WO2013131354A1

WO2013131354A1 - Method and device for compensating indexing error of machine tool

Info

Publication number: WO2013131354A1
Application number: PCT/CN2012/079380
Authority: WO
Inventors: 李杏华; 张国雄; 裘祖荣; 刘书桂; 马艳玲
Original assignee: 天津大学
Priority date: 2012-03-07
Filing date: 2012-07-30
Publication date: 2013-09-12
Also published as: CN102554701A; CN102554701B

Abstract

A device for compensating indexing error of a machine tool comprises a circular standard ball disk (6), N standard balls (34) arranged on the ball disk; the N standard balls are installed in same height at the standard ball disk and uniformly arranged on a circumference concentric with periphery of the standard ball disk; the standard ball disc is arranged on a turntable (4) of the machine tool, and the circumference of the standard ball disc are concentric with the rotating shaft of the turntable of the machine tool. A method for compensating indexing error of machine tool by using the device is also disclosed. The device and the method can measure error compensation of the system online in situ in machining operation, and avoid being influenced by the turntable indexing error of a machine tool and the radial and axial movement errors of a rotating shaft.

Description

Machine tool indexing error compensation method and device

The present invention relates to error compensation for an in-situ in-situ measurement system in machining. Specifically, it relates to a machine tool indexing error compensation method and device. Background technique

The development of the national economy and national defense is increasingly demanding for the accuracy of products, and the proportion of parts with complex shapes is increasing. These high-precision and complex parts have long processing time, high processing cost, and large loss due to non-conforming products. Appropriate detection devices are used in the processing process to timely detect various sizes, shapes and positional parameters of the workpieces, which is of great significance for improving the machining accuracy, ensuring product quality, and preventing or reducing waste products.

At present, a series of in-process testing devices widely used at home and abroad, such as the Italian Marpose company and China Zhongyuan Measuring Instrument Factory, can only be used for the measurement of some simple parameters such as shaft diameter, bore diameter and step height. The national economy and national defense need to process many complicated parts, such as the engine's whole leaf disc, gears, and cabinets. The shape of these parts is complicated, and the measuring devices currently being processed at home and abroad are obviously powerless.

For this type of complex part, the most common method currently is to place some dedicated or general purpose measuring instruments between the two processes of the line. A more comprehensive inspection of the workpiece after completion of a machining process. According to the test results, only the parts that meet the requirements in the previous process are put into the next process. The raw materials of complex parts such as the engine's integral blade and the previously completed process are expensive. If it is a pity that some local parameters in a certain process do not meet the requirements, it should be reworked as much as possible to make it a qualified one. For the method described above, there are many difficulties in finding that some local parameters do not meet the requirements and are returned to the original machine for repair. First, the entire process is not smooth. Second, the workpiece is lost after it is removed from the machine. Reinstallation will cause errors due to baseline changes. In order to solve these two problems, online in-situ inspection is required.

Some CNC machine tools and machining centers have detection devices. The easiest is to use the probes configured on the machine to detect tool wear after machining. This method can only find the wear of the tool and can not find other machining errors. A more advanced method is to change the probe at the tool after the tool exits, and use the machine to drive the probe to detect the workpiece. Although this method can be found to be affected by tool wear, machine vibration, deformation due to cutting force, etc., it is problematic in principle, and it cannot find various errors due to machine motion errors. The tool and the probe are driven by the same control system and motion mechanism, and the motion error of the machine tool affects both the machining error and the measurement error.

A basic principle of metrology is that the inspection device should be independent of the machine tool. In response to the above problems, invented a

(1) Small size, can be installed next to the machine. A measuring system that performs full inspection of various dimensions, shapes and position parameters on complex workpieces without machining the workpiece in the machine tool. (2) It has 5 degrees of freedom and is highly detectable. It can measure in-situ in-situ parts of complex parts such as integral leaf discs and special-shaped gears. (3) Light weight, can be removed from the machine if necessary, does not affect the various work of the machine. (4) It is capable of scanning or automatic point measurement, and the measurement efficiency is high. (5) It has a variety of error compensation measures and high measurement accuracy. (5) With powerful data processing software, the free surface is fitted and reconstructed, and compared with the theoretical model of the measured surface to form a rework instruction. It will be widely used in the production of complex parts Pan-applied, solving many problems that have been difficult to solve in the national economy and national defense, has important academic significance and practical value, and has significant economic and social benefits. This result has been patented separately.

