ISO/WD 10360-10
March 4, 2017 | Author: JD | Category: N/A
Short Description
This part of ISO 10360 is a geometrical product specification (GPS) standard and is to be regarded as a general GPS sta...
Description
ISO/WD 10360-10
Contents
Page
Foreword ............................................................................................................................................................iv Introduction.........................................................................................................................................................v 1
Scope ......................................................................................................................................................1
2
Normative References...........................................................................................................................1
3
Terms and Definitions...........................................................................................................................2
4
Symbols..................................................................................................................................................3
5 5.1 5.2 5.3 5.4 5.5 5.6
Environmental and metrological requirements..................................................................................4 Environmental conditions ....................................................................................................................4 Operating conditions ............................................................................................................................4 Length measurement error, EL .............................................................................................................4 Probing form error, PF ...........................................................................................................................5 Probing size error, PS ............................................................................................................................5 Probing location error, PL .....................................................................................................................5
6 6.1 6.2 6.2.1 6.2.2 6.2.3 6.2.4 6.3 6.3.1 6.3.2 6.3.3 6.3.4 6.4 6.4.1 6.4.2 6.4.3 6.4.4
Acceptance tests and reverification tests ..........................................................................................5 General ...................................................................................................................................................5 Probe errors ...........................................................................................................................................6 Principle..................................................................................................................................................6 Measuring equipment ...........................................................................................................................6 Procedure ...............................................................................................................................................6 Derivation of test results ......................................................................................................................7 Probing location errors (two-face tests) .............................................................................................8 Principle..................................................................................................................................................8 Measuring equipment ...........................................................................................................................8 Procedure ...............................................................................................................................................8 Derivation of test results ......................................................................................................................9 Length errors .........................................................................................................................................9 Principle..................................................................................................................................................9 Measuring equipment ...........................................................................................................................9 Procedure .............................................................................................................................................10 Derivation of test results ....................................................................................................................15
7 7.1 7.2
Compliance with specification ...........................................................................................................16 Acceptance tests .................................................................................................................................16 Reverification tests .............................................................................................................................16
8 8.1 8.2 8.3
Applications .........................................................................................................................................16 Acceptance test ...................................................................................................................................16 Reverification test ...............................................................................................................................17 Interim check........................................................................................................................................17
9
Indication in product documentation and data sheets....................................................................17
Annex A (normative) FORMS ..........................................................................................................................19 Annex B (normative) Calibrated Test Lengths .............................................................................................21 Annex C (normative) THERMAL COMPENSATION OF WORKPIECES .......................................................22 Annex D (informative) ACHIEVING THE ALTERNATIVE MEASURING VOLUME.......................................23 Annex E (informative) INTERIM TESTING......................................................................................................25
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Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 10360-10 was prepared by Technical Committee ISO/TC 213, Dimensional and geometrical specifications and verification. ISO 10360 consists of the following parts, under the general title Introductory element — Main element: ⎯ Part 1: Vocabulary ⎯ Part 2: CMMs used for measuring size ⎯ Part 3: CMMs with the axis of a rotary table as the fourth axis ⎯ Part 4: CMMs used in scanning measuring mode ⎯ Part 5: CMMs probing performance with contacting probing system ⎯ Part 6: Estimation of errors in computing of Gaussian associated features ⎯ Part 7: CMMs equipped with video probing systems ⎯ Part 8: CMMs with optical distance sensors ⎯ Part 9: CMMs with multiple probing systems ⎯ Part 10: Laser Trackers used for measuring point-to-point distances
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Introduction This part of ISO 10360 is a geometrical product specification (GPS) standard and is to be regarded as a general GPS standard (see ISO/TR 14638). It influences link 5 of the chains of standards on size, distance, radius, angle, form, orientation, location, run-out and datums. For more detailed information of the relation of this part of ISO 10360 to other standards and the GPS matrix model see annex B. The tests of this part of ISO 10360 have two technical objectives: (1) to test the error of indication of a calibrated test length using a Laser Tracker and (2) to test the errors in the Laser Tracker. The benefits of these tests are that the measured result has a direct traceability to the unit length, the meter, and that it gives information on how the Laser Tracker will perform on similar length measurements. This part of ISO 10360 is distinct from that of ISO 10360-2, which is for CMMs equipped with contact probing systems, in that the orientation of the test lengths reflect the different instrument geometry and error sources within the instrument. All the definitions in clause 3 will appear in the next issue of ISO 10360-1.
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v
WORKING DRAFT
ISO/WD 10360-10
Geometrical Product Specifications (GPS) — Acceptance and reverification tests for coordinate measuring machines (CMM) — Part 10: Laser Trackers
1
Scope
This part of ISO 10360 specifies the acceptance tests for verifying the performance of a Laser Tracker by measuring calibrated test lengths as stated by the manufacturer. It also specifies the reverification tests that enable the user to periodically reverify the performance of the Laser Tracker. The acceptance and reverification tests given in this part of ISO 10360 are applicable only to Laser Trackers utilising a retroreflector as a probing system. Laser Trackers that use interferometry (IFM), absolute distance meter (ADM) measurement, or both may be verified using this part of ISO 10360. This standard does not explicitly apply to measuring systems that do not use a spherical coordinate frame or to systems that use different probing accessories; however, the parties may apply this part of 10360 to such systems by mutual agreement. This International Standard specifies: ⎯ performance requirements that can be assigned by the manufacture or the user of the Laser Tracker, ⎯ the manner of execution of the acceptance and reverification tests to demonstrate the stated requirements, ⎯ rules for proving conformance, and ⎯ applications for which the acceptance and reverification tests can be used.
