JP2010089182A - Machine tool having workpiece reference measurement position setting function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a machine tool having a workpiece reference measurement position setting function capable of obtaining the center coordinate of a workpiece and setting it as the workpiece reference measurement position. <P>SOLUTION: A workpiece symmetrical to two lines in which machined surfaces are orthogonal to each other is arranged to make the axis of the mechanical coordinate system and two lines parallel to each other. A spherical measurement piece of a probe of an on-machine measurement instrument is relatively moved toward an end face of the workpiece from the top of the machining surface of the workpiece along the first line parallel to the two lines. After the spherical measurement piece is detached from the end face of the workpiece, the coordinate when the moving speed in the axial direction of the probe reaches the predetermined value is stored (S2-S11). Similarly, the coordinate is stored for the second line (S12-S21). Each mid-point is obtained from the stored coordinate. The obtained coordinate of the mid-point is the center coordinate of the workpiece, and can be set as the reference measurement position of the workpiece. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a machine tool provided with an on-machine measuring device for measuring and analyzing the shape of a workpiece (work) on a machine tool, and more particularly, provided with a reference position setting function for measuring the shape of a workpiece. It relates to machine tools.

  In ultra-precision machining, in order to achieve nano-scale shape accuracy, the machined shape is measured (on-machine measurement) on the machine tool without removing the finished workpiece from the machine tool, and the measurement result is used. It is essential to perform correction processing.

  In such on-machine measurement, accurate correction processing is possible by establishing the positional relationship between the cutting edge of the tool and the stylus tip of the probe provided in the on-machine measuring device. Therefore, the relationship between the coordinates when machining the workpiece and the measurement coordinates when measuring on the machine must be established. The relationship between the coordinates when machining the workpiece and the measurement coordinates when measuring on the machine must be established. It is necessary to set the measurement reference position of the workpiece in order to take the relationship between the coordinates when machining the workpiece and the measurement coordinates when measuring on the machine.

Conventionally, the following methods are known as methods for setting the measurement reference position of a workpiece.
The measurement reference position of the workpiece is set as the center of the rotation axis to which the workpiece is attached. For this purpose, first, the centering sphere is placed on the face plate of the rotating shaft to which the work is attached. Then, after the center of the centering sphere is aligned with the center of the rotation axis using the displacement detector, the centering sphere is vertexed using the probe of the on-machine measuring device to determine the center coordinates of the rotation axis. Next, the centering sphere is removed and the work is attached. The method of aligning the center coordinates of the workpiece or workpiece jig with the center of the rotation axis using a displacement detector, and using the calculated center axis of the rotation axis as the reference position of the workpiece or workpiece jig Are known.

  Further, in Patent Document 1, the vertex that is necessarily present in the axially symmetric shape is determined by measuring on the cross machine without matching the center of the workpiece to the rotation axis to which the workpiece is attached, and the vertex that is estimated to be the center of the workpiece is estimated. A technique using as a measurement reference point is disclosed. In this technique, the shape of the target workpiece is limited to an axisymmetric shape only. Moreover, since the shape of the rough-worked workpiece before the main machining is measured on the machine, it is difficult to say that the vertex obtained by the measurement is the center of the workpiece. Therefore, in order to deal with the problem of mismatch between the center of the workpiece and the apex obtained by on-machine measurement, an extra space is provided on the workpiece other than the machining surface, and even if the centers do not match, the extra space is machined. Yes.

  Patent Document 2 discloses a technique for obtaining center coordinates of a workpiece by estimating end surface coordinates of the workpiece. In this technique, when measuring the shape of a workpiece using a contact probe, a rapid change in the displacement of the probe at the end surface of the workpiece is detected to obtain the measurement origin.

  Patent Document 3 discloses a technology of a machine tool having a workpiece reference position setting function based on contact detection. In this technique, a machine tool whose movable shaft is supported by a fluid bearing is used to make a workpiece line-symmetric with respect to two lines whose processing surfaces are orthogonal to each other so that the axis of the machine coordinate system and the two lines are parallel to each other. The measurement ball at the tip of the stylus of the probe is contacted from both sides of the workpiece along a first line parallel to the two lines, the positional deviation increased by the contact is measured, and the contact between the measurement ball and the workpiece Is detected.

  Patent Document 4 discloses a machining origin setting method and a machine tool technique for carrying out the method. This technology is a technology for easily and accurately setting the processing origins of a rotary tool and a workpiece without applying cost. A load torque that does not rotate the rotary tool is applied to the spindle, and the load torque is applied to the spindle. In this state, one of the spindle and the work table is jog-fed so that the tip of the cutting edge moves away from the outer surface, and the coordinates when the rotation of the spindle is detected are set as the machining origin.

JP 2006-21277 A JP 2000-298014 A JP 2008-200808 A JP 2008-62351 A

  The method of setting the reference position of the workpiece by placing the centering sphere, which is the conventional technology described in the background art, on the rotary shaft surface plate to which the workpiece is attached, involves a complicated procedure up to the reference position setting. It takes time. Moreover, it is inevitable that an error occurs when the work piece is attached with the centering sphere removed. Furthermore, unless the workpiece is cylindrical, it is difficult to make the center of the workpiece cylindrical jig coincide with the center of the workpiece. Further, depending on the skill level of the operator, a considerable setting error may occur, which is a problem.

  Recently, in addition to ultra-precision machining that processes the entire surface of a workpiece, the workpiece itself is provided with a precisely finished shape and dimensions, and the machining surface within such workpiece is positioned with high accuracy. Is now required. However, the technique disclosed in Patent Document 1 cannot cope with the recent problems of the overall processing of the workpiece and the accuracy of the shape and dimensions of the workpiece.

  Further, in the technique disclosed in Patent Document 2, since the contact of the contact probe is spherical and the edge of the workpiece end surface cannot be accurately detected, the edge of the workpiece end surface is estimated by processing measurement data. . Therefore, if the number of measurement data samplings is small, accurate estimation cannot be performed. There is a possibility that the workpiece end face shape data differs from the actual end face shape due to vibration of the measuring device, scratches on the end face of the object to be measured or the surface of the spherical contact or adhesion of dust.

