A rotating platform and a spherical coordinate measuring machine based thereon

Abstract

The present invention discloses a rotating platform and a spherical coordinate measuring machine based thereon, comprising a rotating mechanism I, a rotating mechanism II and a fixture; the rotating mechanism I comprises a bracket, and rotating shafts are symmetrically arranged at both ends of the bracket, and the bracket is used for rotational connection with a working platform through two rotating shafts; the rotating mechanism II is installed on the rotating mechanism I, and the rotating mechanism II adopts a rotary table; the fixture is installed on the rotary table, and the fixture is used for clamping spherical shell parts; the rotating shafts symmetrically arranged at both ends of the bracket are coaxial, and the bracket rotates with the axis as the rotating axis, and the rotating axis of the bracket and the rotating axis of the rotary table are perpendicular to each other. The present invention is conducive to achieving the measurement goals of spherical shell parts with high measurement accuracy, high efficiency and wide range.

Description

Technical Field

[0001] The invention relates to the technical field of three-coordinate measuring machines, and in particular to a rotating platform and a spherical coordinate measuring machine based thereon. Background Art

[0002] In recent years, the application of three-dimensional coordinate measuring machines in precision measurement fields such as product design, mold equipment, gear measurement, auto mold parts, and electronic appliances has become more and more widespread. A three-dimensional coordinate measuring machine is a detector that can move in three mutually perpendicular directions. It transmits signals in contact or non-contact ways, and calculates the coordinates of each point of the workpiece through a data processor. Its functions include dimensional accuracy measurement, positioning accuracy measurement, geometric accuracy measurement, and contour accuracy measurement. All geometric quantity measurements can be attributed to the measurement of three-dimensional space points. Therefore, the accurate collection of spatial point coordinates is the basis for evaluating any geometric shape. However, the measurement of spherical shell parts has always had problems such as small measurement range, low accuracy, and low efficiency. Summary of the invention

[0003] The technical problem to be solved by the present invention is: in order to achieve the goal of normal contact between the probe and the spherical shell parts at each measuring point, the traditional three-axis coordinate measuring machine must rely on three-axis linear motion and probe swing, but is limited by the moving range of the probe and can only measure the top cover part of the sphere, and the measurement efficiency is low. The present invention provides a rotating platform and a spherical coordinate measuring machine based on the same to solve the above problem.

[0004] The present invention is achieved through the following technical solutions:

[0005] A rotating platform comprises a rotating mechanism I, a rotating mechanism II and a clamp; the rotating mechanism I comprises a bracket, and rotating shafts are symmetrically arranged at both ends of the bracket, and the bracket is used for rotational connection with the working platform of a three-coordinate measuring instrument through two rotating shafts; the rotating mechanism II is installed on the rotating mechanism I, and the rotating mechanism II adopts a rotary table; the clamp is installed on the rotary table, and the clamp is used for clamping spherical shell parts; the rotating shafts symmetrically arranged at both ends of the bracket are coaxial, and the bracket rotates around the axis as the rotating axis, and the rotating axis of the bracket and the rotating axis of the rotary table are perpendicular to each other.

[0006] The existing three-coordinate measuring machine has always had problems with small measuring range, low precision and low efficiency in measuring spherical shell parts. Therefore, when measuring spherical shell parts, the method of normal contact of measuring points is used to solve the above problems. To achieve normal contact between the surface of spherical shell parts and the probe at each measuring point, the conventional practice is to optimize the rotating structure of the probe of the three-coordinate measuring machine itself. The measurement target can be achieved to a certain extent by relying on the linear motion of the three coordinates and the swing of the probe. However, when there is only one long error chain in the system, the accumulation of measurement errors will increase, resulting in a decrease in measurement accuracy. The long chain error can only be overcome by optimizing the three-coordinate linear motion mechanism, or the probe swing structure, or by optimizing the calculation method, but the effect is not significant.

