JP2002120129A - Cutting tool with electrically conductive film and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid blade breakage of a cutting tool and damage of a standard member under a method to carry out moving control of the cutting tool after making a contact position as a standard by detecting contact of a knife edge of the cutting tool and the standard member by using a fact that an electric current flows as an electric circuit is closed when the knife edge of the cutting tool makes contact with the standard member and detecting a position of a cutting tool moving device at that time. SOLUTION: An overall surface of a cutting tip 112 of the cutting tool 48 is covered with an electrically conductive film. Consequently, the electric current flows from a direct current electric power source in a state where the cutting tip 112 and the standard member 92 make contact with each other through the electrically conductive film, and contact of the cutting tip 112 and the standard member 92 is detected as an electric current detector 100 detects the electric current. It is not necessary to directly make the cutting tip 112 and the standard member 92 contact with each other and it is possible to avoid damage of both of them. It is also possible to cover at least a cutting blade of the rotating cutting tool and its neighbouring part with the electrically conductive film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the position of a cutting tool in a machine tool and an apparatus suitable for carrying out the method. In addition, there are a case where the cutting tool itself constitutes the entire cutting tool like a solid tool, and a case where a cutting tip or a blade as a cutting tool is detachably attached to the cutting tool main body and forms a cutting tool together with the main body. .

[0002]

2. Description of the Related Art In a machine tool, a workpiece is cut by a blade and a workpiece being relatively moved by a relative moving device, and processed into a product (including an intermediate product) having a desired shape and dimensions. Is done. At that time, if the relative position of the cutting tool to the workpiece is not properly controlled, a desired product cannot be obtained. For example, in an automatic machine tool, a moving device that moves at least one of a cutting tool and a workpiece is automatically controlled according to a predetermined program, and as a result, in order to obtain a desired product. In addition, it is necessary to accurately detect the relative position between the cutting tool and the workpiece. Therefore, conventionally, a touch probe (detector of a touch sensor) or a cutting tool is brought into contact with an object to be contacted such as a standard member or a reference portion of a machine tool, and the position of the moving device at the moment of contact (referred to as a contact position) is determined. Reading from a position detecting device and controlling the moving device based on the read contact position are performed.

The present invention is applied to a blade position control method and apparatus of a type which detects a relative position between a blade and a workpiece by bringing the blade itself into contact with a workpiece without using a touch sensor. is there. For example, when the machine tool is an automatic lathe and the processing location of the workpiece is the outer peripheral surface, the cutting tool is moved in the radial direction of the workpiece, and the cutting edge of the cutting tool contacts the contact surface of the workpiece. By doing so, the positions of the cutting edge of the cutting tool and the contact surface of the contact object coincide. Therefore, if the relative position between the contact surface and the workpiece is known, the movement of the cutting tool is controlled based on the contact position of the cutting edge with the contact surface, so that the workpiece can be accurately formed into a desired shape and shape. It can be processed into products with dimensions.

[0004] The same applies to a case where the machine tool is a machining center or the like in which a rotary cutting tool such as an end mill is used as a cutting tool. However, in a machining center, the cutting tool is rotated and at the same time, all necessary movements for machining can be performed.However, both the cutting tool and the workpiece are moved, and the combination of the movements makes it necessary for machining. In many cases, an appropriate relative movement is obtained. In the latter case, the control of the relative movement between the cutting tool and the workpiece is performed by using a workpiece moving device that moves a workpiece holding member such as a workpiece holding table that holds the workpiece, and a cutting tool. This is performed under the control of a tool moving device that moves a tool headstock that rotatably holds a tool spindle that holds and rotates. Further, in order to remove the error of the distance between the rotation center line of the cutting tool and the cutting edge, approach the rotating tool and the contacted object while rotating the rotating tool, and when the position where both contact is detected, In some cases, the contact position is detected without rotating the cutting tool.

[0005] When a touch sensor is used, a touch sensor is required, which increases the cost of the apparatus. In addition, a relative position error between the touch sensor and the blade is included in a position control error of the blade, and the control accuracy is accordingly reduced. Decrease. If the contact position is detected by bringing the blade into contact with the object to be contacted, the above problem can be solved. However, in this case, a peculiar problem occurs due to the fact that the blade is brought into contact. For example, blade contact with the contacted object causes blade spillage, or the contacted object is damaged or cut. When the cutting tool is a cutting tip of a cutting tool, the blade is easily spilled if the object is not rotated, and the object is cut if the object is rotated.
If the hardness is increased so that the contacted object is not cut, the cutting tool is worn or the blade is spilled. When at least the cutting edge of the cutting tool has a high electric resistance or is formed of a material having no conductivity, for example, the cutting tip is made of ceramics, and the cutting edge is formed of a diamond crystal or CBN (hexagonal crystal). When it is formed of a crystalline boron nitride) or the like, it is difficult or impossible to detect contact with an object to be contacted.

In the case where the cutting tool constitutes the entire rotary cutting tool or the cutting edge of the rotary cutting tool, if the rotary cutting tool is brought into contact with an object to be contacted without rotating, the blade is easily spilled. If this is done, the contacted object will be cut. The fact that it is not appropriate to increase the hardness of the object to be contacted or that it is difficult or impossible to detect the contact when the electric resistance of the cutting edge and its vicinity is large is the same as in the case of the cutting tool. .

[0007] In addition, when the cutting tool attached to the machine tool is wrong, the following problem also occurs. For example, when the cutting tool is a cutting tool of a cutting tool, if the cutting tool is incorrect, the cutting tool and the workpiece come into contact with each other at an unscheduled portion during cutting, and either of them is damaged, A product having a desired shape and dimensions may not be obtained. When the cutting tool is a rotary cutting tool, the relative movement trajectory between the tool and the workpiece with respect to the rotation center line of the rotary cutting tool is often controlled, so if the diameter of the rotary cutting tool is different from the expected size. During the cutting process, there is a possibility that the rotary cutting tool may be cut into the workpiece to a large extent unexpectedly, and not only will the product of the desired shape and dimensions not be obtained, but also the rotary cutting tool and the workpiece It may be damaged.

[0008]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has at least one of the above-mentioned problems peculiar to the case of detecting a contact position by bringing a blade into contact with an object to be contacted. The present invention has been made to solve one of the problems, and according to the present invention, a contact detection method, a blade determination method, a blade position control method,
A cutting tool and a conductive sheet suitable for carrying out these methods are obtained. As in the case of the claims, each aspect is divided into sections, each section is numbered, and if necessary, the other sections are cited in a form in which the numbers are cited. This is for the purpose of facilitating the understanding of the present invention and should not be construed as limiting the technical features and combinations thereof described in the present specification to those described in the following sections. . Further, when a plurality of items are described in one section, the plurality of items need not always be adopted together. It is also possible to select and adopt only some of the items.