2
Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the cited editions apply. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 10360-1:2000, Geometrical Product Specifications (GPS) — Acceptance and reverification test for coordinate measuring machines (CMM) — Part 1: Vocabulary ISO 14253-1:1998, Geometrical Product Specifications (GPS) — Inspection by measurement of workpieces and measuring equipment — Part 1: Decision rules for proving conformance or nonconformance with specifications ISO 14660-1:1999, Geometrical Product Specifications (GPS) — Geometrical features — Part 1: General terms and definitions ISO/TS 23165:2006, Geometrical product specifications (GPS) — Guidelines for the evaluation of coordinate measuring machine (CMM) test uncertainty ISO/IEC Guide 99:2007, International vocabulary of metrology - Basic and general concepts and associated terms (VIM).
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3
Terms and Definitions
3.1 interferometric measurement (IFM) mode measurement method that uses a laser displacement interferometer internal to a laser tracker to determine distance (range) to a target NOTE:
The target is typically a retroreflector.
3.2 absolute distance meter (ADM) measurement mode measurement method that uses time of flight techniques to determine the distance (range) to a target NOTE:
The target is typically a retroreflector.
3.3 retroreflector passive device designed to reflect light back parallel to the incident direction over a range of incident angles NOTE 1:
Typical retroreflectors are the cat’s-eye and the cube corner.
NOTE 2:
Retroreflectors are cooperative targets
3.4 spherically mounted retroreflector (SMR) retroreflector that is mounted in a spherical housing NOTE: In the case of an open-air cube corner, the vertex is typically adjusted to be coincident with the sphere center.
3.5 length measurement error EL error of indication when performing a point-to-point distance measurement using a laser tracker with a probe offset length of L NOTE E0 (used throughout this document) corresponds to the common case of no probe offset length, as the retroreflector optical center is coincident with the physical center of the probing system.
3.6 probing form error PF error of indication within which the range of radii can be determined by a least-squares fit of points measured by a laser tracker on a spherical material standard of size 3.7 probing size error PS error of indication within which the diameter of a spherical material standard of size can be determined by a least-squares fit of points measured with a laser tracker 3.8 probing location error PL the apparent Euclidean distance between two measurements taken with the retroreflector placed in a single location, the second measurement being taken with the azimuth axis at approximately 180 degrees from the first measurement and the elevation angle reflected about the vertical (e.g. +82 degrees to -82 degrees).
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NOTE:
This combination of axis rotation is known as a two face, or plunge and reverse test.
NOTE It is often the case that the Range of two measurements is assumed to be the same, as the range information may not be obtainable for the second measurement.
3.9 maximum permissible error of length measurement EL, MPE extreme value of the length measurement error, EL, permitted by specifications NOTE
E0, MPE is used throughout this document.
3.10 maximum permissible error of probing form PF, MPE extreme value of the probing form error, PF, permitted by specifications 3.11 maximum permissible error of probing size PS, MPE extreme value of the probing size error, PS, permitted by specifications 3.12 maximum permissible error of probing location PL, MPE extreme value of the probing location error, PL, permitted by specifications
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Symbols
For the purpose of this part of ISO 10360, the symbols of Table 1 apply. Table 1 - Symbols Symbol
Meaning
EL
Length measurement error
PF
Probing form error
PS
Probing size error
PL
Probing location error (from two face tests)
EL, MPE
Maximum permissible error of length measurement
PF, MPE
Maximum permissible error of probing form
PS, MPE
Maximum permissible error of probing size
PL, MPE
Maximum permissible error of probing location (from two face tests)
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5
Environmental and metrological requirements
A manufacturer’s specification that conforms to this part of ISO 10360 shall include completed Form 1 (General Specifications and Rated Conditions – Annex A) and the specifications of Form 2 (Manufacturer’s Performance Specifications and Test Results – Annex A). The manufacturer shall provide a formula for calculating the maximum permissible error (MPE) for bidirectional length measurements, the MPE for the probing tests and the two face tests that are applicable over the entire range of rated conditions as described in Form 1.
5.1
Environmental conditions
Limits for permissible environmental conditions such as temperature conditions, air pressure, humidity, and vibration at the site of installation that influence the measurements shall be specified by: ⎯ the manufacturer, in the case of acceptance tests; ⎯ the user, in the case of reverification tests. In both cases, the user is free to choose the environmental conditions under which the testing will be performed within the specified limits (as supplied in the data sheet of the manufacturer. See Form 1 – Annex A).
5.2
Operating conditions
The Laser Tracker shall be operated using the procedures given in the manufacturer's operating manual when conducting the tests given in Clause 6. Specific areas in the manufacturer's manual to be adhered to are, for example: a) machine start-up/warm-up cycles, b) machine self-compensation procedures c) cleaning procedures for retroreflector, d) retroreflector qualification, e) location, type, and number of environmental sensors (i.e. "the weather station"), f)
5.3
location, type, number of thermal workpiece sensors.
Length measurement error, EL
The length measurement errors, the EL values, shall not exceed the maximum permissible error, EL, MPE stated by: ⎯ the manufacturer, in the case of acceptance tests, ⎯ the user, in the case of reverification tests. The length measurement errors (the EL values) and the maximum permissible error of length measurement, E0L MPE, are expressed in micrometers. The manufacturer may, at his discretion, specify the maximum permissible error of point-to-point length measurements when measuring radially (when the reference length is oriented along a radial direction of the
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ISO/WD 10360-10
laser tracker) or transverse (when the not-extended point-to-point segment itself is perpendicular to a radial direction of the laser tracker). The notation is E0R with E0R, MPE and E0T with E0T, MPE, respectively.
