JP5197788B2 - Tool measuring device - Google Patents

Description

  The present invention relates to a tool measuring method and apparatus, and more particularly, to a tool for measuring a tool for fine machining such as a drill having a tool diameter of 0.1 mm or less, a ball end mill, and a flat end mill.

  In the field of machine tools, the demand for machining accuracy is increasing year by year, and recently, it is not uncommon to require machining accuracy on the order of submicrons. In order to improve the machining accuracy, there has been proposed an NC machine tool that measures the positional deviation of the tool mounted on the spindle relative to the spindle and the thermal elongation of the rotating spindle.

  As a first conventional technique, Patent Document 1 discloses an NC machine tool having a tool dimension measuring function capable of measuring a tool cutting edge position, a tool diameter, a tool length, a tool shape, and the like of a rotating tool. This NC machine tool is provided with an optical tool measuring device for irradiating a single thread-like light beam between a projector and a light receiver on a table for fixing a work of the machine tool unit, and a tool on a rotating spindle of the machine tool unit. The X, Y, and Z axes are moved relative to the table by moving the tool so that the tool approaches the light beam of the optical tool measuring instrument from a predetermined direction. The center position of the tool tip, the tool diameter, and the tool length of the machining program of the NC machine tool are corrected based on the Z coordinate value.

  As a second conventional technique, Patent Document 2 discloses a machine tool that accurately measures the displacement of the cutting edge position of a tool during high-speed rotation. In this machine tool, a reference block is fixed to an upper surface of a table, a displacement meter for measuring a distance between the reference block and the spindle housing is provided, and an end face of the spindle relative to the spindle housing or a tool holder is provided on the spindle housing. A displacement meter is provided to measure the distance of the tool housing, thereby obtaining the displacement of the spindle housing tip and the displacement of the spindle relative to the spindle housing tip to correct the displacement of the tool edge position.

  As a third prior art, Patent Document 3 discloses a method and an apparatus for measuring the position of a cutting edge of a tool mounted on a spindle in order to perform precision machining with an NC machine tool such as an NC milling machine or a machining center. In this measuring method and apparatus, the position of the spindle end surface of the machine tool is measured in a non-contact manner, and the cutting edge position of the tool is measured by a contact-type measuring device.

JP 11-138392 A JP-A-10-309653 Japanese Patent No. 4229698

  In the first prior art, the center position of the tool tip, the tool diameter, and the tool length are measured in a non-contact manner using light rays while the main shaft is rotating, and the machining program is corrected based on the measured values. . However, since the shape of the cutting edge is complicated at the tip of the tool, in the measurement by the optical measuring instrument, there is a problem that it is unclear which position of the rotating tool tip is measured, and the measurement accuracy is lowered. A non-contact type distance measuring device using electrostatic capacity or eddy current is also unclear as to which position of the rotating tool tip is being measured, and cannot solve the problem of reduced measurement accuracy. In addition, when trying to measure the dimension of a tool thinner than the thickness of the light beam, there is a problem that the measurement error increases because the tool does not completely block the light beam.

  In the second prior art, only the change in the tool length in the direction along the central axis of the main axis, that is, the Z-axis direction can be measured, and an increase in the apparent tool diameter based on the inclination and offset of the tool main axis, There is a problem that the reduction in the tool diameter due to wear of the cutting edge cannot be measured.

  In the third prior art, when the tool to be measured is an ultrafine tool for fine processing, the spring force of the contact-type measuring device may be excessive with respect to the tool diameter, and the tool may be damaged. . In addition, if the moving direction of the probe of the measuring device does not completely match the machine coordinate system of the machine tool, that is, it is not completely parallel to the feed axis of the machine tool, an error that cannot be ignored in the measured value. There are problems including.

  The present invention has a technical problem to solve the problems of the prior art, and measures the position of the cutting edge of the tool mounted on the tip of the spindle of the NC machine tool with higher accuracy and prevents damage to the tool during measurement. It aims at providing the tool measuring device which prevented.

According to the present invention, the position of the cutting tool mounted on the spindle of the machine tool is brought into contact with a probe of a contact-type displacement sensor installed in the machine tool, and the position in the machine coordinate system of the machine tool, and a displacement amount of the probe of the displacement sensor, the device for measuring the edge position of the cutting tool, before the own weight of the front Kipu lobes, the position of the spring force and substantially balances the probe for biasing the probe a displacement sensor as the initial position of Kipu lobe, storage means for storing a displacement amount of the probe of the displacement sensor, and the previous measuring a displacement amount of the probe when the tool is not in contact with the probe, Compared with before the start of measurement this time, if the difference between the two is larger than the predetermined value, the origin position resetting means for setting the displacement of the probe before the start of the current measurement as the origin of the displacement sensor Bei the tool measuring device is provided.