Figure 1 shows a typical layout of a CNC machine tool and machining center. The machined part is mounted on the turntable 4 of the machine table 2, with the tool holder 3 at the rear and two auxiliary stations 1 and 5 in front for loading and unloading. The measuring machine can only be installed in a small area between the two auxiliary stations 1 and 5 (usually only four or five hundred millimeters wide). However, this type of measuring system, regardless of the type of construction, can only measure certain parts close to one end of the measuring machine. It is difficult to reach the back end of the machine tool, that is, to measure at one end of the tool holder 3. Especially for complex parts such as integral leaf discs, the blade has a large twist angle, and the groove between adjacent blades is narrow, and it is very difficult for the probe to protrude from the rear end. A more realistic method is to transfer the machine turning table 4 and transfer the blades or teeth to be measured to the front end of the machine for measurement. However, a new problem has arisen here. The indexing error of the turntable 4 and the radial and axial motion errors of the rotating shaft affect the measurement results. It violates one of the basic principles of metrology: The inspection device should be independent of the machine tool. In order to avoid the influence of the indexing error of the machine table and the radial and axial motion errors of the rotating shaft, an appropriate method is needed to compensate for the above error. Summary of the invention

The present invention aims to overcome the deficiencies of the prior art, and provides a method or device for avoiding the influence of the indexing error of the machine tool table and the radial and axial motion errors of the rotating shaft, and performing error compensation, in order to achieve the above object, the present invention The technical solution adopted is the machine tool indexing error compensation device, which is structured as follows: N standard balls are mounted on a circular standard ball plate; N standard balls are mounted on the same height of the standard ball plate, and are evenly distributed and standard. On the concentric circumference of the outer circumference of the disk, the standard ball plate is mounted on the turntable of the machine tool, and the outer circumference of the standard ball plate is concentric with the rotary shaft of the machine tool.

The standard ball is a steel ball or a ceramic ball. Make a blind hole at one end of the ball, insert a screw into the hole, and glue it to death. The standard ball plate is provided with N ball seats, which are screwed on the standard ball plate chassis in a tangentially uniform manner. The radial position and the tangential position of the ball seat on the chassis can be within the allowable range of the screw holes. Internal adjustment, the screw with the standard ball is inserted into the hole of the ball seat, the screw has a nut on each side of the ball seat, and the screw is fixed on the ball seat by two nuts, and the z-direction and the radial position are both Can be adjusted within a certain range.

A machine tool indexing error compensation method is implemented by means of the aforementioned machine tool indexing error compensation device, comprising the following steps: adjusting the position of each standard ball: The adjustment requirements are: (1) adjusting the center of each standard ball to (2) adjust the center of each standard ball to the same height H; (3) adjust the center of each standard ball to the same interval;

The assembled standard ball plate is mounted on a precision rotating table for testing, and the axis of the precision rotating table is adjusted coaxially by measuring the outer circle of the standard ball disk chassis; then, the position of each standard ball is adjusted by detecting And adjust by measuring the position of a point on the standard ball;

The contour of each standard ball is measured by a side probe: for this purpose, a side probe is adjusted to the position of the top of the measuring standard ball. During the continuous rotation of the turntable, the change of the value of the side probe indicates the height H of the center of the ball. Change, slightly loosen the two nuts of the fixed ball seat, adjust the position of the screw within the gap between the hole of the ball seat and the screw, and then lock the two nuts until the height H of each ball is equal;

Then, during the rotation of the chassis for adjusting the turntable, the uniformity of each standard ball is measured by the side probe. To this end, a side-by-side probe is adjusted to the position of one side of the measuring standard ball. For each pitch angle of the turntable = 360° / N, the side-by-side probe enters the position of the measuring center, and the value is picked up and then exited. In the measurement of the index, the change of the indication value of the side probe indicates the change of the pitch angle of the spherical center. Loosen the screw slightly, adjust the position of the ball seat within the gap between the hole of the chassis and the screw, and then tighten the screw until each ball The pitch angles are equal, and detection and adjustment often need to be repeated;

Finally, during the rotation of the adjusting turret to drive the chassis, the eccentricity of the spherical circle of each standard ball is measured by the axial probe. To this end, an axial probe is adjusted to the position of the outer end of the measuring standard ball, and the rotary table and the shaft are continuously rotated. The position of the distance from the center of the sphere to the center of the turntable is measured to the probe. During the rotation of the chassis, the change of the indication value of the axial probe indicates twice the eccentricity, slightly loosen the screw, adjust the position of the ball seat within the gap between the hole of the chassis and the screw, and then tighten the screw until The distance Ro of each ball to the center of the turntable is equal, and the detection and adjustment often need to be repeated;

The above adjustments may be involved in each other. In particular, the uniformity and eccentricity of the standard ball are adjusted by changing the position of the ball seat. If the two nuts on the screw are not positioned properly, the eccentricity may not be adjusted by changing the position of the ball seat. Very small, then you need to change the position of the two nuts on the screw, and then perform eccentricity detection and adjustment. In this case, the adjustment of the eccentricity and the adjustment of the contour will also be related to each other;

After all the adjustments have been made, the adjusted standard ball plate is mounted as a whole on the machine table, and the chassis is roughly fastened with screws. The outer diameter of the diameter D on the chassis is measured, and the position of the entire standard ball plate is adjusted. , until the outer circumference of the chassis is coaxial with the machine table, and then lock the chassis;

The standard ball plate is mounted on the machine table and is adjusted to be coaxial with the machine table and is not removed.