5.4
Probing form error, PF
The probing form error, PF, shall not exceed the maximum permissible error, PF, MPE, stated by ⎯ the manufacturer, in the case of acceptance tests, ⎯ the user, in the case of reverification tests. The probing form error and the maximum permissible error of probing form are expressed in micrometers.
5.5
Probing size error, PS
The probing size error, PS, shall not exceed the maximum permissible error, PS, MPE, stated by ⎯ the manufacturer, in the case of acceptance tests, ⎯ the user, in the case of reverification tests. The probing size error and the maximum permissible error of probing size are expressed in micrometers.
5.6
Probing location error, PL
The probing location error, PL, shall not exceed the maximum permissible error, PL, MPE, stated by ⎯ the manufacturer, in the case of acceptance tests, ⎯ the user, in the case of reverification tests. The probing location value and the maximum permissible error of probing location are expressed in micrometers.
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6.1
Acceptance tests and reverification tests
General
In the following: ⎯ acceptance tests are executed according to the manufacturer's specifications and procedures ⎯ reverification tests are executed according to the user's specifications and the manufacturer's procedures
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6.2 6.2.1
Probe errors Principle
The principle of this test procedure is to measure the size and form of a test sphere using 25 points probed with the retroreflector and attribute the observed form error to the probing system. A least-squares sphere fit of the 25 points is examined for the errors of indication for form and size. This analysis yields the form error, PF, and the size error, PS. Two types of errors in the SMR may influence the results of this test. If the sphere within which the retroreflector is mounted is out-of-round, this will influence the test result. Also, if the mirrored surfaces which comprise the retroreflector are not mutually orthogonal, or if their point of intersection is not coincident with the sphere center, the test result will be affected. NOTE Most SMRs are of adequate quality such that a properly cared-for SMR will have errors that are small compared to the PF result of the test.
The results of these tests may be highly dependent on the distance of the test sphere from the Laser Tracker. Therefore, the test shall be performed at two distances from the Laser Tracker, as indicated in Table 2. Table 2 - Probe testing locations
6.2.2
Distance from Tracker
Height relative to Tracker
< 2m
~ same height
~10 m
more than 1 m above or below
Measuring equipment
The material standard of size, i.e. the test sphere, shall have a nominal diameter not less than 25 mm and not greater than 51 mm. The test sphere shall be calibrated for size and form. 6.2.3
Procedure
Mount the test sphere with the support located away from the tracker, so that a full hemisphere may be measured. NOTE
The test sphere should be mounted rigidly to minimise errors due to bending.
Measure and record 25 points. The points shall be approximately evenly distributed over at least a hemisphere of the test sphere. Their position shall be at the discretion of the user and, if not specified, the following probing pattern is recommended (see Figure 1): ⎯ One point on the pole (defined by the direction of the stylus shaft) of the test sphere: ⎯ Four points (equally spaced) 22,5º below the pole; ⎯ Eight points (equally spaced) 45º below the pole and rotated 22,5º relative to the previous group; ⎯ Four points (equally spaced) 67,5º below the pole and rotated 22,5º relative to the previous group; ⎯ Eight points (equally spaced) 90º below the pole (i.e. on the equator) and rotated 22,5º relative to the previous group. Note It is suggested that the user follow the manufacturer recommendations for probing locations and SMR orientation while probing. In the absence of these recommendations, a constant attitude of the SMR throughout the test may yield smaller PF values.
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Key A Pole – point on sphere nominally closest to the Laser Tracker Figure 1: Location of probing points
NOTE: The result of this test is highly dependent on the skill of the Laser Tracker operator.
6.2.4
Derivation of test results
6.2.4.1 Using all 25 measurements, compute the Gaussian associated sphere. Record the diameter of this sphere. The difference of this diameter from the calibrated diameter of the test sphere, i.e. DMEAS – DREF, is the probing size error, PS.
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6.2.4.2 For each of the 25 measurements, calculate the Gaussian radial distance, R. Record the range of radii of the 25 points with respect to the least-squares sphere centre, i.e. Rmax – Rmin, the apparent sphere form. The absolute value of this difference is the probing form error, PF.
6.3
Probing location errors (two-face tests)
6.3.1
Principle
The principle of this test procedure is to measure the location of a single retroreflector twice, whilst rotating the azimuth axis by approximately 180 degrees and reflecting the elevation angle about the vertical between the measurements. The apparent distance between the two measurements of the retroreflector yields the test result, PL. NOTE: As this test is easy to perform, and will immediately reveal problems with the tracker geometry and its correction, it is recommended that these tests be performed first.