  In the technique disclosed in Patent Document 3, the positional deviation is increased by a control program in the numerical controller. The setting of the position deviation value, selection of the moving axis, the moving speed of the moving axis and the like need to be changed each time according to the machining operation setup, and therefore they must be set again in the numerical controller. In this resetting operation, if there is a setting error (especially a code), accurate detection cannot be performed. In the worst case, the probe or the movable shaft keeps moving, and the probe and the workpiece collide with a strong force, and the probe and the workpiece may be damaged. Further, in this technique, in order to measure a minute change in position deviation, it is premised that the drive shaft of the machine tool is a mechanism without friction by a fluid bearing. And even if it is a fluid bearing, if it is a screw type thing, there exists a danger that a fluid bearing will bite by contact misdetection, Therefore It is necessary to limit to a linear type.

  In the technique disclosed in Patent Document 4, the surface to be detected is a surface on one side of the workpiece, and the surface on the opposite side is attached to a jig or the like. In order to detect the surface attached to the jig or the like, the main shaft or the work must be rotated 180 degrees. However, it is very difficult to make such a posture in a machine tool, and the main shaft is rotated 180 degrees. Even if the spindle is not accurately positioned, it is very difficult to keep the line segment of both coordinates to be detected level with the moving axis unless the spindle is accurately positioned. Therefore, the center of the work cannot be specified accurately.

  Accordingly, an object of the present invention is to provide a machine tool having a measurement reference point setting function capable of solving the problems of the prior art and setting a center position of a workpiece as a measurement reference position of an on-machine measuring device.

  The invention according to claim 1 of the present application includes an on-machine measuring device for shape measurement and shape analysis of a workpiece that is line-symmetric with respect to two lines in which the machining surfaces of the workpiece are orthogonal to each other. In a machine tool having a plurality of movable shafts controlled by a numerical controller to which a position detection signal is input, the on-machine measuring device includes a contact type probe supported by a fluid bearing inside the on-machine measuring device, and the contact Position detecting means for detecting a movement displacement in the axial direction of the probe and outputting a position detection signal, and the machine tool includes movable axis position detecting means for detecting the position of each movable axis of the machine tool, In the numerical control device, the contact point of the contact-type probe is brought into contact with the machining surface of the workpiece arranged so that the two lines are parallel to the axis of the machine coordinate system at a constant contact pressure. From the end face of the workpiece The movable shaft is moved so that the contact probe moves in the direction parallel to the two lines until the contact probe probe is completely separated from the machining surface of the workpiece toward the end surface. A movable axis driving control means for driving, a probe moving speed calculating means for calculating a moving speed in the axial direction of the contact probe based on a position detection signal output from the position detecting means, and a probe moving speed calculating means. Determining means for determining whether or not the calculated moving speed has reached a predetermined speed; and each of the movable shafts when the determining means determines that the moving speed has reached a predetermined speed. Storage means for storing position data of each movable axis detected by the position detection means, and the center of the workpiece from the position of each movable axis stored in the storage means Is a machine tool having calculated the target setting means for setting a measurement reference point of the workpiece, the workpiece measurement reference point setting function, comprising the.

  In the invention according to claim 2, the position detection signal from the movable shaft position detecting means for detecting the position of each movable shaft of the machine tool is input to the numerical controller via an interface of a motor driving device that drives the motor. 2. The workpiece measurement standard according to claim 1, wherein a position detection signal from the on-machine measuring device is input to the numerical controller via an interface of a motor driving device not connected to a motor. A machine tool having a point setting function.

In the invention according to claim 3, the signals output from the movable shaft position detecting means and the contact type probe position detecting means are composed of two-phase sine wave analog signals whose phases are different by approximately 90 degrees,
The interface includes an A / D conversion device that converts the sine wave analog signal into a digital signal, and a digital signal obtained by dividing the digital signal output from the A / D conversion device into one cycle of the sine wave analog signal. The machine tool having a workpiece measurement reference point setting function according to claim 2, further comprising an interpolation unit for outputting.

  The invention according to claim 4 is characterized in that the position detection device provided in the position detection device or the on-machine measurement device is any one of a linear scale, a pulse coder, and a laser interferometer. It is a machine tool which has the measurement reference point setting function of the workpiece | work as described in any one of Claims 1-3.

  According to a fifth aspect of the present invention, the storage means stores each of the movable shafts detected by the respective movable shaft position detection means when the determination means determines that the moving speed has reached a predetermined speed. 5. A machine tool having a workpiece measurement reference point setting function according to claim 1, wherein position data is automatically stored.

  According to a sixth aspect of the present invention, the setting means obtains a difference in position data of the movable shaft stored in the storage means at the left and right ends of the machining surface in the horizontal direction, and reduces the half of the difference by a smaller value. The coordinate added to the coordinate of the workpiece is set as the center coordinate in the horizontal direction of the workpiece, the difference between the position data of the movable axis stored in the storage means at the upper and lower ends of the vertical direction of the machining surface is obtained, and the value half the difference 6. The center coordinate of the workpiece is obtained by setting the coordinate obtained by adding to the smaller coordinate as the center coordinate in the vertical direction of the workpiece, and set as a measurement reference point of the workpiece. Is a machine tool having a measurement reference point setting function for the workpiece.

  According to the present invention, it is possible to provide a machine tool having a measurement reference point setting function capable of setting a measurement reference point of a workpiece using an on-machine measuring device having a configuration in which a contact probe is hydrodynamically bearing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, an on-machine measuring machine used in the embodiment of the present invention will be described. FIG. 1 shows a cross section of the main part of an on-machine measuring device 1 used in the embodiment of the present invention. This on-machine measuring device 1 includes a probe main body 1b, which is a movable part, built in a case 1a. The probe main body 1b is supported by a bearing (not shown) and is movable in the central axis direction of the probe main body 1b. A fluid bearing such as an air bearing is used as the bearing.
A linear scale 1d is attached to the probe main body 1b. Laser light is irradiated from the laser head 1c onto the linear scale 1d, and reflected light from the linear scale 1d is received by a light receiving element (not shown) to detect the displacement of the probe main body 1b in the axial direction.

  A stylus 1e including a spherical probe 1f is attached to one end of the probe main body 1b. The stylus 1e is a thin rod-shaped member. One end of the stylus 1e is fixed to the probe main body 1b, and a spherical measuring element 1f is attached to the other end. For ease of explanation, hereinafter, the probe body 1b, the stylus 1e, and the spherical probe 1f are collectively referred to as a probe Pr.

