Precision Hole Drilling Using a Polychromatic, Bi-Modal Technique

Technical Report · Tue Jan 01 00:00:00 EST 2002

DOI:https://doi.org/10.2172/15002788· OSTI ID:15002788

Friedman, H

Rapid drilling of precision, submillimeter holes is needed for many industrial products including turbine blades, aircraft wings and fuel injectors. Recent results using ultra-short pulsed lasers shows promise but problems remain associated with poor beam quality, unexplained phenomena associated with deep holes and the difficult task of scaling these lasers to high average powers. This effort makes use of results obtained with inexpensive Diode Pumped Solid State Lasers operating in the near infrared (1064 nm) and the second harmonic (532 nm) to drill precision submillimeter holes with arbitrary shapes in metals and ceramics. These lasers operate in the ablative regime (incident flux = 0.1-1 GW/cm{sup 2}) with short pulse duration (<100 ns) to minimize the Heat Affected Zone. The high average power (300W {at} 10 kHz) of these achieves drilling times of the order of a second or less in millimeter thick substrates. The thermal diffusion depth of these pulses of only a micron and the ablative process removes much of the incident power. By operating just above the ablative threshold and increasing throughput by increasing repetition rate (and therefore average power), harmful thermal effects are minimized. The infrared beam, sized slightly smaller than the final hole diameter, rapidly removes the bulk of the material and allows an escape path for debris in the second step. The second step uses a much lower power, but near diffraction limited laser beam at the second harmonic wavelength. Laser coupling is better at the second harmonic wavelength that further reduces collateral thermal damage. This visible beam is focused to about 1/10 the hole diameter and is used to clean, shape and polish the sides of the hole. With this ''trepanning'' laser, both shape and cross section can be cut to the desired dimensions while maintaining a minimum HAZ.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 15002788
• Report Number(s): UCRL-ID-146727; TRN: US200420%%71
• Resource Relation: Other Information: PBD: 1 Jan 2002
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ACCURACY
CERAMICS
CROSS SECTIONS
DIFFRACTION
DIMENSIONS
DIODE-PUMPED SOLID STATE LASERS
DRILLING
HARMONICS
HEAT AFFECTED ZONE
LASERS
SUBSTRATES
TEMPERATURE DEPENDENCE
THERMAL DIFFUSION
TURBINE BLADES
WAVELENGTHS