The ISO 10360 - Acceptance tests for CMMs
In 1994 the international standard ISO 10360 "Acceptance and reverication tests for coordinate measuring machines (CMMs)" had been established. This Norm describes detailed test procedures for the various applications of a CMM, such as Length measurement, Form inspection, use with and w/o Rotary Table etc.
Before purchasing a Coordinate Measuring Machine / CMM, it is certainly helpful to get familiar with the basics of this standard.
The following is a brief introduction into the ISO 10360, with some examples. It is not intended to be complete and some expressions have been simplified for better understanding. The original standards can be obtained for example from publisher Beuth, contact see links.
Some CMM manufacturers still publish specifications for their Coordinate Measuring Machines according to the old German standard VDI/VDE 2617 or according to the US-standard B89. You should however insist on specifications according to ISO 10360. Only then the performance of different Coordinate Measuring Machines (CMMs) from different makers can be compared.
ISO 10360-1 (2000) “Vocabulary”
The first part of this norm defines all relevant terms of coordinate measuring machines, for example "CMM", "Coordinate Measuring machine", "Probing system" or "Reference sphere". This part is not further elaborated here.
ISO 10360-2 (2001) “CMMs used for measuring linear dimensions”
This part of the norm can be applied for all Coordinate Measuring Machines. It describes the two basic specifications of a CMM:The "Volumetric length measuring error E" and the "Volumetric probing error P".
ISO 10360-3 (2000) “CMMs with the axis of a rotary table as the fourth axis”
The measuring errors of a Coordinate Measuring Machine used in combination with a rotary table are defined in this part of the standard.The specifications are the Four-axis errors FR (R = radial), FT (T = tangential) and FA (A = axial).
ISO 10360-4 (2000) “CMMs used in scanning measuring mode”
This part applies to Coordinate Measuring Machines with the capability of continuous scanning. It describes the measuring error in scanning mode.Most CMM makers specify the "Volumetric scanning probing error THP". Besides THP the norm also specifies THN, TLP and TLN.
ISO 10360-5 (2000) “CMMs using multiple stylus probing systems”
Coordinate Measuring Machines are either equipped with a fixed probe head, which can carry a cluster of styli (for example all CMMs from Leitz). Or they work with one stylus attached to an articulating probe head. This part of the ISO 10360 standard describes the errors obtained, when measuring the same object with either different styli or by using just one stylus and articulating the CMMs probing system.Specifications are the "Multiple Stylus Location Error ML resp. AL", the "Multiple Stylus Form Error MF resp. AF" and the "Multiple Stylus Size Error MS resp. AS".
ISO 10360-6 (1999) „Estimation of errors in computing of Gaussian associated features“
The last part of the standard describes a method for testing the software used for computing associated features from coordinate measurements. This part is not further elaborated here.ISO 10360-2 (2001) „CMMs used for measuring linear dimensions“
This part of the norm applies to all Coordinate Measuring Machines. It describes the two basic specifications of a CMM
| Volumetric Length Measuring Error E | Volumetric Probing Error P | ||
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A set of 5 gauges has to be measured 3 times with one probing at each end, in 7 different directions in space. All results must be within specification "E". |
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A precision sphere has to be measured with 25 equally distributed probings. P is the range of all radii (sphere form). ( P = Rmax - Rmin) Note : In the previous version of this standard, the probing error was indicated as "R". |
| E specifies the CMM error when measuring distances or diameters. | P specifies the CMM error at Form measurements, i.e. when measuring Straightness, Flatness, Roundness, Cylinder form and Contours. | ||
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ISO 10360-3 (2000) "CMMs with the axis of a rotary table as the fourth axis"
The measuring errors of a Coordinate Measuring Machine / CMMs used in combination with a rotary table are defined in this part of the standard.
Four-axis error (Radial) FR, Four-axis error (Tangential) FT, Four-axis error (Axial) FA
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| 8 positions 0º - 720º |
7 positions 720º - 0º |
7 positions 0º - -720º |
8 positions -720º - 0º |
- Fix spheres A and B on the rotary table, (for example Δh = 400, r = 200mm)
- Establish center of the coordinate system in sphere B
- Measure sphere A in 14 positions: 7 from 0º to 720º, 7 from 720º to 0º.
- Measure sphere B in 14 positions: 7 from 0º to 720º, 7 from 720º to 0º.
At the last position (28) measure sphere A one more time. - Calculate range of X, Y and Z for Spheres A and B
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Four-axis error (Radial) FR = Max. range in X (A or B) Four-axis error (Tangential) FT = Max. range in Y (A or B) Four-axis error (Axial) FA = Max. range in Z (A or B)
Important: If you want to measure heavy parts on a rotary table, you should ask for Four-axis errors according to ISO 10360-3 of the RT under load.
