JP2005262385A - Contact detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contact detecting device without causing a variation in detecting accuracy in an AE sensor. <P>SOLUTION: This contact detecting device is arranged in a machine tool (a cylindrical grinding machine 10) having a workpiece support table (a workpiece table 40) for supporting a workpiece W, and a tool post (a wheel spindle stock 30) for supporting a blade tool (a grinding wheel T) and relatively moving to the workpiece support table 40; and detects contact between the workpiece W and the blade tool T; and has an acoustic emission sensor (the AE sensor) 50 arranged on the tool post 30 side and detecting acoustic emission when the workpiece W contacts with the blade tool T. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a contact detection device, and more specifically, is provided in a machine tool including a work support base that supports a work and a blade base that supports the tool and moves relative to the work support base. The present invention relates to a contact detection device that detects contact between a workpiece and a cutting tool.

  In various machine tools such as a cylindrical grinder, a lathe, a milling machine, and a machining center, each of which includes a work support base that supports a work and a tool base that supports the tool and moves relative to the work support base. In order to perform appropriate processing such as positioning of the cutting tool with respect to the workpiece and determining when to change the feed speed from rapid feed to machining feed, it is necessary to accurately specify the position of the actual workpiece. Here, in order to specify the position of the workpiece, a contact type sensor such as a touch probe is provided at an appropriate part of the tool post or the like, and the contact type sensor is moved with respect to the workpiece and brought into contact with the workpiece. A workpiece position detection device that detects the position of a workpiece is generally used. However, if such a workpiece position detecting device is adopted, a device that contacts the workpiece must be provided separately from the blade, and the structure of the entire machine tool becomes complicated. In addition to the substantial machining of the workpiece, the workpiece position must be specified by operating the workpiece position detection device prior to machining, which complicates the entire machining process.

  On the other hand, an acoustic emission sensor (hereinafter referred to as “AE”) that detects a specific acoustic emission (hereinafter referred to as “AE”) such as a breaking sound wave of the cutting tool or a breaking sound wave of the workpiece generated when the work and the cutting tool come into contact with each other. A contact detection device using a "sensor" has been proposed. According to this contact detection device, it is possible to specify the position of the cutting tool that starts to contact the workpiece, thereby positioning the cutting tool with respect to the workpiece during machining, determining when to change the feed speed from rapid feed to machining feed, etc. An appropriate process can be performed. And in such a contact detection apparatus, it is not necessary to equip the apparatus which contacts a workpiece | work separately from a blade tool like the above-mentioned workpiece position detection apparatus, and can simplify the structure of the whole machine tool. . Further, it is not necessary to specify the position of the workpiece by moving the contact type sensor relative to the workpiece prior to machining, and the processing of the entire machining process can be simplified.

JP-A-57-173462

  In the above-mentioned patent document, an AE sensor is provided at an appropriate part such as a headstock for supporting and rotating one end of a work, a tailstock for supporting the other end of the work, a center of a headstock and a tailstock, etc. Is disclosed. However, as described above, when the AE sensor is provided on the headstock, the tailstock, or the like, the AE sensor is provided on the member that supports the workpiece, and the following problem occurs.

  Machine tools are not only used as dedicated machines that always process the same type of workpiece, but also used as general-purpose machines that process different types of workpieces. And when processing a workpiece of various shapes by a machine tool used as a general-purpose machine, since there is a difference in the shape of the workpiece itself, an AE sensor provided on a member that supports the workpiece, and a cutting tool The distance from the blade supported by the table varies. Further, even when machining the same type of workpiece by a machine tool used as a dedicated machine, if the workpiece has a plurality of machining target surfaces, when machining different machining target surfaces, The distance from the cutting tool varies.

  By the way, the AE sensor can detect the AE with higher accuracy as it is closer to the site where the AE occurs. On the other hand, if the AE sensor is moved away from the site where the AE occurs, the weak AE cannot be detected or noise can be easily picked up. As a result, the detection accuracy of AE decreases. Since the AE sensor has such characteristics, if the distance between the AE sensor and the cutting tool is varied as described above, the detection accuracy of the AE sensor varies. And when the detection accuracy varies in this way, the positional accuracy of the cutting tool that starts contact with the workpiece specified by the detection of the contact detection device also varies, and as a result, the workpiece machining accuracy varies. There is a risk of lowering the processing quality.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a contact detection device in which the detection accuracy of the AE sensor does not easily vary.

