JPH0797007B2 - A tool change time detection device based on the amount of wear - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a tool wear amount of a cutting tool or the like to detect a tool replacement time, and more specifically, an electric resistance value between the tool and the workpiece. The amount of tool wear is detected by measuring the change in
The present invention relates to a device for detecting a tool replacement time.

[0002]

2. Description of the Related Art In the field of machining, in order to replace a tool at an appropriate time, it is necessary to constantly monitor or detect the amount of tool wear or damage (hereinafter, these are collectively referred to as wear amount). Is.

Conventionally, the following various techniques have been proposed for detecting the tool wear amount. First, it is known that a television camera is used to detect the wear of a tool while directly monitoring it. In addition, the workpiece is irradiated with a laser beam and the reflected light is analyzed to detect the dimensional change of the workpiece,
It is also known that the tool wear amount is detected by this.
Furthermore, it is also known to detect the amount of tool wear from changes in temperature, cutting resistance, vibration, sound, etc. associated with tool wear.

However, each of the above-mentioned conventional examples has a complicated structure and is not always satisfactory in terms of reliability.

Therefore, the following technique has been proposed and publicly known as a detection method for solving such a problem.
(JP-A-59-81043) The detection method uses a tool having an insulating coating of alumina formed on the surface,
It measures the current flowing between the tool and the workpiece. That is, when the tool is worn and the insulating coating is destroyed, the current flowing between the tool and the workpiece rises sharply, and the sharp rise of this current is detected to determine the life of the tool.

[0006]

However, in the technique of replacing the tool by detecting the breakage of the insulating coating on the tool surface as described above, there are practical problems as follows.

First, since the above-mentioned conventionally known technique does not detect the amount of wear quantitatively (by area), the current value rises sharply even if the insulating film is slightly broken. For this reason, even a tool that is still usable may be determined to have reached the replacement time.

Further, since the tool replacement timing is determined from the state of the current rise, the determination requires skill and accurate knowledge, which cannot be easily determined by anyone.

SUMMARY OF THE INVENTION An object of the present invention is to provide a device for detecting the replacement time, in which the judgment of the replacement time of the tool is reliable and simple.

[0010]

In order to achieve the above object, the present invention is constructed as follows. A tool having an insulating coating formed on the surface of a base material, a fixing member provided in contact with the base material of the tool and fixing the tool to a holder, and an insulating layer electrically insulating the fixing member and the tool rest. , An electrical resistance meter provided to measure the electrical resistance value between the tool and the workpiece, and compares the measured value measured by the electrical resistance meter and a preset replacement time set value, A device for detecting the tool replacement time based on the amount of wear, comprising: a comparator that outputs a signal indicating whether or not it is the replacement time.

[0011]

The present invention operates as follows. The electric resistance value between the base material of the tool having the insulating coating formed on the surface of the base material and the workpiece is measured by an electric resistance meter. Then, the replacement value is detected by comparing the reduction value of the electric resistance due to the increase in the direct contact amount between the base material of the tool and the workpiece due to the wear of the tool with the set value input to the comparator.

[0012]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of a workpiece and a detection device according to the present invention. 2A and 2B are schematic views of a tool and a detection device before and after wear, respectively. FIG. 3 is a circuit diagram of the detection device. FIG. 4 is a correlation diagram between the wear amount and the electric resistance. FIG. 5 is a schematic view showing the entire lathe.

FIG. 5 illustrates a lathe 1 as a machine tool. The lathe 1 has a headstock 4 for supporting the workpiece 2 between the tailstock 3 and giving rotation to the workpiece 2, and a tool (not shown in FIG. 5) attached to the tool rest 5 to attach the workpiece 2 to the workpiece 2. And a carriage 6 for moving back and forth and left and right.

Next, the detection device will be described in detail with reference to FIG. 5 and FIG. A tool 7 is detachably attached to the tool rest 5 of the carriage 6. Tool 7 is a chip (blade) 8
And a holder 10 for holding the tip 8 at the tip by a fixing member 9 or the like.

The tip 8 has a base material 8a made of a conductive material such as cemented carbide, and almost all the surface of the base material 8a is surface-treated from an insulating material such as aluminum oxide (Al ₃ O ₂ ) to form an insulating film. 8b is formed. However, in order to fix the chip 8 to the holder 10, the insulating coating 8b is not formed on the part of the chip 8 that contacts the fixing member 9, and the base material 8a is exposed. The fixing member 9 is made of a conductive material. Therefore, the base material 8 made of a conductive material is used.
An electric current can flow from a to the fixing member 9.

By the way, the chip 8 in which the surface of the cemented carbide is treated with an insulating material such as aluminum oxide as described above is generally used. Aluminum oxide (Al ₃ O ₂ ), boron nitride (BN), silicon nitride (SiN ₃ ), silicon carbide (SiC), etc. have high hardness and high abrasion resistance and heat resistance, but on the other hand, they are brittle. There is. On the other hand, cemented carbide is an alloy formed by mixing tungsten carbide (WC) with cobalt (Co) or the like as a binder and sintering the mixture. This cemented carbide has elasticity and excellent impact resistance. Therefore, it is widely practiced to form chips by surface-treating a cemented carbide with aluminum oxide or the like. The above-mentioned aluminum oxide and the like are insulating materials. Cemented carbide is a conductive material.

Therefore, the tool in which the entire surface of the conductive material is surface-treated with the insulating material may be one that is widely and normally used without the need for special manufacturing for the present invention.
A conductive material other than cemented carbide may be used as the base material.

