breakage of drills, etc. during drilling operations. Moreover, since various structures and installation methods of heat flow sensors are known in addition to those described above, heat flow sensors having a structure other than that shown in FIG. 4 may be used.

[Effects of the Invention] According to the present invention, changes in machining resistance of a tool, wear conditions, and defects such as chipping can be detected efficiently with high accuracy. Furthermore, in addition to detecting tool breakage, it is also possible to predict tool breakage and replacement timing in advance based on changes in heat flow characteristic curves, etc., and replace the tool before it is damaged. Therefore, it will be possible to greatly contribute to unmanned and automated FMS.

Moreover, when compared to the tool monitoring method using AB sensors, ■ it is less affected by ambient noise and can perform stable monitoring, and ■ tool wear during light load machining can be easily evaluated. Furthermore, even if machining oil etc. gets on the tool, it will not be affected and can perform highly accurate and reliable monitoring. ■The heat flow sensor is small and can be installed anywhere, so it can be installed on tools etc. There are few restrictions on the mounting position. Even if the type of tool or workpiece material changes, there is no need to replace the heat flow sensor with a different model or change the mounting position, making it highly versatile. expensive,
■It has advantages such as being able to construct an inexpensive monitoring system.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the basic configuration of an embodiment of the present invention;
2(a) and 2(b) are a plan view and a side view of the same as above, FIG. 3 is a perspective view showing an embodiment in which the heat flow sensor is covered with a heat insulating cover, and FIG. 4 is a principle diagram showing the outline of the heat flow sensor, Figures 5 and 6 are graphs showing the temperature rise characteristics and heat flow change characteristics of the heat flow sensor during the machining process, and Figure 7 is a schematic configuration of an in-process monitoring system that uses heat flow measurement to monitor tool wear, etc. It is a diagram. 1...Bite 2...Heat flow sensor 3...Bite holder

Claims (1)

[Claims] (1) Place a heat flow sensor on the tool or near the tool,
A tool monitoring method using heat flow measurement, characterized in that tool characteristics such as machining resistance, wear state, and chipping state of the tool are monitored by measuring heat flow generated by machining heat of the tool with the heat flow sensor.