  The spherical measuring element 1f of the probe Pr is pressed against the processing surface Wa of the workpiece W with the contact pressure T, and performs shape measurement while following the processing surface Wa. The contact pressure T can be adjusted to a contact pressure of an appropriate size by using a magnet, an elastic body such as a spring, or an urging means (not shown) such as fluid pressure built in the on-machine measuring device 1. The probe Pr can be moved and displaced in the arrow direction of the probe moving direction shown in FIG. Further, the movable displacement range of the probe Pr is regulated by a regulation means in the on-machine measuring device 1 (not shown). For this reason, even if the spherical probe 1 f of the probe Pr is separated from the processing surface Wa of the workpiece W, there is no possibility that the probe main body 1 b of the probe Pr jumps out of the on-machine measuring device 1.

  FIG. 2 shows that the spherical probe 1f of the probe Pr moves relative to both ends of the machining surface Wa of the workpiece W and moves away from the workpiece W in a state where the spherical probe 1f of the probe Pr is in contact with the machining surface Wa of the workpiece W. (Route RR and route RL). Here, the processed surface Wa of the workpiece W is a rough processed surface or a processed surface before correction processing. The symbol AP is a position where the probe Pr contacts the machining surface Wa of the workpiece W in order to detect the position of the end surface of the workpiece W (hereinafter referred to as “approach position AP”). The operation of the probe Pr with respect to the work surface Wa of the workpiece W shown in FIG. 2 is a principle operation of the probe Pr in the present invention.

  First, the probe Pr is relatively moved from the approach position AP of the processing surface Wa of the workpiece W toward the right side of the paper (path RR), and after moving away from the right end surface position RE of the workpiece W, the approach position of the workpiece W again. Returning to AP, the probe Pr is relatively moved from the approach position AP on the processing surface of the workpiece W toward the left side of the drawing (path RL), and is moved until it is separated from the left end surface position LE of the workpiece W. Thus, the position of the both end surfaces of the workpiece | work W is detected by moving the probe Pr relatively with respect to the process surface Wa of the workpiece | work W. FIG.

Next, the principle of the present invention for detecting the position of the end face of the workpiece W described in FIG. 2 will be described in more detail with reference to FIG. First, symbols in FIG. 3 will be described. T is a contact pressure which is a force with which the spherical probe 1f of the probe Pr presses the machining surface Wa of the workpiece W. V ₀ is an initial velocity in the axial direction of the probe Pr when the probe Pr moves away from the machining surface Wa of the workpiece W. V is the moving speed in the axial direction of the probe Pr after the probe Pr is separated from the processing surface Wa of the workpiece W. M is the mass of the probe Pr. α is the acceleration in the axial direction of the probe Pr after the probe Pr leaves the processing surface Wa of the workpiece W. t is the elapsed time from when the spherical probe 1f of the probe Pr is detached from the end surface of the processed surface Wa of the workpiece W. v represents the feed speed along the machining surface Wa of the workpiece W of the probe Pr.

The probe body 1b of the probe Pr provided in the on-machine measuring device 1 is supported by a fluid bearing such as an air bearing. Then, the processing surface Wa of the workpiece W is copied while being pressed by the spherical measuring element 1f with the contact pressure T. The contact pressure T is an external force that acts on the probe body 1b from the biasing means such as the magnetic force described above.
Here, it is assumed that the downward direction in the vertical direction is a direction perpendicular to the paper surface and directed from the front side to the back side of the paper surface, and there is no influence of gravity on the movement of the probe Pr. The contact pressure T is a constant force that does not vary.

  In the state A, since the spherical measuring element 1f is following the processed surface of the workpiece W, the spherical measuring element 1f receives the drag force -T of the contact pressure T from the processed surface of the workpiece W. When the processing surface of the workpiece W is a plane perpendicular to the axis of the probe Pr, the moving speed in the axial direction of the probe main body 1b is almost zero.

  In the state B, the spherical probe 1f of the probe Pr is completely separated from the machining surface of the workpiece W, and the spherical probe 1f does not receive the drag force -T of the contact pressure T from the machining surface Wa of the workpiece W. . Accordingly, the probe Pr moves at a constant acceleration with an external force (size T) equal to the contact pressure T. Here, when the mass of the probe Pr is represented by M and the acceleration of the acceleration motion of the probe Pr is represented by α, the equation of motion of the probe Pr can be represented by T = M * α. The probe Pr can move to the movable range of the probe main body 1b. In the on-machine measuring device 1, the force acting on the probe Pr from the urging means does not instantaneously become zero even if the spherical probe 1 f of the probe Pr is separated from the processing surface Wa of the workpiece W.

  As a result, the feed rate of the probe Pr is the same, the contact pressure T when the spherical probe 1f is separated from the end surface of the processed surface of the workpiece W is the same, and the spherical probe 1f is the workpiece W. If the initial velocity in the axial direction of the probe Pr when moving away from the end surface of the workpiece W is the same, the change in the velocity of the probe Pr after the spherical probe 1f leaves the workpiece W machining surface is the machining surface of the workpiece W. The position of any end face of Wa is the same, and the locus of movement of the probe Pr is the same locus at any end face of the machining surface Wa of the workpiece W.

  Next, changes in the locus and speed of the movement of the probe Pr will be described with reference to FIG. In FIG. 4, only the spherical probe 1f of the probe Pr is shown, and the movement locus of the probe Pr will be described. FIG. 4 illustrates in detail how the spherical probe 1f of the probe Pr moves away from the processing surface Wa (measurement surface) of the workpiece W. It should be noted that it is easy to understand when viewing FIG. 4 while referring to FIG.

In the position P1, the probe Pr is located at the end face position of the workpiece W, but since the spherical probe 1f is spherical, the spherical probe 1f is often not separated from the end face at this point.
● The measurement up to the end of the workpiece W is up to the position P2. Usually, since the spherical probe 1f of the probe Pr moves following the processing surface (measurement surface), the velocity of the probe Pr in the probe axis direction to the position P2 is close to 0 (zero), and a minute velocity change is rough. This is because of a shape error on the processed surface before processing or the processing surface before the correction processing, and a deviation of the actual shape of the processing surface of the workpiece W and the path RR along which the probe Pr moves.
● From the position P2 to the position P3, the center axis of the probe Pr is away from the workpiece end surface, but the spherical probe 1f is spherical, so that there is still contact between the spherical probe 1f and the workpiece W. It is. Since this section is not the assumed machining surface (measurement surface), it cannot move along the shape, and the speed change becomes large. However, since the measurement surface of this part is not a machined surface, the speed change is irregular.

