JP4069323B2 - Automatic centering jig for machine tools - Google Patents

Description

  The present invention relates to an automatic centering jig used as a measurement reference member in a machine tool such as a machining center when measuring a mounting error of a work table or a thermal displacement of the machine using a touch sensor.

In a machine tool, the actual relative position between the tool attached to the spindle and the workpiece installed on the table based on the mounting error of the workpiece on the table, the thermal displacement of the machine, etc. is the relative value set in the machining program between them. Since an error may occur with the position, the error is measured, and the relative feed amount (control shaft feed amount) for machining operation between the spindle and workpiece is corrected based on the error. Has been done.
In order to measure the error, a ring gauge having a reference hole is fixed to the work fixed to the turning table by a magnet, and the touch probe (touch sensor) attached to the main shaft and the work are connected to the X and Y control axes. Based on the X and Y axis coordinate values read when the touch probe touches the top, bottom, left and right of the reference hole of the ring gauge by moving it relative to the drive, the displacement between the spindle center and the workpiece It is known to obtain (error) by calculating (see, for example, Patent Document 1).
It is also known that a reference hole is provided directly in the workpiece instead of the reference hole of the ring gauge, and the positional deviation (error) between the spindle center and the workpiece is calculated and obtained in the same manner as described above. (For example, refer to Patent Document 2).
Japanese Utility Model Publication No. 5-45721 Japanese Unexamined Patent Publication No. 4-171161

  However, since there is usually a variation in the work mounting accuracy to the rotary table or the mounting accuracy of the pallet to which the work is mounted (pallet replacement accuracy), it is provided in the reference hole or work provided in the conventional ring gauge. If the measurement point where the touch probe contacts is on the workpiece (ring gauge fixed to the workpiece), as in the case of measuring the error using a reference hole, the control axis is used for the error measurement for a specific workpiece. The correction of the feed amount cannot cope with the variation in the mounting accuracy. In particular, in boring, it is a deep hole, a stepped hole, etc. that cannot be drilled only from one end side, but the workpiece is reversed 180 degrees and the same hole is drilled from the opposite side (reverse machining). At this time, the error caused by the variation in the mounting accuracy affects the machining accuracy as a double error, so that the matching accuracy of the shaft centers of the reversed holes is deteriorated, and there is a possibility that a defective product is produced.

Therefore, it is conceivable to measure the error every time the workpiece is mounted on the rotary table and obtain the correction amount of the feed amount of the control axis corresponding to the variation in the mounting accuracy. Measuring the error every time it is attached causes a complicated operation and reduces the machining efficiency of the workpiece, and thus there is a problem that it cannot be actually carried out.
In addition, in the case of measuring the error with the conventional ring gauge, no consideration is given to the correction of the feed amount of the control axis by measuring the error in the Z-axis direction, and the workpiece machining accuracy in the Z-axis direction is not considered. There was a problem that could not be improved.

  The present invention has been made in view of the above circumstances, and can accurately measure the positional deviation of the spindle with respect to the workpiece without being affected by variations in the accuracy with which the workpiece is attached to the rotary table. An object of the present invention is to provide a machine tool automatic centering jig capable of accurately obtaining a feed amount correction amount in a Z control axis and improving machining accuracy.

The present invention is characterized by the following points in order to solve the above problems.
That is, the automatic centering jig for a machine tool according to claim 1 places a workpiece on a rotary table supported so as to be indexable and rotatable about a B axis parallel to the Y axis located at the center of the table. In a machine tool for machining a workpiece by attaching a tool to a spindle arranged in the Z-axis direction and moving the table and the spindle in the X, Y, and Z-axis directions relatively , A jig body fixed to the outer periphery, and a measurement ring having a reference hole and a reference surface and attached to the jig body, and the reference hole of the measurement ring includes an X axis and a Z axis. The reference plane is provided along a plane parallel to a plane and on a straight line passing through the center of the B axis, and the reference plane is provided on an outer end surface in the axial direction of the measurement ring, and the reference hole is formed on a plane perpendicular to the central axis, said table Relatively a main axis X, Y, is moved in the Z-axis direction, X-axis origin from the center of the reference hole by read coordinate values of the touch sensor mounted on the spindle is brought into contact with the reference hole of the measuring ring By measuring the distance to the position and correcting the feed amount in the X-axis direction, the workpiece that can be reversed by the rotary table is centered in the X-axis direction .