After the part is finished, the in-situ measurement system installed next to the machine starts to measure the first characteristic element of the workpiece. After measuring the first characteristic element, measure one or several standard balls to obtain the spherical coordinates (xu^A). ), in order to facilitate the measurement of the second characteristic element of the workpiece, after the machine tool turret rotates through the indexing angle = 360°, the position of the center of the same or the same standard ball is measured by the in-situ measuring machine installed beside the machine tool. (x ₂ j3⁄4 ), ΔΖ Ζ ^ - is the axial motion error of the turntable 4 in this rotation, AR _{0 =} /χ ₂ ² + y ₂ ² - /x + y is the diameter of the turntable 4 in this rotation The motion error, A = _arc tan^ - _arc tan - is the angle error of the turntable 4 in this rotation, and the error compensation can be introduced according to this, so that the measurement result is not affected by the rotation error of the machine turntable 4;

Since in general, the number of balls on the standard ball plate is N≠«, the machine table turns one indexing angle θ ₀ each time, and the angular spacing between two adjacent balls on the standard ball disk is = 360° / N, when the machine turret turns over an index, the next ball does not rotate to the original position of the previous ball, but is lagging behind the original position of the previous ball Αθ, = θ _λ - θ ₀

, when N < w, Δ > 0, after the rotation, the next ball lags behind the original position of the previous ball; when N > «, Δ < 0, after the rotation, the next ball leads the original position of the previous ball, Ν Both η and η are known. By detecting the path of the standard ball for correct planning, after measuring one feature element, the turntable turns a total of k, and the position of the standard ball lags a total of M. When |M | exceeds a certain value, the standard ball is detected. The path plan automatically changes one adjacent ball;

After the machine tool turret 4 has rotated the "indexing angle", the measuring machine completes the measurement of the entire workpiece, the measuring task ends, the required workpiece passes the acceptance, or allows it to enter the next process. For deviations from technical requirements, calculate the amount of repair, And form a rework processing program for rework. Technical features and effects of the present invention -

1. According to the invention, the rotation of the machine tool turret can be used to measure the blades, teeth or other parts to be measured to the front end of the machine tool, and the measuring machine can separately measure the parts to be measured one by one, and the indexing error of the turret and the shaft of the rotating shaft Radial and axial motion errors do not affect the measurement results. Improve the measurement accuracy by making the measurement conform to the independent requirements of the metrology requirements.

2. The method of measuring the same standard ball before and after the rotation of the turntable can greatly reduce the requirements for the manufacture and adjustment accuracy of the standard ball plate. It only has strict requirements on the sphericity error, hardness, stability of the standard ball, the diameter and stability of the standard ball, the concentricity of the spherical circle of the standard ball and the axis of the turntable. Therefore, there is a strict requirement for the sphericity error because although the same ball is measured, the different points on the ball are measured. The hardness, stability, and stability of the standard ball are required to ensure long-term stability. The eccentricity of the center circle of the standard ball and the axis of the turntable changes the radius of the center circle of the standard ball. Other factors, such as the uniformity of the standard sphere size, the uniformity of the standard sphere distribution, and the contour height, only affect the convenience of adjustment and measurement, and can reduce the requirements for them. 3. Using the method of measuring the same standard ball before and after the rotation of the turntable, the same standard ball plate can be used to compensate the error of the turntable when measuring the parts with different index angles θ ₀ , thereby reducing the standard ball plate 6 The manufacturing cost avoids the trouble of replacing the standard ball plate and adjusting.

4. The zero position of the in-situ in-situ measuring machine can be calibrated or reviewed using the accurately calibrated standard dial disk diameter D. DRAWINGS

Figure 1 shows a typical layout of the machine tool. In the figure, 1 auxiliary station, 2 machine table, tool holder 3, 4 turntable, and another auxiliary station 5.

Figure 2 is a schematic view of a machine equipped with a standard ball plate. In the figure, 6 standard ball disks.

Figure 3 is a schematic view of the structure of a standard ball plate. In the figure, 31 chassis, 32 screws, 33 ball seats, standard balls 34, 35 inserts. In the screw, 37 screws, the screw 35 is fixed on the ball seat 33 by two nuts 36, and its position can be adjusted. The chassis 31 is fixed to the turntable of the machine tool by a plurality of screws 32. A ball seat 33 is mounted on the chassis 31. These ball seats are evenly distributed on a circle of the chassis 31 which is concentric with the outer circumference of the chassis 31, with screws. 37 is fixed to the chassis 31.

