JLA Vol:4 Iss:1 (Combustion‐Assisted Laser Cutting of a Difficult‐to‐Machine Superalloy)
Authors:
P. A. Molian
M. BaldwinIn laser cutting, the largest single application of lasers in manufacturing, the assist gas plays an important role in affecting the cutting performance. The assist gas is usually oxygen or an inert gas. In this work a mixture of acetylene and oxygen was employed to create combustion reactions during CO2 laser cutting that enabled an improvement in the cutting speed, and cut quality of a difficult‐to‐machine superalloy. A comparison with laser cutting of a plain carbon steel under identical conditions was also made to determine the usefulness of combustion energy. Results indicate that both cutting speed and qual...
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JLA Vol:3 Iss:3 (Impact of International Laser Safety Standards on Manufacturers. Part II)
Authors:
Robert Weiner
Weiner Associates, Manhattan Beach, CAManufacturers have an increasing concern about the need to satisfy different laser safety regulations as they market their products throughout the world. While the national and regional laser safety regulations are similar, the differences which exist do impact the product. The requirements may vary in measurement criteria and limits for classification, engineering features, and manuals and labels, as well as for reporting, testing, and certification. This paper discusses the impact of the primary differing requirements on specific product types and describes the manner in which the laser safety standards are being implemented.
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JLA Vol:3 Iss:3 (ANSI Z136.2 Update: Ocular Effects of Laser Infrared Radiation)
Authors:
William T. Ham
Harold A. Mueller
Division of Biome´dical Engineering, Department of Biostatistics, Virginia Commonwealth University, Richmond, VirginiaLaser radiation employed in fiber optic communications systems is a possible hazard to the eyes of personnel working with or maintaining such equipment. To investigate the potential hazard of infrared laser wavelengths centered around 1550 nm we exposed the corneas of 12 Dutch belted rabbits to a laser diode furnished by Bell Laboratories. Maximum power output through a 4‐meter fiber optic cable was 5.6 mW. Anesthetized and fully dilated rabbits were exposed for time durations of 1, 10 and 100 s to po...
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JLA Vol:3 Iss:3 (Determining Weld Quality in Pulsed Nd:YAG Laser Spot Welds)
Authors:
H. N. Bransch
Z. Y. Wang
J. T. Liu
D. C. Weckman
H. W. Kerr
Department of Mechanical Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1For pulsed Nd:YAG laser spot welding applications, the development of optimum welding procedures ought to include various measures of weld size and quality, such as weld diameter, depth, surface contour and porosity. A split‐specimen technique has been developed that, despite the small size of the welds, allows such measurements to be made faster and more accurately than the traditional metallurgical technique involving sectioning, polishing and etching. In the sp...
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JLA Vol:2 Iss:2 (Composition and Microstructure of Laser Beam Welds between Dissimilar Metals)
Authors:
V. P. Kujanpa¨a¨
J. P. Helin
T. J. I. Moisio
Lappeenranta University of Technology, Lappeenranta, Finland
G. J. Bruck
Westinghouse Electric Corp., Research and Development Center, Pittsburgh, Pennsylvania, U.S.A.An austenitic stainless steel AISI 304 and a low‐carbon steel 1018 were laser welded in the vertical‐up position to form a dissimilar metal joint, by varying the laser beam alignment, gap between the base metals, and filler metal (AISI 309). The welds were inspected visually and by optical microscopy, and composition profiles were measured using electron probe microanalysis. It was found that the ...
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JLA Vol:2 Iss:2 (Binary Phase Gratings for Materials Processing)
Authors:
Paul J. Patt
ArrayThe feasibility of using a diffractive optical element, a phase grating, as a beam handling device for use in industrial laser material processing is examined. The binary phase grating is an efficient beam splitting device and is useful in many materials processing operations (welding, cutting, soldering, drilling) where a high degree of parallelism could significantly improve process throughput. Overall efficiency of etched quartz binary gratings agrees well with published predictions (nominal 70–90%). Copies of the grating formed in PMMA (acrylic) survived preliminary life tests (more than 1000 9‐J pulses from a commercial multimode N...
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JLA Vol:2 Iss:2 (The Segmented Aperture Integrator in Material Processing)
Authors:
Richard L. Pierce
Spawr Optical Research, Inc., P.O. Box 1899, Corona, California, 91718‐1899A patented segmented mirror[1] transforms light beams into flat top intensity profiles for uniform effects in materials processing and testing.
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JLA Vol:2 Iss:3 (Erbium:YAG (2.94 μ<em>m) Laser Effects on Dental Tissues</em>)
Authors:
James A. Hoke
E. Jeff Burkes
Edward D. Gomes
Myron L. WolbarshtPast trials with soft and calcified tissues have demonstrated that long pulse train (2.5 μs) Er:YAG (2.94 μm) laser may be used to ablate tooth structure of human teeth. Determination of physical and thermal damage to surrounding tissue during removal of enamel and dentin is a primary objective of this study. Extracted human teeth with thermal probes imbedded in the pulp chambers were submitted to cavity preparation using an Erbium YAG laser with water mist. Wavelength selection as well as use of a water mist during the procedure resulted in efficient tissue...
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JLA Vol:2 Iss:2 (A Comparison of Methods for Accurate Image Centroid Position Determination with Matrix Sensors)
Authors:
Paul G. Backes
Warren H. Stevenson
School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907Optical methods for the measurement of position, part dimensions, or alignment are finding increased application in manufacturing operations. Several of these methods utilize analog or digital position sensitive detectors to find the centroid of an illuminated spot on the detector. The objective of this study was to determine the accuracy with which the centroids of a direct laser beam and a circular incoherent image could be determined using a matrix array sensor. Centroids were found using five different analytical methods. The results showed t...
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JLA Vol:2 Iss:2 (Laser Induced Photochromic Flow Visualization)
Authors:
Thomas McWaid
Ekkehard Marschall
Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106The photochromic flow visualization technique has been utilized to study several different liquid flows. The technique utilizes radiachromic dyes that can be dissolved in a number of liquids. The resulting dye‐solvent solutions remain colorless in the absence of ultraviolet radiation; however, the solutions turn dark blue when exposed to ultraviolet light. A nitrogen pulse laser has been constructed for use as source of ultraviolet radiation. When sharply focused, the emitted beam of ultraviolet light produces a very narrow, well define...
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