JPS60207742A - On-machine measurement correcting apparatus for machine tool - Google Patents

Abstract

PURPOSE:To improve the accuracy in positioning an NC machine tool by automatically carrying-out calculation correction by the irradiation of laser light and the signals supplied from a light receiving and detecting apparatus and electrical level meters and correcting the shift of a main spindle by the external force such as thermal deformation, transfer load, etc. CONSTITUTION:The laser light outputted from a laser head 13 is formed into two pieces of laser light in the vertical direction by a beam slitter 14 and a beam bender 15, and one is projected onto the light receiving surface of the first semiconductor position detector 18, and the other is projected into a penta prism 19, and the optical path is changed in the direction of shift Z of a headstock 8 which crosses at right angles to the incident optical path, and the laser light is projected onto the light receiving surface of the second semiconductor position detector 21 installed through an installation member 20. The coordinates having the point O1 on a column base 3 as original point and having the vertical line passing through O1 as starting line and the coordinates of the point Q of the stock 8 are calculated from the outputs of electrical level meters 16a and 16b, and the top edge point O of a main spindle 10 or the shift of the position of the cutting edge of a cutting tool is calculated, and the value is input into an NC apparatus, and the measured value is corrected. Thus, the accuracy in positioning a machine tool can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring and correcting positioning errors of an NC (numerical side leg) machine tool on-machine.

In recent years, FMS (flexible znanuf
Acturing system.

With the spread of unmanned machine tools such as complex production systems, machining errors caused by deformation due to external forces such as thermal displacement, cutting force, and gravity have been highlighted as a major problem that hinders unmanned machine tools.

Conventionally, when performing machining that requires particularly high precision even with NC machine tools, workers themselves have to check and correct the deviation of the origin of one machine and the positioning error with respect to the workpiece reference plane from time to time.

This current situation is far from completely unmanned.

Therefore, when proceeding with unmanned operation, it is necessary to ensure the stability of machine accuracy, or to create a system that automatically measures the amount of displacement of the machine tool itself and has the NC device correct the position coordinate values. Above measurement correction is required. Among the deformations of machine tools, it is relatively easy to correct on-machine measurements for those caused by simple expansion and contraction deformations, but it has been extremely difficult to correct for those caused by tilting or curved deformations. there were.

This problem becomes the most serious problem especially when a large workpiece is processed using a large machine tool.

The first reason is that in the case of large machine tools, the amount of thermal displacement generally appears larger than that of small machines, and even a small inclination of the structure causes a change in the tip of the spindle because the distance from the center of rotation to the tip of the spindle is large. This is a large value in terms of position. The second reason is that in the case of a large workpiece, it is difficult for an operator to measure and check the degree of processing. 2. Description of the Related Art Conventionally, as an automatic measurement and correction device for measuring the machining accuracy of a large workpiece, there is one that measures the machining accuracy by fitting a touch sensor to the main shaft and using the NC coordinate axis of the machine as a scale.

However, with this device, as mentioned above, if the machine tool itself is displaced, the accuracy measured by the touch sensor becomes unreliable.

Specific examples of the problems of the conventional machine tools mentioned above will be explained with reference to FIGS. 1 and 2. Figure 1 is a front view of a machine milling machine as an example of a conventional large-scale machine tool.
FIG. 2 is a side view thereof. As shown in both figures, the bend 1 is supported on a floor 2 by a plurality of jacks (not shown), and the column space 3 is supported by a guide member 4 on the bend 1.
a and 4b, and is driven and positioned in the X-axis direction by a drive device (not shown).

The column 6 is erected on the column base 3, and the saddle 5 is provided on the column 6 and includes a guide member 7a having a sliding surface.
, 'yb, and is driven to one position in the Y-axis direction by a drive device such as a feed screw or a motor (not shown). Further, the headstock 8 is guided by guide members 9a and 9b having sliding surfaces provided on the saddle 5, and is driven and positioned in two axial directions by a drive device (not shown). The main shaft 10 is supported by a bearing (not shown) built into the head stock 8, and is rotated and driven by a motor 11 installed on the hentos dock 8 via a drive gear (not shown). A cutting tool (not shown) is attached to the tip of the main spindle 10 to cut a workpiece (not shown) placed on a table facing the column 6.

