Industrial Laser Material Processing Research Articles

Modeling optical emission from a highly multi-mode step-index fiber via ray tracing and the limitations.

Geometric optics is widely applied for diverse optical simulations. In this work, we introduce an incoherent ray model to describe the laser beam radiation emitted from a highly multi-mode step-index fiber, which is frequently applied for industrial laser material processing. First the mathematical validation and the limitation of this model are demonstrated. Then we determine the ray density and the angular spectrum according to measured intensity profiles along the caustic. Furthermore, based on the determined information, we demonstrate the simulation and measurement of the laser beam shaped by an axicon telescope. Not only the reconstruction itself, but also the simulation with free form optics present significant agreements to the measurements. The reasonable modeling of a laser source via geometric optics enables the precise determination of laser radiation and propagation properties with refractive beam shaping technologies.

X-ray radiation protection is necessary for ultrashort laser processing

Study reveals an X-ray hazard being present in industrial laser material processing with ultrashort laser pulses but can be overcome by using steel as shielding material.

Laser drilling in gas turbine blades

AbstractDrilling applications represent about 5 % of the industrial laser materials processing applications. Cooling holes in gas turbines for aircrafts as well as for power plants are one of the main applications. The improvement of productivity has led to several drilling strategies with respect to laser sources (thermal drilling and ablation drilling), the beam handling, beam distribution, and handling of the work piece, all of which contribute to the overall efficiency of the process and a high productivity. We present the successful development and implementation of a combination of laser systems with different pulse durations for drilling complex 3D geometries (see Fig. 1).

Laser Markets in the USA

AbstractThe world market for industrial laser materials processing systems experienced the steepest decline in the history of this sector that dates back to 1970. Over the past 25 years, which show the greatest growth for the technology, only one other period, 1990–1992, experienced a decline (16%) in laser revenues. Even in the U.S.‐ centered recession of 2000 laser sales did not go negative because of the global nature of the market. From the middle of 2008 until the end of 2009 the world market for industrial lasers experienced a sudden and deep decline. For 2009 industrial laser sales declined 24% and industrial laser system revenues declined 20% (note that laser systems for photolithography are not included in this number). As this article will also show there are signs of recovery of the industrial laser market.

Monitoring of laser processing using induced current under applied electric field on laser produced-plasma

A new electrode circuit for measuring the induced current from laser plasma produced during laser material processing has been devised. The new electrode circuit has greatly increased the possible separation between the electrodes and the workable probing distance of the electrodes from the processed sample surface, namely 38 and 22 mm, respectively, sufficing the requirements of actual industrial laser material processing, avoiding direct contact of the electrodes with the big plasmas and profound sputtering. Several possible electrode configurations were investigated to accommodate the specific needs of the actual laser processing. It was shown that this technique is a very effective tool for accurately determining the moment of completion of penetration, as required in the laser piercing process. In contrast to this, the optical method currently in use cannot accurately determine the piercing completion moment due mainly to the disturbance from smoke arising at the processing point. A preliminary work using a CW CO 2 laser normally used in the actual industrial material processing was also made, resulting in a strong induced current signal corresponding to the laser pulse duration and frequency. The signal was successfully used for monitoring the penetration completion in a stainless steel plate drilling process. This reveals that this technique can be used for monitoring actual industrial material processing using high power lasers.

Laser Markets in the USA

AbstractThe world market for industrial laser materials processing systems in 2007 was in excess of $6.1 billion (Figure 1). An additional $2.5 billion is attributable to excimer lasers for photolithography applications, which will not be discussed in this paper. The market covered in this report is that for which lasers produce a physical or visual change in a material that is being processed in a manufacturing environment by automated or semi‐automated systems typically operated by semi‐skilled workers, on a routine production schedule.

Spectroscopic diagnostics of plasma during laser processing of aluminium

The role of the plasma in laser–metal interaction is of considerable interest due to its influence in the energy transfer mechanism in industrial laser materials processing. A 10 kW CO2 laser was used to study its interaction with aluminium under an argon environment. The objective was to determine the absorption and refraction of the laser beam through the plasma during the processing of aluminium. Laser processing of aluminium is becoming an important topic for many industries, including the automobile industry. The spectroscopic relative line to continuum method was used to determine the electron temperature distribution within the plasma by investigating the 4158 Å Ar I line emission and the continuum adjacent to it. The plasmas are induced in 1.0 atm pure Ar environment over a translating Al target, using f/7 and 10 kW CO2 laser. Spectroscopic data indicated that the plasma composition and behaviour were Ar-dominated. Experimental results indicated the plasma core temperature to be 14 000–15 300 K over the incident range of laser powers investigated from 5 to 7 kW. It was found that 7.5–29% of the incident laser power was absorbed by the plasma. Cross-section analysis of the melt pools from the Al samples revealed the absence of any key-hole formation and confirmed that the energy transfer mechanism in the targets was conduction dominated for the reported range of experimental data.

Hydrodynamical phenomena in the process of laser welding and cutting

The main objective of the paper is to outline the 'bridges' existing between the outcomes of fundamental researches and the results of investigations in the field of industrial laser materials processing (LMP). An analysis is presented on the models based on non-stationary hydrodynamic phenomena caused by deeply penetrating high power CW laser beam into materials. This is typical of laser welding (LW) and laser cutting (LC). A physical analysis pertaining to melt removal and melt layer instability mechanisms of gas jet assisted CW–CO2 laser fusion cutting is presented. The models deliberated here are melt squeezing out by gas pressure gradient, melt dragging by the friction force between melt surface and gas flow, formation of moving shelves at the cutting front. In case of high laser intensity, radiative flux interacts with material causing dynamical thermal transport onto the surface and phase transition at solid–liquid–gas interfaces. The solution is based on the non-stationary variables. Under these conditions the Mach number varies significantly due to laser intensity associated with laser flux energy instabilities. The connection among material surface temperature, laser intensity, laser flux and pressure in the plasma cloud is brought out. In addition, novel mechanisms based on hydrodynamics are proposed.

Binary Phase Gratings for Materials Processing

The 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 Nd-Glass laser) with no measurable change in performance. Conventional Small Outline (SO) IC electronic packages were both laser soldered and welded to substrates with one laser pulse. Beam splitting uniformity of desired images is within 10% for the original quartz gratings and for some PMMA copies. Conventional doublet achromat and planoconvex lenses are adequate for maintaining 10% uniformity of intensity. Splitting uniformity is experimentally evaluated with energy and focused spot (burn) tests on kapton (polyimide) and thin and thick metal samples using a pulsed industrial Nd laser.