JPS62176739A - Machine tool straightness correction device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION In order to maintain the straightness and parallelism of the slide tables of a numerically controlled machine tool and the surface angle of the movement between the slide tables, This relates to a straightness correction device for machine tools that improves the machining accuracy of machine tools by measuring the displacement of be. Generally, the machining errors of machine tools that carry out machining by holding a cutter or workpiece and sliding it back and forth include manufacturing errors in guide surfaces, gaps between guide surfaces and slide tables, etc. This error occurs due to deformation due to cutting force during machining, wear, etc., but it is impossible to completely eliminate this error, and there is a limit to increasing accuracy beyond a certain level.

In recent years, with the development of electronic control technology such as numerical control (NC) and optical control technology, it has become possible to control machines with high precision. In order to perform highly accurate feeding and positioning, the accuracy of the machine itself must also be high. However, although it is not impossible to manufacture a machine with a high precision of 1 micron or more, it is actually uneconomical because the manufacturing cost is too high, and the mechanical It is difficult to produce a kW model that even takes into account complex deformations.

Therefore, it has been proposed for some time that it would be better to adopt another method that does not require highly accurate straightness and parallelism of the machine itself. One approach is to continuously measure the deviation of the sliding table from the theoretical required path and feed the results back to the servo motor control unit to correct the control command to satisfy the required accuracy. Although the basic idea of doing so has been proposed, the current situation is that no practical product has been created yet due to the problems of complicated measurement methods and processing of measured values.

The present invention was invented to provide a practical machining error correction device that solves the above-mentioned problems. In other words, a means for forming an ideal straight line as a reference for sliding of the sliding table is provided on either the sliding table or the fixed side, and a means for forming an ideal straight line with the sliding table on the other side. A measuring device is installed to measure the distance between the sliding tables, and whenever the deviation of the measured value measured by the measuring device on one sliding table exceeds a set reference value, a correction signal is sent to the other sliding table. By providing a correction signal generator that sends to the servo motor controller that controls the drive, the overall error in the direction perpendicular to the direction of movement of each slide table can be calculated in real time by controlling the drive of each slide table. It is an object of the present invention to provide a straightness correction device for a machine tool which corrects each other with high precision.

In the embodiment of the present invention, a highly precisely finished reference block is used as a means for forming an ideal straight line,
Its position can be precisely adjusted using an adjustment screw. Of course, there are other means for forming the ideal straight line, such as a laser beam, which is selected depending on the balance between the required degree of precision and cost. The effects of using such means for forming highly accurate straight lines as a reference for guiding the sliding table are as follows.

A. Although it has a simpler shape than a guide surface, it can be easily manufactured with high precision.

B. Since the length only needs to be equal to the net stroke amount of the slide table, the length can be shorter than that of the guide surface.

Since no cutting force is applied to the means for forming the C0 ideal straight line, no wear or deformation occurs. Therefore, high accuracy can be maintained for a long time.

D. Replacement and modification can be done easily.

E, PAFor example, in the case of face milling with a machining center, when processing square objects, it is often necessary to finish the product at an accurate right angle, but since the intersection angle of the means to form an ideal straight line can be adjusted at will, Accurate squareness is easily obtained.

The measuring device used in the present invention is required to be highly accurate. If you use a measuring device that measures displacement without contact, it is possible to measure a medium convexity of 0.1 microns, and although it is a contact type, it is also possible to measure the same level using an electric micrometer. can be done.

In order to make the principle of the present invention easier to understand, an example of simultaneous two-axis control applied to a numerically controlled lathe will be shown and explained below. Fifth
The figure shows an example of this, in which a headstock 2 is placed on a bed 1, and a chuck 4 is attached to the front end of a main shaft 3 rotatably supported on the headstock 2. Holds an object W. A saddle 6 is placed on guide surfaces 5A and 5B formed on the bed 1 so as to be slidable in the direction of the spindle axis, and guide surfaces 7A and 7B formed on the saddle 6 in a direction perpendicular to the spindle axis. A cross slide 8 is slidably mounted on the top.