In such a machine tool, thermal deformation or deformation due to a moving load causes the following displacement of the tip point O of the main shaft 10.

First of all, the thermal inertia is different between the A side and the 8th side of the column 6, and the column 6 bends and deforms in the X-Y plane due to changes in room temperature. and displacement in the Y-axis direction.

Second, if there is a temperature change in the lubricating oil between the saddle 5 and the guide members 7a, 7b, the column 6 will also undergo bending deformation in the XY plane.

Especially in large machine tools, the saddle 5 and guide members 7a, 7b
A hydrostatic oil bearing guide surface is formed between the column 6 and the lubricating oil, and temperature changes in the lubricating oil cause a large bend in the column 6 to deform, causing displacement of the spindle tip point O in the X- and Y-axis directions. It appears as.

Thirdly, by moving the headstock 8 in two axial directions, the synadre 5. 9. A moment load is applied to the column 6 and the column base 3, resulting in rotational displacement of the X-axis rotation of the column base 3, inclination and bending of the column 6 in the Y-Z plane.9. A rotational displacement of xm rotation of the saddle 5 occurs, and a displacement of the main shaft tip point 0 in the Y-axis direction occurs.

Fourth, the column pace 3 and the guide member 4a of the pend 1,
4b, the characteristics of the hydrostatic oil bearing guide surface change due to temperature changes in the lubricating oil, and the X-axis rotation of the column base 3 and the
@ Rotational displacement of mawashi occurs. As a result, the spindle tip point O
displacement occurs in the X-axis direction, Z-axis direction, and Y-axis direction.

Furthermore, fifthly, the temperature of the hentos dock 8 increases due to the heat generation of the bearings that support the drive gear in the main shaft 10 and the headstock 8 due to the rotation of the main shaft 10. In this case, the surface of the headstock 8 on the saddle 5 side is a guide member 9a,
9b, the heat dissipation properties are different from the surface opposite to the saddle 5. Therefore, the entire headstock 8 is
The song undergoes a deformation in the XF-plane. Such thermal deformation of the headstock 8 causes displacement of the spindle tip point 0 in the X-axis direction, and the movement of the hentos dock 8 on the saddle 5 exhibits hysteresis characteristics in the 2-X plane circle, and the spindle tip point 0 The degree of straightness of the motion also deteriorates.

The present invention eliminates the above-mentioned problems.

The purpose of this invention is to provide an on-machine measurement and correction device that can realize a machine tool with n degree of reliability.

The on-machine measurement correction device for a machine tool of the present invention includes a column that stands upright in the vertical direction as described above, and a saddle that is driven and positioned in the vertical direction by being guided by the sliding #lJJ surface provided on the column. , is guided by the sliding surface provided on the saddle and driven in the horizontal direction.

NC that has a hentos dock that is positioned and a main shaft that is supported by a bearing in the headstock and rotated and driven.
In a machine tool, two electric level meters are installed in the vicinity of the lower end of the column or on a member such as a column base that constitutes the lower surface of the column, and two electric level meters are installed in perpendicular directions and two parallel electric level meters are installed in the vertical direction. a first semiconductor device detector provided with a laser head forming a laser optical path, a beam splitter, and a beam bender, and further having a light receiving surface into which one of the two laser beams is incident; and the first semiconductor device. A pentaprism that approaches the detector and receives the other of the two laser beams is provided on the saddle, and a laser beam deflected in the direction of rainbow head stock movement (horizontal direction) is input to the pentaprism. A second semiconductor device detector having a light-receiving surface that is The present invention is characterized in that a means is provided for inputting the displacement of 1 to the NC device as a correction amount. With the above configuration, the displacement of the main shaft caused by thermal deformation or deformation due to external forces such as moving loads is automatically measured on the machine, and correction is performed by inputting this to the NC device. The reliability of the positioning accuracy of the machine tool is much the same as above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the configuration of the present invention will be explained below based on the embodiment shown in the drawings.