The results of these tests may be highly dependent on the distance of the test sphere from the Laser Tracker, and influenced by the tracker's angular orientation. Therefore, the test shall be performed at two distances from the Laser Tracker and at 3 different orientations, as indicated in Table 3. Table 3 - Two-face Measurement positions Position number
Distance from tracker
Description of retroreflector position
Angle(s) with respect to the tracker (degrees)
1-3
1m
Two-face test, retroreflector 1 m below tracker height
0, 120, 240
4-6
1m
Two-face test, retroreflector at tracker height
0, 120, 240
7-9
1m
Two-face test, retroreflector 1 m above tracker height
0, 120, 240
10-12
6m
Two-face test, retroreflector 1 m below tracker height
0, 120, 240
13-15
6m
Two-face test, retroreflector at tracker height
0, 120, 240
16-18
6m
Two-face test, retroreflector 1 m above tracker height
0, 120, 240
6.3.2
Measuring equipment
The equipment for this test is a target nest that may be mounted rigidly at the positions required in Table 3. 6.3.3
Procedure
Mount the target nest so that the nest and its support will not interfere with measurement of the retroreflector. Place the retroreflector in the nest, and measure the location of the retroreflector in both angles and range. Rotate both angular axes of the tracker by the appropriate angles and reacquire the retroreflector. Measure this location of the retroreflector in the angles only, using the range value from the first measurement.
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ISO/WD 10360-10
NOTE 1
For Laser Trackers used in IFM mode, it may not be possible to prevent the beam from being broken during this test. For this reason, only the first range value is used in the PL calculations.
NOTE 2
The target nest should be mounted rigidly to minimise uncertainty in the measurements.
6.3.4
Derivation of test results
Calculate the distance between the two measured locations. This distance between the two locations is the probe location error, PL.
6.4 6.4.1
Length errors Principle
The length measurement error describes the three-dimensional deviation behaviour of the Laser Tracker in the specified measuring volume. This deviation behaviour is caused by the overlapping of different individual deviations such as uncorrected systematic deviations of the length measuring system and the angle encoders, random measuring deviations, geometric imperfections in the rotation and swivelling axes and/or of the spherically mounted retroreflector or the probe. As the deviation behaviour depends, among other things, on the mode of operation, different values of the characteristics may result for different modes of operation (interferometric or absolute distance measurement, vertical or horizontal installation of the Laser Tracker, spherically mounted retroreflector or probe). If the mode of operation is not indicated, the characteristic applies to all permissible modes of operation of the measuring system. 6.4.2
Measuring equipment
A traceable reference length may be realized in a number of ways, including scale bars, target nests mounted on walls or freestanding structures, use of a rail-and-carriage system, gauge blocks, ball bars, etc. While any such lengths may be used, the measurements of these length tests shall be bidirectional. A bidirectional measurement error can be achieved, for example, using a combination of a unidirectional measurement on a reference length and a bidirectional measurement on a short gauge block. See the normative Annex B, which includes all the details of reference lengths and achieving bidirectional measurements. A laser tracker uses one linear axis and two rotary axes to determine the location of a retroreflector. The normative locations in Table 4 include tests that span at least 66% of each axis. Positions 1 and 2 accomplish this for each rotary axis separately, while positions 36-40 accomplishes this for the ranging (linear) axis. The angular range of a measurement is determined by both the length being measured and its distance from the Laser Tracker. It is therefore possible to obtain a variety of angular measurements using a single calibrated reference length. For this reason, the reference lengths in positions 1-29 of Table 4 shall be between 2.25 m and 2.75 m. The manufacturer shall state the upper, and optionally lower, limits of the CTE of the calibrated test length. The manufacturer may calibrate the CTE of a calibrated test length. The manufacturer shall specify the maximum permitted (k = 2) uncertainty of the CTE of the calibrated test length. In the case where the calibrated test length is composed of a unidirectional length and other information (see Annex B), the CTE shall be considered to be that of the unidirectional length. The default for a calibrated test length is a normal CTE material unless the manufacturer's specifications explicitly state otherwise. Check that normal CTE is defined in this part. A laser interferometer that is corrected for the index of refraction of air has a zero CTE (α = 0). Hence, if it is used to produce a calibrated test length it is considered a low CTE material and is subject to 6.3.x.x. Additionally, if the reference laser has a workpiece (material) temperature sensor, then the workpiece CTE in the laser’s software shall be set to 0. If a temperature compensated Laser Tracker is being tested, the workpiece CTE in the Laser Tracker software shall be set to 0 when measuring these reference lengths. If the calibrated test length is not a normal CTE material, then the corresponding E0, MPE values are designated with an asterisk (*) and an explanatory note shall be provided describing the CTE of the calibrated test length. EXAMPLE
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E0, MPE* * Artefact is super-invar with a CTE no greater than 0,5 ⋅ 10−6/°C and with a CTE expanded uncertainty (k = 2) no greater than 0,3 ⋅ 10−6/°C. −6 For the case where the manufacturer's specification for E0, MPE requires a CTE less than 2 x 10 /°C (thus being a nonnormal CTE), an additional measurement shall be performed on a normal CTE material reference length. See normative Annex C.
NOTE: Due to the large size of reference lengths required for testing Laser Trackers, it is common for this low-CTE option to be exercised.
6.4.3
Procedure
Place the reference length(s) at each location and orientation relative to the Laser Tracker described in Table 4. If – in the case of IFM measurements – the beam is broken during a length measurement, the measurement during which the beam was broken must be restarted, but the series of three measurements need not be restarted (unless, of course, the beam was broken during the first length measurement). In the case of ADM measurements, it is suggested that the beam be broken during each length measurement, forcing the Laser Tracker to re-establish the distance to the reflector as part of the measurement process. NOTE:
In many instances, it may be easier to move or reorient the Laser Tracker than to move the reference length.
Table 4 - Measurement positions
Position number
Distance from tracker
Horizontal angle(s) with respect to the tracker (degrees)
Description of reference length position
Horizontal, centered (i.e., the ends of the reference length are equidistant from the tracker), and at tracker height. 1
As close as practical
at any azimuth This tests 66% of the horizontal angle measurement axis of the tracker. Vertical, center of the length at tracker height (ends of the reference length equidistant from the tracker).
