An experimental investigation of laser drilling nitrile butadine (NBR) rubber

This paper focusses on understanding laser-NBR rubber interactions in particular the effect of laser wavelength and pulse width on material removal and thermal damage. Three lasers with wavelengths at 355 nm, 795 nm and 1064 nm and pulse duration at 30 ns, 10 ps and 130 fs, respectively, have been investigated for their optical absorption, heat conduction and their material removal mechanisms in high aspect ratio drilling of NBR rubber. It is interesting to find that under certain conditions, the ultrashort pulse lasers (both the femtosecond and picosecond lasers) did not lead to better results than the nanosecond UV laser in drilling hole profile (straightness and thermal damage), aspect ratio and amount of the ablated material re-deposition on the substrate surfaces. The results implied that there is heat conduction and thermal damage even with ultrashort laser pulses when the processing conditions are not appropriate. Firing laser pulses intermittently was shown to reduce thermal accumulation. Experimental studies showed that the 355-nm Nd:YAG laser (UV laser) achieved higher material removal rate with high aspect ratio as compared to the ultrashort laser pulses in drilling the NBR substrates.