The laser is used increasingly for surgery, as it has proved to be a finely controlled and relatively bloodless means of dissecting and destroying tissue. German physicist Rudolf Walther Ladenburg first observed stimulated emission inalthough at the time it seemed to have no practical use.
Thermal diffusivity, referenced in the above calculations, is a measure of the ability of the material to conduct heat. The lower the diffusivity, the longer the heat remains in the vicinity of the laser beam spot.
Metals with low boiling points produce a large amount of metal vapor, which could initiate gas breakdown and plasma generation in the region of high beam intensity, just above the metal surface. This plasma, which readily absorbs the laser energy, can partially block the beam as it passes, and create bubbles in the weld.
If the viscosity is high, these bubbles do Laser alignment theory escape before the molten metal solidifies, and creates voids in the weld. Zinc is an example of a typical low melting point metal. Although the melting point of metals does not have a significant effect on laser weldability, it must be reached during the initial absorption of energy.
Thus, low melting point metals require less laser energy and are easier to weld than those with a higher melting point. During this cooling, the material contracts, creating tensile stresses in the fusion zone.
To overcome this tendency, special precautions such as pre- and post-weld heat treating of the material is necessary. The low heat input of laser welding has other benefits, such as being able to use fixtures that do not need to withstand large thermal expansion forces, or to act as heat sinks.
Chemical reactions, such as oxidation or nitriding, with atmospheric gasses at high temperatures, can pose problems, particularly when the oxides or other elements formed have disassociation temperatures far above the melting point of the metal. The result is brittle, porous welds.
Covering the weld area with an inert gas such as argon or helium minimizes these reactions in most cases. For some materials, it may be necessary to weld within a sealed vacuum or inert gas chamber to prevent outside contamination.
For welding aluminum to hermetically seal semiconductor packages, the introduction of high silicon aluminum alloys vastly improves the welds by providing a solidification temperature significantly lower than the parent material.
During cooling, the outside interface cools fastest. As the boundary weld passes through the brittle phase, the core of the weld bead acts like warm taffy and yields with the shrinkages, preventing build-up of shrinkage stresses.
In pulsed laser welding, a short duration pulse, generally 1 milliseconds in duration, is used. These pulses, due to their short duration, put minimal heat into the part being processed.
When welding thin metals, pulse repetition rates can be as high as few hundreds of pulses per second or more. This method puts the least amount of heat into the part, but is generally slow, due to the high overlap requirement.
Pulse welds are especially effective on parts with high thermal conductivity, such as aluminum or copper. Continuous laser welds are done with lasers operating at high continuous power levels which remain at that level for as long as the laser is on.
Depending on the laser power level and focused spot size, the lasers can weld in either the conduction or keyhole modes. Primarily used for seam welding, the laser is used to heat and melt the materials being welded.
While these lasers put more heat into the part than the pulsed laser, they have significantly higher processing rates. In addition, to higher throughput, they can also be used to weld thicker parts that require deeper penetration.
Because significant overlap exists in the applicability of the two general types of laser welds, it is highly recommended that the potential user contact a reputable laser company and discuss the process with an applications engineer.When first invented, the laser was a solution looking for a problem to solve.
Early laser welding applications were reserved for only the most exotic applications, where no other welding . Back to Home-Built DPSS Laser Sub-Table of Contents.
Basic Home-Built DPSS Laser Information Introduction to Home-Built DPSS Laser Constructing a Diode Pumped Solid State (DPSS) laser at home is becoming an increasingly attractive project as the availability of the major components increases and their price drops to affordable levels.
"Laser" is an acronym for Light Amplification by Stimulated Emission of Radiation. A laser weapon can cut through steel while a flashlight cannot due to the fact that the laser . Laser Electronics (3rd Edition) [Joseph T.
Verdeyen] on alphabetnyc.com *FREE* shipping on qualifying offers. Best seller for introductory courses in Laser Electronics and Quantum Electronics. This is a practical approach to introductory laser electronics that emphasizes real-world applications and problem-solving skills over theory.
In laser alignment, the LOS of is established by a laser beam instead of a tight wire. the invisible LOS reference has no weight, cannot sag, kink, or be disturbed, nor is it a safety hazard. It constitutes a precise, unvarying reference, determining straightness to within thousandths of an inch.
MZA Associates Corporation has posted a video that summarizes the results of tests of the High Energy Fiber Laser (HEFL) Helicopter Beam Director Subsystem (HBDS) performed at the Air Force Research Laboratory (AFRL) Environmental Laser Test Facility (ELTF).