22 research outputs found
Dynamic behavior analysis for a six axis industrial machining robot
The six axis robots are widely used in automotive industry for their good
repeatability (as defined in the ISO92983) (painting, welding, mastic
deposition, handling etc.). In the aerospace industry, robot starts to be used
for complex applications such as drilling, riveting, fiber placement, NDT, etc.
Given the positioning performance of serial robots, precision applications
require usually external measurement device with complexes calibration
procedure in order to reach the precision needed. New applications in the
machining field of composite material (aerospace, naval, or wind turbine for
example) intend to use off line programming of serial robot without the use of
calibration or external measurement device. For those applications, the
position, orientation and path trajectory precision of the tool center point of
the robot are needed to generate the machining operation. This article presents
the different conditions that currently limit the development of robots in
robotic machining applications. We analyze the dynamical behavior of a robot
KUKA KR240-2 (located at the University of Bordeaux 1) equipped with a HSM
Spindle (42000 rpm, 18kW). This analysis is done in three stages. The first
step is determining the self-excited frequencies of the robot structure for
three different configurations of work. The second phase aims to analyze the
dynamical vibration of the structure as the spindle is activated without
cutting. The third stage consists of vibration analysis during a milling
operation
Self-excited vibrations in turning: cutting moment analysis
This work aims at analysing the moment effects at the tool tip point and at
the central axis, in the framework of a turning process. A testing device in
turning, including a six-component dynamometer, is used to measure the complete
torsor of the cutting actions in the case of self-excited vibrations. Many
results are obtained regarding the mechanical actions torsor. A confrontation
of the moment components at the tool tip and at the central axis is carried
out. It clearly appears that analysing moments at the central axis avoids the
disturbances induced by the transport of the moment of the mechanical actions
resultant at the tool tip point. For instance, the order relation between the
components of the forces is single. Furthermore, the order relation between the
moments components expressed at the tool tip point is also single and the same
one. But at the central axis, two different order relations regarding moments
are conceivable. A modification in the rolling moment localization in the (y,
z) tool plan is associated to these two order relations. Thus, the moments
components at the central axis are particularly sensitive at the disturbances
of machining, here the self-excited vibrations.Comment: 8 page
Modélisation du perçage vibratoire sur UPA
Les unités de perçage automatiques ont été récemment associées à des technologies permettant de percer en mode vibratoire pour favoriser l'évacuation des copeaux métalliques lors des perçages d'empilages multi-matériaux. Après une présentation de l'apport du vibratoire en perçage, un état de l'art des systèmes vibratoires utilisés sur UPA sera présenté. Dans un deuxième temps, une modélisation du système vibratoire à oscillations forcées sera exposée. Des résultats expérimentaux seront confrontés au modèle obtenu afin de vérifier sa robustesse et d'évaluer l'efficacité du perçage vibratoire