The saddle 6 is caused to reciprocate and slide parallel to the main shaft axis via a nut 11 by a screw 10 driven by a Z-axis servo motor 9. In addition, the Sloss slide 8 is
Screw 1 driven by X-axis servo motor 12
3 allows reciprocating sliding at right angles to the main shaft axis via the nut 14. A reference block 15 is attached to the front extension IA from the bed 1 by fixing means such as bolts as a means for forming an imaginary straight line.
The adjusting screw 17 screwed into the block [6 is applied to the reference block 15, and the reference block 15 is slightly swung to properly set the accurately finished reference surface 15A parallel to the spindle axis. The saddle 6 has a reference surface 15A.
The above-mentioned non-contact measuring device 18 is mounted opposite to the saddle, and measures the gap between the non-contact measuring device 18 and the reference surface 15A over the entire stroke of the saddle in the Z-axis direction. Similarly, a reference block 19 is mounted on the saddle 6, and an adjustment screw 21 screwed into the block 20.
Accordingly, the reference plane 19A is correctly set perpendicular to the spindle axis. The cross slide 6 has a reference surface 1.
A non-contact measuring device 22 is attached opposite to 9A, and measures the gap between the measuring device 22 and the reference surface 19A over the entire stroke of the cross slide 8 in the X-axis direction. The reference block 15.19 has a simple shape with a rectangular cross section.

The reference block 5 has a stroke amount in the Z-axis direction, and the reference block 19 has a length equal to the stroke amount in the X-axis direction.
It is desirable that each measuring device 18.22 and reference block 15.19 be covered with a cover or the like to protect the reference surface from chips, cutting oil, etc. A tool rest 23 is mounted on the cross slide 8, and a cutter T is set on the tool rest 23.As shown in FIG. By setting the measuring device 22 to match the position of the cutting edge in the X-axis direction of the cutting tool T, the error at the cutting point can be accurately measured.

31A (a) and (b) show diagrams of the principle of correction.

Now, without giving any movement command to the Z-axis servo motor,
When a movement command is given to the axis servo motor 1, the measurement value obtained from the measuring device 22 as the X-axis moves is pore pressure #L ()
) to the curve in Figure 2 is obtained. Also, when a movement command is given to the Z-axis servo motor without giving a movement command to the X-axis servo motor, the measured value from the measuring device 18 as the Z-axis moves is pore pressure! As (L), what is the curve A in Figure 3 (a)? 2) 7 As shown in Fig. 3 (a), the measured values of the gap measured by the measuring devices 18 and 22 are analog quantities such as -a to the curve, which are converted by an AD converter. It is digitized to the corrected Φ1 position and converted into a step-like curve. Then, it is calculated by a data calculation unit, which will be described later, to calculate the gap at the time of tape start. For <L(,), the intermediate correction amount (for example, 1
As shown in Fig. 3 (b), each time the gap (microns) increases or decreases, a correction pulse on the plus or minus side is generated, and this correction pulse is transmitted to the Z-axis servo motor 9 (X-axis servo motor 12), and the two-axis servo motor 'Ll (X-axis servo motor 12) is driven with the command value from the tape corrected by the correction pulse.

@For the sake of condolence, if there is no command from the tape for the Z-axis, the pulse sent to the Z-axis servo motor 9 will be only the correction pulse, and therefore the saddle 6 will be moved by an amount of 11 correction positions each time a correction pulse is generated. Therefore, the movement of the cutting edge has less error as shown in Fig. 61.9 Figs. is X
It is mounted so as to be slidable in the axial direction and is driven by the X-axis servo motor 26. A table 27 is placed on the saddle 25.
The Z-axis servo motor 28 is mounted so as to be slidable in the axial direction.
It is driven by A spindle head 30 is placed on two columns installed on the side of the bed 2/l so as to be vertically slidable in the Y-axis direction, and is driven by a Y-axis servo motor 31.

As shown in FIG. 1, +iif
A measuring device 32 similar to that described above is housed in a position corresponding to the X-axis direction of the center of the main axis, and the gap L in the Y-axis direction between it and the reference block 33 attached to the 111f surface of the saddle 25 is
, 1. 10ΔL is measured, and the correction pulse is sent to the Z-axis servo motor 28 to move the double 27 by a correction amount to correct the error in the Y-axis direction due to the movement of the saddle la 5 in the X-axis direction.

