The development of technologies and methods that improve the geometric, positioning, and dynamic accuracy of machines and robots is booming in the machine tool sector, which is used to shape metal parts or other solid materials. CIC marGUNE, the Cooperative Research Center for High-Performance Manufacturing, coordinates the MEDCON research line with the aim of increasing the precision of these machines, allowing manufacturers to optimize their product design and thus improve the competitiveness of Basque manufacturers. IK4-Tekniker, IK4-Ideko, Tecnalia, and Aotek are collaborating on this project.
The manufacture of large parts is a driving force in the machine tool industry, and its demand has challenged manufacturers to create competitive designs at ever-increasing scales while maintaining the level of accuracy of smaller machines. However, manufacturers lack the appropriate tools to practically evaluate the positioning accuracy of large machines.
The innovative methodology allows measurements to be obtained using the laser interferometer
“The most suitable measurement technology for this task, called 'multilateration,' is similar to GPS,” explains Eneko Gómez-Acedo, coordinator of the MEDCON research line at IK4-Tekniker. “It involves using a laser interferometer with tracking capabilities, high resolution, and low measurement uncertainty. The idea is to combine linear measurements taken sequentially from different positions by the interferometer. Then, a mathematical calculation is performed to determine the position and orientation of the tool tip, following a scheme similar to that used in satellite navigation systems.”.
When working with large machine tools, some limitations of this technology become apparent. Experiments have shown that the main obstacle to reaching the theoretical limit of multilateration accuracy is the instability of environmental conditions such as changing temperature gradients and the associated thermal behavior of the machine.
To overcome these difficulties, IK4-Tekniker has developed an innovative methodology by which a series of measurements can be obtained by combining the data obtained by the laser interferometer, with which the tool positions are obtained, with tilt measurements obtained with two electronic precision levels, used to measure the orientation of the tool tip.
A double benefit
In this way, the benefit is twofold, since “because the measurement is faster, the machine experiences less thermal deviation, and, in addition, the measurement is more economical. Furthermore, by using the precision levels in conjunction with the measurement, not only is the measurement time reduced, but a valuable indicator of the machine's stability over time is also obtained,” Gómez-Acedo emphasizes.
This methodology uses proprietary software developed by IK4-Tekniker which, in addition to performing the mathematical calculations for the measurement, recommends the best positions, calculated through simulation, in which the equipment should be placed to obtain the lowest measurement uncertainties.
The MEDCON research line has overcome the limitations of traditional machine tool verification techniques, which do not efficiently identify positioning errors across the entire work volume. Furthermore, the potential of the methodology developed by IK4-Tekniker will allow machine tool manufacturers to optimize their machine designs and enable users to perform periodic recalibrations to maximize product quality.
Source: SYNC Platform