2
As close as practical
at any azimuth This tests 66% of the vertical angle measurement axis of the tracker.
10
3-6
3m
Horizontal, centered (i.e., the ends of the reference length are equidistant from the tracker), and at tracker height.
0, 90, 180, 270
7
3m
Vertical, center of the length at tracker height (ends of the reference length equidistant from the tracker).
at any azimuth
8-11
3m
Right diagonal, centered (i.e., the ends of the reference length are equidistant from the tracker), and the center of the length is at tracker height.
0, 90, 180, 270
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12-15
3m
Left diagonal, centered (i.e., the ends of the reference length are equidistant from the tracker), and the center of the length is at tracker height.
0, 90, 180, 270
16-19
6m
Horizontal, centered (i.e., the ends of the reference length are equidistant from the tracker), and at tracker height.
0, 90, 180, 270
20-23
As close as practical
Horizontal, not-centered (i.e, the tracker is directly in front of one end of the length), and at tracker height
0, 90, 180, 270
24
As close as practical
Vertical, not-centered (i.e, the tracker is directly in front of one end of the length)
at any azimuth
25-28
As close as practical
Diagonal, one end below or above the point directly in front of the tracker, the other end to the right or left of the point directly in front of the tracker. The range to the two ends of the length are equal.
0, 90, 180, 270
Horizontal, centered directly above (as much as that ispossible) the laser tracker itself
at any azimuth
29
30-35
Long1
Horizontal, centered (i.e., the ends of the reference lengthare equidistant from the tracker), at tracker height
0, 30, 60, 90, 120,150
36-40
5 Ranging test distances
This tests 66% of the ranging axis of the tracker.
at any azimuth
41
Synthetic length
See Annex C
test 1
In the special “long“ case, a longer reference length (e.g., 8 m) is measured at a longer distance (e.g., 8 m) from the tracker.
In the Ranging tests (lengths 36-40), it is not required that each of the 5 lengths be measured as a two point distance. It is permitted to measure a reference point close to the tracker (e.g. less than 1 m from the tracker) and then 5 points at increasing distances, where the 5 reference lengths are all calculated from the common first point. The user may, at his discretion, require that the first point be measured more than once (up to a maximum of 5 times, once for each length). In explanation, if the points are labeled A (closest) to F (farthest), a sequence of measurements ABCDEF is permitted to evaluate the ranging capability of the laser tracker. The user may, however, require that each length remeasures the A location as in (AB, AC, AD, AE, AF) or (AB, CA, AD, EA, AF).
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B B d
d
d
B d A
A A
A a) 1, 3-6, 16-19, 30-35
b) 2, 7
B d
c) 8-11
d) 12-15
B
B
A d
d
A
d
A A e) 20-23
f) 24
g) 25-28
h) 29
Key: A and B are the ends of the artifact, d is perpendicular to the vertical plane containing the artifact Figure 2: Positions for reference artifact
For
6.4.3.1
User defined positions: alternative 1
The user is free to choose the remaining 64 measurement positions (for a total of 105 measurements). To assist the user in choosing these measurement positions, two alternative default positions are given. Alternative 1 is described in Table 5 below. Table 5 — Supplemental default measurement positions – Alternative 1
position number
Distance from tracker
Angle(s) with respect to the tracker (clocked about vertical axis)
Description of reference length position
1-3
3m
Vertical, centered (i.e., the ends of the reference length are equidistant from the tracker), and the center of the length is at tracker height.
90, 180, 270
4-7
6m
Vertical, center of the length at tracker height (ends of the reference length equidistant from the tracker).
0, 90, 180, 270
8-11
6m
Right diagonal, centered (i.e., the ends of the reference length are equidistant from the tracker), and the center of the length is at tracker height.
0, 90, 180, 270
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position number
Distance from tracker
12-15
6m
16-18
As close practical
19-22
Description of reference length position
Angle(s) with respect to the tracker (clocked about vertical axis)
Left diagonal, centered (i.e., the ends of the reference length are equidistant from the tracker), and the center of the length is at tracker height.
0, 90, 180, 270
as
Vertical, not-centered (i.e, the tracker is directly in front of one end of the length)
90, 180, 270
As close practical
as
Horizontal, not-centered (i.e, the tracker is directly in front of one end of the length), and at tracker height. This is the mirror position corresponding to positions 20-23 in Table 4 (If the tracker were previously directly in front of Target B as in Fig. ?, then, the tracker must now be positioned directly in front of target A)
0, 90, 180, 270
23-26
As close practical
as
Vertical, not-centered (i.e, the tracker is directly in front of one end of the length). This is the mirror position corresponding to positions 24 in Table 4 and positions 16-18 in this Table (If the tracker were previously directly in front of Target B as in Fig. ?, then, the tracker must now be positioned directly in front of target A)
0, 90, 180, 270
27-30
As close practical
as
Diagonal, one end below or above the point directly in front of the
0, 90, 180, 270
tracker, the other end to the right or left of the point directly in front of the tracker. The range to the two ends of the length are equal. This is the mirror position corresponding to positions 25-28 in Table 4 (If the tracker were previously directly in front of Target B as in Fig. ?, then, the tracker must now be positioned directly in front of target A) 31-33
Horizontal, centered directly above (as much as that is
90, 180, 270
possible) the laser tracker itself 34-37
6m
Body diagonal of a cube
0, 90, 180, 270
38-41
As close practical
as
Diagonal, centered (i.e., the ends of the reference length are equidistant from the tracker), and the center of the length is at tracker height.