As shown in FIG. 2, on the rear surface of the bed 24.

A measuring device 34 is installed corresponding to the position in the X-axis direction of the center of the spindle, measures the gap in the Y-axis direction with a reference block 35 attached to the rear surface of the saddle 25, and sends the correction pulse to the Y-axis servo motor. 31 to move the spindle head 30 by a correction amount to correct the error in the Y-axis direction due to the movement of the saddle 25 in the X-axis direction.

As shown in FIG. 1, a measuring device 36 is attached to the lower surface of the table 27, which measures the gap in the Y-axis direction with a reference block 37 housed on the right side of the saddle 25, and outputs the correction pulse. Send it to the Y-axis servo motor 31 and spindle head 3
0 by a correction amount to correct the error in the Y-axis direction due to the movement of the table 27 in the Y-axis direction.

Further, as shown in FIG. 2, a measuring device 38 is attached to the left side of the table 27, which measures the gap in the X-axis direction with a reference block 39 attached to the upper surface of the saddle 25, and sends the correction pulse to the The signal is sent to the axis servo motor 26 to move the saddle 25 by a correction amount to correct the error in the X-axis direction due to the movement of the table 27 in the Y-axis direction.

Further, as shown in FIG. 1, a measuring device 40 is attached to the left side of the spindle head 30 in a position corresponding to the Y-axis direction position of the center of the spindle. The gap in the axial direction is measured, and the correction pulse is sent to the X-axis servo motor 26 to move the saddle 25 by a correction amount to correct the error in the X-axis direction caused by the vertical movement of the spindle head 30 in the Y-axis direction.

Furthermore, as shown in FIG. 2, a measuring device 42 is attached to the rear surface of the spindle head 30 corresponding to the position in the Y-axis direction of the center of the spindle. The gap in the direction is measured, and the correction pulse is sent to the Z-axis servo motor 28 to move the table 27 by a correction amount to correct the error in the Y-axis direction due to the vertical movement of the spindle head 30 in the Y-axis direction.

In other words, the error in the direction perpendicular to the direction of movement between two slides that can slide in directions perpendicular to each other and whose guide surface is parallel to the plane containing one guide surface. By correcting each other, it is possible to accurately correct errors in all directions during slide table movement.

FIG. 6 shows a control block diagram for the X-axis and two axes of the lathe with simultaneous two-axis control shown in FIG. 5, which is an embodiment of the present invention.

Furthermore, when applied to the cross-cut slice shown in the embodiment shown in Fig. 1.2, the same principle can be applied to the two axes x + and h. Also, the X axis and Y axis, and the Y axis and Z41
The same applies to ilh.

The control data punched on the command tape is read by a tape reader, passes through the data control section, and enters the sequential interpolation calculation section.
Arithmetic processing necessary for normal numerical control is added, and the pulse generator enters the X-axis or Z-axis pulse generation section as necessary. The pulses generated by each pulse generation section pass through an acceleration/deceleration section, a droop amount detection section, a D-A conversion section, a speed amplification section, and a servo drive section.
It generates a voltage determined by the direction of movement, distance and set speed, and rotates the X-axis or X-axis servo motor.

A pulse generator and a tacho generator are connected to each servo motor, and the tacho generator L/- generates a voltage proportional to the rotation speed of the servo motor, and feeds this back to the speed amplification section to control the servo motor. The rotation speed is controlled. In addition, the pulse generator generates a pulse proportional to the rotation angle of the servo motor, and feeds this back to the droop amount detection unit via the direction feedback pulse generation unit, thereby rotating the servo motor to the commanded rotation angle position. , it is now possible to hold it.

Next, a control operation for correcting F41i by the X-axis servo motor 9 will be described. When s-t, n,
Analog signal ■ output from the measuring device 22.

211- is amplified to AVz un in the f3 amplification section, and then A-D converted to output digital 1DzLn. Next, in the data transfer section, at the time of t, -tn, the output digital ff1DzLn is stored in the shift register S1, and at the same time, 1, -t, n stored in Sl is stored.
-1, the digital jlDzLn-1 outputted is transferred to the shift register S2. Next, the data calculation section detects the difference Δ02 between DzLn-1 and DzLn. ΔD
Z is output from the correction data output section. There are of course two types of △Dz: bra, s and minus.

