COBEM99

SR20 Metrologia

Title:

CMM POSITIONING ERRORS CALIBRATION AND THE MEASUREMENT UNCERTAINTIES USING A HOLE BAR AND REVERSAL TECHNIQUE

Summary :

THE CALIBRATION AND UNCERTAINTIES MEASUREMENT OF COORDINATE MEASURING MACHINES HAVE BEEN EXTENSIVELY DISCUSSED DUE TO THE GROWING USE OF THESE INSTRUMENTS IN INDUSTRY. BESIDE THIS, THE DEVELOPMENT OF CALIBRATION METHODS FOR COORDINATE MEASURING MACHINE (CMM) USING MECHANICAL ARTEFACTS ENHANCES THE IMPORTANCE OF HAVING FASTER AND RELIABLE SYSTEMS AT LOW COST. DISCUSSIONS ABOUT SELF-CALIBRATION, ESPECIALLY THE USE OF REVERSAL TECHNIQUES FOR THE DETERMINATION OF STRAIGHTNESS, FLATNESS, CIRCULARITY AND ORTHOGONALITY ERRORS CAN BE EASILY FOUND IN TODAY S TECHNICAL LITERATURE. HOWEVER, NOT MUCH OR ALMOST NOTHING IS KNOWN REGARDING THE APPLICATION OF THIS MEASUREMENT TECHNIQUE FOR POSITIONING ERRORS. SELF-CALIBRATION IS A PROCEDURE WHERE ONLY LOCAL STANDARDS ARE USED AS REFERENCE AND THERE ARE MEASUREMENT UNCERTAINTIES DERIVED FROM ITS APPLICATION. THE UNCERTAINTY ANALYSIS SUPPLIES A QUANTITATIVE MEASURE OF THE QUALITY OF THE OBTAINED RESULT. THE PRESENT WORK PROPOSES A METHOD OF SELF-CALIBRATION FOR CMM POSITIONING ERRORS USING A HOLE BAR AND APPLYING THE PRINCIPLES OF THE REVERSAL TECHNIQUES. THE UNCERTAINTIES MEASUREMENT ORIGINATED FROM THE SELF-CALIBRATION PROCESS AND THEIR PROPAGATION THROUGH THE DEVELOPED MATHEMATICAL MODEL ARE ANALYSED ACCORDING TO THE REQUIREMENTS OF THE ISO GUIDE FOR THE EXPRESSION OF MEASUREMENT UNCERTAINTY [ISO, 1993]. KEYWORDS: SELF-CALIBRATION, REVERSAL TECHNIQUE, UNCERTAINTY MEASUREMENT, CMM

Author :

Giacomo, Benedito Di
Orrego, Roxana Martinez
Piratelli Filho, Antonio 0
Zirondi, Renata Belluzzo

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