[0007] Based on this technical background, the present invention provides an optimized clamping rotating platform for spherical shell parts, which realizes the rotation of two degrees of freedom of spherical shell parts, thereby replacing the swing of the probe. On the one hand, the normal contact measurement of spherical points can be achieved through the linkage of the two-degree-of-freedom rotational motion of the spherical shell parts and the three-coordinate linear motion of the probe. While increasing the measurable range of the sphere, the measurement efficiency is effectively improved. On the other hand, the cradle-type rotating platform and the three-coordinate linear motion platform provided by the present invention cancel the swinging degree of freedom of the probe, eliminate the error caused by the swing of the probe, and decompose the single long error chain of the original measuring machine into two short error chains, thereby improving the controllability of the error, which is beneficial to improving the measurement accuracy, thereby facilitating the realization of the measurement goals of spherical shell parts with high measurement accuracy, high efficiency and a wide range.

[0008] Further preferably, the center position of the spherical shell part clamped by the fixture is located at the intersection of the rotation axis of the bracket and the rotation axis of the rotary table.

[0009] The rotation axis of the rotating mechanism I is defined as the rotation axis I, and the rotation axis of the rotary work platform is defined as the rotation axis II. The present invention fixes the spherical shell parts on the rotating mechanism II through a clamp. The rotating mechanism I drives the rotating mechanism II, the clamp and the spherical shell parts to rotate around the rotation axis I, and the rotating mechanism II drives the clamp and the spherical shell parts to rotate around the rotation axis II. The two sets of rotating mechanisms can rotate independently; the center of the spherical shell parts coincides with the intersection of the rotation axis I and the rotation axis II, which is convenient for controlling the rotation position of the spherical shell parts and facilitating the positioning of the coordinate axis to achieve rapid measurement.

[0010] Further preferably, the bracket rotates around the axis as the rotation axis, and the rotation angle range is -90° to +90°.

[0011] If the plane where the fixture is located is taken as a horizontal plane, the bracket rotates around the axis as the rotation axis, that is, the rotating mechanism I drives the spherical shell parts to flip up and down, which is convenient for the measurement of the spherical shell parts along the latitudinal movement.

[0012] Further preferably, the rotation angle range of the rotary table is 360°.

[0013] If the plane where the fixture is located is taken as the horizontal plane, the rotary working platform drives the spherical shell parts to rotate in the horizontal plane, which is convenient for radial movement and measurement of the spherical shell parts.

[0014] Further preferably, the rotating shaft adopts an air-floating rotating shaft, and / or the rotating table adopts an air-floating direct-drive rotating table.

[0015] The cradle-type rotating platform and three-coordinate linear motion platform provided by the present invention cancel the swinging freedom of the probe, eliminate the error caused by the swinging of the probe, and decompose the single long error chain of the original measuring machine into two short error chains. In order to reduce the two-degree-of-freedom rotation error, the present invention introduces air static pressure bearings in the rotating device, which can provide extremely high radial and axial rotation accuracy. Since there is no mechanical contact, the wear degree of the air static pressure bearing is reduced to a minimum, thereby ensuring that the measurement accuracy always remains stable. Its viscous resistance is low, allowing a higher speed and maintaining a lower vibration level at the same time, improving the detection efficiency while ensuring accuracy. The present invention uses ultra-precision gas bearings when designing the clamping and rotation of spherical shell parts to achieve the design requirements.

[0016] Further preferably, the concentricity error of the air-floating rotating shaft is: ≤50nm in radial direction, ≤20nm in axial direction; and the rotation accuracy of the air-floating direct-drive turntable is 50nm-100nm.

[0017] In order to minimize the two-degree-of-freedom rotation error, the present invention preferably has the concentricity error of the air-floating shaft as follows based on actual experiments: radial ≤50nm, axial ≤20nm; the rotation accuracy of the air-floating direct-drive turntable is 50nm-100nm.

[0018] Further preferably, the clamp adopts a vacuum suction cup type tooling, and the vacuum suction cup of the clamp is used to fix the spherical shell parts through negative pressure adsorption.