Figure 4 is a schematic diagram of the center height detection and adjustment of the standard ball.

Figure 5 is a schematic diagram of the detection and adjustment of the standard ball uniformity.

Figure 6 is a schematic diagram of the eccentricity detection and adjustment of the center circle of the standard ball. detailed description

On-line in-situ measurement systems with geometric parameters of complex workpieces are often difficult to measure the entire workpiece. It is necessary to use the turntable of the machine tool to rotate the measuring part to the front of the measuring machine. The invention compensates the machine tool turntable indexing error and the radial and axial motion errors of the rotating shaft by detecting the change of the spherical center position of one or several balls on the standard ball plate mounted on the machine turning table, so that the machine turning table error is measured. The result has no effect and improves measurement accuracy. The invention belongs to testing technology and Instrument field. Specifically, it involves online measurement and error compensation techniques.

The invention provides a technology capable of compensating for the indexing error of the machine tool table and the radial and axial motion errors of the rotating shaft, so that the online in-situ measuring system can utilize the rotation of the machine turning table, and the blade, the tooth to be measured or the tooth to be measured or The other parts are at the front end of the machine. The measuring machine can measure the parts to be measured one by one, and the indexing error of the turntable and the radial and axial motion errors of the rotating shaft do not affect the measurement results.

The basic idea of the invention is: Install a standard ball plate 6 on the machine table, as shown in Figure 2. The meanings of the other symbols in Fig. 2 are the same as those in Fig. 1. The existing in-situ measuring machine detects the change of the spherical center position of one or several balls on the standard ball plate 6 before and after the rotation of the turntable 4, and detects the indexing error of the machine tool table and the radial and axial motion errors of the rotating shaft, and The effect is error compensated. Its main features are:

1. Install a ball plate with N standard balls on the machine table, as shown in Figure 2. N standard balls are mounted on the same height of the standard ball plate 6, and are evenly distributed on a circumference concentric with the outer circumference of the standard ball plate 6. The basic requirements for the ball are small sphericity error, uniform ball diameter, high hardness, and good stability.

2. The basic requirements for the standard ball tray 6 are good stability, small roundness error of the outer circumference of the chassis, and precise diameter calibration. The standard ball tray 6 is mounted on the turntable 4 of the machine tool, and the standard ball tray is adjusted to be concentric with the turntable 4 of the machine tool by using the outer circumference of the standard ball tray 6.

3. When measuring the first characteristic element of the part (such as the first blade of the whole leaf disc) and the turntable 4 in the first position (the position before the rotation), measure the center of a standard ball A with a measuring machine. Position, in the coordinate system with the intersection of the axis of the turntable 4 and the workpiece mounting surface as the origin, the coordinates are (Α, , in order to measure the second characteristic element of the part (such as the second blade of the whole leaf disc), Turn the turntable 4 through an indexing angle. Take the whole leaf disc as an example, for a whole leaf disc with "blade = 360° /«, where

«The number of leaves of the whole leaf disc.

4. After turning the indexing angle ^), measure the spherical center coordinates of the same standard ball A with the measuring machine, and set it to (x ₂ j3⁄4 ).

AZ = Z ₂ is the axial motion error of the turntable 4 in this rotation, AR ₀ = +yl ~ ⁺ y is the radial motion error of the turntable 4 in this rotation, A z arctan^ - arctan^- This time, the rotation angle of the turntable 4 is turned. Error compensation can be introduced according to this, so that the measurement result is not affected by the rotation error of the machine turntable 4.

5. If the machine only processes one part with "characteristic elements, such as a leaf disc with a blade, then the selection of the standard number of balls N=« on the disc 6 is most convenient. At this time, the machine table 4 is rotated by an indexing angle θ ₀ , and the next standard ball on the disk 6 is rotated to the position before the previous ball is rotated. The two positions of the standard ball measured by the measuring machine before and after each rotation are substantially constant. It is only because of the error factor that the two positions of the standard ball will change slightly. But in most cases, the machine tool needs to be used to machine different parts, "not fixed. It is very inconvenient for different "parts to replace the ball plate with different standard ball number N. This is not only because the cost of the ball plate is high, but it is also inconvenient to reinstall the standard ball plate 6 after each replacement of the workpiece. At Ν≠η, the machine table 4 is rotated by an indexing angle each time, and the angular spacing between two adjacent balls on the standard ball plate 6 is = 360° /N. So when the machine table 4 turns over an index, the next ball does not turn to the top. The original position of a ball, but the lag of the original position of the previous ball Δ = - = 360° (1/N - 1/"). At < /?, Δ > 0, the next ball after the rotation is higher than the previous one The original position of the ball lags; at N>", Δ < 0, after the rotation, the next ball leads the original position of the previous ball. Since it is known, the path of the standard ball can be detected by the measuring machine. Correct planning, so that the measuring machine correctly measures the next ball. After measuring the A feature elements, the turntable 4 turns a total of ₀ , and the position of the standard ball is delayed by a total of Μ. Μ When it is too large, it will affect the correct detection of the standard ball. Retesting an adjacent ball requires consideration of this factor when performing the path planning of the measuring machine to detect the standard ball.