0, 90, 180, 270
Distance approximately equal to half the reference length
Horizontal, centered (i.e., the ends of the reference length are equidistant from the tracker), and at tracker height.
Repeatability measurements: 42-45
Repeat the measurement 4 times.
at any azimuth
This tests the repeatability of the horizontal angle measurement capability.
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position number
46-49
Distance from tracker Distance approximately equal to twice the reference length
Angle(s) with respect to the tracker (clocked about vertical axis)
Description of reference length position
Horizontal, centered (i.e., the ends of the reference length are equidistant from the tracker), and at tracker height. Repeat the measurement 4 times.
at any azimuth
This tests the repeatability of the horizontal angle measurement capability. 50-53
54-57
58-61
Distance approximately equal to half the reference length
Vertical, center of the length at tracker height (ends of the reference length equidistant from the tracker).
Distance approximately equal to twice the reference length
Vertical, center of the length at tracker height (ends of the reference length equidistant from the tracker).
3m
Along the radial direction so that the near end of the length is 3 m away from the tracker.
at any azimuth
Repeat the measurement 4 times. This tests the repeatability of the vertical angle measurement capability.
at any azimuth
Repeat the measurement 4 times. This tests the repeatability of the vertical angle measurement capability.
at any azimuth
Repeat the measurement 4 times. This tests the repeatability measurement capability. 62-64
6m
of
the
range
Along the radial direction so that the near end of the length is 6 m away from the tracker. at any azimuth
Repeat the measurement 3 times. This tests the repeatability measurement capability.
6.4.3.2
of
the
range
User defined positions: alternative 2
In this alternative, the laser tracker is positioned centrically in front of the longest side of the measuring volume at a distance of 1.5 m in such a way that the measuring head is approximately equidistant from the upper and lower edge of the measuring volume. The positions are determined by eight different measurement lines. Figure 3 shows a possible arrangement of these eight measurement lines. Other arrangements are also permitted.
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Figure 3: Example showing the arrangement of the measurement lines for the test of the length measurement error For the remaining 64 positions in this alternative of the acceptance test, a measuring volume of 10 m x 6 m x 3 m (length x breadth x height) is recommended. If the laser tracker is preferably used to measure small parts, a measuring volume of 5 m x 3 m x 2 m is then recommended. Other measuring volumes are, however, permitted. In every measurement line, at least three different test lengths must be measured. All in all, 64 reference lengths should be measured along the eight measurement lines, i.e. in individual measurement lines, 3 or 4 separate lengths could be measured, rotating the tracker between measurements. Before each measurement, the laser tracker shall be rotated by approximately 120° about its vertical axis. The shortest test length should amount to at least 1/10 of the shortest side of the specified measuring volume. In each measurement line, the largest reference length has to be chosen in such a way that it is not shorter than 2/3 of the length which is maximally possible in the measurement line within the measuring volume. Annex D indicates how targets on a wall can be used, along with carefully adjusting the laser tracker position, to achieve the effect of the measuring volume above in figure 2. 6.4.4
Derivation of test results
For all 105 measurements, calculate each length measurement error, EL, by calculating the difference between the indicated value and the calibrated value of each reference length (where the calibrated value is taken as the conventional true value of the length). The indicated value of a particular measurement of a calibrated test length may be corrected by the laser tracker to account for systematic errors, or thermally induced errors (including thermal expansion) if the laser tracker has accessory devices for this purpose. Manual correction of the results obtained from the computer output to account for temperature or other corrections shall not be allowed when the environmental conditions satisfy the conditions of 5.1. For each of the 105 length measurement errors (E0 values), calculate a corresponding MPE value (E0, value) based on the manufacturer’s MPE specification.
MPE
NOTE: The manufacturer’s MPE specification will, in general, be a formula.
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7 7.1
Compliance with specification Acceptance tests
The probing performance of the Laser Tracker is verified if: ⎯ the probe form error, PF, is not greater than the relevant maximum permissible probe form error, PF, MPE, as specified by the manufacturer and taking into account the uncertainty of measurement according to ISO 14253-1 and 23165-LT, and ⎯ the probe size error, PS, is not greater than the relevant maximum permissible probe size error, PS, MPE, as specified by the manufacturer and taking into account the uncertainty of measurement according to ISO 14253-1 and 23165-LT. If any of the probing tests fails, repeat the measurement at that position 3 times, attempting to replicate the measurement locations. All three of these repeated tests must be successful.
The two-face (probing location error) performance of the Laser Tracker is verified if: ⎯ the probe location error, PL, is not greater than the relevant maximum permissible probe location error, PL, MPE, as specified by the manufacturer and taking into account the uncertainty of measurement according to ISO 14253-1 and 23165-LT. A single failure of a two-face test is permitted. If one of the two-face tests fails, repeat the measurement at that position 5 times. All five of these repeated tests must be successful.
The length measuring performance of the Laser Tracker is verified if : the length measurement errors (values of EL), are within the maximum permissible error of length measurement, EL, MPE, as specified by the manufacturer, taking into account the uncertainty according to ISO 14253-1 and ISO/TS 23165-LaserTracker, No more than 5 of the 105 test lengths may be outside of specification. For any such length, 5 repeated measurements of any failed length must each be within the specification.
7.2
Reverification tests
As in Clause 7.1, but specifications are made by the user (following manufacturer's procedures).