(1) A method for detecting the contact and separation between the cutting tool and the object to be contacted based on a state change of an electric circuit whose state changes due to the contact and separation of the tool and the object held by the tool holding member. There, between the cutting tool and the cutting tool holding member, at least one of between the cutting tool and the contacted object, in a state where a conductive layer having conductivity is interposed, the cutting tool and the contacted object A contact detection method characterized by contacting (claim 1). The conductive layer is interposed, for example, in the form of a conductive film fixed on the surface of a cutting tool, a cutting tool holding member, an object to be contacted, that is, a conductive film, or in the form of a conductive sheet that is a conductive sheet. Alternatively, it can be interposed in the form of a local conductive film locally adhered only to the cutting edge of the cutting tool and its vicinity. If the conductive layer is interposed between the cutting tool and the contacted object, the cutting tool and the contacted object come into contact with each other via the conductive layer, and the contact can be detected without any trouble. Can be prevented from being brought into direct contact with each other, resulting in spilling of the blade, damage to an object to be contacted, cutting, and the like. The true contact position is
This is the position where the cutting tool and the contact object are in direct contact, but if the thickness of the conductive layer is sufficiently thin in relation to the required processing accuracy,
The contact position via the conductive layer may be the contact position of the cutting tool. When the conductive layer is thick in relation to the required processing accuracy, a position obtained by correcting the contact position of the conductive layer by the thickness of the conductive film may be used as a true contact position. When a conductive film is formed on either the tool or the contacted object, which is a good electrical conductor, the conductive film may be made of a soft or fragile material as compared with the blade or the contacted object. It is effective to have a predetermined electric resistance. In the former case, it is desirable that the conductive film formed on the cutting edge of the cutting tool and the vicinity thereof be rapidly destroyed when cutting of the workpiece is started. In this case, a conductive film is formed on the cutting tool before use, and the contact position is detected before cutting by the cutting tool. However, it is not desirable that the conductive film formed on the cutting edge other than the currently used cutting edge and the vicinity thereof be broken by contact with chips or the like, and the conductive film has an appropriate strength range. . In the latter case, that is, in the case where the conductive film has a predetermined electric resistance, for example, it is possible to prevent an excessive current from flowing to the contact portion between the blade and the contacted object at the time of contact. . In this case, the conductive film is a resistive film. Furthermore, if the conductive film that covers the vicinity of the blade edge of the blade is formed as a resistive film having a different resistance value for each type of blade, the amount of change in the state of the electric circuit when the blade comes into contact with the contacted object is different for each type of blade. Therefore, the type of the cutting tool can be determined based on the difference in the amount of change. For example, the state change amount of the electric circuit is detected by the detector, and when the detected change amount is different from the change amount set in advance for the planned blade, the currently mounted blade is different from the planned one. It is possible to detect a difference, that is, a mounting error of the cutting tool. In addition, instead of comparing the amount of change in the state of the electric circuit with the amount of change in setting, the erroneous attachment of the blade can be detected by comparing the amount of state itself with the amount of set state. As the state quantity or the state change amount of the electric circuit, for example,
The current or resistance of the electric circuit or the amount of change thereof can be employed. By measuring the current and the electric resistance of a circuit including the contacted object, the conductive film, the cutting tool, and the cutting tool holding member which are in contact with each other, it is possible to detect the mounting error of the cutting tool. In this case, the magnitude of the electric resistance of the conductive film is important, and the conductive film should be called a resistance film. On the other hand, either one of the cutting tool and the contacted object,
If at least the contact site is made of an electrically insulating material,
A conductive film is formed in order to impart conductivity to the contact portion and to prevent blade spillage and damage. For example, if the cutting tip is made of ceramics and has high electrical resistance or non-conductivity, if the entire surface of the cutting tip is covered with a conductive film, the cutting tip will be treated as if it were a good electrical conductor. Becomes possible. When the rake face of the cutting tool is covered with a crystal of diamond or crystal of CBN, for example, if the crystal and its adjacent portion are covered with a conductive film, the contact of the cutting edge with the object to be contacted can be achieved. Can be detected. In this case, the conductivity of the conductive film is important. However, it is of course possible to use a conductive film having a predetermined electric resistance. It is also effective to interpose a conductive layer between the blade and the blade holding member. For example, in a state where the conductive layer is interposed between the blade and the blade holding member, both of which are made of an electrically conductive material, if the blade and the contacted member are brought into contact, the state of the electric circuit changes, The state change is affected by the conductive layer. For example, the electric circuit
In the case of (3), when the cutting tool and the contacted object come into contact with each other, an electric current flows through the conductive layer, so that the conductive layer is made of a material having a relatively large electric resistance. If so, the magnitude of the flowing current changes according to the size of the conductive layer. Therefore, when the magnitude of the current is out of the preset range, the width of the conductive layer is not the expected width, and the cutting tool is different from the expected one, that is, the mounting of the cutting tool. It turns out that a mistake has occurred. Furthermore, if a conductive film having a certain electric resistance, that is, a resistive film is formed on a surface of the blade that contacts the blade holding member, and the resistance value of the resistive film is different for each blade,
Since the amount of change in the state of the electric circuit when the blade comes into contact with the contacted object differs for each blade, it is possible to determine the type of blade and to detect an incorrect mounting of the blade based on this change. can do. The conductive film or the resistive film can be formed by, for example, thermal spraying, coating, vapor deposition, or the like of a material having good electric resistance or a material having an appropriate electric resistance. (2) As the electric circuit, at least a cutting tool, a contacted object, and a power supply are connected in series, and a switching circuit that forms a closed circuit when the cutting tool and the contacted object come in contact with each other and that opens when the cutting tool and the contacted object are separated from each other is used. The contact detection method according to claim 1, wherein the contact between the cutting tool and the object to be contacted is detected based on a change of the switching circuit from an open circuit to a closed circuit (claim 2). When the cutting tool itself constitutes a cutting tool, that is, when the cutting tool is a peeling tool, the method of this embodiment is effective. The original tool is
Although the blade portion and the body or shank are formed of an integral tool material, a blade tool such as a welding tool or a brazing tool in which a blade tool is fixed to a cutting tool body so as not to be detachable is also described in this specification. For the sake of convenience, it is assumed that the tool is a kind of peeling tool. A solid tool can be considered to be a cutting tool as a whole. (3) As the electric circuit, at least a cutting tool holding member, a cutting tool, a contacted object, and a power supply are connected in series, and a switching circuit that forms a closed circuit when the cutting tool and the contacted object come into contact with each other and forms an open circuit when separated. Used to detect the contact between the cutting tool and the contacted object based on the change of the open / close circuit from the open circuit to the closed circuit
(1) The contact detection method according to the item (1). In this embodiment,
This is effective when the cutting tool is such that the cutting tool body and the cutting tool main body that are separate from each other are separably fixed. For example, when the cutting tip is a clamp bit that is detachably attached to a shank by a clamp device, or an assembled milling cutter in which a cutting tip or a blade as a cutting tool is detachably attached to a milling body by a clamp device, etc. The method is effective. (4) The conductive layer is a conductive film covering the surface of the blade.
The contact detection method according to any one of (1) to (3) (Claim 4). When the conductive layer is a conductive film that covers the surface of the blade, the conductive layer can be easily interposed between the blade and the blade holding member or between the blade and the contacted object. For example, if the entire surface of the blade is covered with the conductive film, the conductive layer can be easily interposed between both the blade and the blade holding member and between the blade and the contacted object. However, this is not indispensable. For example, it is also possible to cover only the cutting edge of the blade and its vicinity with the conductive film, or to cover at least a part of the contact surface of the blade with the blade holding member with the conductive film. . This point is the same whether the cutting tool is a cutting tool or a rotary cutting tool. (5) The contact detection method according to any one of (2) to (4), wherein the conductive layer is a conductive film that covers a contact surface of the contacted object that contacts the blade. Even if the contact surface of the contact object is covered with the conductive film, the conductive layer can be easily interposed between the cutting tool and the contact object. (6) The contact detection method according to item (5), wherein the contacted object is a standard member having a known size and attached to a workpiece holding device instead of a workpiece cut by the cutting tool. . (7) The conductive layer is a conductive sheet sandwiched between the blade and the contacted object when the blade is in contact with the object.
The contact detection method according to (3). If a conductive sheet is used, it is possible to interpose a conductive layer between the cutting tool and the object to be contacted when both are normal. (8) The cutting tool rotates around a rotation center line, and constitutes at least a cutting edge and its vicinity of a rotary cutting tool for cutting a workpiece by the cutting edge. The contact detection method according to any one of (1) to (3), wherein the method is covered with a conductive film serving as a conductive layer, and the rotary cutting tool is rotated to make contact with the contacted object (Claim 5). There are a case where the cutting tool itself constitutes a rotary cutting tool, and a case where the cutting tool is detachably attached to a tool main body which is rotated around a rotation center line and forms a rotary cutting tool together with the tool main body. In any case, the contact between the rotary cutting tool and the contacted object can be detected without causing the cutting blade of the rotary cutting tool to directly contact the contacted object. (9) The contact detection method according to the above item (8), wherein the rotary cutting tool is brought into contact with the contacted object while rotating the rotary cutting tool at the same rotational speed as when cutting the workpiece with the rotary cutting tool. Even when the rotary cutting tool has a plurality of cutting edges on the outer periphery and the distance from the rotation center line of the rotary cutting tool to the cutting edges varies, according to this aspect, the rotary cutting tool can be brought into contact with the rotary cutting tool without any problem. A contact position with an object can be detected. In addition, since the rotary cutting tool is rotated at the same rotational speed as when cutting the workpiece, the contact position is detected under the influence of the vibration of the rotary cutting tool, etc. By controlling the subsequent relative movement between the cutting tool and the workpiece, a product with high dimensional accuracy can be obtained. (10) The conductive layer is a resistive film that covers at least the cutting edge of the cutting tool and the vicinity thereof, and a state quantity such as a current and an electric resistance of the electric circuit in a state where the cutting tool is in contact with the contacted object. If the size is within a predetermined set range, the blade is a planned blade, and if the size is outside the set range, the blade includes a blade determination step of determining that the blade is not the planned blade (1). The contact detection method according to any one of paragraphs (3) to (3). (11) The conductive layer is a resistive film that covers at least the entire contact surface of the blade with the blade holding member, and the current and the electric resistance of the electric circuit in a state where the blade and the contact object are in contact with each other. When the state quantity such as is a size within a predetermined set range, the blade is a planned blade, and when the size is out of the set range, it is determined that the blade is not a planned blade. The contact detection method according to any one of items (1) to (3), including: (12) At least the cutting blade and its vicinity, and the entire contact surface with the blade holding member, of the blade are covered with a conductive film as the conductive layer, and the blade is held by the blade holding member to make contact with the blade. The contact position, which is the position of the cutting tool when the cutting blade covered with the conductive film comes into contact with the contacted object, is stored, and the movement of the cutting tool is controlled based on the contact position. The resistance and the current of a circuit including the workpiece, the cutting tool, and the cutting tool holding member in series in a state where the conductive film covering the cutting blade is broken by contacting the cutting tool with the workpiece are set in a predetermined setting range. The contact detection method according to any one of paragraphs (1) to (3), wherein when the size is outside the range, the blade is determined not to be the intended blade. If the position of the cutting tool when the cutting blade covered with the conductive film comes into contact with the contact object is set as the contact position, the contact position can be detected while avoiding the contact object from being cut by the cutting tool. Then, when the cutting tool is pressed against the workpiece and the conductive film is destroyed and the cutting tool comes into direct contact with the workpiece, at least the resistance and the current of the circuit including the cutting tool and the cutting tool holding member in series. If one of them is detected and the detected value is out of the set range, it is determined that the cutting tool is different from the intended one, so that the mounting error of the cutting tool can be detected with high reliability. (13) The contact detection method according to the above mode (12), wherein the object to be contacted is an object to be cut by the cutting tool. If the object to be contacted is the object to be processed, it is possible to detect a contact position and a mounting error of the blade in the process of starting the processing of the object with the blade. (14) a step of preparing a plurality of blades of different types, wherein at least the cutting blades and the vicinity thereof are covered with a resistive film made of a material having a different resistance value for each type of blade; Forming one of the plurality of cutting tools on a cutting tool holding member to form an electric circuit including the cutting tools, the cutting tool holding member, and a contacted object that comes into contact with or separates from the cutting tool in series; Discriminating the type of the cutting tool currently held by the cutting tool holding member based on the state of the electric circuit when the cutting blade is brought into contact with the contact object via the resistance film. A method (claim 6). (15) Prepare a plurality of blades of different types, the surfaces of which are held by the blade holding member covered with a resistive film made of a material having a different resistance value for each type of blade. And holding the one of the plurality of blades on the blade holding member via the resistive film,
A step of forming an electric circuit including the blade tool and the blade holding member, and a contact object that comes into contact with or separates from the blade tool in series;
A determining step of determining a type of the cutting tool currently held by the cutting tool holding member based on a state of the electric circuit when the cutting blade of the cutting tool is brought into contact with the contacted object (claim) Item 7). The entire surface of the cutting tool may be covered with a resistive film, in which case it is a suitable cutting tool for carrying out the invention described in the above (14), but from the viewpoint of facilitating discrimination of the cutting tool, It is better not to cover the part in contact with the contact object with the resistance layer. As will be described later in detail in the embodiment section, the electric resistance of a portion of the resistance layer sandwiched between the cutting tool and the contacted object is compared with the electric resistance of a portion sandwiched between the cutting tool and the cutting tool holding member. This is because the electrical resistance often becomes remarkably large, and this electric resistance makes it difficult to determine the cutting tool. (16) The blade discriminating method according to the mode (14) or (15), wherein the state quantity representing the state of the electric circuit used in the discriminating step includes at least one of a current and an electric resistance of the electric circuit. (17) In the determining step, when the current or the electric resistance has a size within a predetermined setting range, the cutting tool is a predetermined cutting tool, and when the current or the electric resistance has a size outside the setting range, the cutting tool has a predetermined size. The cutting tool discrimination method according to item (16), including a cutting tool attachment error judgment step of judging that the cutting tool is not a cutting tool. (18) A cutting tool which is detachably held by a cutting tool holding member and cuts a workpiece, at least a part of the surface of which is covered with a conductive film having conductivity. (19) The cutting tool according to (18), wherein the conductive film is made of a material having higher electric resistance than the material of the cutting tool. (20) The cutting tool according to (18), wherein the conductive film is made of a material having lower electric resistance than a material of the cutting tool. (21) The conductive film covers the entire surface of the blade (1)
The cutting tool according to any one of items 8) to (20). (22) The cutting tool according to any one of (18) to (21), wherein the cutting tool is detachably attached to a shank as the cutting tool holding member, and is a cutting tip that constitutes a cutting tool together with the shank. (23) The cutting tool according to any one of (18) to (22), wherein the cutting tool constitutes at least a cutting blade and a vicinity thereof of a rotary cutting tool that performs cutting by rotating around a rotation center line. Cutting tools. (24) The cutting tool according to item (23), wherein the cutting tool is a cutting tip that is detachably attached to a tool main body that is rotated around a rotation center line and constitutes a rotary cutting tool together with the tool main body. (25) attached to a workpiece holding device instead of a workpiece whose dimensions are known and are cut by a cutting tool,
A standard member to be brought into contact with a cutting tool for cutting the workpiece, the standard member having a surface covered with a conductive film. (26) A conductive sheet formed by forming a conductive material into a sheet.