The output ΔDZ from the correction data output section is further sent to the Z-axis drive pulse generation section, and the command data D from the interpolation calculation section is sent to the Z-axis drive pulse generation section.
While matching with Z, drive pulses are generated and corrected so that ΔDZ becomes zero. This correction operation corrects the error in the direction perpendicular to the direction of movement when the saddle 6 moves in the Z-axis direction.
The case of correction using the X-axis servo motor 12 is also completely the same.

In addition, as another correction method, as shown by the broken line, the correction signal ΔDz from the correction data output section is sent to the direction feedback pulse generation section, and the direction feedback pulse generation section adjusts the correction signal ΔDz with the feedback pulse from the pulse generator. , ΔDZ
It is also possible to correct by generating a drive pulse so that the value becomes zero.

Further, although a control block diagram for simultaneous three axes is not shown, control can be performed on the same principle as the simultaneous two axes control.

As stated above, the present invention is not limited to the configurations shown in the examples, and modifications are expected within the scope of the technical idea of the present invention as shown in the claims. .

[Brief explanation of drawings]

1 and 2 are perspective views showing an embodiment in which the present invention is applied to a numerically controlled tank boring and milling plate; FIG. 3 is a correction principle diagram;
Fig. 4 is a graph showing the movement of the cross slide when correction is applied, Fig. 5 is an example showing the principle applied to numerically controlled liquid temperature, and Fig. 6 is a graph showing the simultaneous X-axis and χ-axis movement of the present invention. The control program l'4 in the case of an axis is 1...Besodo,'5Δ,r, (3...Guiding surface, 0
... Saddle, 7 A, 71' (... Guide surface, 8.
...Cross slide, 0...X-axis servo motor, t2
... X-axis servo motor, ■5.1 () ... Bracket semi-flock, 18.22 ... Measuring device, 20 ... X-axis servo motor, 28 ... X-axis servo motor, 31.・・Y
Shaft servo motor, 2.1...bet, 25...saddle, 30...shaft head 33.35.37.3, l
l, /l';...Reference block, 32.3.1
．． 36.38.・10.・12...Measuring device special 1;'
[Applicant, Shir Seiki Co., Ltd. Dai Ume Tomomi Q jc Seiji Figure 2 Y Figure 4-X (Z) Figure 5

Claims (1)

[Claims] a first sliding table provided so as to be slidable in a first direction along a first guiding surface on the first guiding member; and a first sliding table that is perpendicular to the sliding direction of the first sliding table. a second sliding table provided so as to be slidable in a second direction along a second guiding surface on the second guiding member; and each of the first sliding table and the second sliding table. a third sliding table provided so as to be slidable in a third direction along a third guiding surface on a third guiding member perpendicular to the sliding direction of the first sliding table; a first servo motor that slides along a first guide surface; a first control unit that controls the first servo motor; a second servo motor for sliding, a second control section for controlling the second servo motor, and a third servo motor for sliding the third sliding table along a third guide surface. and a third control unit that controls the third servo motor, and a numerical control machine that processes a workpiece with a tool by a combination of relative movements of the first, second, and third slide tables. In the machine, the first sliding table or the first sliding table
The reference forming means is provided on either one of the guide members and has a first reference surface in the second direction of the first sliding table and a second reference surface in the third direction of the first sliding table. and a first reference surface of the reference forming means provided on the other of the first slider or the first guide member of the first slider and the movement locus of the first slider and the first reference surface of the reference forming means. a first measuring device that measures distance;
The distance between the movement locus of the first sliding table and the second reference plane of the reference forming means is provided on the other of the first sliding table or the first guide member of the first sliding table. When the measured value of the second measuring device and the first measuring device exceeds the reference value in the second direction, a correction value is calculated and sent to the second control unit, and the measured value of the second measuring device is a correction calculation unit that calculates a correction value when the value exceeds a reference value in a third direction and sends it to a third control unit, and the correction calculation unit calculates a correction value when A straightness correction device for a machine tool, characterized in that when a surface deviation amount exceeds a tolerance value, a second servo motor or a third servo motor is driven for correction based on the respective correction amounts.