The main means taken by the present invention to solve the above problems are as follows:
“A contact that is provided in a machine tool that includes a work support base that supports a work and a blade base that supports the cutting tool and moves relative to the work support base, and detects contact between the work and the cutting tool. A detection device,
A contact state detection device comprising an acoustic emission sensor disposed on the blade base side and detecting an acoustic emission when the workpiece and the blade are in contact with each other.
It is.

  In the contact detection device having the above configuration, since the AE sensor is provided on the tool post side, the distance between the AE sensor and the cutting tool even if the shape of the workpiece changes or the surface to be processed changes in a single workpiece. Is always constant. Therefore, variations in detection accuracy with the AE sensor are less likely to occur.

In the means described above,
"The blade is a grinding wheel,
The tool rest has a grinding wheel shaft on which the grinding wheel is mounted,
The acoustic emission sensor is assembled in the grinding wheel shaft.
It is good.

  The contact detection device having the above configuration is a machine tool that processes a workpiece by a grinding wheel, that is, a “grinding machine”, and the AE sensor is assembled to the grinding wheel shaft of the grinding machine. It is what. A grinding wheel shaft on which a grinding wheel as a cutting tool is mounted is a member that is always at a constant distance from the grinding surface of the grinding wheel that contacts the workpiece, and is a member that is close to the grinding surface. Therefore, it is possible to accurately detect AE generated from the contact portion between the workpiece and the grinding surface, and it is difficult to cause variations in detection accuracy, and it is possible to improve the detection accuracy of AE. In addition, since the grinding wheel is mounted directly on the grinding wheel shaft, there are few members interposed between the grinding surface and the AE sensor, and it becomes difficult for the AE sensor to pick up noise. Therefore, also from this point, the detection accuracy of AE can be improved.

In the means described above,
“The grinding wheel includes a grinding wheel for grinding and an elastic grinding stone whose binder is made of an elastic material.
A contact detection device that detects contact between a workpiece and a grinding wheel by bringing the elastic grindstone into contact with the workpiece "
It is good.

  Here, as the elastic material constituting the binder, a flexible material having excellent elasticity such as rubber or resin may be used.

  When the grinding wheel itself for grinding is brought into contact with the workpiece, if the grinding wheel is brought into rapid contact with the workpiece, the grinding wheel is broken or the workpiece is damaged. Therefore, the feed speed when the grinding wheel is brought close to the workpiece must be a sufficiently slow feed speed close to the feed speed at the time of grinding, that is, the “grind feed speed”, which is inferior to use.

  Therefore, in the contact detection device having the above-described configuration, the grindstone to be brought into contact with the workpiece is not an abrasive grindstone but an elastic grindstone. In the elastic grindstone, since the impact when contacting the workpiece is absorbed by the elasticity of the binder itself, the grindstone wheel can be brought into contact with the workpiece at a higher feed rate than the grinding wheel for grinding. Therefore, according to the contact detection device having the above configuration, usability can be improved.

In the means described above,
`` After bringing the cutting tool close to and contacting the work, move the cutting tool away from the work, and again bring the cutting tool close to and contact with the work at a feed rate slower than the previous feed speed. Contact detection device characterized by detecting contact "
It is good.

  When the cutting tool is brought close to and brought into contact with the workpiece at a high feed rate, the blade moves with the workpiece due to inertia, or occurs when the generated AE is detected by the AE sensor or a signal from the AE sensor is processed. There is a possibility that the detection accuracy of the AE may be lowered due to a large influence of the time lag. On the other hand, the AE detection accuracy can be improved by bringing the cutting tool into close contact with the workpiece at a sufficiently slow feed rate. However, if the feed speed when bringing the cutting tool closer to the workpiece is slowed, this time, the time until the cutting tool is brought close to the workpiece and brought into contact with it becomes longer, resulting in a problem that the entire machining process is delayed.