The invention relating to the contact detection method or the cutting tool can be carried out in combination with the invention of the cutting tool position control method or the cutting tool position control device described in the following sections. Alternatively, the reliability of the tool position control can be further enhanced. (1) In a machine tool, a cutting device and a contacted object are relatively moved by a moving device capable of detecting a moving position so that they are brought into contact with each other. A cutting tool position control method for controlling relative movement with a workpiece, wherein a contact detection device that detects contact between the cutting tool and the contacted object can detect a contact between the cutting tool and the contacted object. A normal checking step for confirming that the blade is in a state, and after the normal checking step or while performing the normal checking step, the cutting tool and the contacted object are brought closer to each other by the moving device, and the cutting tool is brought into contact with the contacted object. And a contact detecting step of detecting contact. After confirming that the contact detection device can detect the contact between the cutting tool and the contacted object, or if the cutting tool and the contacted object are approached while confirming, the cutting tool and the contacted object are However, it is possible to prevent any one of them or the holding device holding them from being damaged due to the fact that they are not detected even though they contact with each other, and are brought closer together. In addition,
As soon as the contact between the cutting tool and the contacted object is detected, the approach between the cutting tool and the contacted object by the moving device is stopped. The time required from this contact detection to approach stop is extremely short, and it has been confirmed by experiments that the blade tool or the contacted object is not damaged by overshoot of the tool and the object to be moved. I have. (2) In the machine tool, the cutting tool and the object to be contacted are relatively moved by a moving device capable of detecting the moving position so that they are brought into contact with each other. A cutting tool position control method for controlling relative movement with a workpiece, wherein the cutting tool, the contacted object, and a power source are connected in series, and a closed circuit is formed when the cutting tool and the contacted object are in contact with each other, and the contact is not made. A first circuit forming step of preparing a first circuit to be an open circuit; and a power supply connected to the power supply in parallel with the first circuit and at least having an electric resistance regardless of contact or non-contact between the blade and the contacted object. A second circuit forming step of preparing a second circuit forming a closed circuit including in series, and detecting the state of the power supply with a detector in a state where the first circuit is an open circuit, at least the power supply and the detection The vessel is normal And the normal confirmation process to verify that,
When the detector detects that the state of the power supply has become a state corresponding to the transition from the state of the open circuit to the state of the closed circuit of the first circuit, the moving position of the moving device is determined. A tool position control method for a machine tool, comprising: a contact position reading step of reading as a contact position between the blade and the contacted object. In a state where the cutting tool is not in contact with the contacted object, the first circuit is an open circuit, so that no current flows through the first circuit and current flows only through the second circuit. On the other hand, if the blade and the contact object come into contact with each other, the first circuit becomes a closed circuit, and current flows not only in the second circuit but also in the first circuit. Since these two circuits are parallel to the power supply, the amount of current increases. When the first circuit becomes a closed circuit, in order to avoid that an excessive current flows and the power supply and the detector are damaged, the power supply itself has a current limiting device for limiting the maximum current, Alternatively, it is desirable to provide some resistance in the first circuit. In the first circuit,
Although it is possible to intentionally provide a resistor, it is also possible to use the resistance of the main body of the machine tool itself as the resistance of the first circuit. In any case, the resistance of the second circuit is equal to the resistance of the first circuit so that the difference between the current when the first circuit is closed and the current when the circuit is open is clear. It is preferable that the resistance is equal to or higher than that, and if circumstances permit, the resistance is obviously larger than the resistance of the first circuit. However, even in a state where a current flows only in the second circuit, it is necessary that the fact can be clearly detected by the detector. If the power supply or the detector breaks down, or if a conductive member such as a lead wire comes off or breaks, and the current stops flowing in the second circuit, the fact is surely detected by the detector. And the contact between the blade tool and the contacted object cannot be detected. Therefore, the blade and the object to be contacted are brought closer to each other in a state where the contact cannot be detected, and the blade and the contacted object are further brought closer to each other even after the contact, so that the damage to the blade and the like is favorably avoided. (3) The normality checking step detects a current flowing from the power supply, and determines a first current having a current greater than 0 and a second current having a value greater than the first current. The tool position control method according to the above mode (2), wherein the normality is confirmed when the size is within the range of (2). The detection of the state of the power supply can be performed in various ways. For example, when the first circuit becomes a closed circuit and the voltage between the output terminals of the power supply drops at the moment when the current suddenly increases, by detecting the voltage drop, the contact between the blade and the contacted object is detected. be able to. However, it is a simpler and more reliable method to detect a sudden increase in the current from the power supply using a current detector. (4) The contact position reading step is a step of reading a moving position of the moving device when a current flowing from the power supply exceeds a third current that is predetermined to be larger than the second current. (3) Item 6. A cutting tool position control method according to the above item. The third current is desirably set to a value larger than the current flowing in the first circuit when the cutting edge of the cutting tool and the surface of the contacted object are connected by the cutting fluid. If at least one of the cutting edge of the cutting tool and the surface of the contacted object is brought close to each other in a state of being wet by the cutting fluid, before the two come into direct contact, the first circuit is brought into a semi-closed circuit state by the cutting fluid. Since the current increases, it is desirable that the third current be set so that the contact between the cutting edge of the cutting tool and the surface of the contacted object is not detected in such a current increase. (5) In the machine tool, the cutting tool and the object to be contacted are relatively moved by a moving device capable of detecting the moving position so that they come into contact with each other. A cutting tool position control method for controlling relative movement with respect to a workpiece, wherein a resistance circuit is provided between the cutting tool and the contacted object, the connection circuit connecting the two via a first electrical resistance of a predetermined size. And a normality checking step of confirming that the electrical resistance between the cutting tool and the object to be contacted is substantially equal to the first electrical resistance in a state where the blade is not in contact with the contacted object, and performing the normality checking step. After that, or while performing the normality check step, the cutting tool and the object to be contacted are brought closer to each other by the moving device, and the electric resistance between them becomes smaller than the second electric resistance smaller than the first electric resistance. When the blade A blade position control method, which comprises a contact detection step of detecting a contact between the contacted object. (6) The cutting tool position control method according to any one of the above items (1) to (5), wherein the object to be contacted is a workpiece attached to the machine tool. (7) The cutting tool position control method according to any one of (1) to (5), wherein the contacted object is a standard member attached to the machine tool. The standard member may have a dimension substantially equal to the target dimension of the product to be currently processed, or may have a known dimension different from the target dimension of the product to be currently processed. May be common to all products. (8) The cutting tool position control method according to any one of (1) to (5), wherein the contacted object is a reference portion provided on the machine tool. (9) The cutting tool position control method according to any one of (1) to (8), wherein the cutting tool is a cutting tip fixed to a shank of a cutting tool. (10) The cutting tool position control method according to any one of (1) to (8), wherein the cutting tool is at least a part of a rotary cutting tool attached to a tool spindle of the machine tool. (11) The cutting tool position control method according to (10), wherein in the contact position reading step, the rotary cutting tool is brought into contact with the contacted object while being rotated. (12) In the second circuit, the cutting fluid and the chips are attached to both sides of the electric resistance, are electrically insulated from each other, and adhere to the two members connected by the electric resistance. A circuit that bypasses the electric resistance is formed, and even though the cutting tool and the contacted object are not in contact, the first circuit erroneously transitions from the open circuit state to the closed circuit state. Any of (2) to (4), including a step of covering at least a part of at least one surface of a member located on both sides of the electric resistance with a layer of an electrically insulating material to prevent the determination. The cutting tool position control method according to any one of the above. The technology described in this section for covering the surface of a necessary member with a layer of an electrically insulating material can be employed also in the above modes (5) to (11). (13) Despite that it is clear that the cutting tool and the contacted object are at a relative position to be contacted, when contact between the cutting tool and the contacted object is not detected, the cutting tool has a defect. Including a loss determination step to determine that there is a possibility (1)
Item 14. The method for controlling the position of a cutting tool according to any one of the above items 12 to 12. For example, at the start of the cutting of the workpiece, in the process of bringing the blade tool and the workpiece close to each other, the operation for detecting contact is continued, and it is certain that the blade tool comes into contact with the workpiece. Contact is not detected when both are brought close to the relative position but no contact is detected, or even when the operation for detecting the contact is continued during the cutting of the workpiece, the contact is not detected When the state appears, it is determined that there is a possibility that the cutting tool has been lost. The operator can check the condition of the cutting tool according to the operation of the alarm based on the determination and the display on the display, and can take necessary measures. As described above, according to the present embodiment, it is possible to easily detect the loss of the cutting edge of the cutting tool. When it is determined that there is a possibility that the cutting tool has been lost, it is desirable that the relative movement between the cutting tool and the contacted object be automatically stopped. (14) The touch probe is provided so as to be immovable relative to the blade, and a contact detection step of detecting a contact between the touch probe and the contacted object is performed. The cutting tool position control method described in the above. If a touch probe is provided, it becomes possible to detect an impossible or inappropriate position depending on the contact of the blade. For example, in a lathe, if a touch probe having a spherical contact end is used, the contact end of the touch probe is placed at two locations separated in the diameter direction on the outer peripheral surface of the workpiece or the standard member held by the chuck. Contact can be made to detect the position of the center line of rotation of the workpiece or standard member, but it is impossible or inappropriate to use the tool in that way. If the position of the rotation center line of the workpiece or the standard member is detected and the relative position between the touch probe and the cutting tool is known, the movement control of the cutting tool can be performed based on the contact position of the touch probe. Note that it is desirable, but not essential, to perform the normality check step for the touch probe. Conversely, it is also possible to perform only the normality check process for the touch probe alone without performing the normality check process for the blade tool. (15) In the contact detecting step, the contact between the cutting tool and the contacted object is detected under a condition that can be determined as a state where the cutting tool and the contacted object are separated by the cutting fluid despite being separated from each other. The cutting tool position control method according to any one of the above modes (1) to (14). For example, in the aspect of the above item (2), the threshold value for detecting the transition of the first circuit to the closed circuit state is determined by the detection of the detector when the cutting tool and the contacted object are connected by the cutting fluid. The value is set to a value different from the value (if it