8 8.1
Applications Acceptance test
In a contractual situation between a manufacturer and a user such as that described in a: ⎯ purchasing contract, ⎯ maintenance contract, ⎯ repair contract,
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⎯ renovation contract, or ⎯ upgrading contract etc., the acceptance test specified in this part of ISO 10360 may be used as a test for verifying the performance of the Laser Tracker used for measuring linear dimensions in accordance with the specification for the stated maximum permissible errors, E0, MPE, PF, MPE, PS, MPE, and PL, MPE, as agreed upon by the manufacturer and the user. The manufacturer is permitted to specify detailed limitations applicable for E0, MPE, PF, MPE, and PS, MPE and PL, MPE. If no such specification is given, E0, MPE, PF, MPE, PS, MPE and PL, MPE apply for any location and orientation in the measuring volume of the Laser Tracker.
8.2
Reverification test
In an organization's internal quality assurance system, the performance verification described in this part of ISO 10360 can be used as a reverification test to verify the performance of the Laser Tracker used for measuring linear dimensions in accordance with the specification for the maximum permissible errors, E0, MPE, PF, MPE, PS, MPE, and PL, MPE, as stated by the user. The user is permitted to state the values of, and to specify detailed limitation applicable to, E0, MPE, PF, MPE, and PS, MPE. NOTE 1 The tester accounts for the test uncertainty according to ISO 14253-1; accordingly a reverification test (where typically the tester is the user) may have a different conformance zone than in an acceptance test. NOTE 2 In acceptance testing, the conformance zone is derived from the manufacturer’s specifications. In reverification testing, the reverification limits may be derived from the user’s metrological needs.
8.3
Interim check
In an organization's internal quality assurance system, a reduced performance verification may be used periodically to demonstrate the probability that the Laser Tracker conforms with specified requirements regarding the maximum permissible errors, E0, MPE, PF, MPE, PS, MPE and PL, MPE. The extent of the performance verification as described in this part of ISO 10360 may be reduced by using fewer measurements and positions (see Annex E). NOTE This International Standard is primarily concerned with acceptance and reverification testing. Interim testing is often associated with quality assurance.
9
Indication in product documentation and data sheets
The symbols of Clause 0 are not well suited for use in product documentation, drawings, data sheets, etc. Table 5 gives the corresponding indications which are also allowed. Table 5 — Symbols and corresponding indications in product documentation, drawings, data sheets, etc. Symbol used in this document
Corresponding indication
E0
E0
PF
PF
PS
PS
PL
PL
E0, MPE
MPE(E0)
PF, MPE
MPE(PF)
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Symbol used in this document
Corresponding indication
PS, MPE
MPE(PS)
PL, MPE
MPE(PL)
© ISO 2010 – All rights reserved
ISO/WD 10360-10
Annex A (normative) FORMS
Form 1 General Specifications and Rated Conditions RATED CONDITIONS Measurement Envelope Distance (Range) Horizontal Angle (Azimuth) Vertical Angle (Elevation / Zenith) or Length x width x height (Prismatic Volume) a.
b.
c.
Min. ______ m Min. ______ deg Min. ______ deg
Max. ______ m Max. ______ deg Max. ______ deg
______ m by ______ m by ______ m
Temperature Range Operating Thermal gradient limits
Min. ______ C o Max. ______ C/m
Max. ______ C o Max. ______ C/hr
Humidity Range Operating
Min. ______ %RH
Max. ______ %RH
Barometric Pressure Range Operating
Min. ______ mm Hg
Max. ______ mm Hg
o
o
d.
Ambient Light: The manufacturer shall identify conditions, if any, under which ambient light degrades specifications.
e.
Electrical
Voltage ______ V Frequency ______ Hz Transient max. ______ V
f.
Allowable orientations (vertical, horizontal, etc.)
________________________
g.
Probe type: The probe diameter and reflector type (e.g., cube corner, glass prism) used during performance testing shall be specified. Diameter ______ mm Reflector type ____________
h.
Reference artefact CTE CTE uncertainty
-6 o
Min. ______ 10 / C
Current ______ A Surge/sag ______ V Transient duration ______ s
-6 o
Max. ______ 10 / C -6 o Max. ______ 10 / C
i.
Sampling Strategy: The manufacturer shall state the measurement acquisition time (averaging time) and sampling frequency (points per second) to meet specification. Acq. time ______ s Frequency ________ points/s
j.
Warm up time Warm up time ______ minutes
LIMITING CONDITIONS o
o
k.
Temperature Range
Min. ______ C
Max. ______ C
l.
Humidity Range
Min. ______ % RH
Max. ______ % RH
m.
Barometric Pressure Range
Min. ______ mm Hg
Max. ______ mm Hg
© ISO 2010 – All rights reserved
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Form 2 Manufacturer’s Performance Specifications and Test Results (All Units µm)
Length Errors
E0, MPE E0 Pass/Fail PS, MPE PS
Probing size and form errors
Pass/Fail PF, MPE PF
As different MPE's are permitted for different tests, this table may be extended to accommodate the complete specification.
Pass/Fail PL, MPE Probing location errors
PL Pass/Fail
Test Performed by Date Serial number Final test results (Pass/Fail)
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Annex B (normative) CALIBRATED TEST LENGTHS
Calibrated Artifacts: Gage Blocks, Ball Bars
Scale bars: End-to-end distance of spheres in the nests is calibrated
Rigid nests: Center-center distance determined from traceable measurement + short bi-directional length.