  Therefore, in the contact detection device having the above configuration, after the cutting tool is brought into contact with the workpiece at a high feed rate, the cutting tool is moved away from the workpiece, and the cutting tool is brought close to the workpiece again at a feeding speed slower than the previous feeding speed. The contact between the workpiece and the cutting tool is detected by the contact. Thereby, the detection accuracy of AE can be improved without delaying the entire machining process. Note that the number of times the workpiece and the cutting tool are repeatedly brought into contact with each other may be two or more, but if the number of times is three or more, the AE detection accuracy can be further improved.

In the means described above,
“With coolant pressure monitoring means for monitoring the coolant pressure between the workpiece and the blade that fluctuates when the blade is brought close to the workpiece,
Based on the monitoring result of the coolant pressure monitoring means, the contact between the workpiece and the blade tool is detected by bringing the blade tool into contact with the workpiece by slowing the feed rate after the coolant pressure has increased beyond a preset pressure. Touch detection device featuring
It is good.

  In machine tools, it is common practice to apply coolant between the workpiece and the blade for cooling the workpiece and the blade, lubricating the workpiece and the blade, and the like. Here, when the cutting tool is brought closer to the work, the distance between the work and the cutting tool is shortened, so that the pressure (dynamic pressure) of the coolant flowing during this time increases.

  Therefore, in the contact detection device configured as described above, the coolant pressure is monitored by the coolant pressure monitoring means to detect that the cutting tool has approached the workpiece, and the subsequent feed rate is slowed down, with a slow feed rate. Bring the cutting tool into contact with the workpiece. Thereby, the detection accuracy of AE can be improved without delaying the entire machining process.

  The coolant pressure monitoring means is not particularly limited, but is one that uses a pressure sensor that measures the pressure of the coolant between the workpiece and the blade, or an appropriate device for rotating or moving the workpiece or the blade. The thing etc. which monitor motive power in a drive apparatus can be illustrated. Here, when monitoring the power of the driving equipment, the coolant pressure is applied to the workpiece and the cutting tool when the coolant pressure increases. Therefore, the power (motor, etc.) required to rotate or move the workpiece or the cutting tool. If this is the case, the driving power (watts) will increase. Therefore, the coolant pressure can be indirectly detected by monitoring this power.

  As described above, according to the present invention, it is possible to provide a contact detection device that is unlikely to vary in the detection accuracy of the AE sensor.

  Next, an example of an embodiment of a contact detection device according to the present invention will be described in detail with reference to the drawings. In the following, an example in which a cylindrical grinder as a machine tool is equipped with the contact detection device according to the present invention will be described. However, the contact detection device according to the present invention is not limited to the cylindrical grinder, but other grinders and lathes. It can be widely applied to various machine tools such as a milling machine and a machining center.

  First, FIG. 1 shows an example of a cylindrical grinder 10, and an outline of the cylindrical grinder 10 will be described. The cylindrical grinding machine 10 includes a bed 20 constituting a base portion, a grinding wheel base 30 mounted on the bed 20 so as to be movable in the X-axis direction, and mounted on the bed 20 so as to be movable in the Z-axis direction. The work table 40 is provided. Here, the grinding wheel base 30 supports the grinding wheel T as a cutting tool, and constitutes a cutting tool base. The work table 40 supports the work W and constitutes a work support.

  The grinding wheel base 30 rotates and drives the grinding wheel T in the X-axis direction. The grinding wheel shaft 31 on which the grinding wheel T is mounted, and the head 32 that rotatably supports the grinding wheel shaft 31. A rotation drive device (not shown) such as a motor for rotating the grindstone shaft 31 is provided. The grindstone platform 30 is moved and driven in the X-axis direction on the bed 20 by a known movement drive device (not shown) configured using a servo motor, a feed screw mechanism, or the like.