  The automatic centering jig for a machine tool according to claim 2 is the automatic centering jig for the machine tool according to claim 1, wherein the reference surface is a column of the outer end surface of the measuring ring. It is characterized in that it is formed on the end face of the projecting portion that protrudes to the side.

  The automatic centering jig for machine tools according to claim 3 is the automatic centering jig for machine tools according to claim 1 or 2, wherein the measuring ring has an inner side of the reference hole. A cover is provided to close the opening and cover the upper side of the reference surface.

  According to the automatic centering jig for a machine tool according to claim 1 of the present invention, the measuring ring is provided on the table with the reference hole and the reference surface, and is provided on the workpiece as in the prior art. As a result, the measurement of the mechanical relative displacement in the X, Y, and Z axis directions of the center of the spindle relative to the workpiece is accurate without being affected by variations in the exchange accuracy of the pallet rotary table where the workpiece is placed on the table. Thus, based on the relative displacement amount, the feed amount set and commanded by the machining program in the X, Y, and Z control axes is corrected and each control axis is operated, so that the machining accuracy can be improved. Improvements can be made.

According to the automatic centering jig of the machine tool according to claim 2, since the reference surface is provided on the protruding portion of a part of the measuring ring, it is necessary to finish the entire end surface of the measuring ring as the reference surface. In addition, the finishing process of the reference surface is easy and the processing accuracy can be increased, and the contact operation by the touch sensor at the time of measurement can be performed smoothly and easily.
According to the automatic centering jig of the machine tool according to claim 3, it is ensured that chips and dust generated during machining of the workpiece enter the reference hole of the measuring ring or adhere to the reference surface by the cover. The reference holes and reference surfaces can be kept clean, and the measurement accuracy by the touch sensor can be kept good.

Hereinafter, an automatic centering jig for a machine tool according to an embodiment of the present invention will be described with reference to the accompanying drawings.
In FIG. 1, 1 is an example of a horizontal machining center provided with an automatic centering jig for a machine tool according to an embodiment of the present invention. The machining center 1 is supported on X-axis guide rails 2a and 2a of a bed 2 and is moved in the X-axis direction (left-right direction in FIG. 1) x by an X-axis servo motor (not shown), A column 4 supported on the Z-axis guide rails 2b and 2b of the bed 2 and moved in a Z-axis direction (front-rear direction in FIG. 1) z perpendicular to the X-axis by a Z-axis servomotor (not shown); A spindle head 5 supported by Y-axis guide rails 4a and 4a of the column 4 and moved in a Y-axis direction y (vertical direction in FIG. 1) perpendicular to the X and Z axes by a Y-axis servo motor (not shown); A rotary table 6 supported on the table 3 and indexed and rotated by a B-axis servomotor (not shown) around a B-axis parallel to the Y-axis located at the center c of the table 3. ing.

The pallet 7 is carried in and fixed to the rotary table 6 by an automatic pallet changer or the like (not shown), and is released from the fixed state. A work W (see FIGS. 4 to 6) fixed via a not-shown part is carried into and out of the rotary table 6. A spindle 8 that is rotatably supported around the spindle is supported by the spindle head 5, and the workpiece W on the rotary table 6 is processed by a tool attached to the spindle 8. On one side surface of the column 4 (left side surface in FIG. 1), a tool magazine 9 storing a plurality of tools and a measurement touch probe (touch sensor) is provided. A tool exchange arm 10 is provided for exchanging old and new tools and exchanging the tool and the touch probe.
And in the outer peripheral part (right side part in FIG. 1) in the opposite side to the side where the said pallet 7 is carried in / out of the said rotary table 6, it is for the automatic centering of the machine tool which concerns on one embodiment of this invention. A jig 11 is provided.