The position P3 is when the spherical measuring element 1f is completely separated from the workpiece W. From this point of time, there is no influence of friction with the work surface Wa (measurement surface) of the work and no drag from the work surface. Since the probe body 1b of the probe Pr is supported by the fluid bearing as described above, no frictional force acts on the probe body 1b. Therefore, from this point of time, the speed of the probe Pr in the axial direction becomes a linear speed change based on the contact pressure T (pushing force) (however, the contact force T is constant). The speed at the time of leaving is represented by Va. The change in the velocity of the probe Pr in the axial direction is as described with reference to FIG. In the case where the contact pressure T is adjusted by the inclination of the probe Pr, the speed change of the probe Pr depends on the gravitational acceleration and the inclination angle.

The position P4 is a coordinate when the speed Vb determined in advance for detection is reached (hereinafter referred to as “detection coordinate”). If the posture of the probe Pr, the moving speed of the probe Pr in the scanning direction, and the contact pressure T are the same, the difference between the end surface position (position P1) of the workpiece W and the detection coordinates (position P4) is constant at any end surface. The exact end face position can be obtained. Based on this, an accurate center position of the workpiece W is obtained.
In FIG. 4, as shown in FIG. 4C, the end face is detected when the axial movement speed of the probe is Vb.

  In the above description, the contact pressure T is constant and is not affected by gravity. However, when the probe Pr is brought into contact with the machining surface of the workpiece W shown in FIG. 2 from the direction in which gravity acts on the probe Pr and the right end surface position RE and the left end surface position LE of the workpiece W are detected, the gravity is equal to the probe Pr. Therefore, the difference between the position of the end face of the workpiece W and the detected coordinates is constant at any end face, as in the case where there is no influence of gravity. Further, when the right end surface position RE and the left end surface position LE are detected, the variation of the contact pressure T with time may be the same, and the contact pressure T is not necessarily limited to be constant. In other words, the same physical condition is required at any end surface position of the workpiece W.

  Next, an embodiment of the present invention of a machine tool having a workpiece measurement reference point setting function using the above-described measurement principle will be described. FIG. 5 is an example of a machine tool that is controlled by a numerical control device and each axis is driven by a linear motion axis or a rotation axis. In FIG. 5, the X axis, the Y axis, and the Z axis have linear motion axes, the X axis is the B axis that is the rotation axis, and the Y axis is the C axis that is the rotation axis. The main part of a machine tool capable of being shown is shown. Since the basic principle of the present invention is to detect the end face of the workpiece in the direction in which the contact type probe of the on-machine measuring device is detached, the present invention is not limited to a fluid bearing for the movable shaft of a machine tool. Applicable to movable shaft.

  FIG. 6 is a schematic configuration diagram of an embodiment of a machine tool that inputs a position detection signal from the on-machine measuring device and a position detection signal from each drive shaft of the machine tool to the numerical control device. In this embodiment, the servo controller 8b of the numerical controller 8 receives a position that is a measurement signal related to the displacement of the probe main body 1b from the on-machine measuring device 1 attached to the B axis that measures the surface shape of the workpiece W. The detection signal ipf is input via the interface 2 (see FIG. 8B). A position detection signal output from a position detection device provided on each movable shaft of the machine tool is also input to the servo control unit 8b through an interface (not shown) while being simply synchronized. In this interface, the position detection signal output from the position detection device 96 (see FIG. 7) built in the servo motor 95 and the measurement signal output from the on-machine measurement device 1 are converted into a servo control unit of the numerical control device 8. It is configured to input in synchronization with 8b.

  In the embodiment of the present invention, the position detection device that detects the displacement of the probe main body 1b of the on-machine measuring device 1 and the position detection device that detects the position of the linear motion axis of the machine tool include, for example, a linear scale, a laser interferometer. It is preferable to use a high-precision detection device such as The position detection device for detecting the position of the rotation axis of the machine tool may be a pulse coder.

  Further, the numerical control device 8 stores the position information of each movable axis of the machine tool and the measurement information (position information) from the on-machine measuring device 1, and the position information stored in the storage means to the outside. An interface for sending to the personal computer 11 of the storage device is provided. The axial movement speed of the probe Pr can be calculated from position information stored in the numerical controller 8. For example, the speed can be obtained from the difference in position information for each control cycle.

  A servo control unit of the numerical control device 8 via an interface (see FIG. 8) having the same circuit configuration as the position detection signal that is a feedback signal from each movable axis of the machine tool and the position detection signal from the on-machine measuring device 1 8b, the measurement signals from the position detection device for each axis and the on-machine measurement device (that is, the axis position detection signal for each axis and the position detection signal for the on-machine measurement device) are obtained from the numerical control device 8. Input in sync with. Then, the read axis position detection signal and position detection signal are stored as position information in a storage means (not shown) that is a register of the numerical controller 8 for each control cycle of the numerical controller.

  In the present invention, as means for detecting the position of the end face of the workpiece W and storing it as detection coordinates, when the moving speed of the probe Pr in the axial direction exceeds a predetermined value, the position data of the movable shaft is rewritten for each control cycle. This can be done by a ladder program such as a method of interrupting rewriting of a stored register (ladder normally closed contact) or a method of transferring to another storage register (DIFU, MOV). DIFU is a signal rise detection command, and MOV is a data transfer command.

  Further, the numerical control device 8 performs LAN communication with the personal computer 11 which is an external device via the Ethernet (registered trademark) 12, and the storage device 11 a connected to or built in the personal computer 11 has position information and a function from each axis. The measurement signal from the upper measuring device 1 is sent to the personal computer 11. The personal computer 11 stores the position information from each axis and the position information from the on-machine measuring device 1 in synchronization with the storage device 11a for each sampling period.

  Measurement software is stored in the personal computer 11 and necessary arithmetic processing such as measurement of the shape of the workpiece is executed based on the position information read via the numerical controller 8. Necessary arithmetic processing such as shape measurement is the same as in the prior art. The personal computer 11 stores a measuring NC program, a machining NC program, and a machining correction NC program.