  The work table 40 includes a headstock 41 mounted on one end side of the upper surface thereof, and a tailstock 43 mounted on the other end side, and the worktable 40 is supported by the headstock 41 and the tailstock 43. Then, the workpiece W is driven to rotate and moved in the Z-axis direction. Here, the main spindle 41 is provided with a main spindle 42 that supports one end side of the workpiece W. The main spindle 42 is rotationally driven by a rotary drive device (not shown) such as a motor built in the main spindle 41. Is done. Further, the tailstock 43 includes a center 44 that is inserted into a center hole formed in the other end side of the work W, and the other end side of the work W is rotatably supported by the center 44. Furthermore, the work table 40 is driven to move in the Z-axis direction on the bed 20 by a known movement drive device (not shown) configured using a servo motor, a feed screw mechanism, or the like.

  In the cylindrical grinding machine 10 provided with the grinding wheel base 30 and the work table 40, the grinding wheel T supported by the grinding wheel base 30 and the work W supported by the work table 40 are used for the X axis and the Z axis. By actuating each of these movement drive devices, the workpiece W is ground by the grinding wheel T by being relatively moved in the X-axis direction and the Z-axis direction. Here, in this example, in the cylindrical workpiece W including the small diameter portion W1 and the large diameter portion W2, the outer peripheral surface of the small diameter portion W1 is ground from one end of the workpiece W to the end surface of the large diameter portion W2. . In this grinding process, plunge cut grinding for grinding the grinding wheel T by feeding the grinding wheel T to the workpiece W at the grinding feed speed in the X-axis direction is repeatedly performed at an appropriate pitch in the Z-axis direction. The entire Z-axis direction of W1 is finished by traverse cut grinding in which the grinding wheel T is fixed in the X-axis direction and ground at a grinding feed rate in the Z-axis direction to finish the processing. At the start of machining, the grinding wheel T is positioned with its end face in contact with the end face of the large-diameter portion W2 of the workpiece W, and then the first plunge cut grinding is performed. When positioning the grinding wheel T at this time, the grinding wheel T is moved in the Z-axis direction with respect to the workpiece W without contacting the small-diameter portion W1, and the grinding wheel T is brought close to the large-diameter portion W2 to detect contact described later. By detecting the contact between the workpiece W and the grinding wheel T by the apparatus, the grinding wheel T is positioned. Here, the contact detection device is accompanied by an AE sensor 50 that detects AE generated when the workpiece W and the grinding wheel T are in contact with each other, signal processing from the AE sensor 50, and signal processing from the AE sensor 50. And a contact detection control device that controls driving of various devices. The AE sensor 50 is attached to a member on the grindstone base 30 side. Specifically, it is mounted inside the grinding wheel shaft 31 of the grinding wheel base 30.

  Although not described in detail, the cylindrical grinding machine 10 is for processing the workpiece W by numerical control by executing a processing program, and is configured using a computer having a CPU, a ROM, a RAM, a hard disk, and the like. A known CNC control device (not shown) is provided. The driving of various devices such as the driving drive of the grinding wheel base 30 in the X-axis direction, the rotational driving of the grinding wheel shaft 32, the driving of the work table 40 in the Z-axis direction, and the rotational driving of the main shaft 42 are controlled by the CNC control device. The Further, the above-described signal processing from the AE sensor 50 is also performed by this CNC control device. Therefore, in this example, the contact detection control device is constituted by a part of the CNC control device. The contact detection control device is not limited to the one that also serves as the CNC control device, and may be provided separately from the CNC control device.

  By the way, the hard disk of the CNC control apparatus stores a machining program to be executed when machining the workpiece W, and various devices are controlled during the machining by executing the machining program. Therefore, if a program related to the control of the contact detection device is written in the machining program, automatic positioning of the grinding wheel T can be realized every time the workpiece W is machined by executing the machining program. Not limited to this, a contact detection device control program related to the control of the contact detection device is stored separately from the machining program, and the contact detection device control program is executed in a timely manner. Automatic positioning may be performed.

  Next, details of the contact detection device will be described below, including details of the AE sensor 50 and the grinding wheel T, and details of the operation mode.

