WO2022018546A1 - Configuration de sondage - Google Patents

Configuration de sondage Download PDF

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Publication number
WO2022018546A1
WO2022018546A1 PCT/IB2021/055852 IB2021055852W WO2022018546A1 WO 2022018546 A1 WO2022018546 A1 WO 2022018546A1 IB 2021055852 W IB2021055852 W IB 2021055852W WO 2022018546 A1 WO2022018546 A1 WO 2022018546A1
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WO
WIPO (PCT)
Prior art keywords
probe
curved track
track section
arm
centre
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/IB2021/055852
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English (en)
Inventor
Oelof Abraham KRUGER
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
National Metrology Institute Of South Africa
Original Assignee
National Metrology Institute Of South Africa
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by National Metrology Institute Of South Africa filed Critical National Metrology Institute Of South Africa
Publication of WO2022018546A1 publication Critical patent/WO2022018546A1/fr
Anticipated expiration legal-status Critical
Priority to ZA2023/01681A priority Critical patent/ZA202301681B/en
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
    • G01B21/02—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness
    • G01B21/04—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness by measuring coordinates of points
    • G01B21/047—Accessories, e.g. for positioning, for tool-setting, for measuring probes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
    • G01B5/0002—Arrangements for supporting, fixing or guiding the measuring instrument or the object to be measured
    • G01B5/0004—Supports
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
    • G01B5/004—Measuring arrangements characterised by the use of mechanical techniques for measuring coordinates of points
    • G01B5/008—Measuring arrangements characterised by the use of mechanical techniques for measuring coordinates of points using coordinate measuring machines
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
    • G01B5/004—Measuring arrangements characterised by the use of mechanical techniques for measuring coordinates of points
    • G01B5/008—Measuring arrangements characterised by the use of mechanical techniques for measuring coordinates of points using coordinate measuring machines
    • G01B5/012—Contact-making feeler heads therefor