  FIG. 7 is a diagram for explaining that signals from each movable shaft of the machine tool and the on-machine measuring device are simultaneously feedback-controlled by the numerical controller in the machine tool shown in FIG. FIG. 7 shows that the movable axes X, Y, Z, B, and C of the machine tool shown in FIG. 6 are controlled by the servo control units 8bX, 8bY, 8bZ, 8bB, and 8bC of the numerical controller 8. It is a figure which shows that feedback control is carried out. This feedback control is control normally performed by a numerical control device that controls a machine tool. The X-axis servo control unit 8bX will be described as an example. In FIG. 6, parts having similar functions are described with the same reference numerals. It comprises a speed control unit 92 and a current control unit 93 that controls the current loop.

The position control unit 91 includes an error register 91a and a position loop gain K amplifier 91b. The position control unit 91 receives the movement command from the numerical control unit 8 a, processes the position deviation amount obtained by subtracting the position feedback amount (position FB), and outputs the speed command to the speed control unit 92. This position deviation amount is calculated by the error register 91a as shown in FIG. The positional deviation amount calculated by the error register 91a is also output to the numerical control unit 8a.
Based on the speed deviation amount obtained by subtracting the speed feedback amount (speed FB) from the speed command, the speed control unit 92 performs speed loop control by the speed control unit 92 and outputs the current command to the current control unit 93. .

  The current control unit is obtained by subtracting current feedback (current FB) from a current sensor (not shown) that detects a current flowing through the servo motor 95 built in the amplifier 94 that drives the servo motor 95 from the current command. Current loop control is performed based on the current deviation amount. The servo motor 95 is drive means for driving the X-axis, and a detection device (hereinafter referred to as “position detection device”) 96 for detecting the position / velocity is attached to the servo motor 95. The position fadeback amount (position FB) from the position detection device 96 is fed back to the position control unit 91, and the speed feedback amount (speed FB) is fed back to the speed control unit 92.

  The above is the description of the configuration of the X-axis servo control unit 8bX. The other movable-axis servo control units 8bY, 8bZ, 8bB, and 8bC have the same configuration as the X-axis servo control unit 8bX. Omitted. Note that the X axis, the Y axis, and the Z axis are linear motion axes, and the B axis and the C axis are rotation axes.

  In the present embodiment, a servo controller 8bF that does not connect a motor that drives the movable shaft of the machine tool and its position / speed detection means is provided. Note that “F” of reference numeral 8bF means “free” in the sense that the movable axis of the machine tool is not controlled, and does not mean any movable axis of the machine tool.

  The numerical control unit 8 recognizes that the servo control unit 8bF is simply increased by one control axis. The increased servo control unit 8bF is connected to an amplifier similarly to the other servo control units 8bX to 8bC that control the movable shaft of the machine tool. Since no servo motor is connected to the servo control unit 8bF, the numerical control device 8 is configured so that the position detection signal is counted as usual using the follow-up function while the servo control unit 8bF is turned off. Parameters and control software are changed.

  The on-machine measuring device 1 is connected to the servo controller 8bF instead of the servo motor. In this embodiment, the servo control unit 8bF is replaced with a position detection signal from the position detection device 96 built in the servo motor 95 via an interface of an amplifier connected to the servo control unit 8bF. A measurement signal ipf from the measurement apparatus 1 is input. The interface is provided in an amplifier and is not different from the prior art.

  FIG. 8 is a block diagram showing an example of an interface used in the embodiment of the present invention. As shown in FIG. 8A, the amplifier unit is provided with an amplifier 94 which is a motor driving means, an A / D conversion device 97, and an interpolation division device 98. An original signal (sine wave, cosine wave) output from the position detection device 96 built in the servo motor 95 is input to the A / D conversion device 97.

  The A / D conversion device 97 converts the original signal, which is an analog signal from the position detection device, into a digital signal, and outputs this digital signal to the interpolation division device 98. The interpolation / splitting device 98 performs a process of dividing the digital signal for one cycle of the original signal (one cycle of the sine wave). As processing performed when a finer resolution is required than the resolution of a normal analog signal, one period of the original signal is divided finely, and the divided period is set as the resolution.

  The same applies to FIG. 8B. FIG. 8B is an example of the interface 2 in FIG. As described above, the on-machine measuring device 1 can also be used to easily capture the signal in the numerical control device 8 in synchronization with the use of the servo motor drive control interface. It is not necessary to prepare a special interface for, and cost increase can be avoided. In addition, the input of the position detection signal from the on-machine measuring device 1 to the numerical control device 8 is not limited to the interface shown in FIG.

  FIG. 9 is an explanatory diagram when the workpiece W is a rectangular parallelepiped and the center coordinates of the machining surface Wa are obtained and set as the reference position of the workpiece in the embodiment of the present invention. Here, the workpiece W is attached to the machine tool as shown in FIG. In this rectangular parallelepiped work W, as shown in FIG. 9A, the machining surface Wa is a vertical surface, and the machining surface Wa is two orthogonal directions in the vertical direction (Y-axis direction) and the horizontal direction (X-axis direction). This is a line-symmetric shape with respect to the straight line. Note that the processing surface Wa is not limited to a flat surface, and for example, the shape of the processing surface Wa projected onto the XY plane may be a line-symmetric shape with respect to two orthogonal lines.

  When such a center coordinate of the workpiece W is detected and set as a measurement reference point of the workpiece, the spherical probe 1f provided on the stylus 1e of the probe Pr in the on-machine measuring device 1 is used for the machining surface Wa of the workpiece W. The approach position AP is moved while following the machining surface Wa along a line parallel to the line symmetry line, and moved until the spherical measuring element 1f is completely separated from the end of the machining surface Wa. And the coordinate when the moving speed of the probe Pr in the axial direction becomes a predetermined value is stored as the detected coordinate.

  9B and 9C, the workpiece W and the probe Pr are relatively moved in the horizontal direction (X-axis direction), so that the spherical probe 1f is completely separated from the machining surface Wa of the workpiece W. It is operation | movement explanatory drawing which calculates | requires the detection coordinate at the time. FIG. 9B is a diagram when the upper surface Wb of the workpiece W is viewed from above, and is a diagram as viewed from above in FIG. FIG. 9C is a diagram when the machining surface Wa of the workpiece W is viewed from above, and is a diagram in which the machining surface of the workpiece W is looked down from the direction of the on-machine measuring device 1 in FIG.