FIG. 3 is a side view showing an embodiment in which the present invention is applied to the boring and milling machine described in FIGS. 1 and 2. FIG. In the figure, the mounting plate 12 is fixed on the column base 3.

A laser head (13%), a beam splitter (14°), a beam bender (15), and two electric level gauges (16a, 16b) arranged perpendicular to each other are installed. The laser beam emitted from the laser head 13 is formed into two parallel laser beam paths in the vertical direction by a beam splitter 14 and a beam bender 15.

A first semiconductor device detector 18 and a pentaprism 19 are installed on the saddle 54C via a mounting member 17.

One of the two parallel laser beams is incident on the light receiving surface of the first semiconductor device detector 18, and the other laser beam is incident on the pentaprism 19. The laser beam incident on the pentaprism 19 has its optical path changed in the moving direction (Z-axis direction) of the headstock 8 orthogonal to the incident optical path, and is directed to a laser beam installed near the tip of the headstock 8 via a mounting member 20. The light is incident on the receiving surface of the semiconductor device detector 21 of No. 2.

The semiconductor device detectors 18 and 21 are original spot position detectors using silicon diodes, and detect the two-dimensional displacement of the original spot projected onto the light receiving surface with high precision (for example, resolution 1
0 μm). The pentagonal prism 19 is also called an orthogonal bender, and the rotational displacement θBX of the X-axis (axis perpendicular to the plane of the paper) on the saddle 5 is 6D.
Even if a rotational displacement θszi of the lZ-axis rotation occurs, the incident optical path has a property of maintaining orthogonality with the original exit optical path 61.

FIG. 4 shows the outputs of the semiconductor device detector 18, 21 and the electric level meters 16a, 16b.

Calculate the coordinates of point P□ on saddle 5 and the coordinates of point Q near the tip of headstock 8 in a coordinate system whose origin is point 0□ on column base 3 and the starting line is a vertical line passing through 0□. 2 is an fc block diagram showing the configuration of a circuit for calculating the tip point 0 of the main spindle 10 or the displacement of the cutting edge position of the tool fitted on the main spindle 10 and inputting it to the NC device as a correction company.

In the same figure, the outputs of the electrical levels 1t16a and 16b are input to the D/A converters 23a and 23b via the signals ji122a and 22b, respectively, and are converted into digital amounts as the level change amounts θBX and θBZ of the column base 3. Each signal line 24a.

The signal is input to the interface circuit 25 via 24b. Signals related to the displacement of the saddle 5 in the X-axis direction and the two-axis direction with respect to the laser beam path in FIG. Ru. Similarly, signals related to the displacement of the tip of the hentos dock 8 in the X-axis direction and the Y-axis direction with respect to the laser beam path rearward in FIG. It is input to the circuit 27.

The switching circuit 27 receives the switching command signal 29 from the interface circuit 25 and inputs the signal from either the signal transmission path 26 or 28 to the signal processing circuit 31 via the signal transmission path 30.

In the signal processing circuit 31, the semiconductor device detector 18 or 21
Based on the signals from The digital signal (x2.y2) regarding the displacement in the axial direction is sent to the signal transmission path 3.
2 to the interface circuit 25.

When the interface circuit 25 receives the data acquisition signal 34 output based on the internal user macro of the NC device 33 and the program in the area, the interface circuit 25 transmits a switching command signal 29 to the switching circuit 27, so that the laser beam path changes to the saddle 5 with respect to H. and a signal (X21y2) regarding the displacement of the tip of the hentos dock 8 with respect to the laser optical path PzQ are sequentially input.

Signal θBXIθ regarding the level change amount of column base 3
After inputting B2, these signals are input to the NC device 33 via the signal transmission path 35. The signal input from the signal transmission path 35 is stored in a data memory in the user macro area inside the NC device 33. The NC device 33 sets the tip point 0 or 1 of the spindle 10 according to a program provided in the data memory described above.
The displacement of the cutting edge position of the tool to be fitted at 0 is calculated, and the correction value is calculated for the NC setting value.

FIG. 5 is a diagram showing the principle of the pentaprism 19.