[0019] For the clamping of spherical shell parts, the macro deformation caused by traditional mechanical chuck-type fixtures is large, which will affect the measurement accuracy to a certain extent. Therefore, a vacuum suction cup-type tooling is used to clamp the spherical shell parts on the cradle-type rotating platform provided by the present invention, ensuring that the macro deformation is reduced while the entire surface of the spherical shell parts can be measured.

[0020] Further preferably, the bracket includes a base plate and two side plates, and the base plate and the two side plates are connected to form a U-shaped structure; the rotating mechanism II is installed on the base plate and located between the two side plates; one end of the rotating shaft is installed on the outer wall of the side plate, and the other end is used for rotational connection with the working platform.

[0021] The present invention adopts a U-shaped structure as a support of the rotating mechanism I, and two rotating shafts are fixed on the side walls of the U-shaped structure to form a symmetrical cradle structure, forming a cradle-type rotating platform. The rotating mechanism II is installed in the U-shaped structure, and the structure is simple and stable.

[0022] A spherical coordinate measuring machine comprises a three-coordinate measuring instrument and the above-mentioned rotating platform.

[0023] The present invention introduces the above-mentioned rotating platform into the traditional three-coordinate measuring instrument to replace the swing of the probe, and realizes high-precision and efficient measurement of spherical shell parts through the linkage of the two-degree-of-freedom rotational motion of the spherical shell parts and the three-coordinate linear motion of the probe.

[0024] Further preferably, the three-coordinate measuring instrument includes a working platform, a three-coordinate linear motion platform and a probe; the working platform is a vibration isolation platform; the three-coordinate linear motion platform and the rotating mechanism I are both installed on the working platform; the three-coordinate linear motion platform includes an X-axis linear motion guide, a Y-axis linear motion guide and a Z-axis linear guide, and the X-axis linear motion guide, the Y-axis linear motion guide and the Z-axis linear guide are coupled into a three-dimensional linear motion mechanism; the probe is installed at the free end of the Z-axis linear guide for measuring spherical shell parts.

[0025] The present invention has the following advantages and beneficial effects:

[0026] 1. For the measurement of precision spherical shell parts, compared with the traditional three-dimensional coordinate measuring machine, the present invention provides a structural design with an ultra-precision air-floating rotating shaft. A rotating platform is provided above the vibration isolation platform to realize the two-degree-of-freedom rotation of the parts, and coupled with the three-degree-of-freedom linear motion of the probe, it can realize the normal contact measurement of the spherical surface points. While increasing the measurable range of the spherical surface, the measurement efficiency is effectively improved.

[0027] 2. The present invention uses ultra-precision gas bearings when designing the rotating platform and eliminates the swing freedom of the probe. On the one hand, it eliminates the error caused by the swing of the probe, and on the other hand, it decomposes the single long error chain of the original measuring machine into two short error chains. At the same time, compared with the mechanical swing of the probe of the traditional three-dimensional coordinate measuring machine, the rotating spindle adopts a high-precision air-floating shaft, which reduces the motion error in the detection process and can significantly improve the measurement accuracy of the measuring machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0029] Figure 1 It is a structural schematic diagram of the spherical coordinate measuring machine of the present invention;

[0030] Figure 2It is a schematic diagram of the three-dimensional structure of the cradle-type rotating platform of the present invention;

[0031] Figure 3 It is a front view of the cradle type rotating platform of the present invention.

[0032] Markings and corresponding parts names in the attached drawings: 1-rotation mechanism I, 11-bracket, 12-rotation shaft, 2-rotation mechanism II, 3-fixture, 4-working platform, 5-three-coordinate linear motion platform, 51-X-axis linear motion guide, 52-Y-axis linear motion guide, 53-Z-axis linear guide, 6-probe. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0034] Example 1

[0035] A rotating platform includes a rotating mechanism I1, a rotating mechanism II2 and a clamp 3, wherein the rotating mechanism I1 and the rotating mechanism II2 are two independent rotating drive devices; the rotating mechanism I1 includes a bracket 11, each of the two ends of the bracket 11 is provided with a rotating shaft 12, the two rotating shafts 12 are symmetrically distributed relative to the bracket 11, one end of the rotating shaft 12 is fixedly connected to the end of the bracket 11, and the other end is rotatably connected to the working platform 4; the rotating mechanism II2 adopts a rotary worktable, the bottom end of the rotary work platform is installed on the bracket 11 of the rotating mechanism I1, and the top end is provided with a clamp 3; the clamp 3 is used for clamping spherical shell parts.