is a current value, the current value is larger than the current value in a state of being connected by the cutting fluid). (16) In the machine tool, the cutting tool and the object to be contacted are relatively moved by a moving device capable of detecting the moving position so that they are brought into contact with each other. A tool position control method for controlling relative movement with respect to a workpiece, wherein the blade is in contact with a workpiece as the workpiece, and the moving device when the blade and the workpiece are just contacted. A dimension measuring step of measuring the dimension of the workpiece based on the movement position of the workpiece, and a control step of controlling the subsequent relative movement between the cutting tool and the workpiece based on the dimension of the workpiece measured in the dimension measuring step And a cutting tool position control method. A dedicated machine for measuring the dimensions of the workpiece is provided on the machine tool, the dimensions of the workpiece are measured on the machine, and the relative movement between the blade and the workpiece is determined based on the measurement results. Control is performed, and this is effective when the required accuracy of the dimensions is high. However, the measurable range of the dimension measuring device used for that purpose is usually very narrow. On the other hand, a wide range of dimensions can be accurately detected by using a blade as a contact, a blade moving device as a contact moving device, and a moving position detecting device for detecting a moving position of the blade moving device as a scale. It becomes possible. Therefore, according to the present invention, it is possible to process a workpiece having a plurality of parts having greatly different dimensions and a plurality of workpieces having greatly different dimensions with high accuracy. It should be noted that the present invention can be adopted in combination with any one of the above items (1) to (15). (17) In the machine tool, the cutting tool and the object to be contacted are relatively moved by a moving device capable of detecting the moving position so that they come into contact with each other. A cutting tool position control device that controls relative movement with a workpiece, wherein a contact detection device that detects contact between the cutting tool and the contacted object can detect a contact between the cutting tool and the contacted object if the cutting tool contacts the contacted object. A confirmation unit for confirming that the state is in a state, and after the confirmation by the confirmation unit or in a state where the confirmation is continued, the cutter and the contacted object are brought closer to the moving device, and the blade and the contacted object are And a contact detector for detecting that the blade has come into contact with the blade. If you use the blade position control device, the above (1)
The method for controlling the position of the cutting tool as described in the above item can be satisfactorily performed. (18) In the machine tool, the cutting tool and the object to be contacted are relatively moved by a moving device capable of detecting the moving position so that they are brought into contact with each other. A cutting tool position control device for controlling relative movement with a workpiece, wherein the cutting tool, the contacted object, and a power supply are connected in series, and a closed circuit is formed when the cutting tool and the contacted object are in contact with each other, and no contact is made. In the first circuit to be an open circuit, connected to the power supply in parallel with the first circuit,
A second circuit for forming a closed circuit including at least an electric resistance in series regardless of whether the blade tool and the contact object are in contact with or not in contact with each other, a detector for detecting a state of the power supply, and an opening of the first circuit. When the detection result of the detector indicates that at least the detector and the power supply are normal in a circuit state, the cutting tool and the object are brought closer to the moving device, and the detection is performed. And a controller for controlling the moving device based on the moving position of the moving device at the time when the detection result of the tool indicates the contact between the cutting tool and the contacted object. . If the present blade position control device is used, the blade position control method of the above item (2) can be favorably implemented. (19) An insulating device that electrically insulates between the cutting tool or a cutting tool side portion which is a part in electrical conduction with the cutting tool and a main body of the machine tool, wherein the electric resistance is equal to the cutting tool side portion. The cutting tool position control device according to the above mode (18), which is disposed between the cutting tool and the main body of the machine. The “main part of the machine tool” is a part that includes not only the main body frame but also all members that are in electrical communication with the main body frame. That is, the portion closer to the main body frame than the insulating device is the main body portion. This is the same in the next section. (20) The workpiece holding member itself that holds the workpiece of the machine tool, or the workpiece holding member side portion that is a portion that is in electrical conduction with the workpiece holding member, and the main body of the machine tool And a cutting tool position control device according to (18), wherein the electrical resistance is disposed between the workpiece holding member side portion and the main body of the machine tool. . (21) The cutting tool position control device according to any one of (18) to (20), wherein the electric resistance is formed of a resistance layer sandwiched between conductors. Each component of a tool holding member, a cutting tool holding member, a workpiece holding member, a main body, and the like of a machine tool is generally formed of a good electrical conductor such as steel or brass. The second circuit can be easily configured by providing the second circuit between them. However, it is necessary that the fixing device for fixing the members on both sides of the resistance layer to each other can fix both members while preventing electrical conduction between the members on both sides. If the resistance layer also has a function of fixing the members on both sides to each other, a fixing device is not required. (22) The cutting tool position control device according to any one of (18) to (20), wherein the electric resistance is a fixed resistor provided with a pair of terminals at both ends of an electric resistor. The resistance layer described in the previous section comes in contact with the members on both sides in a large area, and since the resistance value varies depending on the contact area, it is relatively difficult to accurately obtain the desired resistance value. Thus, it is easy to obtain a desired resistance value. (23) The item (18), (19) or (22) wherein the electric resistance is incorporated in at least one of a cutting tool provided with the cutting tool and a tool holding member for holding the cutting tool. A cutting tool position control device as described in the above. When the cutting tool is detachably attached to the cutting tool main body, the cutting tool includes the cutting tool and the cutting tool main body, but the peeling tool includes only the cutting tool. (24) The electric resistance is a fixed resistor incorporated in one of a workpiece holding member for holding the workpiece and one of the constituent members of the main body of the machine tool. (20) 3. The cutting tool position control device according to claim 1. (25) an insulating device that electrically insulates the cutting tool from the main body of the machine tool, a first conductive path having one end connected to the cutting tool side of the insulating device and the other end connected to the power supply; A second conductive path that connects to the main body of the machine tool, and a current detector as the detector that detects a current flowing through the first circuit including the first conductive path and the second conductive path,
A third conductive path as the second circuit connecting the cutting tool side of the insulating device and the main body of the machine tool via the electrical resistance, wherein the third conductive path is at least shorter than the first conductive path
The cutting tool position control device according to any one of the modes (18) to (23). If the power supply is arranged near the cutting tool, the first conductive member can be shortened, and the possibility of the first conductive member coming off or being damaged can be reduced. Power supply or detector is easily damaged by the influence of cutting fluid or chips, so the power supply must be installed at a position away from the cutting tool in many cases. In that case, the first conductive path must be lengthened. On the other hand, since the electrical resistance is relatively insensitive to cutting fluid and chips, the third conductive path can be easily shortened. If the third conductive path is damaged or detached, the control device determines that the power supply and the like are not normal even though the power supply, the detector, the first conductive path, and the like are normal, and notifies the mobile device of the failure. It is desirable that the third conductive path be as short as possible so as to reduce the possibility of breakage or detachment so that the blade and the contact object do not approach each other. (26) The electric resistance is a fixed resistor provided with a pair of terminals at both ends of an electric resistor, and the third conductive path holds the cutting tool provided with the cutting tool together with the fixed resistor and the cutting tool. Built in either one of the tool holding members
The cutting tool position control device according to the above mode (25). If the third conductive path as well as the electrical resistance is incorporated in either the cutting tool or the tool holding member, the third conductive path is also protected by one of them, so it can be damaged or come off. Can be satisfactorily avoided. The same applies to the next term. (27) The electric resistance is a fixed resistor provided with a pair of terminals at both ends of an electric resistor, and the third conductive path is formed between the work holding member and the main body of the machine tool together with the fixed resistor. Built into one of the components
The cutting tool position control device according to the above mode (25). (28) In the second circuit, at least a portion of the surface of at least one of the members located on both sides of the electric resistance, which is adjacent to the surface of the other member, is covered with a layer of an electrically insulating material. The cutting tool position control device according to any one of items (27) to (27). (29) a touch probe immovable relative to the blade tool;
The touch probe, the contacted object, and the power supply are connected in series, and the switching circuit includes a closed circuit when the touch probe and the contacted object are in contact with each other and an open circuit when the touch probe is not in contact with each other. 28) The cutting tool position control device according to any one of the above items. At least one of the contacted object and the power supply may be separate from or common to the contacted object and the power supply of the first circuit. Further, the configuration of this section can be adopted separately from the configuration described in section (18). However, the "moving device for relatively moving the touch probe and the cutting tool and the object to be contacted", "connected to a power source in parallel with the first circuit as the opening / closing circuit, and the contact and non-contact between the touch probe and the object to be contacted. Regardless of the second circuit that forms a closed circuit that includes at least the electrical resistance in series "," the detector that detects the state of the power supply "
And `` When the detection result of the detector indicates that at least the detector and the power supply are normal in the state where the first circuit is open circuit, the touch probe and the contact object are brought closer to the moving device. It is effective to provide a control device for controlling the subsequent moving device based on the moving position of the moving device at the time when the detection result of the detector indicates the contact between the touch probe and the contacted object ". It is. (30) The control device determines the contact between the cutting tool and the contacted object with the detection result of the detector in a state where the cutting tool and the contacted object are separated by a cutting fluid despite being separated from each other. The blade tool position control device according to any one of the above modes (18) to (29), wherein the detection is performed in accordance with a possible detection result. (31) If the controller does not detect contact between the cutting tool and the contacted object even though it is clear that the cutting tool and the contacted object are at a relative position to be brought into contact with the cutting tool, The cutting tool position control device according to any one of the above modes (18) to (30), including a loss determining unit that determines that there is a possibility that a defect has occurred in the cutting tool.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to an example in which the present invention is applied to a tool position control device for an automatic lathe. In FIG. 1, reference numeral 10 denotes a main body frame as an apparatus main body of the automatic lathe. Body frame 10
Is provided with a base 12, a column 14 rising upward from the base 12, a bed 16 and a headstock 18 fixed to an intermediate portion of the column 14. The headstock 18 holds the spindle 22 so as to be rotatable about a horizontal rotation center line and immovable in the axial direction. A tailstock 24 is provided on the bed 16 so as to be able to approach and separate from the headstock 18. ing. The tailstock 24 holds the center 26 in a state of being coaxially opposed to the main shaft 22. A three-jaw chuck 28 (hereinafter simply referred to as a chuck 28) as a workpiece holder is attached to the spindle 22, and the workpiece 32
Is rotated by holding both ends thereof by the chuck 28 or the center 26 of the tailstock 24 and the center (not shown) attached to the chuck 28 or the chuck 28 instead.