As shown in FIGS. 2 and 3, the automatic centering jig 11 includes a jig body 12 made of an L-shaped member having a horizontal portion 12a and a vertical portion 12b, a cylindrical portion 13a, and one end side thereof. A measuring ring 13 made of a cylindrical member integrally formed with a flange 13b is provided on the outer periphery (right side in FIG. 2). The jig body 12 is formed on the upper surface of the outer periphery of the rotary table 6 (the position at the B-axis origin (0 degree), the center in the X-axis direction x of the table 3 and the column 4 side). It is fixed by a bolt 12c through a horizontal portion 12a.
The measuring ring 13 has an outer peripheral portion 13c of the cylindrical portion 13a fitted in a mounting hole 12d formed in the vertical portion 12b of the jig main body 12, and the vertical portion by a bolt or the like through the flange portion 13b. It is attached to the part 12b.

The measurement ring 13 is provided with a reference hole 13d precisely finished at the center thereof, and the outer end surface of the flange 13b (the end surface far from the center c of the B-axis, at the B-axis origin). , The end surface on the column 4 side) on both sides (left and right sides in FIG. 3) in the diameter direction (left and right direction in FIG. 3) along the plane parallel to the plane including the X and Z axes with the center of the reference hole 13d interposed therebetween. Is provided with a protruding portion 13e protruding outward (side facing the column 4 at the B-axis origin), and a reference surface on the outer end surface (end surface facing the column 4 at the B-axis origin) of the protruding portion 13e. 13f is provided with a fine finish.
The reference hole 13d has a center axis S whose upper surface (the surface on which the workpiece W is placed on the rotary table 6) 7a of the pallet 7 or a plane parallel to the upper surface (a plane parallel to the plane including the X and Z axes). ) And on a straight line passing through the center c of the B-axis (at the position of the origin of the B-axis, on a line along the Z-axis direction z passing through the center of the B-axis), and the reference plane 13f is formed on a plane perpendicular to the central axis S of the reference hole 13d (at the position of the origin of the B axis, a plane perpendicular to the Z axis, that is, a plane parallel to the plane including the X and Y axes).
Further, the measurement ring 13 includes a vertical closing plate portion 14a for closing an opening portion on the inner side of the reference hole 13d (the pallet 7 side or the side close to the center c of the B axis), and the reference A cover 14 having a horizontal top plate portion 14b covering the upper side of the surface 13d is provided by fixing the top plate portion 14b to the upper end of the vertical portion 12b of the jig body 12 with a bolt or the like. .

Next, regarding the operation of the automatic centering jig of the machine tool having the above-described configuration, the front wall and the rear wall portions 15a and 15b of the workpiece W are on the same axis L in the Z-axis direction z with reference to FIGS. An example in which a pair of shaft holes 15a1 and 15b1 having the same diameter is reversed by a boring tool (tool) T will be described.
First, as shown in FIG. 4, the NC device (not shown) of the machining center 1 is operated, and the touch probe M stored in the tool magazine 9 is attached to the spindle 8 by the tool changing arm 10, and then the X control is performed. The shaft 3 is operated to move the table 3 from the X-axis origin position Xo to a position where the center c reaches the front center of the column 4, and the B-axis control shaft is operated to move the rotary table 6 to the B-axis origin. The automatic centering jig 11 is positioned on the column 4 side by indexing and rotating to a position (0 degree). Then, after operating the Y and Z control axes to insert the probe Ma of the touch probe M into the reference hole 13d of the measurement ring 13, the X and Y control axes are operated as in the conventional case. The touch probe M is moved left and right, up and down, and the coordinate value of each control axis read when the measuring element Ma contacts the inner surface of the reference hole 13d, the reference hole 13d (spindle 8, measuring element Ma). A distance D from the center to the X-axis origin position Xo is measured. When the measurement operation has no thermal displacement before the machine is operated (see FIG. 4 (a)), and when there is a thermal displacement (e.g., extension of the ball screw for the X control shaft) due to the machine's operation, etc. 4 (b)), the amount of thermal displacement (error amount) α is obtained from the difference between the measured values. In FIG. 4, for convenience, the spindle head 5 (spindle 8) is shown to move instead of the table 3 (the same applies to FIGS. 5 and 6).