[0036] Two rotating shafts 12 symmetrically arranged at both ends of the bracket 11 are coaxial, and the bracket 11 rotates around the axis as the rotating axis. The rotating axis of the bracket 11 and the rotating axis of the rotary table are perpendicular to each other.

[0037] The rotation axis of the rotating mechanism I is defined as the rotation axis I, and the rotation axis of the rotary work platform is defined as the rotation axis II. The rotating mechanism II2 can drive the spherical shell part fixture to rotate around the rotation axis II while using the rotating mechanism I to rotate around the rotation axis I. The two sets of rotating drive devices can operate independently or simultaneously, which can greatly increase the adjustment speed of the measuring point and improve the measuring efficiency.

[0038] Example 2

[0039] Based on the further improvement of Example 1, the center position of the spherical shell part clamped by the clamp 3 is located at the intersection of the rotation axis of the bracket 11 and the rotation axis of the rotary table.

[0040] The bracket 11 rotates with the axis as the rotation axis, and the rotation angle range is -90°~+90°; the rotation angle range of the rotary table is 360°. The rotating shaft 12 adopts an air-floating rotating shaft, and the concentricity error of the air-floating rotating shaft is: radial 50nm, axial 20nm; the rotary table adopts an air-floating direct-drive turntable, and the rotation accuracy of the air-floating direct-drive turntable is 50nm~100nm. A high-precision rotary encoder is provided as a position control guarantee, which is installed at the center of the turntable of the rotating mechanism 2, which is sufficient to meet the high-precision requirements of the measuring machine. The fixture 3 adopts a vacuum suction cup type fixture. A sealed volume is formed between the vacuum suction cup of the fixture 3 and the surface of the spherical shell part. A certain amount of gas is extracted through a vacuum source to generate a vacuum negative pressure, and then suction is generated to fix the spherical shell parts, reduce the clamping deformation error, and increase the part measurement area.

[0041] As a further optimization of this embodiment, the bracket 11 includes a base plate and two side plates, and the base plate and the two side plates are connected to form a symmetrical U-shaped structure; the rotating mechanism II2 is installed on the base plate and is located between the two side plates; one end of the rotating shaft 12 is installed on the outer wall of the side plate, and the other end is used for rotational connection with the working platform 4.

[0042] Example 3

[0043] This embodiment provides a spherical coordinate measuring machine, including a three-coordinate measuring instrument and a rotating platform provided in Example 2, that is, a cradle-type rotating platform with an ultra-precision air-floating rotating shaft is added to the traditional three-coordinate measuring instrument, which has two rotational degrees of freedom.

[0044] The three-coordinate measuring machine includes a working platform 4, a three-coordinate linear motion platform 5 and a probe 6. The working platform 4 is a vibration isolation platform, which is isolated by vibration through structures such as rubber pads and air springs, and is provided with a concave platform for fixing the rotating mechanism I1. The vibration isolation platform is the base of the entire spherical coordinate measuring machine, which is used to carry the rotating platform and the three-coordinate linear motion platform, and provide the basic accuracy of the measuring working area. The three-coordinate linear motion platform 5 and the rotating mechanism I1 are both installed on the working platform 4, wherein a groove is opened on the working platform 4, and the bracket 11 is placed in the groove. The two side walls of the bracket 11 are rotatably connected to the inner wall of the groove through the rotating shaft 12. There is a gap between the bottom plate of the bracket 11 and the bottom of the groove, allowing the bracket 11 to rotate; the three-coordinate linear motion platform 5 includes an X-direction linear motion guide rail 51, a Y-direction linear motion guide rail 52 and a Z-direction linear motion guide rail 53. The X-direction linear motion guide rail 51, the Y-direction linear motion guide rail 52 and the Z-direction linear motion guide rail 53 are coupled into a three-dimensional linear motion mechanism to provide the three-coordinate movement function of the probe. Specifically, the fixed end of the Y-axis linear motion guide 52 is installed on the vibration isolation platform, the fixed end of the X-axis linear motion guide 51 is installed on the moving slider of the Y-axis linear motion guide 52, the fixed end of the Z-axis linear motion guide 53 is installed on the moving slider of the X-axis linear motion guide 51, and a fixed probe 6 is installed on the moving slider of the Z-axis linear guide 53, and the probe 6 is used to measure spherical shell parts.