  According to the present invention, since the position of the probe where the weight of the probe and the spring force for biasing the probe are substantially balanced is set as the initial position, the spring force acting on the tool during the measurement of the tool is reduced. This prevents the tool from being damaged during measurement. The present invention is particularly effective for measuring an ultrafine tool for micromachining.

Further, storage means for storing a displacement amount of the displacement sensor is provided, stored in the storage means, comparison with the scheduled measuring preceding the displacement amount of the probe when the tool is not in contact with the probe, and the current measured before the start In addition, when the difference between the two is larger than a predetermined value, the origin reset means for setting the displacement amount of the probe before the start of the current measurement as the origin of the displacement sensor is further provided, so that the origin of the conventional displacement sensor is determined in advance. Compared with the case of a single position, the measurement accuracy is improved.

1 is a schematic block diagram of a tool measuring device according to a preferred embodiment of the present invention. It is a schematic sectional drawing of the measuring apparatus which consists of a contact type displacement sensor. It is a graph which shows the spring force which acts on a tool during a measurement with the measuring apparatus by FIG. 2A. 1 is a schematic cross-sectional view of a measuring device including a contact displacement sensor according to a preferred embodiment of the present invention. It is a graph which shows the spring force which acts on a tool during measurement with the measuring device of Drawing 3A. It is the schematic for demonstrating the measurement error based on the attachment error of a measuring apparatus. It is a graph which shows the change of an error. It is the schematic which shows the fluctuation | variation of the origin when attaching a weight to a probe. It is a flowchart which shows reset of an origin position.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, referring to FIG. 1, a tool measuring device 100 as an example of the present invention and an NC machine tool 10 to which the tool measuring device 100 is applied are shown. The machine tool 10 includes a bed 12 fixed to a floor surface of a factory, a column 14 standing on the bed 12, a spindle head 16 attached to a front surface of the column 14 so as to be movable in the vertical Z-axis direction, A main shaft 18 that is rotatably supported by the main shaft head 16 about the Z axis, and faces the main shaft 18 with respect to the main shaft 18 in the X axis and Y axis directions which are two directions perpendicular to the Z axis on the upper surface of the bed 12. The table 20 is mounted so as to be relatively movable. Further, the positions of the X, Y, and Z feed axes of the machine tool 10 are measured by a position reading device 22 such as a digital scale in the X, Y, and Z axis directions. In this way, the work (not shown) fixed on the upper surface of the table 20 and the tool T attached to the tip of the rotating main shaft 18 are relatively moved in the three orthogonal directions of the X, Y, and Z axes, The workpiece is cut into a desired shape. Here, the tool T can be a tool for fine processing, for example, a drill having a tool diameter of 0.1 mm or less, a ball end mill, a flat end mill, or the like.

  The machine tool 10 is also provided with a measuring device 30 for specifying the position in the Z-axis direction of the cutting edge of the tool T in the machine coordinate system of the machine tool. In FIG. 1, the measuring device 30 is illustrated as being attached to the table 20, but when the column 14 is movably provided with respect to the bed 12, the measuring device 30 is attached to the bed 12. You may make it attach.

  Referring to FIG. 2A, the measuring device 30 is a contact-type displacement sensor similar to the tool edge position measuring device in Patent Document 3 (Patent No. 4229698) described above, and includes a hollow housing 32 and the housing 32. A coil spring 34 disposed therein, a probe 36 attached to one end of the coil spring 34 and protruding from the housing 32, and a part of the housing 32 adjacent to the probe 36 of the coil spring 34. A stopper 38 and a displacement meter 40 that outputs an electric signal indicating the amount of axial displacement of the coil spring 34 are provided. The tip of the tool T in the machine coordinate system (Z axis) of the machine tool is obtained from the output of the displacement meter 40 when the tip of the tool T is brought into contact with the probe 36 of the measuring device 30 and the spindle 18 is fed and pushed in the Z axis direction. A location is identified.

  As described in Patent Document 3, in addition to the measuring device 30, a non-contact type measuring device (not shown) is disposed on the machine tool 10, and the machine tool 10 has a machine coordinate system. The position of the end face of the main shaft 18 can be measured.