6. The number of balls N on the standard ball tray 6 is too large, which not only increases the manufacturing cost of the standard ball tray 6, but also makes the position adjustment of the standard ball difficult. In addition, too large N will make the adjacent standard balls close together, which makes the detection more difficult, so N should not be too large. However, when N is too small, two adjacent standard balls are far apart, which makes the detection difficult. It is generally recommended that the measuring machine can detect three adjacent standard balls in its range, which is suitable, and the number of balls on the standard ball plate 6 can be selected accordingly.

7. It should be said that the measuring machine detects the position of a standard ball before and after the rotation of the turntable 4, which can meet the requirements of the turntable error compensation. However, it is also common to simultaneously detect the position of two or more standard balls before and after the turntable 4 index. The advantages of simultaneously detecting two or more standard spheres are: (1) increasing the confidence of the measurement results; (2) reducing the effects of measuring random errors and improving measurement accuracy; (3) detecting two or more criteria simultaneously The position of the ball before and after the rotation of the turntable 4 can also obtain the tilting angle motion error of the rotating shaft of the turntable 4 around the X and the axis. Strictly speaking, a characteristic element of the device under test has a certain distribution range in the ^ and > directions, and the axial motion error and the radial motion error of the turntable 4 at different points are different. After measuring the movement error of the rotation axis of the turntable 4 around the X and the axis, the axial motion error and the radial motion error of the turntable 4 at each point of the feature element can be calculated. However, it is generally said that a characteristic element has a limited distribution range in the X and > directions, and it can be considered that the difference between the axial motion error and the radial motion error is small.

8. Figure 3 is a schematic diagram of the structure of a standard ball plate. In the figure, 31 is the chassis of the standard ball plate, which is a ring. Its inner diameter d and outer diameter D are determined according to the ease of installation on the machine table. It should have a thickness h to prevent deformation during heat treatment. The chassis 31 is fixed to the turntable of the machine tool by a plurality of screws 32 and is adjusted to be coaxial with the machine table. N ball seats 33 are mounted on the chassis 31, and these ball seats are evenly distributed on a circle of the chassis 31 which is centered on the outer circumference of the chassis 31, and is fixed to the chassis 31 by screws 37, and its position can be adjusted. The standard ball 34 is sleeved on the screw 35 and glued to death. The screw 35 is fixed to the ball seat 33 by two nuts 36, and its position can be adjusted. Select the height H of the standard ball 34 and its diameter of the center of the circle. A) The convenience of detecting these standard balls should be considered, and the machining and measuring of the workpiece should not be affected.

9. Figures 4 to 6 are schematic diagrams for detecting and adjusting the contour, eccentricity and uniformity of the standard ball center.

The object of the present invention is to provide a machine tool turntable error compensation technique for an in-situ in-situ measurement system. For complex parts such as leaf discs and special-shaped gears, it is difficult for the measuring machine to extend into the part slot for measurement from the rear end of the machine. The more realistic method is to use the rotation of the machine table to transfer the blades, teeth or other parts to be machined. At the front end, the measuring machine can measure each part that needs to be measured one by one. The invention can compensate the turntable indexing error and the radial and axial motion errors of the rotating shaft so that they do not affect the measurement result. Embodiments of the invention are as follows.

1. Select the number N of balls on the standard dome according to the measurement range that the measuring machine can cover.

2. Process N standard spheres 34 with small sphericity error and small spherical diameter difference (Fig. 3). The material requirements for the standard ball 34 are high hardness, stable performance, and easy processing, and may be steel or ceramic. Make a blind hole at one end of the ball, insert a screw 35 into the hole, and glue it to death.

3. Fix the N ball seats 33 to the chassis 31 with screws 37 in a tangentially uniform manner, as shown in Figure 3.

The radial position and the tangential position on the chassis 33 of the ball seat 33 can be adjusted within the allowable range of the screw holes.

4. The screw 35 to which the standard ball 34 is bonded is inserted into the hole of the ball seat 33. The screw 35 has a nut 36 on each side of the ball seat, and the screw 35 is fixed to the ball seat 33 by two nuts 36. Both the position and the radial position can be adjusted within a certain range.

5. After assembling the standard ball plate into the overall structure shown in Figure 3, the position of each standard ball 34 needs to be adjusted.

