Home > Tetronom - the 3D verification artifact for CMMs

Tetronom - the 3D verification artifact for CMMs

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article image Consists of six individual bars ensuring a tension-free and symmetrical set-up.

COORDINATE measuring machines (CMMs) play a crucial role in the quality assurance processes of modern manufacturing industries and it is important to verify its performance according to its nameplate accuracy.

The tetronom now offers the possibility to regularly verify the volumetric accuracy of a coordinate measuring system in a fast, efficient and traceable way. It is available from Metronom Pacific .

The verification and evaluation takes only a few minutes and gives the operator the confidence the equipment is within specification and the obtained measurement readings are correct.

The tetronom also complies with the ISO 10360 Part 2 standard and is traceable to national and international length standards. Each bar of the tetronom is calibrated every 12 months by a NATA approved laboratory.

The tetronom consists of six individual bars, which are assembled to form a tetrahedron, ensuring a tension-free and symmetrical set-up.

Each bar consists of a carbon fibre rod with two magnetic tips, which hold the high precision spheres.

The magnetic tips have a patented thermal compensation granting a very small expansion or contraction when used in environments without temperature control.

The high precision spheres (± 0.25µm) have a diameter of 1 1/2" (38.1mm).

The standard spheres for tactile measuring systems are manufactured in chrome steel, however, there are different types of spheres specific to the measurement equipment. For example, opaque spheres are used for laser scanners, optical targets for photogrammetric systems or theodolites, or spherical mounted reflectors (SMR) for laser trackers.

The tetronom is mounted on a 3-2-1 mount, which again ensures no tension is exerted to the tetrahedron. The 3-2-1 mounts can also be attached to magnetic chucks for fixation on steel tables.

The tetronom is suitable to evaluate CMMs, measuring arms, photogrammetric systems, laser trackers and laser-radar measuring systems

The tetronom is assembled at the CMM following a specific sequence by the CMM operator, who then measures the four spheres of the tetronom. The stylus position should not be changed during the measurement sequence. On each sphere a minimum of twelve points, sixteen preferable, have to be measured.

With the CMM software the X-Y-Z coordinates of the centre of each sphere has to be determined. These values are required to proceed with the evaluation.

Before the evaluation of the measured points can be performed, a database has to be set up within the tetronom with the analyser software. For the client or the operator, details of the measuring equipments have to be stored in this database.

The four sets of coordinates are then transferred or keyed into the tetronom analyser software for evaluation of the measurement equipment.

Based on the measurements performed on the tetronom, different parameters can be calculated and compared to the calibrated values of the artifact.

The tetronom analyser software offers the following functions:

* Management of different clients and operators

* Management of different measurement systems

* Management of different testing artifacts (single bar, ball-bar or tetrahedron)

* Saving of all the evaluation measurements and results in a database with multi-user access

* Graphical and alphanumerical display of the evaluation results, offering trend analysis of the measurement systems

* Fast evaluation of the measurement and simple interpretation of the result (green-yellow-red message depending of the result)

* Incorporated within the software is a wizard function that guides the operator from assembly of the tetronom to the measurement and to the evaluation of the results

* Easy export of the data and results to other systems

* Calculation of CMM deviation parameters (three linear scales and corresponding angles of the axis)

* Automatic generation of the evaluation report

* The software is protected by hardware dongle.

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