Definitions

  • This invention relates to a probe assembly and a probing configuration used in a coordinate measuring machine (CMM).
  • CMM coordinate measuring machine
  • the invention relates to a probe assembly and a probing configuration adapted to eliminate or at least reduce the Abbe error when taking measurements.
  • the invention also relates to a CMM incorporating said probe assembly and/or probing configuration, and methods of determining coordinates on an object using said CMM.
  • the probe assembly may also find application in laser trackers.
  • Abbe error One type of error frequently encountered in the field of metrology, is the so called “Abbe” error which relates to the magnification of an angular error over a measured distance.
  • An Abbe error occurs where the measured distance is not a straight-line extension of the scale that serves as reference for the measurement, and therefore, the Abbe error occurs whenever an offset is present between the measured distance and the scale.
  • the accuracy of the measured distance will be determined by the degree of relative rotation, pivoting or displacement which is not purely parallel to the measuring scale. If the movement itself is not purely parallel, the measurement will be inaccurate and will include an Abbe error.
  • a measuring instrument that conforms with the Abbe principle of alignment is one where the measured distance is a straight-line extension of the measuring scale.
  • a measuring instrument that conforms with the Abbe principle of alignment is a hand micrometer.
  • a measurement is made on an object that is received between two opposing points on a substantially C-shaped body.
  • the measuring scale extends along an axis connecting the two opposing points. Therefore, the measured distance can be said to be a straight-line extension of the measuring scale.
  • an example of a measuring instrument that does not conform with the Abbe principle of alignment is a Vernier scale (also known as a Vernier calliper).
  • Vernier scale also known as a Vernier calliper
  • the measurement is made between the tips of two callipers which are axially displaceable relative to one another.
  • the measuring scale is located towards the bases of the callipers, and is spaced from the measured distance. Therefore, in cases where the callipers are allowed relative rotational or pivotable movement, albeit very slight, the distance on the measuring scale will differ from the measured distance, and the measurement will include an Abbe error.
  • Coordinate measuring machines are devices with which a geometry of an object is measured, and are mainly used in the field of dimensional metrology.
  • a CMM comprises a probe which is moved within a three- dimensional space along a Cartesian coordinate system (x, y and z axes).
  • CMM systems making use of different measuring configurations, such as articulated arms, are also known in the art.
  • a tip of the probe is brought into contact with various points of the object, the outer geometry of which is measured, and distinct measurements of these contact points are taken by measuring the position of the probe within the Cartesian coordinate system.
  • the probes are also allowed rotational degrees of freedom, to increase the probe’s range of motion, and to enable the measurement of more complex geometries. Since the probe needs to be displaceable at least linearly along the three axes of the Cartesian coordinate system, the probes are typically mounted to at least three displaceable arms. By reading from linear scales, the relative axial displacements of the arms are used to determine the coordinates of the probe at all times.
  • the probe is typically pivotably fixed to front ends of the arms, and extends vertically downward by a predetermined distance from such pivotable connection points, to prevent interference between the arms and the object being measured.
  • CMMs exist, such as CT scanners, laser scanners, laser trackers and articulated arms.
  • a probe assembly comprising: a reference body having an outer reference surface in the form of a spherical dome, defining a centre point; and a probe having a tip which defines a probe centre, the probe being fixed relative to the reference body and arranged such that the centre point of the spherical dome and the probe centre coincide, wherein the spherical dome defines a measurement datum for taking of at least one measurement associated with a position of the probe tip when a reading axis of a measurement instrument is normally aligned to the spherical dome such that the reading axis intersects the probe centre and coinciding centre point of the spherical dome, the measurement being taken referenced from the spherical dome of the probe assembly.
  • the reference surface may be manufactured from a conductive material.
  • the reference surface may be reflective.
  • the reference surface may be formed by a mirror.
  • the reflective reference surface may have a polished outer surface.
  • a probing configuration for a coordinate measuring machine comprising: a probe assembly as described above; a first curved track section attached to the probe, the first curved track section defining a radius about a centre point such that the probe centre of the probe coincides with the centre point; a second curved track section attached to the probe, the second curved track section defining a radius about the centre point; a first arm attached to the first curved track section so as to be displaceable along the first curved track section so that the first arm is pivotably displaceable about the centre point and a longitudinal axis of the first arm continuously intersects the probe centre; and a second arm attached to the second curved track section so as to be displaceable along the second curved track section so that the second arm is pivotably displaceable about the centre point and a longitudinal axis of the second arm continuously intersects the probe centre.
  • the probing configuration may further comprise: a third curved track section attached to the probe, the third curved track section defining a radius about the centre point; and a third arm fixed to the third curved track section so as to be displaceable along the third curved track section so that the third arm is pivotably displaceable about the centre point and a longitudinal axis of the third arm continuously intersects the probe centre.
