Main Researcher: Eduardo Cuesta González
Financing entity: Ministerio de Economía y Competitividad
Cod. Reference: DPI2012-36642-C02-01
Scope: National
Abstract: The main technological goal is to guarantee the reliability, oriented to the process, in dimensional measurement
with portable coordinate measuring systems, in particular, this project focused on Coordinate Measuring Systems
Arms (AACMM or CMAs) and Laser-tracker stations. They are portable measuring instruments that work under
the same metrological concept of Coordinate Measuring Machines (CMMs): geometrical entities are
reconstructed from the spatial coordinates of a series of points acquired with or without contact (laser
triangulation sensors). Subsequently, dimensions and deviations can be obtained by means of processing either
the captured points or the reconstructed entities (planes, spheres, cylinders, freeform surfaces, etc.).
This conceptual similarity has often led manufacturers to use the same control software with some modifications.
Most of them are actually constraints when working with portable measuring systems with regard to CMMs.
Although software works in the same way, the point acquiring is very different in one machine than in the other
one. In case of CMMs, point acquiring is completely automated: approaching direction to the points, path between
points, speeds, accelerations, contact forces (probe deflection when touch triggers), etc. are fixed. However, point
probing with portable measuring systems is carried out manually and, from that point of view, they are more
similar to a conventional measuring instrument, which entails the need for quality assurance.
Thanks to the previous experience on this subject of this research group, the need for obtaining, correcting and
modelling the knowledge of portable measuring systems (CMAs and laser tracker) has been identified in order to
ensure the measurement results and even to improve the accuracy and reliability of these measurement results.
To make matters worse, calibrations (both first calibration derived from the initial certification and the subsequent
periodical calibrations) are always performed externally by the manufacturer in their own facilities under no
standardized procedures. It can be stated that those calibrations do not guarantee measurements “in situ” (during
inspection process) made by different operators, with entities different from the entities of the calibration standard,
with different environmental conditions, etc.
With the methodology, tests and actions proposed in this project, the objective is to ensure the reliability and
quality of the measurement results made with CMAs and laser tracker, also achieving a significant reduction for
the uncertainty of measurement in the process (approaching to the uncertainty of calibration). The ways to
achieve these objectives involves various actions, such as analysing the contact forces during probing or the
influence of the positioning of the reflector by the user, developing procedures for estimating uncertainty of
measurement in the process, statistical analysing (ANOVA, r&R tests) and ultimately implementing a Knowledgebased
System (KBE) for assuring the reliability of Coordinate Measuring Arms and Laser Trackers. The KBE
system will include, in a computer application that monitors the portable measuring systems studied in this
project, all the aforementioned actions thus reducing the uncertainty of measurement during process.
Start date: 01/01/2013
End date: 31/12/2015