An X guide 36 is provided above the column 14.
It is fixed in a posture extending in the X-axis direction parallel to the rotation center line of the main shaft 22, and the X guide 36 holds an X slide 38 movably in the X-axis direction. X slide 38
, A Y guide 42 is provided in a posture extending in a Y-axis direction perpendicular to the rotation center line of the main shaft 22, and a Y slide 44 is held by the Y guide 42 so as to be movable in the Y-axis direction. A tool rest 46, which is a kind of tool holding member, is fixed to the Y slide 44, and a cutting tool 48, which is a kind of cutting tool, is attached to the tool rest 46. The X slide 38 is moved by an X moving device 56 having an X drive motor 52 and a feed screw 54, and the X slide 3 is moved.
The Y slide 44 is moved by a Y moving device 66 provided with a Y drive motor 62 and a feed screw 64 on the tool 8 so that the tool rest 46 and the cutting tool 48 attached thereto are moved in both the X-axis direction and the Y-axis direction. Moved to.

X drive motor 52 and Y drive motor 62
Are servomotors that can be numerically controlled, and the drive motors 52 and 62 are provided with encoders 72 and 74, respectively. The encoders 72 and 74 are connected to a control device 78 as shown in FIG.
Are the moving positions of the X moving device 56 and the Y moving device 66 based on the output signals of the encoders 72 and 74, that is,
The position of the tool rest 46 or the cutting tool 48 is calculated. The automatic lathe is an example of a machine tool having a control axis having a scale. The control device 78 is mainly composed of a computer 80, a drive circuit for driving the X drive motor 52, the Y drive motor 62, and the like, and a conversion for converting a detection signal supplied from the outside into digital data that can be input to the computer 80. It has a circuit and the like. Computer 80 is a RO
M (read only memory) 82, RAM (random access memory) 84, PU (processing unit) 86
And an I / O port 88, and a ROM 82 stores a program for processing the workpiece 32.

The control device 78 is connected to a contact detection circuit 94 for detecting the contact of the cutting tool 48 with the standard member 92. The contact detection circuit 94 includes a first circuit 96, a second circuit 98, and a current detector 100. The first circuit 96 connects the cutting tool 48 as a cutting tool, the standard member 92 as an object to be contacted, and the DC power supply 104 as a power supply in series, and closes the circuit when the cutting tool 48 and the standard member 92 are in contact with each other. The circuit is an open circuit when no contact is made. The standard member 92 is a member having a dimension substantially equal to a target dimension (specifically, a target diameter) of a product processed from the workpiece 32, and is attached to the chuck 28 instead of the workpiece 32. The second circuit 98 is
This circuit is connected to the DC power supply 100 in parallel with the first circuit 96, and forms a closed circuit including at least the resistor 106 in series regardless of whether or not the cutting tool 48 is in contact with the standard member 92. The current detector 100 is a type of a detector that detects the state of the DC power supply 104, and detects a current flowing from the DC power supply 104 to the first circuit 96 and the second circuit 98.

As shown in FIG. 2, the cutting tool 48 is provided with a cutting tip 112 on a shank 110 as a cutting tool body.
Are fixed by a fixing device (not shown), the cutting tip 112 is made of an electrically conductive material, and the entire surface is covered with a conductive film 113 having conductivity as shown in FIG. The conductive film 113 is formed of a material having an appropriate electric resistance (hereinafter simply referred to as resistance), for example, a mixture of an electric insulating material such as a synthetic resin or ceramics and an electric conductive material such as a metal on the surface of the cutting tip 112. It is fixed with a uniform and accurate thickness. For this fixation, a method such as painting, thermal spraying, CVD (chemical vapor deposition), or PVD (physical vapor deposition) can be used, but PVD that does not require heating the cutting tip 112 to a higher temperature than CVD is preferable.

As for the thickness of the conductive film 113, for example, it is sufficient that at least the thickness of the cutting edge of the cutting tip 112 is known, but it is desirable that the entire thickness be uniform. The thicker the conductive film 113 is, the easier it is to avoid spilling of the cutting tip and damage to the standard member 92. However, contact between the cutting tip 112 and the standard member 92 is detected, and the approach between them is stopped accordingly. In this case, it is sufficient that the conductive film 113 has a remaining thickness without being completely destroyed. Also,
Even if the conductive film 113 is completely destroyed when the approach is stopped, the effects of the present invention can be enjoyed as long as the cutting tip 112 and the standard member 92 are in contact only to such an extent that they are not damaged.

The resistor 106 is provided between the cutting tip 112 and the main body of the automatic lathe. Specifically, as shown in FIG. 4, it is disposed between the shank 110 and the tool rest 46. The resistor 106 is a fixed resistor in which a pair of terminals 116 and 118 are provided at both ends of an electric resistor 114, and a compression coil spring 124, which is a kind of an elastic member, is accommodated in a housing recess 122 formed in the tool rest 46. (Hereinafter, simply referred to as a spring 124).

The resistor 106 and the spring 124 are accommodated in a housing 128 made of an electrically insulating material so as to be movable in the axial direction.
By being press-fitted into the housing 22, it is held in the housing recess 122. In the illustrated example, the housing recess 122 is formed as a hole with a bottom, and the housing 128 is a cylindrical member having generally open both ends. A radially inward flange 130 is provided at one opening end of the tubular member, and the housing recessed portion is oriented such that the opening end on the side where the flange 130 is provided is the opening end side of the housing recess 122. 122. In this state, the spring 124 is compressed and urges the resistor 106 toward the flange 130. A protrusion 132 projects from the center of one terminal 116 of the resistor 106. The protrusion 132 has a length that protrudes outward from the flange 130 when the resistor 106 is in contact with the flange 130. Have.

Both the shank 110 and the cutting tip 112 of the cutting tool 48 and the tool rest 46 are made of an electric conductor, but the shank 110 and the tool rest 46 are insulated by an electric insulator. In the illustrated example, the shank 110 of the tool post 46 is used.
An insulating layer 138 is formed on a surface that contacts the shank 110, and a pad 144 having an insulating layer 142 formed on one surface is provided between a bolt 140 serving as a fixing device for fixing the shank 110 to the tool rest 46 and the shank 110. It is arranged. When the cutting tool 48 is fixed to the tool rest 46, the shank 110 is connected to the projection 1 of the resistor 106.
32, the resistor 106 is pushed into the recess 122 against the urging force of the spring 124,
The shank 110, the resistor 106, the spring 124, and the tool rest 46 are pressed against each other. Therefore, when the cutting tool 48 is fixed to the tool rest 46, the cutting tool 48 and the tool rest 46 are electrically connected by a series circuit of the resistor 106 and the spring 124. The formation of the insulating layer 138 can be performed by, for example, thermal spraying of an electrically insulating material such as ceramics, PVD, CVD, or the like.

As shown in FIG. 5, the tool rest 46 is further provided with a connection part 150 for connecting the cutting tool 48 to the DC power source 104 while electrically insulating the tool 48 from the tool rest 46. The connection part 150 is a terminal 154 fixed to the tool rest 46 in an insulated state by the electric insulator 152.
And a conduction securing section 156 for securing conduction between the terminal 154 and the shank 110 of the cutting tool 48. The conduction securing section 156 includes a housing 160, a contact 162, and a spring 164. The elastic force of the spring 164 causes the shank 110, the contact 162, and the spring 1.
64 and the terminal 154 are pressed against each other to ensure electrical continuity. Terminal 154 has lead wire 1
66, and this lead wire is connected to one terminal of the DC power supply 104 via the current detector 100 as shown in FIG. Another terminal of the DC power supply 104 is another lead 168.
Thereby, it is connected to one component of the main body of the automatic lathe, for example, the main body frame 10.

As apparent from the above description, in the present embodiment, the insulating layers 138 and 142 constitute an insulating device for electrically insulating the cutting tip 112 as a cutting tool from the main body of the automatic lathe. I have. The contact 162, the spring 164, the lead wire 166, and the like constitute a first conductive path having one end connected to the blade side of the insulating device and the other end connected to a DC power supply.
8 constitutes a second conductive path for connecting the DC power supply 104 to the main body of the automatic lathe. The spring 124 forms a third conductive path that connects the blade side of the insulating device and the main body of the automatic lathe through the resistor 106. The spring 124, which is the third conductive path, is very short in comparison with the first conductive path including the contact 162, the spring 164, the lead wire 166, and the like, and has a small resistance.
6 are built in a tool rest 46 as a tool holding member, and both ends are connected to a resistor 106 by its own elastic force.
And is elastically pressed against the tool rest 46,
There is little risk that electrical continuity will be impaired.

The contact detection circuit 94 configured as described above
In the automatic lathe provided with, processing of the workpiece 32 is performed as follows. First, a tool 48 is attached to the tool post 46.
However, a standard member 92 is attached to the chuck 28, respectively. Thereby, the cutting tool 48, the current detector 10
0, a DC power supply 104, a first circuit 96 for connecting the main body of the automatic lathe and the standard member 92 in series, and a cutting tool 48, a DC power supply 104, a second circuit 98 for connecting the main body of the automatic lathe and the resistor 106 in series. Is formed. FIG.
_The resistance represented by ₁ represents the resistance between the resistor 106 and the portion of the main body of the automatic lathe including the tool rest 46, but since the resistance of the main body is small, the resistance of the resistor 106 is substantially reduced. It can be considered to represent resistance. The resistance value of the resistor 106 is desirably selected from a range of 50Ω or more and less than 500Ω in relation to a resistance value of a cutting fluid described later and a resistance value of a main body of the automatic lathe.
Ω is set.

The code R_TwoThe resistance expressed by
The resistance of the portion of the main body of the panel including the main shaft 22
No.R_ThreeIs a cutting tip of the conductive film 113.
Resistance of the portion interposed between the step 112 and the shank 110
And the sign R_FourIs the resistance of the conductive film 113,
The cutting tip 112 is connected to the standard member 92 via the conductive film 113.
When it comes into contact with the cutting tip 112 and the standard member 92
This is the resistance of the part that is sandwiched. The resistance R of the resistor 106₁And
The resistance R of the two portions of the conductive film 113_Three, R_FourIs an automatic lathe
The resistance R of the main body_TwoVery large compared to. Ma
The resistance R_ThreeAnd resistance R_FourBetween the conductive film 113
Difference in cross-sectional area of conductive path formed by two parts
By R_Four≫R_ThreeUsually, the following relationship holds.
Further, the resistance R_FourIs the resistance R of the resistor 106₁Less than or equal
It is desirable to have the size. The current is in the second circuit 98
From the state flowing only from the cutting tip 112, the conductive film 1
13 and contacts the standard member 92, and the second circuit 98 and the
When transitioning to a state in which the current flows from both the circuit 96,
In order for the fact to be clearly detected, the current
This is because it is desirably twice or more. This embodiment
, The resistance R _FourIs the resistance R₁Is a fraction of
You. After all, in this embodiment, R₁> R_Four≫R_Three≫R_TwoNoseki
That is, the engagement is established.

Initially, the cutting edge of the cutting tool 48, that is, the tip of the cutting tip 112 is at a position away from the standard member 92, in which state the first circuit 96 is in an open circuit state.
Therefore, in the related art, no current flows from the DC power supply 104, but in the present embodiment, even if the cutting edge of the cutting tool 48 is separated from the standard member 92, the second circuit 98 is in a closed circuit state. Therefore, a weak current flows.
This current is detected by the current detector 100, the detection value of the current due to the large resistance value of the resistor R ₁ is small. However, the magnitude is clearly larger than 0 and is between a predetermined first current and a second current larger than the first current. The computer 80 of the control device 78 reads the detected value of the current by executing the program, and if the read value is between the first current and the second current, the touch detection circuit 94 However, if a voltage is applied between the cutting edge of the cutting tool 48 and the standard member 92 and they come into contact with each other, it is determined that the state is in a normal state where it can be detected.
This process is a normality check process.
In the step 0, when the normality cannot be confirmed in this step, the movement control for bringing the cutting tool 48 close to the standard member 92 is not performed. Therefore, even though the cutting edge of the cutting tool 48 contacts the standard member 92, the fact is not detected, and the movement of the cutting tool 48 is continued, and the cutting tool 4
8. The occurrence of a situation in which the standard members 92 and their holding devices are damaged is satisfactorily avoided, and a highly reliable contact detection circuit 94 is provided.
Is obtained.