  • the first, second and third curved track sections may be pivotably displaceable relative to the probe and relative to each other about an axis extending axially along a length of the probe.
  • the probing configuration may include a socket section which surrounds a main body of the probe.
  • the first curved track may have a first end and a second end.
  • the first end of the first curved track may comprise a collar within which the socket section of the main body may be received.
  • the first curved track may be arranged to pivot about the socket section.
  • An outer surface of the socket section may be polished or relatively smooth to reduce friction between the outer surface of the socket section and the collar.
  • the probe assembly may include a ring-shaped track.
  • the spherical dome may extend between the socket section and the ring-shaped track.
  • the first curved track section may comprise a slide formation towards the second end thereof.
  • the slide formation may be arranged to slide on the ring shaped track, when the first curved track section is pivotably displaced relative to the probe.
  • the first curved track section may be polished.
  • the ring- shaped track may be polished.
  • the second and third curved track sections may be of similar construction to the first curved track section.
  • the radii of the first, second and third curved track sections may be substantially equal.
  • the collars of the first, second and third curved track sections may be stacked axially along the socket section.
  • the first arm may comprise a first end and a second end.
  • the first end of the first arm may be fixed to a first base member, which connects the first arm to the first curved track section.
  • the first base member may be configured to allow displacement of the first arm along the first curved track section.
  • the first base member may be configured to retain the first arm in a substantially radial direction relative to the first curved track section, at any point along the first curved track section.
  • the first base member may take the form of a first slide formation.
  • a contact surface of the first slide formation may be curved and may have a radius equal to the radius of the first curved track section.
  • the contact surface of the first slide formation may be formed by a low-friction contact liner, fixed to an inner surface of the first slide formation.
  • the first base member may comprise a roller arrangement, arranged to make contact with the first curved track section.
  • the first arm may be supported towards the second end thereof, by a support structure.
  • the first arm may be axially and pivotably displaceable relative to the support structure.
  • the first arm may be fixed to the support structure by a first linear bearing within which the first arm may be allowed to be displaced axially.
  • the first linear bearing may be fixed pivotably to the support structure to allow the first arm to be displaced pivotably relative to the support structure.
  • a first linear reader may be provided for measuring the linear position or displacement of the first arm relative to the support structure.
  • the first linear reader may be one of a linear variable differential transformer (LVDT), a linear scale system, or a laser measuring device.
  • LVDT linear variable differential transformer
  • the first linear reader may measure the position or displacement of the first arm relative to the support structure, by measuring the axial displacement of the first arm within, or relative to, the first linear bearing.
  • the support structure may comprise a support structure spherical reference surface.
  • the first linear reader may measure a distance between the support structure spherical reference surface and the first curved track.
  • the second and third arms may be similar to the first arm.
  • the probe may comprise a probe assembly according to the first aspect of the invention.
  • the reference body of the probe assembly may be integrally formed with the main body of the probing configuration.
  • the spherical dome-shaped outer reference surface may extend between the socket section and the ring- shaped track, and may retain the socket section and the ring-shaped track relative to each other.
  • Each of the arms may be provided with a capacitance sensor arranged towards the spherical dome portion.
  • the capacitance sensor of a particular arm may be used to measure an extent by which an axis along the length of the arm deviates from the centre point.
  • the first linear reader may measure a distance between the support structure spherical reference surface and the reference surface of the probe assembly.
  • a coordinate measuring machine including the probe assembly according to the first aspect of the invention.
  • a coordinate measuring machine including the probing configuration as described above and a support structure which includes at least two multi-axial pivots, each configured for supporting a linear bearing for receiving one arm of the probing configuration.
  • the coordinate measuring machine may comprise a bed for receiving an object in use.
  • the coordinate measuring machine may further comprise a support structure.
  • a volume may be defined between the bed and the support structure.
  • the support structure may include a multi-axial pivot, for supporting a linear bearing receiving the first arm.
  • the multi-axial pivot may comprise a spherical dome shaped outer surface, and may serve as a reference surface.
  • a method of determining a coordinate of a point on an object including the steps of: placing the object on a bed of a coordinate measuring machine as described above; bringing the probe of the probing configuration into contact with the point on the object; measuring the axial position and/or displacement of each of the first and second arms of the probing configuration relative to the support structure in relation to a reference point; and determining a coordinate of the point on the object, based on the measured axial positions and/or displacements of the first and second arms.