Pentaprism 19ij: The laser source enters or exits through the surfaces indicated by HI and Hl, and the laser source that originally passes through the roadside is reflected at the 0 point on the reflective surface LK and then returns to the point D on the irregular surface stone. It is reflected again and goes out through the light path bean. The pentaprism 19 has a property that the orthogonality between the original shoulder and the optical path (2) is maintained even if the angle of incidence at the shoulder of the optical path changes. However, as shown in Figure 6, butts
), when B moves in parallel by δ in the ■ direction of the two axes and changes to 7, the optical path correction of one reflection source moves in parallel by δ in the ■ direction of the Y axis and changes to E'F''. Assuming that the intersection point between the center plane and the surface is P2, when the incident optical path moves in parallel by δ in the Z-axis ■ direction, point P2 moves by δ in the Z-axis ■ direction.

It moves to point P2' displaced by δ in the ■ direction of the Y-axis.

Next, the principle of measurement and the calculation contents of the correction I within the user macro area will be explained.

In FIG. 3, the laser head 13. Beam splitter 14, beam bender 15, and electrical level meter 1
6a and 16b are actually arranged close to each other, and the laser head 13 and beam splitter 14
1 beam bender 15 level changes 11! It shall be detected by the air level 1f-16 & 116b.

In this case, point 0□ is the origin and the vertical line passing through one point 0□ is Y
Considering a coordinate system having the Y-axis as an axis, which is orthogonal to the Y-axis and is the moving direction of the column pace 3, the equation of the straight line of the V-zer optical path G is uniquely determined from the outputs of the electric level meters 16a and 16b. be done.

That is, the program in the user macro area of the NC device 33 (hereinafter simply referred to as the program) first calculates the equation of the straight line of the optical path O12 based on the output data of the % electric level meters 16a and 16b. .

Next, from the NC coordinate value of saddle 5 in the Y-axis direction.

The distance y□ in the Y-axis direction of the light receiving point P□ of the first semiconductor device detector 18 with respect to point 0□ is uniquely determined, and in the program, it is determined from the equation of the straight line 10J7 and the distance y. The coordinate values of point P in the coordinate system with one point O1 as the origin are calculated.

Next, in the program, the coordinates of the reflection point 02 of the beam bender 15 are calculated as a point obtained by moving one point O1 by a distance in the negative direction of the two axes. Here, strictly speaking, column base 3
When there is a level change in , point 02 is displaced in the Y-axis direction in the coordinate system with point 0□ as the origin, but 0, 0 .
=l□ is small, and the level change itself of the column base 3 is actually small, so there is no practical problem in ignoring the displacement of point 0□ in the Y-axis direction. In addition, the % origin O process itself causes displacement in the Y-axis direction and the Z-axis direction with respect to the floor 2, but this displacement can be ignored in practice for the following reason. Namely.

The column base 3 is subject to changes in the characteristics of the hydrostatic oil bearing guide surface formed between the guide members 4a and 4b, distortion deformation of the bend 1,
Due to distortion and deformation of multiple jacks (not shown) between bed 1 and floor 2, level changes and changes in the Y-axis direction and Z-axis direction may occur.
causes displacement in the axial direction. However, in general large machine tools, the sheath degree is maintained and managed regularly, and the accuracy of the movement of the column base 3 in the X-axis direction perpendicular to the plane of the paper is also controlled by regular inspections. Sh.

At least the displacement is suppressed to within the adjusted range. The problem here is the point 0 on column pace 3 for large machine tools. Since the distance between the tip point 0 of the main shaft 10 and the Y-axis direction and the Z-axis direction is large, the column base 3
Even the slightest level change appears as a magnified and larger change at the tip point O of the main shaft 10, and one of the objects of the present invention is to correct such a displacement.

In the program, after determining the coordinate values of the point 02 as described above, the equation of the line ItilO□P2 is calculated as a straight line passing through the point 0□ and parallel to the point 0□.

Next, the program calculates the coordinate values of point P2 in the coordinate system with point 01 as the origin as follows. 6th
As already explained in the figure, when the pentaprism 19 is displaced by a in the ZM direction with respect to the laser beam propagation,
The apparent reflection point P2 is also displaced by δ in the ■ direction of the Y-axis.

