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GRANT

journal

ISSN 1805-062X, 1805-0638 (online), ETTN 072-11-00002-09-4

EUROPEAN GRANT PROJECTS | RESULTS | RESEARCH & DEVELOPMENT | SCIENCE

Influence of the number of points on the contact scanning process during
measuring on the CMM

Dana Kubátová
Aneta Kaufnerová

Jan Kutlwašer

University of West Bohemia in Pilsen, Univerzitní 8, 301 00 PILSEN, CZ, kubatova@rti.zcu.cz

University of West Bohemia in Pilsen, Univerzitní 8, 301 00 PILSEN, CZ, akaufner@rti.zcu.cz

University of West Bohemia in Pilsen, Univerzitní 8, 301 00 PILSEN, CZ, kutlis@rti.zcu.cz

Grant: SGS-2019-008
Name of the Grant: Research and development for innovation in the field of manufacturing processes – Technology of metal cutting III
Subject: JR - Other machinery industry

Abstrakt Coordinate measuring machines (CMMs) have been a
major advance in the field of engineering measurement in recent
decades. They were designed to measure complex shaped parts in
the automotive and aerospace industries. The rapid development of
CMMs is based on the need for increasingly accurate dimensional
control. On average, every 10 to 15 years, manufacturing accuracy
increases by one level of IT. That is why it is necessary to constantly
improve and streamline measurement methodologies.

The purpose of the tests performed and described in this article is to
map the effect of the number of points when measuring the CMM
by contact scanning. The task of the tests was to find the optimal
setting of the machine while constantly maintaining the accuracy
and repeatability of measurements. If the optimal number of points
is found, the results of the experiment will lead to the optimization
of the measurement processes on the CMM.

Key words CMM points, fixed head, contct scanning, statistics,
measurement plans, calibration ring

INTRODUCTION

The main function of a CMM is the comprehensive measurement of
a workpiece, i.e. measuring its actual shape, comparison with the
desired shape, and evaluation of metrological parameters such as
size, shape, etc. It follows that a CMM is very frequently used for
quality control of the geometric tolerances of a product. Due to the
abundance of generally shaped surfaces, CMM is widely applied in
the measurement and quality control of these surfaces. With its wide
range of applications, CMM is a versatile quality control device
while maintaining high productivity.

This article describes and evaluates a test which aimed to map the
effect of the number of measuring points on the measured values of
the selected elements. Because the more information we have about
the measuring process, the more accurately and effectively we can
perform the measurements. And based on the results of the test, we
can then modify and thus streamline the measurement procedures in

the Metrology Laboratory of the University of West Bohemia in
Pilsen.

DESCRIPTION oF THE MACHINE

A CMM is a measuring system that includes tools for manipulating
a system of probes with the ability to determine the spatial
coordinates of a workpiece surface. Among the most important
features of the CMM are its movable machine construction, the
encoder system, the measuring head with the stylus and the
measuring software.

This article mainly focuses on the measuring head with contact
measurement. The sensing head and contact form the connection
between the machine and the part to be measured. It is used to
evaluate the position of the points captured on the workpiece
relative to the CMM coordinate system. Probe systems usually refer
to the number of axes in which they can operate. They are divided
into linear (1 D), planar (2 D) and three-dimensional (3 D) operating
systems.

The sensor mounting head can be fixed or rotatable. A fixed head
cannot be converted into a rotating head, but a rotating head can be
fixed.

EXPERIMENT DESCRIPTION

A fixed probe head was used in the test, as shown in Fig. 1. It was
fitted with a ruby ball stylus with a diameter of 1.5 mm Fig. 2

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