If normality is confirmed in the normality confirmation step,
The computer 80 controls the drive motors 52 and 62 of the X moving device 56 and the Y moving device 66 by executing the program, and causes the cutting tool 48 to approach the outer peripheral surface of the standard member 92 from the radial direction of the standard member 92. Byte 48 is
While being moved away from the standard member 92 at high speed, it is decelerated when it reaches a preset deceleration position near the standard member 92, and thereafter is brought close to the standard member 92 at low speed. This approach is desirably performed by moving the cutting tool 48 only in the radial direction of the standard member 92, that is, by moving only the Y-axis direction.

Eventually, the cutting edge of the cutting tool 48 becomes the standard member 92.
Contact the outer peripheral surface of the
The cutting edge of the cutting tool 48 and the standard member 92 may be connected by the cutting fluid. For example, if the cutting tool 48 is brought close to the standard member 92 while the cutting edge is wet with the cutting fluid, the cutting fluid contacts before the cutting edge contacts the standard member 92, and the cutting fluid has conductivity. Therefore, the cutting edge of the cutting tool 48 and the standard member 92 are electrically connected by the cutting fluid. Therefore, the first circuit 96 is in a semi-closed state, and the DC power supply 100
, The current flows through both the first circuit 96 and the second circuit 98, and the current detection value of the current detector 100 increases. However, although the electrical resistance of the cutting fluid varies depending on the contained components, it does not become smaller than 500Ω in the present embodiment, and the increase in the current detection value by the current detector 100 is relatively small. Therefore, the detected value of the current does not exceed the third current set to a value larger than the second current, and the computer 80 detects that the cutting edge of the cutting tool 48 has contacted the outer peripheral surface of the standard member 92. There is no.

On the other hand, when the cutting edge of the cutting tool 48, that is, the cutting edge of the cutting tip 112 comes into contact with the outer peripheral surface of the standard member 92, the first circuit 96 is in a closed circuit state. However, since the cutting tip 112 is covered with the conductive film 113 as described above, the cutting blade comes into contact with the standard member 92 via the conductive film 113, and the current of the first circuit 96 is reduced by the resistance R ₃ , It will flow through the series circuit of R ₄ and R ₂ . Then, since the not consist relationship R ₄ >> R ₃ >> R ₂ as described above, the magnitude of the current flowing through the first circuit 96 is determined generally by the resistor R _4, the resistor R ₄ the resistance as described above Since the size is a fraction of R ₁ , the current detection value of the current detector 100 increases several times. If the computer 80 detects that the detected value of the current has exceeded the third current that is larger than the second current, the cutting edge of the cutting tool 48 contacts the outer peripheral surface of the standard member 92 via the conductive film 113. Is detected. This step is a contact detection step. Since the conductive film 113 is formed of a material that is softer than the cutting tip 112 and the standard member 92, damage to the cutting tip 112 and the standard member 92 is better than when the cutting tip 112 and the standard member 92 are in direct contact. Can be avoided.

In the contact detection step, before the cutting tool 48 and the standard member 92 come into contact with each other, the cutting tool 48 and the standard member 92 may be connected to each other by a cutting fluid. In this case, a current may flow through the cutting fluid, and it may be erroneously detected that “the cutting tool 48 has come into contact with the standard member 92”. Therefore, it is desirable that the third current be set to a value sufficiently larger than the current flowing through the cutting fluid.

In this embodiment, before the contact detection step is carried out, the cutting tool 4 as a cutting tool having a cutting tool is used.
A cleaning step is provided for removing cutting fluid and chips adhering to the surface of the standard member 8 and the standard member 92 as an object to be contacted by air blowing from the injection nozzle 168. It is desirable that the surfaces of the tool rest 46 as a cutting tool holding member and the chuck 28 as a contact holding member for holding a contact object such as the workpiece 32 and the standard member 92 are also cleaned. By performing this cleaning step, it is possible to satisfactorily avoid occurrence of erroneous detection that the cutting tip 112 has come into contact with the standard member 92 (or the workpiece 32).

Based on the detection of the contact between the cutting tool 48 and the standard member 92, the computer 80 detects the Y moving device 66 (X
The moving device 56 is also stopped (if the moving device 56 is also moved), and the encoder 74 at that time is stopped.
The position of the cutting tool 48 with the conductive film 113 (the position in the Y-axis direction) is calculated based on the output signal of (72). And
The position is corrected by a known conductive film thickness and the conductive film 11 is corrected.
The position of the cutting edge of the cutting tool 48 after 3 is removed is calculated and stored in the contact position memory of the RAM 84 as the contact position. This step is a contact position detection step. This step is performed at a predetermined time, such as when the operator is to be replaced, when the automatic lathe is first started in the morning, or when the cutting tool 48 or the cutting tip 112 is replaced. This is executed before the start of machining the first workpiece 32 or the like. In order to eliminate the influence of abrasion of the cutting tip 112 and expansion and contraction caused by a temperature change of the main body of the automatic lathe, the processing may be executed at predetermined time intervals or at every processing number.

The position of the rotation center line of the main shaft 22 is calculated based on the contact position where the cutting edge of the cutting tool 48 contacts the standard member 92 and the known radius of the standard member 92, and the position of the rotation center line is calculated. RAM 84 as a reference position in the Y-axis direction
May be stored in the reference position memory. If necessary, the cutting tool 48 is moved in the axial direction of the standard member 92, and the contact position of the standard member 92 with the end face is
It may be detected as a reference position in the X-axis direction.

After that, the computer 80 corrects the portion related to the movement control of the byte 48 of the program stored in the ROM 82 based on the data of the contact position. Therefore, if the workpiece 32 is attached to the chuck 28 instead of the standard member 92 and the movement of the cutting tool 48 is controlled in accordance with the above-mentioned modified program, the workpiece 3
2 is processed into a product with high dimensional accuracy. Even if there is some error in the center height of the cutting edge of the cutting tool 48, the same cutting tool 48 is brought into contact with the standard member 92 to correct the movement control data. Never. When the touch sensor is used to correct the movement control data, if there is a difference in the center height between the touch sensor and the cutting edge of the cutting tool 48, the difference will contribute to the dimensional error of the product. According to the present embodiment, the inconvenience can be avoided.

When the cutting of the workpiece 32 is started, the computer 80 continues reading the detection value of the current detector 100 while the cutting tool 48 is approached to the workpiece 32, and the cutting tool 48 controls the conductive film 113. Workpiece 32 through
Is detected, and subsequently, the conductive film 113 is destroyed, and the cutting tool 48 directly contacts the workpiece 32. When the cutting tool 48 contacts the workpiece through the conductive film 113, the current detector 100
Since the detected value of the current exceeds the third current, the computer 80 can detect that the cutting tool 48 has contacted the workpiece 32 via the conductive film 113 based on the fact. The conductive film 113 is broken, if the contact byte 48 directly on the workpiece 32, the resistance R ₄ is 0, the resistance to current flowing through the first circuit 96 R
₂ + R ₃ , which is significantly smaller than the resistance R ₂ + R ₃ + R ₄ when contact is made via the conductive film 113,
The current increases accordingly. The computer 80 detects that the cutting tool 48 has directly contacted the workpiece 32 based on the fact.

The magnitude of the current flowing when the cutting tool 48 comes into direct contact with the workpiece 32 is determined by the resistance R ₂ + R ₃ as described above, but the resistance R ₂ is significantly higher than the resistance R _3. Since it is small, almost all of the resistance R _3, that is, the conductive film 11
3 is determined by the resistance of the portion interposed between the cutting tip 112 and the shank 110. The magnitude of the resistance R ₃ are cross-sectional area of the conductive path formed by said portion of the conductive film 113, i.e. approximately proportional to the size of the portion of the conductive film 113. Therefore, the cutting tip 112
If the current detection value of the current detector 100 is in a set range corresponding to the cutting tip 112 in a state where the cutting tip 112 is in direct contact with the workpiece 32, the cutting tip 112 is determined to be correct. If it is out of the setting range, it is determined that the mounting error of the cutting tip 112 (and eventually the cutting tool 48) has occurred. Is operated, and the fact is displayed on the display device to notify the operator of the fact. This step is a tool mounting error detection step.

If the detected value of the current does not exceed the third current even though the cutting tool 48 is moved to a position where it is certain that the cutting tool 48 will contact the workpiece 32, It is determined that there is a possibility that the cutting tip 112 of the cutting tool 48 may be broken, and the X moving device 56 and the Y
The approach of the cutting tool 48 to the workpiece 32 by the moving device 66 is stopped, an alarm device such as a buzzer or an alarm lamp is activated, and the fact is displayed on a display device to notify the operator of the fact. . This step is a first defect detection step.

Further, the computer 80 controls the work 3
The reading of the detected value of the current detector 100 is continued even after the cutting process of No. 2 is started, and if the detected value drops below the fourth current during the cutting process, the cutting tip 1 of the cutting tool 48
It is determined that there is a possibility that a defect has occurred in the workpiece 12, and the X moving device 56 and the Y moving device 66 separate the cutting tool 48 from the workpiece 32 to interrupt the cutting process, and activate a buzzer and an alarm lamp. And the fact is displayed on the display device. The fourth current is set to be larger than the magnitude of the current flowing when the cutting tool 48 and the workpiece 32 are connected by the cutting fluid. This step is a second loss detection step. In any of the above cases, the operator checks the status of the cutting tool 48 or the like in response to the alarm of the alarm and takes necessary measures. As described above, in the present embodiment, the loss of the cutting edge of the cutting tool 48 can be easily detected.

As is clear from the above description, the conductive film 1
13, between the cutting tip 112 and the shank 110
Of the cutting tip 11 function as a resistive film.
2 contacts the standard member 92 via the conductive film 113
The part sandwiched between the cutting tip 112 and the standard member 92
Functions as a conductive film. Therefore, the former resistance value R _Three
Is preferably large, and the latter resistance value R_FourIs small
Is desirable. However, in the present embodiment, the conductive
From the viewpoint of facilitating the production of a cutting tip with a film, the conductive film 11
3 has the same thickness and the same material. And the above
Between the cutting tip 112 and the shank 110
The area of the intervening part is the cutting tip 112 and the standard member 9
Because it is significantly wider than the area between the two
The former resistance value R_ThreeIs the latter resistance value R_FourSignificantly smaller
It will be cheap. This is desirable from the functional point of view.
Because the conductive film is not
And the cutting tip 112
The portion sandwiched between the standard member 92 reduces the thickness and material
At least one of them must be different, and the former must have a higher resistance.
And reducing the resistance of the latter.
It is desirable to implement In this case, cut the conductive film
Cannot be formed to cover the entire surface of chip 112
Not a chip, but as shown in FIG.
A portion 113a interposed between the chuck 110 and the cutting
Part 113b sandwiched between the tap 112 and the standard member 92;
May be formed apart from each other.

