Abstract
The investigation of the temperature rise of the joint, during heating in the high power diode laser pre-activation of the most common adhesives used in car body assembly, shows the necessity of a process temperature monitoring and control to obtain good and reproducible results.
For this purpose, a processing head for the temperature control during pre-activation process has been developed. The pyrometer is based on a dual wavelength technique to avoid the signal dependency on the material emissivity. The sensor system consists of sensor head, electronic card, data acquisition board and software. It has been designed taking into account the low radiant intensity (below 10 -2 [Wm -2 sr -1 mm -1 ]) at the temperature of the process (180 ± 20 °C), the low detectivity of the available detectors, and the transmission of the optics at the working wavelengths for which the radiant intensity curve is on the peek zone .
The pyrometer has been tested at different temperatures on different materials and shows a good S/N ratio over 150°C with a temperature measurement accuracy better than ±3%. At temperature lower than 60 °C the radiant intensity is low with respect to the noise and the measures are not reliable.