The system they have developed is capable of measuring the temperature of machining or cutting processes in areas inaccessible to conventional techniques. Infrared thermography cameras cannot be used in these environments because there is no clear line of sight to the tool's cutting point, nor can thermocouples or other sensors be attached due to their deterioration and the difficulty of finding an accessible location. Instead, the researchers have overcome this challenge by using a fiber optic pyrometer (a pyrometer is an instrument capable of measuring temperature without contact with the object).
Fiber optics is a transmission medium that sends pulses of light to represent the data. Thanks to its small size (the fiber measures 62.5 microns), it can access very small areas. "To give you an idea, the average diameter of a young person's hair is about 100 microns," the researchers explain. In their case, they used a typical communications fiber, like those used to transmit high-speed signals in data networks.
The pyrometer determines the temperature of an object by the amount of radiation it emits: as the radiation increases, so does the temperature. It measures radiation in two different colors and calculates the temperature from the ratio of both signals. The system is calibrated so that it can “start measuring from 300 degrees and could reach up to 1,000 degrees because the fiber, which is made of silica, withstands very high temperatures,” explains Carmen Vázquez, professor in the Department of Electronic Technology at UC3M and coordinator of the project.
Obtaining data on temperature changes during cutting helps analyze tool wear. Consequently, “it’s possible to optimize tool life, improving productivity,” explains Carmen. Likewise, ensuring the surface integrity of the machined material is crucial; in most cases, temperature is an indicative parameter of the damage caused by machining.
This system is applicable in environments where machine tools are used to manufacture parts. It is relevant, for example, in the aerospace sector. In machining parts for engine components, it is very important “to avoid excessive temperatures during machining, which can lead to excessive residual stresses or phase changes related to poorer fatigue performance,” thus preventing potential problems during flight. Carmen Vázquez states that “the prototype could already be implemented in the field and be operating on different machines in the sector.”
The project researchers, in addition to Carmen Vázquez, are Alberto Tapetado, a doctoral student at UC3M; Henar Miguélez, a professor in the Department of Mechanical Engineering; José Díaz Álvarez, a professor in the Department of Aerospace Engineering; and Ernesto García, all from UC3M. The research was conducted within the framework of a National Plan project funded by the Ministry of Economy and Competitiveness and the SINFOTON-CM research program funded by the Community of Madrid. It was carried out by the Displays and Photonic Applications group of the Department of Electronic Technology, in collaboration with the Manufacturing Technologies and Design of Mechanical and Biomechanical Components group of the Department of Mechanical Engineering.