In this embodiment, the control device 78
The part for detecting the contact position of the cutting edge of the cutting tool 48 with the standard member 92 is described as follows. "In a state where the first circuit is open circuit, the detection result of the detector indicates that at least the detector and the power supply are normal. In the case shown, the cutting tool and the contacted object are brought closer to the moving device, and the subsequent movement is performed based on the moving position of the moving device at the time when the detection result of the detector indicates the contact between the cutting tool and the contacted object. It is evident that the present invention constitutes a "control device for controlling the device". Further, the first circuit 96 and the current detector 100 constitute a contact detection device, and the portion of the control device 78 that performs the normality check step cooperates with the second circuit 98 to say "the contact detection device is And a confirmation unit for confirming that the contacted object can be detected when it comes into contact with the object. Further, the part of the control device 78 that performs the contact detection step constitutes a “contact detection unit that makes the blade and the contacted object approach the moving device and detects that the blade has contacted the contacted object. Also, the first circuit 96
An open / close circuit is configured such that a closed circuit is formed when the blade tool comes into contact with the contacted object, and an open circuit is formed when the blade tool is separated.

In the above embodiment, the electric resistor 11
Although a resistor 106 having terminals 116 at both ends of 4 is used, a resistor layer 170 conceptually shown in FIG. 7 can be used instead of the resistor 106. In the illustrated example, the resistance layer 170 is sandwiched between the cutting tool 172 and the tool rest 174, both of which are conductors (good electrical conductors). The resistance layer 170 may be formed by being fixed to one surface of either the cutting tool 172 or the tool rest 174, or may be formed by independently forming a sheet between the cutting tool 172 and the tool rest 174. Good. In any case, the cutting tool 17
2 and the tool rest 174 need to be fixed to each other with the resistance layer 170 interposed therebetween, and a fixing device for that purpose does not electrically connect the cutting tool 172 and the tool rest 174. It is necessary.

As the resistance layer 170, for example, a layer obtained by mixing a good conductor powder such as a metal powder into an electrically insulating material such as a synthetic resin or ceramics can be adopted. The formation of the resistance layer 170 on the surface of the conductor can be performed by, for example, thermal spraying, coating, PVD, CVD, or the like. The PVD method requires a lower conductor temperature at the time of implementation than the CVD method. Therefore, when forming a resistive layer on the surface of a conductor whose hardness is desirably high, such as a member for holding a cutting tool or a tool holder, Is preferably a PVD method.

Also in this embodiment, as in the previous embodiment, a cutting tool 112 in which the cutting tip 112 whose entire surface is covered with the conductive film 113 is removably attached to the tool body is used as in the above embodiment. Confirmation process,
A contact position detecting step, a cutting tip mounting error detecting step, and the like are performed.

In the above-described embodiment, the cutting edge of the cutting tool 48 is brought into contact with the outer peripheral surface of the standard member 92 held by the chuck 28. However, as shown in FIG. The cutting edge of the cutting tool 48 can be brought into contact with the outer peripheral surface of the workpiece 32 itself. For example, if the diameter of the workpiece 32 is known in advance by being measured, for example, the cutting edge of the cutting tool 48 is brought into contact with the outer peripheral surface of the workpiece 32 to detect the contact position. If cutting is performed with the cutting tool 48 cut by an amount determined based on the diameter of the workpiece 32 and the target diameter of the product, a product having desired dimensions can be obtained.

When a plurality of workpieces 32 are machined, the control data of the cutting tool 48 is corrected based on the contact position obtained as described above, and cutting is performed using the corrected control data. However, as a result of measuring the obtained product, if the dimensions of the product are within a range that does not require correction, cutting with the same control data is continued. On the other hand, if the dimensions of the product are within the range requiring correction, the control data is corrected based on the deviation from the target dimensions, and subsequent cutting is performed using the corrected control data.

Further, as shown in FIG.
If the touch probe 180 is attached together with the cutting tool 48, and the contact position detection circuit 94 is provided for the touch probe 180, the touch probe 180 is moved in the diameter direction of the outer peripheral surface of the standard member 92 (or the workpiece 32). The contact position is determined by contacting the two separated positions, and the rotational center line position of the standard member 92, that is, the rotational center line position of the main shaft 22, can be calculated as an average value of the two contact positions. In order to use the data of the rotation center line position for the movement control of the cutting tool 48, it is necessary to obtain the relative position between the touch probe 180 and the cutting edge of the cutting tool 48.
This relative position is, for example, to bring the touch probe 180 and the cutting edge of the cutting tool 48 into contact with the same portion of the standard member 92,
It can be obtained by calculation based on the moving distance of the tool rest 46 during that time.

Further, the surface of the cutting tool, cutting tool, cutting tool holding member, etc. can be covered with an insulating film. For example, as shown in FIG.
0 is covered with the insulating film 181. However, the surface of the shank 110 that contacts the cutting tip 112, the terminal 116 of the resistor 106 and the contact 162
It is necessary to prevent the insulating film 181 from being formed in a portion that should be in contact with. Thus, the shank 11
If the surface of the shank 110 is covered with the insulating film 181, the cutting fluid 112
And the tool rest 46 are electrically connected to each other by bypassing the resistor 106, thereby avoiding erroneous detection that the cutting tip 112 has contacted the standard member 92 (or the workpiece 32). can do. If the above-described cleaning step is performed together with the formation of the insulating film, erroneous detection can be avoided more favorably.

In the above-described embodiment, the cutting edge of the cutting tool 48 is made to contact the standard member 92 held by the chuck 28. However, as shown in FIG. You may make it contact. In this case, the main body 178 forms a reference portion as a contacted object. As described above, when the cutting tool is brought into contact with the reference portion, it is necessary to particularly surely prevent the reference portion from being damaged by contact with the cutting tool. In this case, the blade can be brought into contact with the reference portion via the conductive film, and the reference portion can be prevented from being damaged by the blade. In addition, when the hardness is increased so that the reference portion is not damaged, it is possible to prevent the blade from spilling.

As shown in FIG. 11, a reference portion 184 fixedly provided on a main body frame 182 such as a machining center, a milling machine, a boring machine or the like can be used as an object to be contacted. The reference portion 184 includes three reference surfaces 18 formed at right angles to three axes of the X axis, the Y axis, and the Z axis.
It is desirable to have 6,188,190. The cutting edge of the rotary cutting tool 192 as a kind of the cutting tool is brought into contact with any of these reference surfaces, and the contact position is set in the rotary cutting tool 1 in each of the X-axis, Y-axis, and Z-axis directions.
It is effective to use it as a 92 reference position.

The rotary cutting tool 192 may be brought into contact with the reference surfaces 186, 188, and 190 in a state where it is not rotated, or may be brought into contact with it while rotating. In the latter case, when there are a plurality of cutting edges of the rotary cutting tool 192 and the distances from the rotation center line to the plurality of cutting edges are slightly different from each other,
The position at which the blade edge having the largest distance contacts the reference surfaces 186, 188, 190 is determined by using the rotary cutting tool 192 and the reference surfaces 186, 1
88, 190. 193
Is a workpiece.

FIG. 11 shows another example in which a resistance is provided between the cutting tool and the main body of the machine tool. In the illustrated example, the rotary cutting tool 19 as a cutting tool is used.
Tool holder 194 as a tool holding member for holding the tool 2
A resistance layer 198 is provided between the tool main shaft 196 to which the resistance layer 198 is attached. Specifically, the tool spindle 19
The resistance layer 198 is coated on the inner peripheral surface of the tapered hole 200 which is the tool holding hole of No. 6. Also in this case, the fixing device for detachably fixing the tool holder 194 to the rotary spindle 196 includes the tool holder 194 and the rotary spindle 196.
Must not be electrically conducted.

It is also possible to form a conductive film on the rotary cutting tool. For example, in the end mill 202 as an example of the rotary cutting tool 192 shown in FIG.
3 is entirely covered with a conductive film 204. The conductive film can be formed so as to cover the shank 205 as well, but in this embodiment, no conductive film is formed on the shank 205. The end mill 202 only needs to cover at least the cutting edge and the vicinity thereof with the conductive film 204. In the present embodiment, the entire body 203 is covered to facilitate the formation of the conductive film 204.

The workpiece 193 is rotated by the rotary cutting tool 192 in which the body 203 is covered with the conductive film 204.
When cutting is performed, first, the tool holder 194 holding the rotary cutting tool 192 is attached to the tool spindle 196, and the workpiece 193 is attached to the work table 206. Thereby, the DC power supply 104 and the current detector 10
0, tool holder 194, rotary cutting tool 192, reference part 1
84 (or workpiece 193, work table 206)
Circuit 207 that includes in series and frame body 182
, DC power supply 104, current detector 100, tool holder 1
A second circuit 208, which is a closed circuit including the resistor 94, the resistance layer 198, the tool spindle 196, and the frame body 182 in series, is formed.

The tool main shaft 196 and the reference portion 184 are brought close to each other while the normality checking process is being performed based on the current flowing through the second circuit 208, and the contact position detecting process is performed. At this time, the rotary cutting tool 192 is
Is rotated at the same rotational speed as when cutting the workpiece.
Eventually, the rotary cutting tool 192 contacts one of the reference surfaces 186, 188, and 190 of the reference portion 184 via the conductive film 204. Thereby, the first circuit 207 becomes a closed circuit, current flows from both the first circuit 207 and the second circuit 208, and the fact is detected by the control device 78,
At this time, the position of the relative moving device that relatively moves the rotary cutting tool 192 and the reference portion 184 is detected. This position is corrected by the thickness of the conductive film 204, and the rotational cutting tool 19 is corrected.
The contact position between the reference 2 and the reference unit 184 is acquired.

When the rotary cutting tool 192 is brought into contact with the reference portion 184 while rotating as described above,
Even when the distance from the rotation center line to the plurality of cutting edges varies, the contact position between the cutting edge having the largest distance from the rotation center line and the reference portion 184 can be detected without any trouble. Further, since the rotary cutting tool 192 is brought into contact with the reference portion 184 via the conductive film 204, the reference portion 184 is not cut even when the rotary cutting tool 192 is rotated.

The control data of the rotary cutting tool 192 is corrected based on the contact position detected in the contact position detecting step, and the work 193 is machined with the corrected control data. The rotary cutting tool 192 first
After contacting the workpiece 193 via the conductive film 204 and breaking the conductive film 204, the cutting blade of the rotary cutting tool 102 directly contacts the workpiece 193 and starts cutting the workpiece 193. .