  First, the X-axis, Y-axis, and Z-axis are moved to bring the spherical probe 1f of the probe Pr into contact with the approach position AP (see FIG. 9C) of the work surface Wa of the workpiece W with the contact pressure T. Then, the spherical measuring element 1f moves from the approach position AP by driving the X axis in the horizontal direction (X axis direction) as shown in FIG. 9B. In this case, first, the spherical probe 1f moves in the horizontal direction with respect to the machining surface Wa while following the machining surface Wa toward the right side of the drawing, and when the spherical probe 1f is completely separated from the machining surface Wa. As described above, the probe Pr starts acceleration motion by the contact pressure T in the axial direction of the probe Pr. Then, the coordinates when the probe Pr reaches the preset axial speed are stored as one detected coordinate (X coordinate). The detected coordinates are the terms already described with reference to FIG.

  Next, the X-axis, Y-axis, and Z-axis are moved to reposition the spherical probe 1f of the probe Pr at the approach position AP, and the spherical probe 1f is processed in the direction opposite to the above-described direction Wa. The X axis is driven so as to move relatively. Similarly, the coordinates when the probe Pr reaches the preset axial speed are stored as the other detected coordinates (X coordinates). In addition, the approach position AP of the processing surface Wa may not be limited to being the same point. That is, when detecting the end face of the workpiece W by relatively moving the probe Pr in the opposite direction, it may be on the straight line of movement when the probe Pr is moved in one direction and within the machining surface Wa of the workpiece W. That's fine.

  If the two X coordinate values thus obtained are added and divided by 2, intermediate coordinates in the horizontal direction (X-axis direction) of the machining surface Wa of the workpiece W can be obtained. This coordinate represents the horizontal center position of the processing surface Wa, that is, the X-axis center coordinate. Note that the two X coordinate values that are the two detected coordinates are values obtained by driving the X axis in opposite directions, so that the process of adding the two X coordinate values causes the X axis drive system to Mechanical errors such as having backlash are offset. Thereby, the X-axis center coordinate can be obtained with high accuracy.

9D and 9E, the workpiece W and the probe Pr are relatively moved in the horizontal direction (X-axis direction), so that the spherical measuring element 1f is completely separated from the machining surface Wa of the workpiece W. It is operation | movement explanatory drawing which calculates | requires the detection coordinate at the time.
First, the X-axis, Y-axis, and Z-axis are moved to bring the spherical probe 1f of the probe Pr into contact with the approach position AP ′ (see FIG. 9E) of the processing surface Wa of the workpiece W with the contact pressure T. Then, from the approach position AP ′, the spherical measuring element 1f is moved by driving the Y axis in the vertical direction (Y axis direction) as shown in FIG. 9D. Here, first, the spherical measuring element 1f moves in the vertical direction with respect to the processing surface Wa while following the processing surface Wa toward the upper side, and when the spherical measuring element 1f is completely separated from the processing surface Wa, As described above, the probe Pr starts an acceleration motion in the axial direction of the probe Pr. Then, the coordinates at the time when the probe Pr reaches the preset axial speed are stored as one detected coordinate (Y coordinate).

  Next, the X-axis, Y-axis, and Z-axis are moved to reposition the spherical probe 1f of the probe Pr at the approach position AP ′, so that the spherical probe 1f is in a direction opposite to the aforementioned direction (lower side) The Y axis is driven so as to move relative to the processing surface Wa in the direction). Similarly, the coordinates when the probe Pr reaches the preset axial speed are stored as the other detected coordinates (Y coordinates). Note that the approach position AP ′ of the processing surface Wa may not be limited to the same point. That is, when detecting the end face of the workpiece W by relatively moving the probe Pr in the opposite direction, it may be on the straight line of movement when the probe Pr is moved in one direction and within the machining surface Wa of the workpiece W. That's fine.

If the two Y coordinate values thus obtained are added and divided by 2, intermediate coordinates in the vertical direction (Y-axis direction) of the machining surface Wa of the workpiece W can be obtained. This coordinate represents the vertical center position of the processing surface Wa, that is, the Y-axis center coordinate. Note that the two Y coordinate values that are the two detected coordinates are values obtained by driving the Y axis in opposite directions, so that the process of adding the two Y coordinate values causes the Y axis drive system to Mechanical errors such as having backlash are offset. Thereby, the Y-axis center coordinates can be obtained with high accuracy.
As shown in FIGS. 9B to 9E, the workpiece end surface detection method of the present invention is an operation in a direction in which the probe Pr is relatively separated from the workpiece W. The risk of collision is eliminated, and damage to the expensive on-machine measuring device 1 and the workpiece W can be prevented.

  FIG. 10 is an explanatory diagram in the case where the workpiece W is cylindrical and the center coordinates of the processed surface Wa are obtained and set as the reference position of the workpiece W in the embodiment of the present invention. Also in this example, as shown in FIG. 6, the processing surface Wa is attached to be a vertical surface. The processing surface Wa is line symmetric with respect to the horizontal X axis and the vertical Y axis. Then, as in the case where the workpiece W is a rectangular parallelepiped, the operation of detecting the end surface of the machining surface Wa of the workpiece W is performed using FIG. If the detection coordinates in the horizontal direction (X-axis direction) and the detection coordinates in the vertical direction (Y-axis direction) are detected, and an intermediate point between the detection coordinates obtained in the horizontal direction and the vertical direction is obtained, a cylindrical shape is obtained. The center coordinates of the X and Y coordinates of the machining surface Wa of the workpiece W are obtained.

  Also, in the cylindrical workpiece W, similarly to the rectangular parallelepiped workpiece W, mechanical errors such as backlash of the X-axis and Y-axis drive systems are canceled out, and the probe Pr is moved away from the workpiece W in a relative direction. Since it is an operation, there is no danger of collision between the probe Pr and the workpiece W, and damage to the expensive on-machine measuring device 1 and the workpiece W can be prevented.

  If the center coordinates of the workpiece W thus determined are set as the reference position, the correspondence between the tip position of the spherical probe 1f of the probe Pr of the on-machine measuring device 1 and the tool edge position can be established. For example, if the origin of the coordinate system of the machining program is the workpiece center position, the tip position of the spherical probe 1f and the tool edge position indicate the same position by using the set coordinates as the origin, and accurate correction machining is performed. Can be executed.