  The AE sensor 50 is a known sensor that detects AE, and is attached to the inside of the tip portion of the grindstone shaft 31 by a sensor attachment member 51 as shown in FIG. The AE sensor 50 is connected to a CNC control device. Here, in this example, the grindstone shaft 31 is shown in a cantilevered manner supported by the bearing 32a of the shaft head 32. However, as shown in FIG. However, it is preferable to incorporate the AE sensor 50 at the tip of the grindstone shaft 31 because the AE sensor 50 can be easily mounted. Further, since an accessory such as the AE sensor 50 is attached to the grindstone shaft 31, there is a possibility that the rotational balance of the grindstone shaft 31 is lost. In this case, as shown in FIGS. 2 and 3, it is preferable to provide an appropriate balancer 52 together with the AE sensor 50 in the grindstone shaft 31 so as to ensure a good rotational balance of the grindstone shaft 31. .

  The grinding wheel T is positioned by bringing its end face into contact with the end face of the large-diameter portion W2 of the workpiece W. Therefore, as shown in FIG. 4, the grinding wheel Ta for grinding and the end face are provided on the outer peripheral face. An elastic grindstone Tb is provided.

  As shown in FIG. 5, the grinding wheel T is moved in the Z-axis direction with respect to the workpiece W by the contact detection device to which the AE sensor 50 and the grinding wheel T configured as described above are applied. When contact is started with the end face of the large-diameter portion W2 of the workpiece W, the grinding wheel T is stopped by stopping the movement of the grinding wheel T in the Z-axis direction. This will be specifically described below.

  At the stage before the start of the operation of the cylindrical grinding machine 10, the grinding wheel T is located at the origin, which is a part sufficiently separated from the workpiece W. At the start of the operation, the grinding wheel T is moved at a fast feed speed. Move in the X-axis direction and the Z-axis direction to approach the workpiece W. At this time, based on the set position of the workpiece W, not the actual position of the actual workpiece W, there is a sufficient distance between the workpiece W and the grinding wheel T so that the grinding wheel T does not reliably collide with the workpiece W. The grinding wheel T is brought close to the workpiece W to the secured position. Hereinafter, the position of the grinding wheel T is referred to as a first approach position.

  Next, the grinding wheel T is moved from the first approach position at the first approach speed slower than the rapid feed speed in the Z-axis direction to approach the large diameter portion W2 of the workpiece W, and the large diameter portion W2 is moved. Contact (shown arrow A). Then, AE occurs due to the contact between the workpiece W and the grinding wheel T. Therefore, by detecting this AE by the AE sensor 50, the current position of the grinding wheel T can be specified as the position where the contact with the workpiece W is started. Here, since the AE sensor 50 is provided on the grinding wheel base 30 side, particularly on the grinding wheel shaft 31, the AE sensor 50 detects AE with high accuracy. Further, since the elastic grinding wheel Tb provided on the end face of the grinding wheel T is brought into contact with the workpiece W, even if the grinding wheel T is brought into contact with the workpiece W at a somewhat high feed rate, the grinding wheel T is damaged or the workpiece W Will not be damaged.

  Next, the grinding wheel T is slightly retracted at a rapid feed speed from the position in contact with the work W at the first approach speed to the second approach position that is closer to the work W than the first approach position. Move away from the large diameter portion W2 of W (arrow B in the figure). Next, again, the grinding wheel T is moved closer to the large diameter portion W2 of the workpiece W from the second approach position at a second approach speed that is slower than the first approach speed, AE is generated by contact (arrow C in the figure). Then, by detecting this AE by the AE sensor 50, the position of the grinding wheel T in a state where the contact with the workpiece W is started is specified with high accuracy, and the grinding wheel T is stopped at this position, and the grinding wheel The positioning of the vehicle T in the Z-axis direction is completed. Thereafter, the grinding wheel T is moved in the X-axis direction at a grinding feed speed, and a predetermined grinding process for performing plunge cut grinding on the small diameter portion W1 of the workpiece W is executed.