  • the method may further comprise measuring the axial position and/or displacement of a third arm of the coordinate measuring machine, and utilising the measured axial position and/or displacement of the third arm in determining the coordinate of the point on the object.
  • the coordinate may be a coordinate within a Cartesian coordinate system.
  • the step of determining the coordinate based on the measured axial positions and/or displacements may involve the use of triangulation.
  • the method includes measuring a geometric shape of the object by determining the coordinates of a plurality of points on the object in accordance with the method as described above.
  • Figure 1 shows a perspective view of a probing configuration in accordance with the invention, in which details about a spherical dome portion which serves as a reference surface has been omitted, and wherein three arms are located in first positions relative to three curved track sections;
  • Figure 2 shows a perspective view of the probing configuration of Figure 1 , in which the three arms have been displaced along the three curved track sections, to second positions;
  • Figure 3 shows a perspective view of the probing configuration of Figure 1 , with details in broken lines showing the arms in the second positions of Figure 2;
  • Figure 4 shows a perspective view of the probing configuration of Figure 1 , where details in broken lines show the curved track portions pivoted away from their original positions;
  • Figure 5 shows a side view of the probing configuration of Figure 1 , where details of the spherical dome shaped portion are included;
  • Figure 6 shows a bottom perspective view of the probing configuration of Figure 1 ;
  • Figure 7 shows a perspective view of a coordinate measuring machine including a probing configuration of Figure 1 , with the probing configuration located in a first location;
  • Figure 8 shows a perspective view of the coordinate measuring machine of Figure 7, wherein the probing configuration is located in a second location;
  • Figure 9 shows a perspective view of the coordinate measuring machine of Figure 7, with the detail in broken lines showing the probing configuration in the second location of Figure 8;
  • Figure 10 shows a perspective view of a probe assembly, in accordance with the invention.
  • Figure 11 shows a side view of the probe assembly of Figure 10.
  • the terms “mounted”, “connected”, “engaged” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings and are thus intended to include direct connections between two members without any other members interposed therebetween and indirect connections between members in which one or more other members are interposed therebetween. Further, “connected” and “engaged” are not restricted to physical or mechanical connections or couplings. Additionally, the words “lower”, “upper”, “upward”, “down” and “downward” designate directions in the drawings to which reference is made. The terminology includes the words specifically mentioned above, derivatives thereof, and words of similar import.
  • a non limiting example of a probing configuration in accordance with the invention is generally indicated by reference numeral 10.
  • the probing configuration 10 is typically used as part of a coordinate measuring machine (“CMM”), designated generally by reference numeral 12 (see figures 7 to 9).
  • CMM coordinate measuring machine
  • the probing configuration 10 includes a probe assembly, which is illustrated in isolation in figures 10 and 11 and designated by reference numeral 100.
  • the probe assembly 100 comprises a reference body 102 with an outer reference surface 104 in the form of a spherical dome, having a centre point 106.
  • the spherical dome defines a first radius 108 which extends from the centre point 106 to the reference surface 104.
  • the probe assembly 100 also includes an elongate probe 14 which is connected to the reference body 102 and extends radially inward, away from the reference body 102.
  • the probe 14 has a distal, ball shaped tip which defines a point of contact or probe centre 16 at its centre. As shown in figures 10 and 11 , the point of contact 16 of the probe tip and the centre point 106 coincide.
  • a position or coordinates of the probe centre 16 can be determined by taking measurements referenced from the reference surface 104.
  • the reference surface 104 may be manufactured from a conductive material, such as a metal, which may be polished. Accordingly, or alternatively, the reference surface 104 may be reflective. The reference surface 104 may take the form of a mirror. Accordingly, the reference surface 104 may be configured to reflect incident rays thus rendering the probe assembly 100 useful with a laser tracker.
  • the probe assembly 100 may include a handle which is operatively connected to an outer periphery of the reference body 102. A user can therefore grip the handle in order to hold and move the probe assembly 100 around whilst the tip of the probe 14 contacts an object and the laser tracker tracks the probe 14 by measuring rays reflected off the reference surface 104.
  • the probing configuration 10 comprises the probe 14, which defines the point of contact or probe centre 16.
  • the point of contact or probe centre 16 is defined in the centre of the ball-shaped tip of the probe 14.
  • the probe 14 is of the known kind generally associated with CMMs.
  • the probe 14 comprises a substantially cylindrical main body 18, terminating, towards the ball-shaped tip, in a cone-shaped portion 20.
  • the probing configuration 10 further comprises a first curved track section 22, which is, as is discussed more clearly below, connected to the probe 14.
  • the first curved track section 22 defines a radius 24 extending from a centre point 26.
  • the arrangement of the probe 14 and the first curved track section 22 is such that the point of contact or probe centre 16 coincides with the centre point 26.
  • the coinciding of the centre point 26 and the probe centre 16 is critical in reducing or even eliminating the Abbe error when using the CMM 12.