Example: CMM with RT - Four-axis error evaluation according to ISO 10360-3
| Nr. | Position | Test sphere A | Test sphere B | ||||
| XA | YA | ZA | XB | YB | ZB | ||
| 0 | 0 | 401.6647 | 0.0000 | -398.,2276 | 0.0000 | 0.0000 | 0.0000 |
| 1 | 103 | 401.,6632 | 0.0011 | -398.2285 | - | - | - |
| 2 | 206 | 401.6631 | -0.0016 | -398.2270 | - | - | - |
| 3 | 309 | 401.,6625 | -0.0014 | -398.2292 | - | - | - |
| 4 | 412 | 401.,6652 | 0.0012 | -398.2285 | - | - | - |
| 5 | 515 | 401.6648 | 0.0009 | -398.2290 | - | - | - |
| 6 | 618 | 401.6660 | -0.0011 | -398.2270 | - | - | - |
| 7 | 721 | 401.6646 | -0.0018 | -398.2263 | - | - | - |
| 8 | 618 | 401.6658 | -0.0015 | -398.2273 | - | - | - |
| 9 | 515 | 401.6635 | 0.0006 | -398.2265 | - | - | - |
| 10 | 412 | 401.6623 | 0.0003 | -398.2260 | - | - | - |
| 11 | 309 | 401.6649 | -0.0011 | -398.2264 | - | - | - |
| 12 | 206 | 401.6640 | 0.0009 | -398.2278 | - | - | - |
| 13 | 103 | 401.6638 | 0.0004 | -398.2285 | - | - | - |
| 14 | 0 | 401.6655 | -0.0013 | -398.2277 | 0.0012 | -0.0011 | 0.0015 |
| 15 | -103 | - | - | - | -0.0005 | 0.0005 | 0.0007 |
| 16 | -206 | - | - | - | -0.0011 | 0.0009 | -0.0003 |
| 17 | -309 | - | - | - | 0.0014 | 0.0014 | -0.0010 |
| 18 | -412 | - | - | - | 0.0020 | 0.0000 | 0.0002 |
| 19 | -515 | - | - | - | 0.0001 | -0.0019 | 0.0012 |
| 20 | -618 | - | - | - | -0.0010 | -0.0010 | 0.0012 |
| 21 | -721 | - | - | - | 0.0017 | 0.0016 | 0.0009 |
| 22 | -618 | - | - | - | -0.0003 | 0.0003 | 0.0013 |
| 23 | -515 | - | - | - | -0.0009 | -0.0003 | -0.0008 |
| 24 | -412 | - | - | - | -0.0017 | -0.0018 | -0.0003 |
| 25 | -309 | - | - | - | 0.0011 | 0.0004 | 0.0006 |
| 26 | -206 | - | - | - | 0.0018 | 0.0015 | 0.0004 |
| 27 | -103 | - | - | - | 0.0005 | 0.0004 | 0.0014 |
| 28 | 0 | 401.6628 | 0.0020 | -398.2290 | -0.0018 | -0.0009 | -0.0007 |
| Four-axis- | FRA | FTA | FAA | FRB | FTB | FAB | |
| errors | 3.7µm | 3.8µm | 3.2µm | 3.8 | 3.5 | 2.5 | |
| Test result: | |||||||
| Four-axis error in radial direction | FR = | 3.8 µm | |||||
| Four-axis error in tangential direction | FT = | 3.8 µm | |||||
| Four-axis error in axial direction | FA = | 3.2 µm | |||||
ISO 10360-4 (2000) "CMMs used in scanning measuring mode"
High End Coordinate Measuring Machines / CMMs not only work in single-point-probing mode but can follow an unknown curve or contour continuously and can collect measuring points permanently during the movement. This feature is known as continuous scanning or High-Speed-Scanning. The ISO 10360-4 deals with the measuring error when measuring a part by using the "scanning" modus.
Scanning Probing Error THP
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A precision sphere of 25mm diameter is to be scanned with 4 defined lines. Then a sphere is calculated over all lines resp. over all the points taken. THP is the range of all radii (sphere form). THP = Rmax - Rmin = CMM form error in scanning mode. Note: The specification for THP must also include the total measuring time, for example THP = 1.5µm at 45 sec. THP indicates the CMMs scanning performance at high point density on a known path. The ISO 10360-4 further specifies: |
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| THP specifies the error of a 3D Measuring Machine at Form measurements, i.e. when measuring Straightness, Flatness, Roundness, Cylinder form or contour in scanning mode. | |
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ISO 10360-5 (2000) "CMMs using multiple stylus probing systems"
3D Coordinate Measuring Machines / CMMs are either equipped with a fixed probe head, which can carry a cluster of styli (for example all CMMs from Leitz). Or they work with one stylus attached to an articulating probe head. This part of the ISO 10360 standard describes the errors obtained by a CNC Coordinate Measuring Machine, when measuring the same object with either different probes or by articulating the probing system.
Multiple stylus errors of Location, Size and Form
| CMM with Fixed Probe Head | CMM with Articulating Probe Head |
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Test procedure to determine the CMMs multiple stylus errors:
A. Fixed probe head: 5 orthogonal styli of length L are qualified
B. Articulating probe head: 1 styli (length 20mm) with extension LE is qualified in 5 orthogonal positions.
A reference sphere is measured with each stylus resp. with each qualified position.
Every measurement takes 25 probings, total number of probings is 5 x 25 = 125.
Evaluations:
| Multiple Stylus Location error | ML resp. AL = Max. Range of the 5 centre coordinates in X, Y or Z. |
| Multiple Stylus Size error | MS resp. AS = Deviation from the certified sphere diameter (over all 125 points). |
| Multiple Stylus Form error | MF resp. AF = Form error of the calculated sphere (over all 125 points). |
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AS / MSSize error over 125 points (from 5 different styli (fixedhead) or 5 different orientations(articulating head) |
| Location error Biggest axial distance In X, Y or Z between the 5 measured centerpoints |
AF / MF Form error over 125 points |
Inspection of a part by different Coordinate Measuring Machines / CMMs, using multiple styli
| CMM with Fixed Probe Head | CMM with Articulating Probe Head |
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