As described above, in the embodiment in which the conductive film is formed on the rotary cutting tool, it is also possible to form the conductive film from a plurality of materials having different electric resistances. For example, in the above embodiment, the body 20 of the rotary cutting tool 192
When the conductive film 204 is covered with the conductive film 204, the material for forming the conductive film 204 has different electric resistances. A more specific example will be given. Assuming that the rotary cutting tools 192 used for processing one type of workpiece 193 in one machining center are of five types different from each other in at least one of length and diameter. Five types of rotary cutting tools 192
Of the body 203 is covered with five types of materials having different electric resistances, and the conductive films 2 have the same thickness.
04 is formed. Then, they can be processed 19
The magnitude of the current flowing through the first circuit 207 when it comes into contact with the rotary cutting tool 3 differs for each type of the rotary cutting tool 192.
Therefore, when the first type of the workpiece 193 is processed, each time the rotary cutting tool 192 of each type is brought into contact with the workpiece 193, it flows through the first circuit 207 and the second circuit 208. Detect the current and find the closest one of the preset current values (or the one whose current matches within an allowable error) among all the five types of rotary cutting tools 192 scheduled to be used this time. For example, it can be determined that the rotary cutting tool 192 corresponding to the current value is the rotary cutting tool 192 that has been brought into contact with the workpiece 193 this time. Alternatively, when the rotary cutting tool 192 to be brought into contact with the workpiece 193 this time is known, the set current preset for the rotary cutting tool 192 and the current detected this time have an allowable error. If they match within the range, it is determined that the rotary cutting tool 192 is attached as planned, and if it exceeds the allowable error range, the rotary cutting tool 192 is not the fixed one, that is, a tool mounting error occurs. It can also be determined that it has been done. As is clear from the above description, the conductive film 204 in the present embodiment should be called a resistance film.

Instead of covering the entire body of the rotary cutting tool with a conductive film (resistive film) having a different resistance value, only the cutting edge and its vicinity, or only a more limited part thereof (for example, only the tip of the drill) May be covered, and the surface of the portion of the rotary cutting tool held by the tool holding member (the entire contact surface with the tool holding member) may be covered. In any case, it is possible to discriminate a rotary cutting tool or to detect a tool mounting error. Further, in a cutting tool in which a cutting tip is detachably attached to a shank, the cutting tip as a cutting tool, only the cutting edge and its vicinity, the entire contact surface with the shank or the entire surface is covered with a conductive film having a different resistance value. It is also possible to apply the invention of this embodiment to the tool discrimination or the mounting error detection in the cutting tool described above.

In each of the above embodiments, the resistance is provided between the cutting tool and the main body of the machine tool.
As shown in FIG. 3, a workpiece holding member for holding the workpiece may be provided between the main body and the workpiece holding member. In the illustrated example, the jig 212 to which the workpiece 210 is attached and the main body frame 2
14 is a resistor. Further, as shown in FIG. 14, a work table 220 which is moved by a moving device with respect to the main body frame.
It is also possible to provide a resistor 226 between the jig 224 to which the workpiece 222 is attached. Resistor 22
6 can be provided in the same manner as in the embodiment of FIG. 4, for example.

In the above embodiment, all the blades and standard members are made of an electric conductive material, but they may be made of an electric insulating material or a high electric resistance material.
An example is shown in FIG. In this example, the electrical resistance is high,
The entire surface of the cutting tip 228 made of ceramics belonging to an electrically insulating material is covered with a conductive film 229. This chip with a conductive film is the same as a cutting tip made of a normal electric conductive material until the portion covering the cutting edge of the conductive film 229 and the vicinity thereof is destroyed and removed by cutting the workpiece. Can be used.

In the above-described embodiment, the blade is covered with the conductive film. However, a similar effect can be obtained by covering the contact surface of the object to be contacted with the blade with the conductive film. For example, as shown in FIG. 16, the surface of the standard member 230 attached to the workpiece holding device instead of the workpiece having a known size and being cut by the cutting tool is formed by a conductive film 232.
It is covered with. By using this standard member 230 in combination with a normal blade not covered with the conductive film, the effect of the present invention that the blade is not spilled or the standard member is not damaged when the standard member 230 contacts the blade. You can enjoy.

As shown in FIG. 17, when the cutting tool 240 contacts the contact object 242, the conductive sheet 24
The above effect can also be obtained by sandwiching 4.

Although some embodiments of the present invention have been described in detail above, these are merely examples, and the present invention is described in the above section [Problems to be solved by the invention, means for solving problems and effects]. The present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art, including the described embodiment.

[Brief description of the drawings]

FIG. 1 is a front view showing an automatic lathe provided with a cutting tool position control device suitable for implementing a method for detecting contact of a cutting tool with a contacted object according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the cutting tool position control device.

FIG. 3 is a sectional view conceptually showing a cutting tip according to an embodiment of the present invention.

FIG. 4 is a sectional view showing a part of the blade position control device.

FIG. 5 is a sectional view showing another part of the cutting tool position control device.

FIG. 6 is a sectional view conceptually showing a cutting tip according to another embodiment of the present invention.

FIG. 7 is a block diagram showing a blade position control device different from the above-described blade position control device.

FIG. 8 is a block diagram showing still another cutting tool position control device.

FIG. 9 is a block diagram showing still another cutting tool position control device.

FIG. 10 is a sectional view conceptually showing a cutting tool according to another embodiment of the present invention.

FIG. 11 is a block diagram showing still another cutting tool position control device.

FIG. 12 is a front view showing a rotary cutting tool according to still another embodiment of the present invention.

FIG. 13 is a block diagram showing still another cutting tool position control device.

FIG. 14 is a block diagram showing still another tool position control device.

FIG. 15 is a cross-sectional view conceptually showing a cutting tip according to still another embodiment of the present invention.

FIG. 16 is a sectional view conceptually showing a standard member used in still another embodiment of the present invention.

FIG. 17 is a view conceptually showing a conductive sheet according to still another embodiment of the present invention as a cutting tool and a contacted object.

[Explanation of symbols]

10: body frame 52: X moving device 66: Y
Moving device 72, 74: Encoder 78: Control device 92: Standard member 92 92: Contact detection circuit
96: First circuit 98: Second circuit 100: Current detector 104: DC power supply 106: Resistor 11
0: shank 112: cutting tip 113, 113a, 113b: conductive film 124: compression coil spring 138, 142: insulating layer 15
0: connection part 166: lead wire 170: resistance layer
172: Cutting tool 174: Tool post 178: Main body of chuck 184: Reference part 192: Rotary cutting tool 194:
Tool holder 196: Tool spindle 198: Resistance layer
202: End mill 203: Body 204:
Conductive film 205: Shank 207: First circuit
208: second circuit 212: jig 214: body frame 216: resistance layer 220: work table 224: jig
226: resistor 228: cutting tip 229: conductive film 230: standard member 232: conductive film Blade: 240 242: contact object 244: conductive sheet

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hajime Mizutani 26, Hirako Yoshiwara-cho, Toyota City, Aichi Prefecture Inside Fuji Seiko Co., Ltd. (72) Inventor Eiji Goto 26, Hirako Yoshiwara-cho, Toyota-shi, Aichi Prefecture Inside Fuji Seiko Co., Ltd. 3-2, Shobo-cho, Chikusa-ku, Nagoya-shi, Aichi F-term (reference) 3C029 AA16 AA22 AA25 AA26 3C046 BB01 MM07

Claims (12)

[Claims] In a machine tool, contact and separation between a cutting tool and an object to be contacted are detected based on a state change of an electric circuit whose state changes due to contact and separation of the cutting tool and a contact object held by a cutting tool holding member. In a method, between the blade and the blade holding member, and at least one of between the blade and the contacted object, in a state where a conductive layer having conductivity is interposed, the blade is contacted with A contact detection method characterized by contacting an object. 2. An open / close circuit that connects at least a cutting tool, a contacted object, and a power supply in series as an electric circuit, forms a closed circuit when the cutting tool comes into contact with the contacted object, and forms an open circuit when separated. 2. The contact detection method according to claim 1, wherein the contact between the cutting tool and the object to be contacted is detected based on a change of the switching circuit from an open circuit to a closed circuit. 3. The opening and closing of the electric circuit, wherein at least a blade holding member, a blade, a contacted object, and a power source are connected in series, and a closed circuit is formed when the blade and the contacted object come into contact, and an open circuit is formed when the blade is separated. The contact detection method according to claim 1, wherein a contact between the cutting tool and the object to be contacted is detected based on a change in the switching circuit from an open circuit to a closed circuit. 4. The contact detection method according to claim 1, wherein the conductive layer is a conductive film covering a surface of the blade. 5. A rotary cutting tool for rotating a cutting tool around a rotation center line and cutting a workpiece by the cutting blade, and constitutes at least the cutting blade and its vicinity, and the cutting blade and its vicinity. The contact detection method according to any one of claims 1 to 4, wherein the contact member is covered with a conductive film as the conductive layer, and the rotary cutting tool is rotated to make contact with the contacted object. 6. A step of preparing a plurality of blades of different types, wherein at least the cutting blades and the vicinity thereof are covered with a resistive film made of a material having a different resistance value for each type of blade. A step of holding one of the plurality of cutting tools on a cutting tool holding member to form an electric circuit including the cutting tool and the cutting tool holding member, and an object to be contacted with and separated from the cutting tool in series. Based on the state of the electric circuit when the cutting blade of the cutting tool is brought into contact with the contact object through the resistance film,
A step of determining the type of the blade currently held by the blade holding member. 7. A plurality of blades of different types, the surfaces of which are held by a blade holding member,
A step of preparing a material covered with a resistance film made of a material having a different resistance value for each type of blade, and holding one of the plurality of blades on the blade holding member via the resistance film; A step of forming an electric circuit including a cutting tool, a cutting tool holding member, and an object to be contacted or separated from the cutting tool in series; and a state of the electric circuit when the cutting blade of the cutting tool is brought into contact with the object to be contacted. And a discriminating step of discriminating the type of the cutter currently held by the cutter holder on the basis of the above. 8. A cutting tool which is detachably held by a cutting tool holding member and cuts a workpiece, at least a part of the surface of which is covered with a conductive film having conductivity. 9. The cutting tool according to claim 8, wherein the conductive film is made of a material having higher electric resistance than a material of the cutting tool. 10. The cutting tool according to claim 8, wherein the conductive film is made of a material having lower electric resistance than a material of the cutting tool. 11. The cutting tool according to claim 8, wherein the conductive film covers the entire surface of the cutting tool. 12. In a machine tool, a cutting tool and an object to be contacted are relatively moved by a moving device capable of detecting a moving position so that they are brought into contact with each other, and a subsequent cutting tool is determined based on the moving position of the moving device at the time of contact. And a cutting tool position control method for controlling the relative movement of the workpiece, between the cutting tool and a cutting tool holding member that holds the cutting tool,
A step of interposing a conductive layer having conductivity on at least one of the cutting tool and the contacted object; and a contact detection device for detecting contact between the cutting tool and the contacted object. The blade tool and the object to be contacted by the moving device after the normality checking step for confirming that it is in a state where it can be detected if the tool comes into contact with the blade. And a contact detecting step of detecting that the cutting tool has come into contact with the object to be contacted.