SBIR-STTR Award

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 the process 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) than for the more common long pulse laser drilling ( > 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 speed and 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 and standard 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.

Benefits:
The ability to drill precise, high aspect ratio holes 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 and in the airframe industry. Small diameter precision holes have long been considered for the leading edges of airfoils (wings and stabilizers)for drag reduction, but lack of cost effective capability has stifled development of this concept Although these types of holes can be drilled on a limited, ideal condition basis, the time (schedule) and cost make it prohibitive to incorporate large numbers of these holes in concept designs. The benefit of consistent quality, high speed hole drilling on a virtually lights out 24/7 basis would enable these concepts to be a reality.

Program Objectives: Laser Fare has two objectives for the proposed Phase II SBIR program. The first involves gathering sufficient statistically significant data, based upon diagnostic examination of a laser trepanned test plate from each of the following sub-contractors: LASAG, Spectra-Physics, Trumpf, Lumonics, and Convergent. Each test plate will include 12,288 laser trepanned holes through an Inconel 600 coupon 635 micrometers (8m) thick. The second objective is the subsequent design, development, assembly, test, calibration, system qualification, and operational demonstration of a state-of-the-art Laser Hole Drilling System or íLHDSí". The LHDS developed shall be capable of rapidly drilling many millions of precision, cylindrical, 170 +/- 10 8m diameter holes, through Inconel 600, Inconel 718, or Hastalloy X plates 635 8m thick. The precision holes are required for the fabrication of injection heads for the Singlet Oxygen Generator (SOG) portion of the USAF ABL program. Laser Fareíªs goal will be to develop and demonstrate a LHDS capable of ultimately satisfying all aspects of the required hole quality and completing all SOG injection heads required for seven ABL systems within one year of production laser hole drilling.

Keywords:
Laser Drilling, Optical Beam Splitting, Heat Effected Zone, Hole Taper, Trepanning, Precision Holes, Hole Eccentricity, Lens