If electricity is conducted between the workpiece 2 and the base material 8a of the chip 8 through the lathe 1 as a whole,
It is not possible to determine the change in the electric resistance value between the workpiece 2 and the base material 8a of the chip 8 (in this case, the electric resistance value is always zero). Therefore, in this example, an insulating layer 11 is formed on the inner surface of the mounting portion of the tool rest 5, and the tool rest 5 and the tool 7 are electrically insulated by this insulating layer 11.

An electric resistance meter 1 is provided between the tip 8 and the workpiece 2.
2 is connected. That is, the tip 8 is connected to the electrical resistance meter 12 via the fixing member 9 and the wiring 13, and the workpiece 2 is connected to the electric resistance meter 12 via the headstock 4 or the tailstock 3 and the wiring 14. The electric resistance meter 12 measures the electric resistance between the base material 8 a of the chip 8 and the workpiece 2. The electric resistance meter 12 supplies a current I and obtains the resistance R according to Ohm's law (resistance R = voltage E / current I). However, since the configuration of the electric resistance meter 12 is well known, detailed description will be omitted here.

A wear amount calculator 15 for determining the wear amount of the workpiece 2 from the electric resistance value is connected to the subsequent stage of the electric resistance meter 12. At the subsequent stage of the wear amount calculator 15, the obtained wear amount is compared with a preset set value, and when the wear amount reaches or exceeds the set value, a signal for replacing the tip 8 is issued. The comparator 16 is connected.

Electric resistance with the tip 8 and the workpiece 2 before and after wear
A total of 12 and 12 are shown in FIGS. 2 (a) and 2 (b), respectively.
It FIG. 3 shows this FIG. 3 as an electric circuit.
In FIG. 3, the insulating film 8b of the chip 8 of FIG.
The contact electric resistance between₁I am trying. Also a tip
The contact electric resistance between the base material 8a of No. 8 and the workpiece 2 is R_TwoWhen
is doing. Resistance R₁And R_TwoAnd are connected in parallel.
In addition to this, the specific resistance of the insulating film 8b of the chip 8 is ρ
₁, Ρ is the resistivity of the base material 8a of the chip 8_TwoOf chip 8
The contact area between the insulating coating 8b and the workpiece 2 is S₁, Tip 8
The contact area between the base material 8a of the_Two, Total resistance is R
Then, the following equation holds. 1 / R = 1 / R₁+ 1 / R_Two  = S₁/ Ρ₁+ S_Two/ Ρ_Two  ρ₁Is insulation, so ρ₁= ∞, S₁/ Ρ₁
= 0. Therefore, the formula is as follows. 1 / R = S_Two/ Ρ_Two  The formula can be rewritten as: R = ρ_Two/ S_Two  ρ_TwoIs constant, so we understand that the formula is an inverse formula
it can. That is, contact between the base material 8a of the chip 8 and the workpiece 2
Area (S_Two) Increases, the resistance value R decreases.
It FIG. 4 is a graph of this correlation. This
Based on the correlation shown in Fig. 4, the above friction amount calculation
The device 15 obtains the wear area (wear amount) from the measured resistance value R.
It is possible.

The embodiment configured as described above operates as follows.

As shown in FIG. 1, the tool 7 is attached to the rotating workpiece 2.
The chip 8 is applied and the workpiece 2 is cut. During the initial period, the tip 8 is not worn as shown in FIG. As time passes, the tip 8 wears as shown in FIG. Also, in addition to wear, defects such as those in FIG.
Although it becomes as shown in (b), it is assumed here that a defect is treated in the same manner as wear.

The electrical resistance between the base material 8a of the chip 8 and the workpiece 2 is measured by the electrical resistance meter 12. Next, the wear amount calculator 15 calculates the wear amount of the workpiece 2 from the measured electric resistance value based on the correlation diagram of FIG. Next, in the comparator 16, the wear amount is compared with a preset set value, and when the wear amount reaches or exceeds the set value, a signal indicating that the tip 8 should be replaced is issued.

The present invention is not limited to the above embodiment, and various modifications can be implemented. For example, in the above embodiment, the electric resistance meter 12 was connected to the headstock 4 or the tailstock 3 and the fixing member 9, but the electric resistance meter 12 is not limited to this connection point, and the workpiece 2 and the base material 8a of the tool are connected. The electric resistance meter 12 may be connected to any place where the electric resistance between them can be measured.

[0027]

According to the present invention described above, the following effects can be obtained.

First, since the amount of wear is quantitatively detected, there is no risk of exchanging a tool that is still usable, and the judgment of the exchange time is reliable.

Further, it is possible for anyone to easily determine the tool replacement timing without requiring skill or accurate knowledge.

[Brief description of drawings]

FIG. 1 is a schematic view of a tool, a work piece, and a detection device according to this example.

2A and 2B are schematic views of a tool and a detection device before and after wear, respectively.

FIG. 3 is a circuit diagram of a detection device.

FIG. 4 is a correlation diagram between a worn area and electric resistance.

FIG. 5 is a schematic view showing an entire lathe.

[Explanation of symbols]

 2 Workpiece 7 Tool 8 Chip 8a Base material 8b Insulation film 12 Electric resistance meter

Claims (1)

[Claims] 1. A tool having an insulating coating formed on the surface of a base material,
It is provided in contact with the base material of the tool to fix the tool to the holder
Fixing member, and electrically insulates the fixing member from the tool rest
The insulating layer and the electrical resistance between the tool and the workpiece.
Electric resistance meter provided for measurement, and the electric resistance meter
And the preset replacement time set value
Comparator that compares the signals and issues a signal indicating whether it is time to replace
And tool exchange depending on the amount of wear.
Replacement time detection device.