Rail or carriage system:
Location of different instances of a sphere or nest + short bi-directional length.
[A paragraph discussing the addition of a short bi-directional measurement to a uni-directional measurement will be added here].
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Annex C (normative) THERMAL COMPENSATION OF WORKPIECES
Measurement of a synthetic test length for proportional consideration of the thermal specimen expansion The acceptance and reverification of laser trackers close to the practice requires the measurement of large test lengths which can easily be established in situ with the aid of a calibrated laser interferometer (see Annex A). Test lengths "in air“ with a thermal expansion coefficient of approx. 1·10−6/K place, however, lower demands on the accuracy of the temperature determination compared to test lengths on gauge blocks of steel with a thermal expansion coefficient of 11,5•10−6/K. In the first case, an error of 1 K causes a change in length of approx. 1 μm per meter. When a steel gauge block is measured, the same temperature deviation of 1 K would, however, cause a change in length of 11,5 μm per meter. In addition it can, in some situations, be advantageous to use, for the realization of large lengths, artefacts with a small thermal expansion coefficient to reduce influences resulting from the fact that the artefact is not in thermal equilibrium. This means that in cases in which the test length is not made of a material with a thermal expansion coefficient between 8·10−6/K and 13·10−6/K and in which the influence of the temperature on the length is smaller than 2·10−6/K, a mathematical correction of the length measurement errors is required which allows for the thermal expansion of an artefact with a normal thermal linear expansion coefficient when the length measurement error of an artefact is determined. For this purpose, a "synthetic“ test length is measured which is at least half as long as the longest side of the measuring volume. With a calibrated reference interferometer, which has been traced back and which may also be the calibrated interferometer of a second laser tracker, a test length between two ball nests is established. Air temperature, air pressure and air humidity are measured by the weather station of the reference interferometer and, thus, the refractive index of the air is determined and the refractive index of the test length compensated. The measurement result is the calibrated length L of the test length. The length L is now used to calculate a "synthetic“ test length LS, equivalent to the length of a gauge block with the thermal expansion coefficient of exactly αS = 11.5 μm/m/K. The effect of this calculation is that the test length is being changed in such a way that it corresponds to a length with a thermal expansion coefficient of 11,5 • 10-6/K. LS = L x [1 - αS x (T-20°C) ] = L x [1 – (11,5 x 10-6) x (T-20°C) ] The specimen temperature T required for the calculation is measured with a calibrated thermometer on a piece of steel and not with the aid of any temperature measuring system delivered with the laser tracker. The piece of steel is in thermal equilibrium with its environment. After that, the "synthetic“ test length between the two ball nests is measured with the laser tracker to be tested. For this purpose, it is recommended to install the laser tracker at a short distance and in direct extension to the test length. As thermal expansion coefficient, αS = 11.5·10-6/K must be entered for the specimen. For the laser tracker, the test length thus seems to be made of steel. To compensate the thermal expansion of the specimen, the temperature of a piece of steel which has reached thermal equilibrium with its environment, is measured – as above - with the sensor for the specimen temperature. If the laser tracker is not equipped with a sensor of its own for the specimen temperature, it must be proceeded as in usual operation. The measurement of the "synthetic“ test length with the laser tracker is repeated three times. The "synthetic“ length measurement error ES results from the difference between the test length La, measured with the laser tracker, and the "synthetic“ test length LS. ES = La – LS For proportional consideration of the thermal expansion of the specimen during testing of the length measurement error, the mean synthetic length measurement error ESM = (ES1+ES2+ES3)/3 is required and added in proportion to the length to all other length measurement errors. For this purpose, an individual correction value Eki is calculated for each test length Lr. EKi = Lr x ESM /LS This section has been taken from the VDI/VDE document – needs further discussion
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Annex D (informative) ACHIEVING THE ALTERNATIVE MEASURING VOLUME
For testing of the length measurement error it is permitted to arrange all measuring lines e.g. in one plane. In that case, before test lengths along a measuring line are measured, the laser tracker must each time be newly positioned so that the relative relation between laser tracker and measuring line with respect to position and orientation is preserved. Figure D1 shows for the recommended measuring volume of 10 m x 6 m x 3 m a possible plane arrangement of the measuring lines with changing positions for the laser tracker, equivalent to the measurement of test lengths from a permanent position as shown in Figure 3 (see clause Fejl! Henvisningskilde ikke fundet.).
Figure D1: Example of a plane arrangement of the measuring lines for testing of the length measurement error. The laser tracker is standing on changing positions. A measuring and test arrangement as shown in Figure D1 can be realized with the aid of stable tripods or by means of a stable wall. It is, for example, possible to mount magnetic nests for spherically mounted retroreflectors on one wall. The distances between the nests then represent the test lengths. If the distances have been calibrated before the laser tracker is tested, the distances have to be stable only for the duration of the test. It is recommended to calibrate the respective test lengths only immediately before a measuring line is measured and to determine them again for control immediately after the lengths have been measured with the laser tracker to be tested. For the acceptance test, a measuring volume of 10.000 mm x 6.000 mm x 3.000 mm (length x width x height) is recommended (see 4.2.3) in which 32 test lengths must be measured along eight measuring lines from a position outside the measuring volume, supplemented by three additional test lengths which must be measured "from the centre". For the recommended arrangement of the measuring line (see Figure D1) the following measures are obtained for the shortest and the longest length to be tested (see Table D1).
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Table D1: Shortest and longest test length along the measuring lines in figure.
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Annex E (informative) INTERIM TESTING
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