The adjustment requirements are: (1) adjusting the center of each standard ball 34 to a circle concentric with the outer circumference of the chassis 31;

(2) The center of each standard ball 34 is adjusted to the same height H; (3) The center of each standard ball 34 is adjusted to be equal to each other. The first requirement of these three requirements is the most important, because after the standard ball plate is mounted on the machine table, the outer circumference of the chassis 31 is adjusted to be coaxial with the machine table by measuring the outer circumference of the chassis 31, thereby ensuring each The center circle of the standard ball 34 is coaxial with the machine table. The eccentricity between the center circle of each standard ball 34 and the axis of the machine tool turret causes the radius of the spherical circle of each standard ball 34 to vary with the rotation angle, resulting in measurement errors. The spherical height and uniformity of the standard ball 34 have no direct influence on the measurement results. It is more convenient to measure in the case of equal height and uniformity, and it is easier to make all measuring points within the linear range of the measuring machine.

6. Install the standard ball plate assembled according to Figure 3 on a precision turret for inspection (Fig. 4). Adjust the axis of the chassis 31 and the precision turret for inspection by measuring the outer circumference of the chassis 31. Then, by detecting, the position of each standard ball 34 is adjusted. It stands to reason that since the adjustment requirements are for the position of the center of the ball, the position of each center of the ball should also be detected during the test. However, to detect the position of a sphere, at least the position of 34 points on the same plane that are not on the same plane needs to be detected. These points need to be detected from different directions, requiring a three-dimensional probe. The measurement uncertainty of the three-dimensional probe is larger than that of the one-dimensional probe. The adjustment of the three requirements of the concentric, contour and uniform distribution of the spherical center of the standard ball is related to each other. If the adjustment is made by detecting the position of each center of the ball, the entire adjustment process is troublesome. If the sphericity error of each standard ball is small and the spherical diameter difference is small, the position of the center of the ball can be determined by measuring the position of a certain point on the spherical surface, which simplifies the adjustment process. It is not difficult to achieve a standard ball with small sphericity error and good ball diameter consistency. It is recommended to use a standard ball with small sphericity error and good ball diameter, and then adjust by measuring the position of a certain point.

7. First, the height of each standard ball 34 is measured by a side probe while the turntable drives the chassis 31 to rotate.

To do this, adjust a side probe to the top of the measurement standard ball, as shown in Figure 4. The change in the indication value of the side probe during the continuous rotation of the turntable indicates the change in the height H of the center of the ball. The two nuts 36 are slightly loosened, the position of the screw 35 is adjusted within the gap of the hole of the ball seat 33 and the screw 35, and the two nuts 36 are locked until the heights H of the respective centers are equal. Detection and adjustment often need to be repeated. The adjustment accuracy of the contour is not high, it does not directly affect the accuracy of the error compensation, but only after the standard ball is mounted on the machine table, the ball The height is within the measuring range of the online in-situ measuring machine.

8. Next, during the rotation of the adjustment turret to drive the chassis 31, the uniformity of each standard ball 34 is measured by a side probe. To do this, adjust a side probe to the side of the measurement standard ball, as shown in Figure 5. Each pitch of the turntable = 360° IN, the side probe enters the position of the measuring center, picks up the indication and exits. The change in the indication value of the side probe in the measurement of the N index indicates the change in the pitch angle of the center of the sphere. Slightly loosen the screw 37, adjust the position of the ball seat 33 within the clearance of the hole of the chassis 31 and the screw 37, and then tighten the screw 37 until the pitch angles of the balls are equal. Detection and adjustment often need to be repeated. The adjustment accuracy of the uniformity is not high, it does not directly affect the error compensation accuracy, but only after the standard ball is mounted on the machine table, the position of each ball is within the measurement range of the in-situ measuring machine.

9. Finally, during the rotation of the adjustment turret to drive the chassis 31, the eccentricity of the center circle of each standard ball 34 is measured by the axial probe. To this end, an axial probe is adjusted to the position of the outer end of the measuring standard ball, as shown in FIG. The turntable is continuously rotated, and the axial probe measures the position of the distance Ro from the center of the ball to the center of the turntable. The change in the indication value of the axial probe during the rotation of the turret to drive the chassis 31 represents twice the eccentricity. The screw 37 is slightly loosened, the position of the ball seat 33 is adjusted within the gap of the hole of the chassis 31 and the screw 37, and the screw 37 is locked until the distance R _{Q of} each ball to the center of the turntable is equal. Detection and adjustment often need to be repeated. The accuracy of the adjustment of the coaxiality is high because it directly affects the accuracy of the error compensation and needs to be carefully performed.

