Programa

Large Machine tool 5 DOF Verification

Aitor Olarra
IK4 – Tekniker - Spain

Resumen de la ponencia

Nowadays, manufacturing of large parts is a driving force in machine tool industry. This demand has challenged machine tool builders to materialize designs in a new scale and even more, to keep the accuracy of these machines at the level of smaller machines.

On the other hand, builders lack appropriate tools to assess positioning accuracy of big machines in practical ways. The classical set of instruments used to setup the machine, such us precision levels, squares or linear interferometers with different kinds of optics is becoming obsolete when addressing this new family of machines.

The way to overcome these difficulties seems to be grounded on the way instruments are used more than in the development of new instruments.

The base measuring technology best suited for this task seems to be laser interferometry. Other devices such as Ball Bars are able to provide accurate measurements although they get impractical when verifying very large machines.

Nowadays more and more workshops have access to Laser Tracker devices. These are very handy during machine tool assembly or during the setup of jigs; on the other hand, they lack accuracy to verify machine tool positioning accuracy.

Lately several approaches have arisen that take advantage of the high accuracy of the laser interferometer while disregarding the information from the rotational encoders. The basic idea relies on combining linear interferometer measurements from sequential measurements in a multi-lateration scheme..

However, when experimenting with very large machine tools some limitations become evident. In house experiments have shown that the main obstacle to achieve the limiting accuracy of this approach is inestability of the ambient conditions and machine tool thermal behavior. Due to these factors, accuracies expected from pure multi-lateration become meaningless.

In this work an intermediate approach has been developed, where linear and rotational measurements are merged, so the maximum benefit of standard Laser Tracker devices is exploited.

Información sobre el ponente

Aitor Olarra received his Msc In Industrial Engineering by the Basque Country University in 2001. Then he joined IK4-Tekniker.
During the last ten years he has been involved in a wide variety of research projects, most of them related with precision engineering.
Nowadays he coordinates the research and developments in relation with dimensional metrology in IK4-Tekniker.