Assuming that the Venta prism 19 is placed as close as the first semiconductor device detector 18, it is possible to
2, the above-mentioned displacement ζ is calculated from the output data of the first semiconductor device detector 18, and therefore the coordinate values of the above-mentioned apparent reflection point P2 are calculated.

Next, in the program, the second semiconductor device detector 2 at the source of the laser whose optical path is changed by the self-sigma self-bentuff rhythm 19
The coordinates of the receiving claw Q of No. 1 are calculated as ffL'(I'').

It is assumed that the coordinate values of point Q in the two axis directions are calculated from the NC coordinate values, and P2Q = z2 in FIG. 3 is also calculated from the NC coordinate values.

Considering the Y-Z plane that meets the reflection point P2 in the coordinate system with point 02 as the origin, the direct ffko projected onto this plane is
Let xPz be 0'2P2, and pass through point P2 in this plane to
□' Let the straight line extending to P2 be P2Q'. In the program, the displacement of the tip of the hentos dock 8 in the X-axis direction and the Y-axis direction obtained from the output data of the second semiconductor device detector 21 is regarded as the displacement with respect to the straight line PgQ', and the equation calculated from the NC coordinate value and the 2 semiconductor device detection value 1
Out of 9.

From the data, the displacement of the tip end of the hentos dock 8 in the x, y, and z axis directions in the coordinate system with the origin at the point O is calculated.

The displacement of the tip of the head stock 8 in the X-axis direction calculated by such a calculation method has the following problem, which will be explained below.

The symbols are determined as follows.

△XS Displacement in the X-axis direction in a coordinate system with two points 0□ as the origin △XH: Displacement in the X-axis direction of the tip of the hentos dock 8 in the above coordinate system θY: Rotational displacement of the Y-axis rotation 9 of the saddle 5 As shown in FIG. 7, when the saddle 5 is rotationally displaced by θY about the vertical line (Y-axis) passing through P2, the optical path P2Q is rotationally displaced by θY on the z-X plane circle and becomes P. Therefore, ΔXH calculated by the program includes an error of z2θY. Therefore, in actuality, ΔXH can be regarded as the sum of the displacement of the saddle 5 in the X-axis direction with respect to the point O□ and the displacement with respect to another coordinate axis fixed inside the saddle 5. That is, in addition to the x-y-z coordinate system whose origin is one point O0, there is a coordinate system Xs -Ys- whose origin is a fixed point 08 in the saddle 5.
Z, and assuming that it is parallel to the x, y, and z axes in the initial state, the fixed point 05 in the saddle in the coordinate system with one point O1 as the origin is the displacement △XH calculated by the program. Displacement in the X-axis direction and coordinate system X with 1 point 08 as the origin
It can be considered as the addition of the displacement to the XB-axis axial force at B-Y and -Z.

Next, in the program, the tip point OOY axis direction position Δy, and the displacement direction zo in the z axis direction are calculated as follows. Here, the symbols are defined as follows.

Y(): Distance in the Y-axis direction from point 01 to point O calculated from N C coordinate values △Ya: A straight line perpendicular to the straight line projected on the Y-Z plane including P2 is also a straight line. The Y-axis of the tip of the Hentos dock 8 in the coordinate system whose origin is the point 0□ obtained from the equation of r, Z 2 = P2Q calculated from the NC coordinate value, and the output data of the second semiconductor device detector 21. Displacement in direction Zo: Point 0 calculated from NC coordinate values. Distance in the z-axis direction to point O (Zo=Z□+Z2+Z3)△zo: Point O! Displacement of point 0 in the two-axis direction in the coordinate system with origin ΔYo: Displacement of point 0 in the Y-axis direction in the coordinate system with point 0 □ Total 0 □ θBX: Column base 3 detected by the electric level meter 16a The amount of rotational displacement △z of
The biaxial force positions ΔYo and Δzo of the saddle 5 in the coordinate system having the origin at the point O□, which are computed from the output data of the semiconductor device detector 18, are computed by the following equation.