[0045] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A rotating platform, It is characterized in that It comprises a rotating mechanism I (1), a rotating mechanism II (2) and a clamp (3); The rotating mechanism I (1) comprises a bracket (11), and rotating shafts (12) are symmetrically provided at both ends of the bracket (11), and the bracket (11) is used for rotationally connecting with the working platform (4) of the three-dimensional coordinate measuring instrument through the two rotating shafts (12); The rotating mechanism II (2) is installed on the rotating mechanism I (1), and the rotating mechanism II (2) adopts a rotary table; The fixture (3) is installed on a rotary workbench, and the fixture (3) is used to clamp spherical shell parts; The rotating shafts (12) symmetrically arranged at both ends of the bracket (11) are coaxial, and the bracket (11) rotates around the axis as the rotating axis, and the rotating axis of the bracket (11) and the rotating axis of the rotary table are perpendicular to each other; The center position of the spherical shell part clamped by the clamp (3) is located at the intersection of the rotation axis of the bracket (11) and the rotation axis of the rotary table.

2. A rotating platform according to claim 1, It is characterized in that The bracket (11) rotates around the axis as a rotation axis, and the rotation angle range is -90° to +90°.

3. A rotating platform according to claim 1, It is characterized in that The rotation angle range of the rotary table is 360°.

4. A rotating platform according to claim 1, It is characterized in that The rotating shaft (12) is an air-floating rotating shaft, and / or the rotary table is an air-floating direct-drive rotary table.

5. A rotating platform according to claim 4, It is characterized in that The rotation accuracy of the air-floating direct-drive turntable is 50nm to 100nm.

6. A rotating platform according to claim 1, It is characterized in that The clamp (3) is a vacuum suction cup type fixture, and the vacuum suction cup of the clamp (3) is used to fix the spherical shell parts by negative pressure adsorption.

7. A rotating platform according to claim 1, It is characterized in that The bracket (11) comprises a bottom plate and two side plates, the bottom plate and the two side plates being connected to form a U-shaped structure; the rotating mechanism II (2) is mounted on the bottom plate and located between the two side plates; one end of the rotating shaft (12) is mounted on the outer wall of the side plate, and the other end is used for rotationally connecting to the working platform (4).

8. A spherical coordinate measuring machine, It is characterized in that It comprises a three-coordinate measuring machine and a rotating platform as claimed in any one of claims 1 to 7.

9. A spherical coordinate measuring machine according to claim 8, It is characterized in that The three-coordinate measuring machine comprises a working platform (4), a three-coordinate linear motion platform (5) and a probe (6); the working platform (4) is a vibration isolation platform; the three-coordinate linear motion platform (5) and the rotating mechanism I (1) are both mounted on the working platform (4); the three-coordinate linear motion platform (5) comprises an X-axis linear motion guide rail (51), a Y-axis linear motion guide rail (52) and a Z-axis linear motion guide rail (53); the X-axis linear motion guide rail (51), the Y-axis linear motion guide rail (52) and the Z-axis linear motion guide rail (53) are coupled to form a three-dimensional linear motion mechanism; the probe (6) is mounted on the free end of the Z-axis linear motion guide rail (53) and is used to measure spherical shell parts.

Images