Drilling 170 Micron Diameter Holes

"The U.S. Air Force must develop the ability to rapidly drill many millions of 170 micron diameter holes through metal plates, to form injector heads as part of its ABL program. The holes must be high quality, non-invasive to the surrounding metal, and theprocess must be less labor and time intensive than present methods. As discussed in this proposal the physics of material removal with pulsed lasers is uniquely different for short pulse laser drilling (pulse duration 20 ps.). During the proposed Phase I program we will perform analytical modeling of both long pulse and short pulse laser systems. Also, we will down-select the best candidate laser(s), based upon anticipated drilling speedand hole quality. Next, we will assemble/locate prototype candidate laser systems. This prototype system(s) will drill 300 holes in each of three 316 stainless steel plates, 0.2 mm, 1.0 mm, and 5 mm thick. Statistically significant mean value andstandard deviation values of : (1) hole drilling time, (2) inlet diameter, (3) inlet eccentricity, (4) outlet diameter, (5) outlet eccentricity, and (6) surface roughness will be demonstrated in Phase I. The ability to drill precise, high aspect ratioholes at a highly productive, cost efficient rate is not only critical to the ABL lasing process, but it is also an enabling capability for other applications such as in the filtration industry