△Yo = △YH ten (Z, -Z, -Z2)・θBX...
...(1st formula) △2. =△Z, +(Y, -11)"θ
Bx------<2nd formula) Next, in the program, the displacement of the tip point 0 of the main shaft 10 in the X-axis direction is expressed as 2
Calculations are performed by selecting one of the two methods at the appropriate time.

The first method is to consider the displacement ΔxH of the tip of the headstock 8 in the X-axis direction as the displacement ΔXo of the tip point 0 of the main shaft 10 in the X-axis direction. The second method is
As shown in the figure, the headstock 8 is moved in the direction of two axes e, and the trajectory of the tip of the headstock 8 in the X-2 plane obtained from ΔzH calculated at each movement position is plotted on the two axes. This is a method in which the displacement of point 0 obtained by extending by 23 in the direction of e and extrapolating is regarded as ΔXo.

As explained above, the on-machine measurement correction device for a machine tool of the present invention is provided with a laser beam emitting and light receiving detection device and an electric level meter at required locations on the machine tool body, and automatically adjusts the accuracy based on signals from these devices. It is configured to perform calculations and make corrections, and because the three-dimensional displacement of the spindle tip point is automatically measured at the appropriate time, it is possible to prevent changes in the level of the column base, reverse deformation of the column curve, and bearing heat generation. The displacement of the spindle tip point caused by thermal deformation of the headstock, etc. is completely corrected, and the reliability of positioning the machine tool by 8 degrees can be significantly improved. In addition, by applying the present invention to a machine tool, the reliability of the measurement scale can be improved even when measuring the machining accuracy of a workpiece by fitting a touch sensor to the main axis of the machine tool and using the NC coordinate axis as a measurement scale. This makes it possible to perform highly reliable measurements, which is particularly effective in measuring thick workpieces, which have conventionally had problems with reliability.

[Brief explanation of the drawing]

Figure 1 is a front view of a conventional cross-sweeping milling machine. FIG. 2 is a side view thereof, FIG. 3 is a side view of an embodiment of a horizontal milling machine to which the present invention is applied, and FIG. 4 is a block diagram of an embodiment of a circuit used in the present invention. *5 Figure 6 is a diagram of the principle of a pentaprism, Figure 7 is an explanatory diagram of the rotational displacement of the optical path, and Figure 8 is a diagram showing the method of calculating the displacement of the tip of the main axis. In the drawing. 1 is the bed, 3 is the column base. 4a and 4b are guide members. 5 is the saddle. 6 is a column. 7a and 7b are guide members. 8 is the headstock. 9a and 9b are guide members. 10 is the main axis. 13 is the laser head. 14Fi beam splitter-1 15 is a beam bender. 16a and 16b are electric level meters. 18 is a first semiconductor device detector. 19 is a pentaprism. 21 is a second semiconductor device detector. Patent Applicant: Mitsubishi Heavy Industries, Ltd. Sub-Agent Patent Attorney: Former Ishi Shibu (and 1 other person) Figure 1 Figure 5 U Figure 6 Figure 7 Figure 8 Xθ

Claims (1)

[Claims] A column installed in the vertical direction, a saddle that is guided by a sliding surface provided on the column and driven and positioned in the vertical direction, and a saddle that is guided by the sliding surface provided on the saddle and moved horizontally. Drive 1: In an NC machine tool having a positioned hentostok and a main shaft supported by a bearing in the hentostok and rotated and driven, Two electric level meters arranged in orthogonal directions, a laser head, a beam splitter, and a beam bender that form two parallel laser beam paths in the vertical direction are installed, and the two laser beams are a first semiconductor device detector having a light-receiving surface into which one of the two laser beams is incident, and a pentaprism which is close to the first semiconductor detector and into which the other of the two laser beams is incident, on the saddle; A second semiconductor device detector having a light-receiving surface into which the laser beam deflected in the direction of movement of the headstock by the pentaprism is installed at the tip of the headstock, and the two electric level meters and the two semiconductors The output of the device detector and N
NC using the displacement of the main axis calculated from the C coordinate value as the correction amount
An on-machine measurement correction device for a machine tool, characterized in that the device is provided with a means for overcoming the problem.