10. The above adjustments may be related to each other. In particular, the uniformity and eccentricity of the standard ball are adjusted by changing the position of the tee 33. If the two nuts 36 on the screw 35 are improperly positioned, it is also possible to make the eccentricity small by changing the position of the ball seat 33. In this case, the position of the two nuts 36 on the screw 35 needs to be appropriately changed, and then the eccentricity detection is performed. And adjustments. In this case, the adjustment of the eccentricity and the adjustment of the contours are also related to each other. The first recommendation is to put the eccentricity adjustment at the end, so that even if it affects the uniformity and contour of the sphere, but because the adjustment accuracy of the latter two is not high, it is possible that the three adjustments can still meet the requirements. Within the scope. Second, after all three adjustments have been made, a second test is required to verify that all three adjustments are within the required range.

11. After completing all adjustments, install the adjusted standard dome as a unit on the machine table. After the chassis 31 is substantially fastened by screws 32 (Fig. 3), the outer circumference of the chassis 31 having a diameter of /) is measured, and the position of the entire standard ball tray is adjusted until the outer circumference of the chassis 31 is coaxial with the machine table. The chassis 31 is locked again. This eccentricity directly affects the accuracy of error compensation and is therefore highly demanding.

12. In principle, the standard ball plate should be directly affixed to the machine table, in which case only one standard ball plate is required.

When it is difficult to directly attach the standard ball plate to the machine table, the standard ball plate can be fixed to the fixture used to machine the part and then fixed to the machine table with the clamp. In this case, the standard ball and the clamp should always be fixed together throughout the processing of a batch of parts, and their relative positions are unchanged. On many machine tools, two clamps are used. After the part has been machined, the fixture is sent to the auxiliary station along with the machined part, where the part is removed. On the other auxiliary station, the other part of the fixture has been installed and processed. In this case, two standard ball plates are required, which are mounted on two clamps.

13. The standard ball plate is mounted on the machine table and adjusted to be coaxial with the machine table and will not be removed. In the part plus During the process, although it does not participate in the work, it is subject to the influence of vibration, coolant and chips in the processing environment, and the processing environment is required to have no effect on the performance of the standard ball plate.

14. After the part has been machined, the in-situ measurement system installed next to the machine begins to measure the first characteristic element of the workpiece, such as the first blade. After measuring the first feature element, measure one (or several) standard balls, such as ball A in Figure 2, to obtain its spherical coordinates ( ). In order to facilitate the measurement of the second characteristic element of the workpiece, the machine tool turret is rotated over the indexing angle = 360° /«, and the position of the same (or several) standard ball A is measured using an in-situ measuring machine installed next to the machine. , set to (x ₂ j3⁄4 ). Δζ = ζ ₂ - ζ^3⁄4 is the axial motion error of the turntable 4 during this rotation, AR. ₌ /χ ₂ ² + y ₂ ² -"x + y is the radial motion error of the turntable 4 in this rotation, ΑΘ = arctan^- - arctan^ - ^ ₀ is the rotation angle error of the turntable 4 in this rotation . Error compensation can be introduced according to this, so that the measurement result is not affected by the rotation error of the machine turntable 4.

15. Since in general, the number of balls on the standard ball plate is N≠«, the machine table 4 is rotated by an indexing angle θ ₀ each time, and the angular spacing between two adjacent balls on the standard ball plate 6 is = 360° /N, so that when the machine table 4 turns over an index, the next ball does not rotate to the original position of the previous ball, but is lagging behind the original position of the previous ball Δ = — ^ = 360° (1 /N-1//ί). When N < w, Δ > 0, after the rotation, the next ball lags behind the original position of the previous ball; when N > «, Λ < 0, after the rotation, the next ball leads the original position of the previous ball. It is known that it is necessary to correctly plan the path of the standard ball by the measuring machine so that the measuring machine can correctly measure the next ball. After measuring one of the characteristic elements, the turntable 4 is rotated altogether, and the positions of the standard balls are delayed by a total of Μ. When a certain value is exceeded, the path plan of the test standard ball automatically changes to an adjacent ball.

16. After the machine tool turret 4 has turned "the indexing angle, the measuring machine completes the measurement of the entire workpiece, the measurement task ends, the required workpiece passes the acceptance, or allows it to proceed to the next step. For deviations from the technical requirements, calculate the amount of repair, and form a rework processing program for rework.

Claims

Rights request

1. A machine tool indexing error compensating device, characterized in that: the structure is: a standard ball plate with a circular mounted N standard balls; N standard balls are mounted on the same height of the standard ball plate, and are evenly distributed On the circumference concentric with the outer circumference of the standard disc, the standard disc is mounted on the turntable of the machine, and the outer circumference of the standard disc is concentric with the rotary shaft of the machine.

2. Apparatus according to claim 1 wherein the standard ball is a steel ball or a ceramic ball, a blind hole is formed at one end of the ball, a screw is inserted into the hole, and glued to death.