Next, when there is no thermal displacement or the like, as shown in FIG. 5, the touch probe M is returned to the tool magazine 9 by the tool changing arm 10, the boring tool T is taken out from the tool magazine 9 and mounted on the spindle 8, The rotary table 6 on which the pallet 7 to which the workpiece W is fixed is placed is moved by the distance F in the X-axis direction x from the X-axis origin position Xo through the table 3 by the operation of the X control axis, and the center of the spindle 8 is moved to the workpiece. The shaft hole 15a1 is drilled by the boring tool T at the drilling position P1 so as to coincide with the W drilling position P1. When the indexing rotation position (B-axis coordinate value) of the rotary table 6 on which the pallet 7 is placed is 0 degree (origin position), the hole position P1 is one of the x-axis direction x from the center c of the B-axis. It is assumed that the position is close to the side by a distance H (see FIG. 5A). When the drilling of the shaft hole 15a1 is finished, the rotary table 6 is rotated 180 degrees, and the index rotation position (B-axis coordinate value) is set to 180 degrees.
At this time, the drilling position P2 of the shaft hole 15b1 coaxial with the shaft hole 15a1 is a position shifted from the center c of the B axis to the other side in the X axis direction x by the same amount as the distance H. 6 is the operation of the X control axis, moved from the position of the distance F through the table 3 to the other side in the X-axis direction x from the position of the distance F, and after being positioned at the position of the distance G from the X-axis origin position Xo, Drilling of the shaft hole 15b1 is performed with the tool T (see FIG. 5B). As a result, the shaft hole 15a1 and the shaft hole 15b1 are accurately drilled in a straight line without causing a shift (error) in their axial center positions (see FIG. 5C).

  However, when there is a displacement amount α in the X-axis direction x due to thermal displacement or the like, as shown in FIG. 6, as in the case where there is no thermal displacement or the like, the rotary table on which the pallet 7 to which the workpiece W is fixed is placed. 6 is moved by the distance F in the X-axis direction x from the X-axis origin position Xo through the table 3 by the operation of the X control axis, but it is actually moved by the distance (F + α), and the B-axis coordinate value 0 The hole position P1 of the shaft hole 15a1 at a degree is a position that is offset from the center of the B axis by one distance (H + α) in one direction in the X axis direction x (see FIG. 6A), and the B axis coordinate value 180 The hole position P2 of the shaft hole 15b1 at a degree is a position that is offset by a distance (H-α) from the center of the B axis to the other side in the X axis direction x (see FIG. 6B). The table 6 is operated by the X control axis through the table 3 from the position of the distance F by the distance 2H in the X axis direction x. When moving to the other side, positioning at a distance G from the X-axis origin position Xo, and drilling the shaft hole 15b1 with the boring tool T, the shaft hole 15a1 and the shaft hole 15b1 are Are displaced (error) by 2α, and drilling cannot be performed accurately on a straight line (see FIG. 6C).

  Therefore, as described above, based on the error amount α in the X-axis direction x of the table 3 (rotary table 6) obtained using the measurement ring 13, the NC device of the machine tool is set and commanded by the machining program. The X control axis is operated by correcting the feed amount of the control axis. As a result, the shaft holes 15a1 and 15b1 to be formed at opposite positions on the same axis L are drilled by reversing the rotary table 6 180 degrees on the workpiece W mounted on the rotary table 6 via the pallet 7. In this case, the influence of the relative displacement between the workpiece W and the main shaft 8 due to thermal displacement or the like is removed, and the shaft holes 15a1 and 15b1 are processed with high precision by accurately matching their axis L (L1, L2). Can do.