  By the way, in the grinding process, a coolant is poured between the workpiece W and the grinding wheel T. Therefore, by contacting the workpiece W and the grinding wheel T a plurality of times as described above, the feed speed of the grinding wheel T when finally contacting the workpiece W is not limited to being set, Instead of this mode, or in combination with this mode, the grinding wheel T feeds when contacting the workpiece W by utilizing the pressure fluctuation of the coolant flowing between the workpiece W and the grinding wheel T. The speed may be set slower. Specifically, the pressure of the coolant flowing between the workpiece W and the grinding wheel T is monitored by the coolant pressure monitoring means, and the coolant pressure increases to a preset pressure or greater, thereby increasing the diameter of the workpiece W. You may make it specify that the grinding wheel T approached the part W2, make the subsequent feed speed slow, and make the grinding wheel T contact the workpiece | work W at slow feed speed. Here, the rotational driving device such as a motor for rotating the grinding wheel T rotates the grinding wheel T at a high speed and at a constant speed with high accuracy, so that the stress applied to the grinding wheel T varies. Then, the power of this rotary drive device fluctuates greatly. Therefore, the coolant pressure applied to the grinding wheel T can be detected with high accuracy by monitoring the power of the rotary drive device. Therefore, it is preferable to employ a coolant pressure monitoring means that monitors the power of the rotational drive device that rotationally drives the grinding wheel T and indirectly monitors the coolant pressure.

  In the above, an example of the contact detection device according to the present invention has been described. However, the contact detection device according to the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention.

  For example, the usage mode of the contact detection device is not limited to positioning a cutting tool such as a grinding wheel with respect to the workpiece in the Z-axis direction, but for positioning the cutting tool in the X-axis direction, or other than the X-axis and the Z-axis. In a machine tool having other axes, the cutting tool may be used for positioning in other axial directions. In addition to the positioning of the cutting tool, for example, a contact detection device may be used to change the feed speed to a processing feed speed for processing after the cutting tool is brought into contact with the workpiece at an appropriate feed speed.

It is a top view which shows an example of a cylindrical grinder. It is a section partial top view showing an example of a grindstone axis. It is a section partial top view showing another example of a grindstone axis. It is a section partial top view showing an example of a grinding wheel. It is the schematic which shows the operation | movement aspect of a contact detection apparatus.

Explanation of symbols

T grinding wheel (blade)
Ta Grinding wheel Tb Elastic grinding wheel W Workpiece W1 Small diameter part W2 Large diameter part 10 Cylindrical grinding machine (machine tool)
20 beds 30 grinding wheel stand (tool stand)
31 Grinding wheel shaft 32 Shaft head 32a Bearing 40 Work table (work support base)
41 Spindle block 42 Spindle 43 Tailstock 44 Center 50 AE sensor 51 Mounting member 52 Balancer

Claims (5)

Contact detection for detecting contact between the workpiece and the blade tool provided in a machine tool including a workpiece support table that supports the workpiece and a blade tool table that supports the blade and moves relative to the workpiece support table. A device,
A contact state detection apparatus comprising an acoustic emission sensor that is disposed on the blade base side and detects an acoustic emission when the workpiece and the blade are in contact with each other. The cutting tool is a grinding wheel,
The tool rest has a grinding wheel shaft on which the grinding wheel is mounted,
The contact detection apparatus according to claim 1, wherein the acoustic emission sensor is assembled inside the grindstone shaft. The grinding wheel includes a grinding wheel for grinding, and an elastic grinding stone whose binder is made of an elastic material,
The contact detection apparatus according to claim 2, wherein contact between the workpiece and the grinding wheel is detected by bringing the elastic grindstone into contact with the workpiece.   After bringing the cutting tool into contact with the work, move the cutting tool away from the work, and again bring the cutting tool into contact with the work at a feeding speed slower than the previous feeding speed, thereby contacting the work and the cutting tool. The contact detection device according to claim 1, wherein the contact detection device detects the contact. A coolant pressure monitoring means for monitoring a coolant pressure between the workpiece and the blade that fluctuates when the blade is brought close to the workpiece;
Based on the monitoring result of the coolant pressure monitoring means, the contact between the workpiece and the blade tool is detected by bringing the blade tool into contact with the workpiece by slowing the feed rate after the coolant pressure has increased beyond a preset pressure. The contact detection device according to any one of claims 1 to 4, wherein the contact detection device is characterized in that:

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