3. The apparatus according to claim 1, wherein the standard ball tray is provided with N ball seats, which are screwed to the standard ball tray chassis in a tangentially uniform manner, and the ball seat is on the chassis. The radial position and the tangential position can be adjusted within the allowable range of the screw hole. The screw with the standard ball is inserted into the hole of the ball seat. The screw has a nut on each side of the ball seat, and the screw is placed by two nuts. Fixed on the ball seat, its z-direction position and radial position can be adjusted within a certain range.

4. A machine tool indexing error compensation method, which is implemented by means of the aforementioned machine tool indexing error compensation device, comprising the following steps: adjusting the position of each standard ball: The adjustment requirements are: (1) the center of each standard ball Adjust to the circle concentric with the outer circle of the chassis; (2) adjust the center of each standard ball to the same height H; (3) adjust the center of each standard ball to the same interval;

Then, during the rotation of the chassis for adjusting the turntable, the uniformity of each standard ball is measured by the side probe. To this end, a side-by-side probe is adjusted to the position of one side of the measuring standard ball. Each time the turntable is rotated by a pitch angle Θ, = 360 Ν, the side-by-side probe enters the position of the measuring center, and the value is picked up and then exited. In the measurement of the index, the change of the indication value of the side probe indicates the change of the pitch angle of the spherical center. Loosen the screw slightly, adjust the position of the ball seat within the gap between the hole of the chassis and the screw, and then tighten the screw until each ball The pitch angles are equal, and detection and adjustment often need to be repeated;

Finally, during the rotation of the adjusting turret to drive the chassis, the eccentricity of the spherical circle of each standard ball is measured by the axial probe. To this end, an axial probe is adjusted to the position of the outer end of the measuring standard ball, and the rotary table and the shaft are continuously rotated. The distance R from the center of the ball to the center of the turntable is measured to the probe. s position. During the rotation of the chassis, the change of the indication value of the axial probe indicates twice the eccentricity, slightly loosen the screw, adjust the position of the ball seat within the gap between the hole of the chassis and the screw, and then tighten the screw until The distance from each ball to the center of the turntable is equal, and detection and adjustment often need to be repeated;

The above adjustments may be involved in each other. In particular, the uniformity and eccentricity of the standard ball are adjusted by changing the position of the ball seat. If the two nuts on the screw are not positioned properly, the eccentricity may not be adjusted by changing the position of the ball seat. Very small, then you need to properly change the position of the two nuts on the screw, and then perform eccentricity detection and adjustment, In this case, the adjustment of the eccentricity and the adjustment of the contours are also related to each other;

After all the adjustments have been made, the adjusted standard ball plate is mounted as a whole on the machine table, and the chassis is substantially fastened with screws, the outer diameter of the chassis is measured, and the position of the entire standard ball plate is adjusted. Until the outer circumference of the chassis is coaxial with the machine table, and then lock the chassis;

After the part is finished, the in-situ measurement system installed next to the machine starts to measure the first characteristic element of the workpiece. After measuring the first characteristic element, measure one or several standard balls to obtain the spherical coordinates (x^i). ^), in order to facilitate the measurement of the second characteristic element of the workpiece, after the machine table turns over the indexing angle = 360° /«, the position of the center of the same or the same standard ball is measured by the in-situ measuring machine installed next to the machine tool. , = ζ _{2 -} ζ ₁ is the axial motion error of the turntable 4 in this rotation, AR. ₌ /χ ₂ ² +y ₂ ²

The radial motion error of the transfer table 4, A = arctan^-arctan - is the rotation angle error of the turntable 4 in this rotation, and the error compensation can be introduced according to this, so that the measurement result is not affected by the rotation error of the machine turntable 4;

Since in general, the number of balls on the standard ball plate is N≠«, the machine turning table is rotated by one indexing angle each time, and the angular spacing between two adjacent balls on the standard ball disk is =360° /N, Thus, when the machine table turns an index, the next ball does not rotate to the original position of the previous ball, but lags behind the original position of the previous ball.

Αθ, =θ -θ ₀ =360°{\ΙΝ-\Ιή), when N<«, Δ >0, after the rotation, the next ball lags behind the original position of the previous ball; when N>«, Δ < 0, after the rotation, the next ball is ahead of the original position of the previous ball, Ν and "all are known. By correcting the path of the standard ball for correct planning, after measuring the A feature elements, the turntable is rotated altogether, the standard ball Position total hysteresis Μ , |Μ | When a certain value is exceeded, the path plan of the test standard ball automatically changes to an adjacent ball;

After the machine turntable 4 has been rotated by w indexing angles, the measuring machine completes the measurement of the entire workpiece, the measurement task is completed, the required workpiece passes the acceptance, or it is allowed to enter the next process. For deviations from the technical requirements, calculate the amount of repair, and form a rework processing program for rework.