  • the probing configuration 10 furthermore comprises a second curved track section 28 and a third curved track section 30.
  • Both the second and third curved track sections (28, 30) define radii about the centre point 26. It will be understood that, for practical purposes, the radii defined by the first, second and third curved track sections (22, 28, 30) are equal, though, in some cases, these radii may differ. In such cases, suitable calibration of measuring equipment may be required.
  • the second and third curved track sections (28, 30) are attached to the probe 14 in similar fashion as the first curved track section 22.
  • a first arm 32 is attached to the first curved track section 22, such that the first arm 32 is displaceable relative to the first curved track section 22 along at least a part of the first curved track section 22.
  • the first arm 32 extends and remains normal to the first curved track section, irrespective of the displacement along or the specific position of the first arm 32 relative to the first curved track section 22. It follows that displacement of the arm 32 along the first curved track section 22 defines an angular displacement of the first arm 32, likened with a pivoting of the first arm 32 about the centre point 26. An axis extending axially or longitudinally along the first arm 32, intersects the centre point 26, irrespective of the displacement along or the specific position of the first arm 32 along the first curved track section 22.
  • the probing configuration 10 furthermore comprises a second arm 34 which is attached to the second curved track section 28 in similar fashion to the way in which the first arm 32 is attached to the first curved track section 22, and a third arm 36 which is attached to the third curved track section 30 in similar fashion to the way in which the first and second arms (32, 34) are attached to the first and second curved track sections (22, 28), respectively.
  • the first, second and third curved track sections (22, 28, 30) are pivotable relative to the probe 14 and relative to each other, about an axis which extends through the centre point 26, and axially or longitudinally along the main body 18 of the probe 14.
  • the axis about which the first, second and third curved track sections (22, 28, 30) are pivotable, is perpendicular to all three of the axes about which the first, second and third arms (32, 34, 36) pivot.
  • the relative pivoting of the first, second and third curved track sections (22, 28, 30) and the pivoting of the first, second and third arms (32, 34, 36) relative to the first, second and third curved track sections (22, 28, 30) respectively, are required to facilitate three-dimensional translation of the probe 14, as is discussed below.
  • the probing configuration 10 includes a socket section 38, within which the cylindrical main body 18 of the probe 14 is received and held.
  • first, second and third curved track sections (22, 28, 30) are similar.
  • similar features which are associated with different ones of the first, second and third curved track sections (22, 28, 30), are indicated by similar reference numerals, but distinguished by different suffixes, denoting the track number to which they relate.
  • the first curved track section 22 has a first end 40 and a second end 42.
  • a first collar 44.1 is formed at the first end 40 of the first curved track section 22.
  • the socket section 38 of the main body is received within the first collar 44.1 , so that the first collar 44.1 is free to pivot about the first socket section 38.
  • the fit between an outer surface of the socket section 38 and an inner surface of the first collar 44.1 is very fine.
  • the outer surface of the socket section 38 and the inner surface of the first collar 44.1 are polished to reduce friction between the surfaces.
  • the probing configuration 10 also comprises a ring-shaped track 46 with a smooth and polished outer surface.
  • the first curved track section 22 comprises a slide formation 48.1 towards the second end 42.
  • the slide formation is arranged to slide along the ring-shaped track 46 when the first curved track section 22 pivots about the probe 14.
  • An outer surface of the first curved track section 22 is polished to reduce friction when the first arm 32 is displaced along the outer surface.
  • the radii of the first, second and third curved track sections (22, 28, 30) are substantially identical.
  • the collars (44.1 , 44.2, 44.3) of the first to third curved track sections (22, 28, 30) are received in stacked formation about the socket section 38.
  • the collars (44.1 , 44.2, 44.3) are free to rotate relative to each other.
  • the construction and configuration of the first, second and third arms (32, 34, 36) are also similar. Again, the features of the first arm 32 discussed below, therefore have equivalents which are present in the second and third arms (34, 36).
  • similar features which are associated with different ones of the first, second and third arms (32, 34, 36) are again indicated by similar reference numerals, but distinguished by different suffixes denoting the number of the arm to which they relate.
  • First arm 32 comprises a first end 50 and a second end 52.1 (see Figure 7), and is of a predetermined length.
  • a base member 54.1 is located at the first end 50, which connects the first arm 32 to the first curved track section 22.
  • the base member 54.1 can be displaced along the first curved track section 22 in sliding fashion.
  • the base member 54.1 is configured to retain the first arm 32 in a substantially radial direction, and therefore substantially normal to the first curved track section 22, at any point along the first curved track section 22, and during displacement.
  • the base member 54 takes the form of a slide formation.
  • the slide formation comprises an internal contact surface which runs on an outer surface of the first curved track section 22.
  • the contact surface is manufactured from a material selected to limit friction between the slide formation and the first curved track section 22.