  The above shows an example of drilling when thermal displacement occurs in the X-axis direction x. However, the present invention is not limited to this, and the Y- and Z-axis directions are affected by thermal displacement of the main shaft, Y-axis ball screw, and the like. Similarly, when a thermal displacement amount occurs in y and z, an error amount in the Y-axis direction y is obtained by a measurement operation performed by bringing the probe Ma of the touch probe M into contact with the reference hole 13d of the measurement ring 13, Further, an error amount in the Z-axis direction z is obtained by a measurement operation performed by bringing the probe Ma of the touch probe M into contact with the reference surface 13f of the measurement ring 13, and based on these, the NC device of the machine tool is a machining program. By correcting the feed amount of the Y and Z control axes that have been commanded and operating the Y and Z control axes, the workpiece W and the spindle 8 in the Y and Z axis directions y due to mechanical displacement including thermal displacement, etc. , Due to relative displacement in z By removing the sound, it is possible to perform boring machining of the workpiece W, and other necessary machining with high precision.

  As described above, the automatic centering jig 11 of the machine tool according to the embodiment has the jig main body 12 fixed to the outer peripheral portion of the rotary table 6 supported by the table 3 so as to be indexable and rotatable about the B axis. And a measurement ring 13 having a reference hole 13d and a reference surface 13f and attached to the jig body 12, and relatively moving the table 3 and the main shaft 8 in the X, Y, and Z axis directions x, y, a tool for automatic centering of a machine tool for measuring an error of the machine by moving to z and bringing the touch sensor M mounted on the spindle 8 into contact with the reference hole 13d and the reference surface 13f of the measuring ring 13; The reference hole 13d of the measurement ring 13 is provided so that the center axis S thereof is located on a straight line along a plane parallel to a plane including the X and Z axes and passing through the center c of the B axis. The reference surface 13 f is in the axial direction of the measurement ring 13. That provided on the outer end face, and and is the structure formed on a plane perpendicular to the central axis S of the reference hole 13d.

  Therefore, according to the automatic centering jig of the machine tool according to the embodiment, the measuring ring 13 is provided on the rotary table 6 with the reference hole 13d and the reference surface 13f, as in the conventional case. Since the workpiece W is not provided, the center X of the spindle 8 relative to the workpiece W is not affected by variations in the replacement accuracy (mounting accuracy) of the pallet 7 for setting the workpiece W on the rotary table 6 with respect to the rotary table 6. , Y, and Z axis directions x, y, and z can be accurately measured (mechanical error measurement) of the relative displacement (positional deviation, error amount), and based on the relative displacement amount. Thus, the machining accuracy can be improved by correcting the feed amount set and commanded by the machining program for the X, Y, and Z control axes and operating each control axis. In addition, the reference hole 13d and the reference surface 13f need not be provided on the workpiece W, the pallet 7, and the jig for attaching the workpiece W to the pallet 7, and there is no need to perform unnecessary processing on them.

In addition, according to the automatic centering jig of the machine tool according to the embodiment, the reference surface 13f of the measurement ring 13 is provided with the protruding portion 13e provided by protruding the outer end surface of the measurement ring 13 only partially outward. Since it is configured to be formed on the outer end surface, it is not necessary to finish the entire end surface of the measuring ring 13 as a reference surface 13f, the finishing of the reference surface 13f is easy and the processing accuracy can be increased. The contact operation by the touch probe M during measurement can be performed smoothly and easily.
Further, the measuring ring 13 is provided with a cover 14 that closes the opening on the inner side of the reference hole 13d and covers the upper side of the reference surface 13f. Chips and dust generated during processing of W can be reliably prevented from entering the reference hole 13d of the measuring ring 13 and adhering to the reference surface 13f, and the reference hole 13d and the reference surface 13f can be kept clean. Thus, the measurement accuracy by the touch probe M can be kept good.