FIG. 11 is a flowchart showing an algorithm for workpiece reference position setting processing according to the embodiment of the present invention.
The work W is mounted on the machine tool so that the axis of the machine coordinate system and the symmetry line of the work W are parallel to each other, and the central axis of the probe Pr of the on-machine measuring device 1 is perpendicular to the machining surface of the work W. When a machining program to be executed is input to the numerical control device 8 and a reference position setting command for the workpiece W is input to the numerical control device using a manual input device (not shown) or the like, the numerical control device 8 The processor of the numerical controller 8a (see FIG. 7) starts the process shown in FIG.

[Step S1] First, according to the input machining program, a line parallel to two symmetry lines on the machining surface of the workpiece W is changed to a first approach line (in this embodiment, the first approach line is a horizontal X axis). ), A second approach line (in this embodiment, the second approach line is a line parallel to the Y axis of the vertical line), and on the first approach line and the second approach line Thus, two approach positions in the horizontal direction of the machining surface Wa of the workpiece W and two approach positions in the vertical direction of the machining surface Wa of the workpiece W are obtained, and the process proceeds to step S2.
[Step S2] The probe Pr is moved to one approach position of the first approach line in the horizontal direction obtained in Step S1, and the spherical probe 1f is brought into contact with the contact pressure T for positioning.

[Step S3] The probe Pr is moved in the horizontal direction toward one end surface of the workpiece W. That is, the X-axis motor 95x is driven, the X-axis table is moved, and the spherical probe 1f of the probe Pr is moved relatively toward one end of the workpiece W while following the machining surface Wa of the workpiece W.
[Step S4] Then, it is determined whether or not the moving speed of the probe Pr in the axial direction exceeds a reference value.
[Step S5] If it is determined in step S4 that the moving speed of the probe Pr in the axial direction exceeds the reference value, the movement of the probe Pr is stopped. That is, the driving of the X-axis motor 95x is stopped and the movement of the X-axis table is stopped. At this time, the spherical probe 1f of the probe Pr is completely detached from the workpiece W.

[Step S6] In step S4, the coordinate of the moving axis when it is determined that the moving speed of the probe Pr in the axial direction exceeds the reference value, that is, the X coordinate, is stored in the register R1 as the detected coordinate.
[Step S7] The probe Pr is retracted so as not to come into contact with the workpiece W, and the spherical probe 1f of the probe Pr is brought into contact with the contact pressure T at the other horizontal measurement approach position obtained in step S1 and positioned. .
[Step S8] The probe Pr is moved in the horizontal direction toward the other end surface of the workpiece W. That is, the X-axis motor 95x is driven to move the X-axis table (in the direction opposite to the movement of the X-axis table in step S3), so that the spherical probe 1f of the probe Pr is moved over the machining surface Wa of the workpiece W. It moves relatively toward the other end of the workpiece W while copying. The speed at which the probe Pr is moved relatively is the same for movement in one direction and movement in the opposite direction.

[Step S9] Then, it is determined whether or not the moving speed of the probe Pr in the axial direction exceeds a reference value.
[Step S10] If it is determined in step S9 that the moving speed of the probe Pr in the axial direction exceeds the reference value, the movement of the probe Pr is stopped. That is, the driving of the X-axis motor 95x is stopped and the movement of the X-axis table is stopped. At this time, the spherical probe 1f of the probe Pr is completely detached from the workpiece W.
[Step S11] In step S9, the coordinate of the movement axis when it is determined that the moving speed of the probe Pr in the axial direction exceeds the reference value, that is, the X coordinate is stored in the register R2 as the detection coordinate.

[Step S12] The probe Pr is retracted, the probe Pr is moved to one approach position of the second approach line in the vertical direction obtained in step S1, and the spherical probe 1f is brought into contact with the contact pressure T for positioning. .
[Step S13] The probe Pr is moved in the vertical direction toward one end surface of the workpiece W. That is, the Y-axis motor 95y is driven, the X-axis table is moved, and the spherical probe 1f of the probe Pr is moved relatively toward one end of the workpiece W while following the machining surface Wa of the workpiece W.
[Step S14] Then, it is determined whether or not the moving speed of the probe Pr in the axial direction exceeds a reference value.

[Step S15] If it is determined in step S14 that the moving speed of the probe Pr in the axial direction exceeds the reference value, the movement of the probe Pr is stopped. That is, the drive of the Y-axis motor 95y is stopped, and the movement of the Y-axis table is stopped. At this time, the spherical probe 1f of the probe Pr is completely detached from the workpiece W.
[Step S16] In step S14, the coordinate of the movement axis when it is determined that the movement speed of the probe Pr in the axial direction exceeds the reference value, that is, the Y coordinate is stored in the register R3 as the detection coordinate.
[Step S17] The probe Pr is retracted so as not to contact the workpiece W, and the spherical probe 1f of the probe Pr is brought into contact pressure T at the other measurement approach position of the second approach line in the vertical direction obtained in Step S1. Position by touching with.

[Step S18] The probe Pr is moved in the vertical direction toward the other end surface of the workpiece W. That is, the Y-axis motor 95y is driven, the Y-axis table is moved (in the direction opposite to the movement of the Y-axis table in step S13), and the spherical probe 1f of the probe Pr is moved over the machining surface Wa of the workpiece W. It moves relatively toward the other end of the workpiece W while copying.
[Step S19] Then, it is determined whether or not the moving speed of the probe Pr in the axial direction exceeds a reference value.
[Step S20] If it is determined in step S19 that the axial movement speed of the probe Pr has exceeded the reference value, the movement of the probe Pr is stopped. That is, the drive of the Y-axis motor 95y is stopped, and the movement of the X-axis table is stopped. At this time, the spherical probe 1f of the probe Pr is completely detached from the workpiece W.

[Step S21] In step S19, the coordinate of the movement axis when it is determined that the moving speed of the probe Pr in the axial direction exceeds the reference value, that is, the Y coordinate is stored in the register R4 as the detection coordinate.
[Step S22] The work center coordinates are obtained from the detected coordinates stored in the registers R1 to R4, and set as measurement reference points for the work W. More specifically, the intermediate coordinates of the two X coordinates are obtained by adding the X coordinates of the detected coordinates stored in the registers R1 and R2 and dividing by two. Further, the Y coordinate of the detected coordinate stored in the register R3 and the register R4 is added to obtain an intermediate coordinate between the two Y coordinates.