  • the contact surface is concave and matches the radius of the first curved track section 22.
  • the CMM 12 comprises a support structure 56 and a bed 58.
  • a volume 60 is defined between the structure 56 and the bed 58, within which the probing configuration 10 may be displaced.
  • the operation of the CMM 12 is discussed below.
  • the first arm 32 is supported relative to the support structure 56, towards the second end 52.1 of the first arm 32.
  • the first arm 32 is received by a linear bearing 64.1 which allows the first arm 32 to be axially displaced relative to the support structure 56.
  • the linear bearing 64.1 in turn is mounted to the support structure 56 via a multi-axial pivot 66, which allows the first arm 32 to pivot relative to the support structure 56.
  • the multi-axial pivot 66 comprises a substantially spherical dome shaped outer surface, which may be used as a reference surface.
  • the multi-axial pivot pivots about a centre point of the substantially spherical dome shaped outer surface.
  • the reference body 102 of the probe assembly 100 is integrally formed with the main body 18 of the probing configuration 10 and extends between the socket section 38 and the ring-shaped track 46 and retains the socket section 38 and the ring-shaped track 46 relative to each other.
  • the reference surface 104 of the substantially spherical dome reference body 102 is also used as a reference surface.
  • a first reader (not shown) is provided for measuring a linear position or displacement of the first arm 32 relative to the support structure 56. The first reader therefore measures axial displacement or an axial position of the first arm 32, relative to the linear bearing 64.1 within which the first arm 32 is received.
  • linear readers such as a linear transducer (linear variable differential transformer or “LVDT”), a linear scale system or a laser measuring device.
  • LVDT linear variable differential transformer
  • reference surface 104 has a reflective, mirror outer surface finish, to reflect a beam projected by the laser measuring device.
  • the reference surface 104 is manufactured from a conductive material, such as a metal.
  • a capacitance sensor (not shown) may be employed in close proximity with the reference surface 104, to determine or measure small deviations (typically caused by imperfect fit between cooperating components) of the first arm from a purely radial position relative to the centre point 26 of the first curved track section 22.
  • An actuator of the known type (not shown) is provided for axially displacing the first arm 32 relative to the linear bearing 64.1 .
  • the second arm 34 and the third arm 36 are both also associated with linear bearings 64, multi-axial pivots 66, linear readers, and actuators. It will be understood that the linear actuators of the three arms (32, 34, 36) may be used to displace the probe 14 within the volume 60.
  • the CMM 12 is used to measure or determine one or more coordinates on a surface of an object (not shown).
  • the object is placed and secured on the bed 58 of the CMM 12.
  • the linear actuators of the three arms (32, 34, 36) are now used to displace the probing configuration 10 towards the object, and to bring the ball-shaped tip of the probe 14 into contact with a distinct point on the surface of the object.
  • the specific position or axial displacement of each of the three arms is measured by the three linear readers or encoders.
  • the various spherical dome shaped reference surfaces may be used to serve as references for taking the measurements and to account for any small amount of deviation.
  • the measurements of the linear readers or encoders are now used to determine the coordinates of the position within the volume, by means of triangulation, and may be expressed as a coordinate within a Cartesian coordinate system.
  • a reference or zero position may be determined before determining further coordinates.
  • the reference or zero position may be a first position on the object, or may be taken at another position within the volume 60. It will be understood that the base members 54 of the three arms (32, 34, 36) slide along the three curved track sections (22, 28, 30) as the probing configuration 10 is displaced within the volume.
  • the first, second and third curved track sections (22, 28, 30) also pivot relative to each other. In this way, longitudinal extensions of the three arms continue to intersect the probe centre 16.
  • the probe assembly 100 and probing configuration 10 are configured to be used to take measurements on an object having one or more cavities due to the fact that the tip of the main body 18 of the probe 14 can extend into the cavity to measure coordinates of points on the object inside the cavity whilst the measurements are referenced off the spherical dome.
  • references to coinciding points or alignment of components or axes will be understood not to exclude the possibility of small or infinitesimal deviations between the points or from the alignment, as can be expected from interacting mechanical componentry. It will be understood that manufacturing tolerances of the various components are very fine and selected to ensure that the deviations as mentioned fall within limits acceptable to the application. Furthermore, provision may be made as mentioned, to account for such deviations, at least to a degree, by using the spherical dome shaped portions or surfaces as reference surfaces.
  • the CMM 12 may instead be adapted for determining two-dimensional coordinates, in which case only two arms, and two curved track sections will be utilised.
  • the two curved track sections may be integrally formed.
  • the radius 24, or the radius of the spherical dome shaped portion may be selected based on the specific application, the size of the CMM 12, or the permissible size of the object in respect of which the coordinates are determined. It will be appreciated that the above description only provides an example embodiment of the invention and that there may be many variations without departing from the spirit and/or the scope of the invention.
  • the base members 54 may comprise a roller arrangement, arranged to make contact with the first curved track section.