In the automatic centering jig of the machine tool according to the above-described embodiment, the reference surface 13f is formed on both side portions in the diametrical direction along a plane parallel to the plane including the X and Z axes of the flange 13b. Although the present invention is not limited to this, the present invention is not limited to this, and it may be provided on the protrusion 13f provided only on one side in the diameter direction, or a recess may be formed instead of the protrusion 13f. The reference surface 13f may be provided in the recess, and the reference surface 13f may be provided on one side or both sides in the diameter direction (vertical direction in FIG. 3) parallel to the Y axis of the flange 13b.
In the above, the automatic centering jig 11 supports the table 3 on the bed 2 so as to be movable in the X-axis direction x, and supports the column 4 on the base 2 so as to be movable in the Z-axis direction z. The spindle head 5 is supported by a column so as to be movable in the Y-axis direction y, and between the table (work W placed on the rotary table 6 via the pallet 7) and the spindle 8 of the spindle head 5, Although an example in which the present invention is applied to the machining center 1 in which relative movements in the X, Y, and Z axis directions x, y, and z are given has been shown, the present invention is not limited thereto, and the table 3 is fixed to the bed 2. The column 4 is supported by the bed 2 movably in the X-axis direction x and the Z-axis direction z, or the table 3 is supported by the bed 2 movably in the Z-axis direction z and the column 4 is supported by the X-axis. Supports bed 2 so that it can move in direction x Alternatively, the table 3 is supported on the bed 2 so as to be movable in the X and Z axis directions x and z, and the column 4 is fixed and supported on the bed 2. The present invention can also be applied to a machining center in which relative movements in the Y and Z axis directions x, y, and z are given.

It is a perspective view showing a machine tool provided with an automatic centering jig for a machine tool according to an embodiment of the present invention. It is the side view which showed the automatic centering jig | tool of the machine tool which concerns on one embodiment of this invention in the partial cross section. FIG. 3 is a view taken in the direction of arrow A in FIG. 2. It is explanatory drawing which shows the measuring method of a machine displacement using the automatic centering jig | tool of the machine tool which concerns on one embodiment of this invention. It is explanatory drawing of the reversal process (when there is no thermal displacement etc.) of the shaft hole by a boring tool. It is explanatory drawing of the reversal process (when there exists a thermal displacement etc.) of the shaft hole by a boring tool.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Machining center 2 Bed 3 Table 4 Column 5 Spindle head 6 Rotary table 7 Pallet 7a The upper surface of a pallet (work mounting surface of a rotary table)
8 Spindle 9 Tool magazine 10 Tool change arm 11 Automatic centering jig 12 Jig body 13 Measuring ring 13a Reference hole 13b Reference surface 14 Cover 15a1, 15b1 Axis hole B B axis M Touch probe (touch sensor)
S Center axis of reference hole T Boring tool (tool)
W Work α Thermal displacement (error amount)

Claims (3)

The work is placed on a rotary table supported so as to be indexable and rotatable about the B axis parallel to the Y axis located at the center of the table, and a tool is mounted on the spindle arranged in the Z axis direction. In machine tools that process workpieces by relatively moving the table and spindle in the X, Y, and Z axis directions,
Wherein comprising a jig body fixed to the outer periphery of the rotary table, and a measuring ring attached to the jig body and a reference hole and a reference plane,
The reference hole of the measurement ring is provided so that its central axis is located on a straight line passing through a plane parallel to a plane including the X and Z axes and passing through the center of the B axis, and the reference plane is , Provided on the outer end surface in the axial direction of the measuring ring, and formed on a plane perpendicular to the central axis of the reference hole ,
The table and the spindle are moved relative to each other in the X, Y, and Z axis directions, and the touch sensor mounted on the spindle is brought into contact with the reference hole of the measurement ring from the center of the reference hole according to the read coordinate value. By measuring the distance to the X-axis origin position and correcting the feed amount in the X-axis direction, the workpiece that can be reversed by the rotary table is centered in the X-axis direction. Automatic centering jig for machine tools.   2. The automatic centering jig for a machine tool according to claim 1, wherein the reference surface is formed on an end surface of a protruding portion provided by protruding a part of an outer end surface of the measuring ring toward the column side. 3. The machine tool according to claim 1, wherein the measuring ring is provided with a cover that closes an opening portion on an inner side of the reference hole and covers an upper side of the reference surface. Automatic centering jig.

Images