  As shown in FIG. 2A, in the case of the contact-type measuring device, the coil spring 34 is provided with a stopper 38 that contacts the inner surface of the upper wall of the housing 32. The coil spring 34 is compressed at the zero point of the displacement meter 40. It is in the state. Therefore, when the tool T comes into contact with the probe 36, the preload Fp is applied to the coil spring 34. Therefore, in order to displace the probe 36 in the Z-axis direction, the tool T is shown in FIG. 2B. Thus, at least the force of Fp acts in the axial direction. When the tool T is a normal size tool, there is no particular problem, but when the tool T is a tool for fine processing, for example, an extremely fine tool having a tool diameter of about 10 μm, a spring acting on the tool T by the coil spring 34. It can happen that the force T is too high and the tool T is damaged.

  Therefore, it is desirable to reduce the spring force acting on the tool T. In a preferred embodiment of the present invention, as shown in FIG. 3A, a predetermined weight 42 is attached to the probe 36 in the Z-axis direction to reduce the force acting on the tool T as shown in FIG. 3B. In this case, the weight 42 may have any weight within the range of movement of the probe 36, but it is desirable that the weight of the stopper 38 does not slightly separate from the inner surface of the upper wall of the housing 32.

For example, in the case of the measuring device of FIG. 2A, the preload is 40 g, but in the case of the measuring device of FIG. 3A, the preload is almost 0 g. If the spring force when measuring by pushing the tool T by 10 μm is 10 g, the measuring device in FIG. 2A has a contact pressure of 50 g in total, and for example, a tool with a tool diameter of 10 μm may be damaged. However, in the measuring apparatus of FIG. 3A, only a contact pressure of 10 g acts on the measurement and there is no fear of breakage.

  In this embodiment, the weight 42 is used to balance the own weight of the probe 36 and the spring force of the coil spring 34. However, the stopper 38 is not located at the position where the coil spring 34 is fully extended without using the weight 42. A coil spring having a spring constant of whether or not to contact the inner surface of the upper wall may be selected.

  As shown in FIG. 4, when a pin gauge is attached to the main shaft 18 and brought into contact with the probe 36, if the moving direction of the probe 36 is not completely parallel to the Z axis, the displacement amount δs of the probe 36 is The change amount δm of the Z-axis position in the machine coordinate system does not match, and the measured value is an error ε = δm (1 / cos θ−1), where θ is the angle between the Z-axis and the moving direction of the probe 36. ) Will be included. In an actual tool measurement scene, when the tool T is a tool for fine processing, it may not be ignored even if the angle θ is small.

Therefore, the tool measuring apparatus according to the present embodiment corrects such errors.
Referring to FIG. 1 again, in the present embodiment, the tool measuring device 100 is, for example, software as a part of a program incorporated in a machine control device (not shown) of the machine tool 10 or a machine control device. It can be configured in hardware as part of an electric circuit, and includes a measurement control unit 102, a displacement storage unit 104, a reset control unit 106, a displacement average unit 108, a displacement correction unit 110, a comparison determination unit 112, and a correction The control part 114, the addition part 116, and the blade edge position calculating part 118 are included as main components.

  The output from the displacement meter 40 of the measuring device 30 is read into the displacement amount correction unit 110 via the displacement amount average unit 108. In order to measure the tool T on the order of μm, it is desirable that the displacement meter 40 of the measuring device 30 can output on the order of 0.1 μm. In such a case, the output from the displacement meter 40 becomes unstable and includes minute fluctuations on the order of submicrons. The displacement amount averaging unit 108 acts as a filter that averages the output from the displacement meter 40 of the measuring device 30 over a predetermined time width and removes such minute fluctuations.

  The comparison determination unit 112 compares the output from the displacement amount correction unit 110 with the output from the position reading device 22 such as a digital scale of the machine tool 10. Originally, the output value from the displacement amount correction unit 110 and the output value from the position reading device 22 coincide as shown by a solid line in FIG. However, when the moving direction of the probe 36 and the Z-axis do not coincide with each other, an error ε is included as shown by a one-dot chain line. The comparison determination unit 112 outputs the comparison result to the correction control unit 114, and the correction control unit 114 outputs a command to the effect that the error ε should be corrected to the displacement amount correction unit 110. In FIG. 5, the error ε is illustrated to be obtained at only one point when the probe 36 is pushed with a predetermined push amount, for example, 10 μm. However, while the probe 36 is pushed with the predetermined push amount, the error ε is discrete. It may be obtained at a plurality of positions. Further, when the error ε is larger than a predetermined value, the correction control unit 114 obtains the angle θ from the above-described equation, for example, and outputs a warning to the operator that the attachment of the measuring device 30 should be adjusted. You may do it. The attachment of the measuring device 30 can be adjusted by moving a guide for guiding the probe 36 by a minute amount so as to be parallel to the Z-axis by mechanical means such as an adjusting screw.