  Since the intermediate coordinates of the X coordinate and the Y coordinate represent the center coordinates of the workpiece W, the center coordinates of the workpiece W are set as the reference position of the workpiece, and the reference position setting process is terminated. The difference between the coordinate values at both ends in the horizontal direction is obtained, and the coordinate value obtained by adding half of the difference to the smaller coordinate value is set as the center coordinate in the horizontal direction of the workpiece W, and the difference between the coordinate values at both ends in the vertical direction is calculated. The center coordinate of the workpiece W may be obtained using the coordinate value obtained by adding half of the difference to the smaller coordinate value as the center coordinate in the vertical direction of the workpiece W and set as the reference position of the workpiece W.

  Based on the reference position of the workpiece W thus set, the tip of the spherical probe 1f attached to the tip of the stylus 1e of the probe Pr is brought into contact with the workpiece surface, and the workpiece W is moved on the machine tool by the on-machine measuring device. measure. Since the tip of the spherical probe 1f and the cutting edge of the blade are related via the reference position of the workpiece W, the correction processing becomes clear based on the measured shape.

It is principal part sectional drawing of the on-machine measuring device used by embodiment of this invention. It shows that the probe moves toward both ends of the workpiece W and leaves the workpiece W in a state where the probe is in contact with the processing surface (measurement surface) of the workpiece. It is a figure explaining the measurement principle of this invention. It is a figure explaining in detail the mode at the time of a probe leaving | separating from the end surface of a workpiece | work. It is a figure explaining the 5-axis movable part used by embodiment of this invention. It is a schematic block diagram of the machine tool which inputs the position detection signal from an on-machine measuring device and the position detection signal from each drive shaft of a machine tool into a numerical control apparatus. In the machine tool shown in FIG. 6, it is a figure explaining that the signal from each movable axis | shaft of a machine tool and an on-machine measuring device is feedback-controlled simultaneously by a numerical controller. It is a block diagram which shows the interface used for embodiment of this invention. In embodiment of this invention, it is explanatory drawing when a workpiece | work is a rectangular parallelepiped and the center coordinate of the processing surface is calculated | required and set as a reference | standard position of a workpiece | work. In embodiment of this invention, it is explanatory drawing in case a workpiece | work is a cylinder and the center coordinate of the processing surface is calculated | required and set as a reference | standard position of a workpiece | work. It is a flowchart which shows the algorithm of the reference position setting process of the workpiece | work in embodiment of this invention.

Explanation of symbols

Pr Probe 1b Probe body 1e Stylus 1f Spherical probe W Work Wa Machining surface AP Approach position RE Right end face position LE Left end face position

Claims (6)

A numerical control device comprising an on-machine measuring device for measuring and analyzing a shape of a workpiece that is line-symmetric with respect to two lines whose work planes are orthogonal to each other, and to which a position detection signal is input from the on-machine measuring device In a machine tool having a plurality of movable axes controlled by
The on-machine measuring device is
A contact type probe supported by a hydrodynamic bearing inside the on-machine measuring device, and a position detection means for detecting a displacement in the axial direction of the contact type probe and outputting a position detection signal;
The machine tool includes movable shaft position detection means for detecting the position of each movable shaft of the machine tool and outputting an axis position detection signal,
The numerical controller is
The contact point of the contact probe is brought into contact with the machining surface of the workpiece arranged so that the two lines are parallel to the axis of the machine coordinate system at a constant contact pressure from the end surface of the workpiece. The movable shaft is driven so as to move the contact probe in the direction parallel to the two lines until the contact probe probe is completely separated from the machining surface of the workpiece toward the end surface. Movable axis drive control means for
Probe moving speed calculating means for calculating the axial moving speed of the contact probe based on a position detection signal output from the position detecting means;
Determining means for determining whether or not the moving speed calculated by the probe moving speed calculating means has reached a predetermined speed;
Storage means for storing position data of each movable axis detected by each movable axis position detection means when the determination means determines that the movement speed has reached a predetermined speed;
Setting means for calculating the center coordinates of the workpiece from the position of each movable axis stored in the storage means and setting as a measurement reference point of the workpiece;
A machine tool having a workpiece measurement reference point setting function.   A shaft position detection signal from a movable shaft position detecting means for detecting the position of each movable shaft of the machine tool is input to the numerical controller via an interface of a motor driving device that drives a motor, and the on-machine measuring device 2. The workpiece measurement reference point setting according to claim 1, wherein a position detection signal from the position detection means is input to the numerical control device via an interface of a motor driving device not connected to a motor. A machine tool with functions. The position detection signals output from the movable shaft position detection means and the position detection means of the on-machine measuring device are each composed of a two-phase sine wave analog signal having a phase difference of approximately 90 degrees,
The interface includes an A / D conversion device that converts the sine wave analog signal into a digital signal, and a digital signal obtained by dividing the digital signal output from the A / D conversion device into one cycle of the sine wave analog signal. The machine tool having a workpiece measurement reference point setting function according to claim 2, further comprising an interpolation division device that outputs the workpiece.   The position detecting means provided in the movable axis position detecting means or the on-machine measuring device is any one of a linear scale, a pulse coder, and a laser interferometer. A machine tool having a workpiece measurement reference point setting function according to any one of the above.   The storage means automatically stores position data of each movable axis detected by each movable axis position detection means when it is determined by the determination means that the moving speed has reached a predetermined speed. A machine tool having a measurement reference point setting function for a workpiece according to any one of claims 1 to 4.   The setting means obtains a difference between the position data of the movable shaft stored in the storage means at both the left and right ends of the machining surface in the horizontal direction, and adds a value obtained by adding half the difference to the smaller coordinate to the work piece. The difference between the position data of the movable axis stored in the storage means at the upper and lower ends in the vertical direction of the machining surface is obtained, and half the difference is added to the smaller coordinate. The workpiece measurement reference point according to claim 1, wherein the coordinate of the workpiece is the center coordinate in the vertical direction of the workpiece, the center coordinate of the workpiece is obtained and set as the measurement reference point of the workpiece. A machine tool with a setting function.

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