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  • A Measuring Device Byusing Mechanical Method (AREA)

Abstract

La présente invention se rapporte à un ensemble sonde (100), une configuration de sondage (10), une machine de mesure de coordonnées (CMM) (12) comprenant la configuration de sondage (10) et un procédé de détermination d'une coordonnée d'un point sur un objet à l'aide de la CMM. L'ensemble sonde (100) est caractérisé en ce qu'il comprend un corps de référence (102) doté d'une surface de référence externe (104) sous la forme d'un dôme sphérique définissant un point central (106). L'ensemble sonde (100) comprend également une sonde (14) dotée d'une pointe qui définit un centre de sonde (16), la sonde étant reliée au corps de référence et agencée de telle sorte que le point central et le centre de sonde coïncident. Grâce à cette configuration, une donnée de mesure permettant la prise d'au moins une mesure associée à une position de la pointe de sonde est définie par le dôme sphérique lorsqu'un axe de lecture d'un instrument de mesure est normalement aligné sur le dôme sphérique de telle sorte que l'axe de lecture coupe le centre de sonde, ce qui permet de faciliter la réduction ou l'élimination d'erreurs d'aplanétisme.
PCT/IB2021/055852 2020-07-20 2021-06-30 Configuration de sondage Ceased WO2022018546A1 (fr)

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ZA2023/01681A ZA202301681B (en) 2020-07-20 2023-02-10 Probing configuration

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ZA2020/04445 2020-07-20
ZA202004445 2020-07-20

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WO2022018546A1 true WO2022018546A1 (fr) 2022-01-27

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PCT/IB2021/055852 Ceased WO2022018546A1 (fr) 2020-07-20 2021-06-30 Configuration de sondage

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WO (1) WO2022018546A1 (fr)
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002034461A2 (fr) * 2000-10-27 2002-05-02 Makex Limited Ameliorations dans la conception de machines a elements de liaison paralleles
US6503033B1 (en) * 2000-06-21 2003-01-07 Jongwon Kim Parallel mechanism structure for controlling three-dimensional position and orientation
EP2244052A1 (fr) * 2009-04-24 2010-10-27 Xpress Holding B.V. Porte-objet de précision

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6503033B1 (en) * 2000-06-21 2003-01-07 Jongwon Kim Parallel mechanism structure for controlling three-dimensional position and orientation
WO2002034461A2 (fr) * 2000-10-27 2002-05-02 Makex Limited Ameliorations dans la conception de machines a elements de liaison paralleles
EP2244052A1 (fr) * 2009-04-24 2010-10-27 Xpress Holding B.V. Porte-objet de précision

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
FERN FLORIAN ET AL: "In-situ-Messung von Bewegungsabweichungenserieller Rotationsachsen zur Anwendung in Nanomessmaschinen", TM - TECHNISCHES MESSEN/PLATTFORM FÜR METHODEN, SYSTEME UND ANWENDUNGEN DER MESSTECHNIK, vol. 86, no. s1, 1 September 2019 (2019-09-01), DE, pages 77 - 81, XP055837054, ISSN: 0171-8096, Retrieved from the Internet <URL:http://dx.doi.org/10.1515/teme-2019-0040> DOI: 10.1515/teme-2019-0040 *
RUGBANI ALI ET AL: "The kinematics and error modelling of a novel micro-CMM", THE INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY, SPRINGER, LONDON, vol. 78, no. 5, 23 December 2014 (2014-12-23), pages 961 - 969, XP035491771, ISSN: 0268-3768, [retrieved on 20141223], DOI: 10.1007/S00170-014-6566-0 *
SCHIENBEIN RALF: "Grundlegende Untersuchungen zum konstruktiven Aufbau von Fünfachs-Nanopositionier- und Nanomessmaschinen", 19 June 2020 (2020-06-19), pages 1 - 207, XP055837145, ISBN: 978-3-86360-229-1, Retrieved from the Internet <URL:https://www.db-thueringen.de/servlets/MCRFileNodeServlet/dbt_derivate_00051163/ilm1-2020000376.pdf> [retrieved on 20210902] *

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