  Furthermore, as described above, when the measuring device 30 is used with the weight 42 attached to the probe 36 and the stopper 38 separated from the inner surface of the upper wall of the housing 32, the initial state when the tool T is not in contact with the probe 36 is used. As shown in FIG. 6, the position (origin position) may not necessarily match every measurement. The tool measuring apparatus 100 can further include an origin position reset unit that resets the origin position when the difference between the origin position at the previous measurement and the current origin position becomes large. In the conventional measuring apparatus, as shown in FIGS. 2A and 2B, the magnitude of the spring force is set in the initial state, and therefore, it has no problem even if the origin position is determined as one predetermined position.

  At the start of tool measurement, the operator turns on a tool measurement switch on the machine control device, or automatically measures at the time of tool replacement or at the end of a predetermined number of machining processes, from the measurement control unit 102 When the start command is sent to the reset control unit 106 (step S10), the reset control unit 106 receives the current displacement amount before the tool T contacts the probe 36 from the displacement amount correction unit 110 (step S12). Then, the displacement amount at the end of the previous tool measurement is received from the displacement amount storage unit 104 (step S14). Next, the reset control unit 106 compares the two (step S16), and if the difference between the two is larger than a predetermined value (Yes in step S16), the current displacement amount, and accordingly, the tip or cutting edge of the tool T The reset control unit 106 sends a reset signal to the displacement amount correcting unit 110 so that the current reading of the displacement meter 40 in a state in which the sensor is not in contact with the probe 36 of the measuring device 30 is zero (step S18). If the difference between the two is smaller than the predetermined value (No in step S16), the measurement of the blade edge position is started without resetting the origin position (step S20).

  In this way, the output from the displacement amount correcting unit 110 and the output from the position reading device 22 are summed by the adding unit 116, whereby the cutting edge position of the tool T in the machine coordinate system of the machine tool 10 is specified (118). The tool length can be calculated from the cutting edge position of the tool T.

  In addition, when the machine tool 10 has a horizontal main shaft, a horizontal tool mounted on the main shaft can be brought into contact with the probe 36 from the radial direction, and the cutting edge position in the radial direction of the tool can be measured. The tool diameter can also be calculated from the measured radial edge position.

DESCRIPTION OF SYMBOLS 10 Machine tool 12 Bed 14 Column 16 Spindle head 18 Spindle 20 Bed 22 Position reading device 30 Measuring device 32 Housing 34 Coil spring 36 Probe 38 Stopper 40 Displacement meter 42 Weight 100 Tool measuring device 102 Measurement control part 104 Displacement amount memory | storage part 106 Reset Control unit 108 Average unit 110 Displacement correction unit 112 Comparison determination unit 114 Correction control unit 116 Addition unit 118 Cutting edge position specifying unit

Claims (4)

The position of the cutting tool mounted on the spindle of the machine tool is brought into contact with the probe of a contact-type displacement sensor installed on the machine tool, and the position of the machine tool in the machine coordinate system and the probe of the displacement sensor In the apparatus for measuring the position of the cutting edge of the cutting tool from the amount of displacement,
And its own weight before Kipu lobe, a displacement sensor as the initial position before Kipu lobes the position of the spring force and substantially balances the probe for urging the probe,
Storage means for storing the displacement amount of the probe of the displacement sensor;
Compare the displacement of the probe when the tool is not in contact with the probe at the time of the previous measurement and before the start of the current measurement, and when the difference between the two is larger than a predetermined value, the probe before the start of the current measurement A tool measuring device comprising: an origin position resetting means for setting the amount of displacement at the origin of the displacement sensor . The probe displacement amount of the displacement sensor when the probe of the displacement sensor is pushed in and the position change amount of the machine coordinate system of the machine tool are compared, and based on the difference, the displacement sensor is based on the mounting error of the displacement sensor. The tool measuring apparatus according to claim 1, further comprising correction means for correcting an error in a displacement amount of the probe of the displacement sensor . The tool measuring apparatus according to claim 2, wherein an error when the probe is pushed in with a predetermined pushing amount is calculated . The tool measuring device according to claim 3, wherein an error is calculated at a plurality of discrete positions while the probe is pushed in with a predetermined pushing amount .

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