October 2009

By: Dr Jack Gabzdyl

The new generation of ns fiber lasers offer a range of highly flexible compact beam sources with tailored beam quality options to give a further dimension for process enhancement. Combined with increases in peak powers and pulse energies new applications beyond the standard marking and micro-machining have opened. MOPA designs with directly modulated seeds also allow control of the pulse shape and duration using a range of preset pulse waveforms adding further flexibility.

The fundamental beam quality has a significant effect on many applications and beam quality should be taken in the context of fitness for purpose.

A comparative study clearly shows the impact of the spot size on marking and drilling applications. Marks made by single pulses on anodised aluminium and drilled holes in ceramic show strong correlation between spot size and focused spot diameters. Changing the M2 from 1.2 to 3.2 more than doubles the effective spot size and hence mark feature.

Additionally the beam quality can impact the depth and hole profile that is achieved. The single moded pulsed laser generates a narrow and deep high aspect ratio hole while the higher moded lasers generate progressively wider and shallower holes given the same number of laser pulses.

Other characteristics such as pulse energy and peak power are also prime requirements for applications such as deep engraving and processing reflective materials.

Deep metallic engraving has conventionally been an application dominated by the high pulse energy, low rep rate lamp pumped YAG laser. Fiber lasers lacked both the peak power and pulse energy required by this application, but with >20kW peak power and pulse energy >1.25mJ SPI’s 40W HM laser is well suited to this application. The higher mode does result in a larger spot size but can be mitigated by using higher beam expansion and this is more than compensated for by the additional pulse energy and peak power available. The requirements for deep engraved marks in the engineering industry are growing and typical examples are alphanumeric codes and 2D data matrices. Modest material removal rates of circa 3mm3/min are achievable.

The higher peak powers can also enable the processing of reflective metal such as copper and brass.

Nanosecond fiber lasers are maturing and elevating themselves from just simple marking lasers to far more capable micromachining tools.

The above brief overview was extracted from its original abstract and paper presented at The International Congress on Applications of Lasers & Electro-Optics (ICALEO) in Orlando, FL. To order a copy of the complete proceedings from this conference click here

By: D. Reitemeyer1, T. Seefeld1, F. Vollertsen1, J. P. Bergmann2
1 BIAS – Bremer Institut für angewandte Strahltechnik GmbH, Bremen, 28359, Germany
2 Jenoptik Automatisierungstechnik GmbH, Jena, 07745, Germany

In materials processing with solid state laser sources a fiber optical waveguide is used to transport the
beam to the work station where the beam is focused on the work piece by a processing head. The high
beam quality of state of the art diode pumped solid state lasers allows concentrating the high output
power in a small focus diameter. This forwards the advantage of laser beam welding, the locally
concentrated energy input which enables precise processing.
Along with today’s high beam quality new challenges arise in the systems technology with increasing
requirements for the processing head. The high energy density in the laser beam path heats up the beam
guiding and forming optics, despite the fact that they have an absorption level below 1%. The
temperature increases when fume and spatter from the welding process are locally enhancing the
absorption on the cover glass which protects the beam outlet of the welding head. Figure 1a shows the
measured temperature distribution on the surface, at 5 kW a maximum rise of 170 K was detected.
This temperature rise influences the refractive index and the surface shape. Figure 1b shows the surface
deformation of a contaminated cover glass at 5 kW laser power measured by the fringe reflexion
technique. This influences the optical properties of the optics and thus the beam geometry at the work
piece. Figure 2 shows the influence on the focus’ position and diameter in dependence of the laser
power. The so called focus shift effect may influence the precision of the process.
At ICALEO 2009 a new way to analyze the influences on the focus shift will be presented. This work is
part of a project where BIAS and Jenoptik Automatisierungstechnik GmbH are working on new
approaches for systems technology for material processing with high brightness laser sources.

The above brief overview was extracted from its original abstract and paper presented at The International Congress on Applications of Lasers & Electro-Optics (ICALEO) in Orlando, FL. To order a copy of the complete proceedings from this conference click here

Welcome to Laser Insights

October 30, 2009

Laser Insights is a feature that gives insight into the very latest developments of Laser Materials Processing and the possible applications. These overviews are designed to give you insight into the content and applications of the papers presented at our conferences and workshops. LIA conferences and workshops are considered worldwide to be the best forum […]

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Surface Plasmon Polaritons for Micro and Nano-Texturing of Metal Surfaces

October 30, 2009

BY: L. Mellor, S.P. Edwardson, W. Perrie, G. Dearden, K.G. Watkins Laser Group, Department of Engineering, The University of Liverpool, Liverpool L69 3GQ, UK A study has been carried out on the production of micron and sub-micron features on the surface of a range of metallic materials through laser illumination. Possible application areas for such […]

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Prevention of porosity by oxygen in partial penetration laser and laser-gma hybrid welding

October 30, 2009

Prevention of porosity by oxygen in partial penetration laser and laser-gma hybrid welding can stabilize the laser welding process and then prevent the weld defects.

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Pulse Control improves the micromachining of hard materials

October 30, 2009

Pulse Control improves the micromachining of hard materials demonstrates a factor of two improvements in cutting time and material removal if pulse peak power, energy and shape are controlled and optimized

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Laser Beam Welding of Experimental Trip Steels

October 30, 2009

Laser Beam Welding of Experimental Trip Steels

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Hybrid Laser-GMAW Welding

October 30, 2009

Hybrid Laser-GMAW Welding has benefits including;Higher travel speeds and deeper penetration than conventional GMAW, Lower heat input and less distortion than arc welding, Less filler metal usage for a given thickness and smaller melt volume than arc welding, Greater gap tolerance than autogenous laser welding, Alloying addition and joint filling that is not possible with autogenous laser welding and can be used in industries such as; Steel, Stainless, Aluminum, Copper, Nickel / Inconel, Titanium, Zirconium, Aerospace, Automotive, Defense, Energy, Heavy Manufacturing, Oil and Gas

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On the Temperature Distributions and Thermal Stresses Induced in Laser Solid Freeform Fabrication of Multi-material Structures

October 30, 2009

In many different multidisciplinary engineering applications such as biomedical applications inconsistent material properties are required in order to enhance mechanical properties and functionality of an object. Laser Solid Freeform Fabricationas, an additive manufacturing technique can be used to manufacture fully functional near-net-shape three dimensional objects directly from their CAD model by successive layer-by-layer deposition of metallic materials.

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Analysis of penetration depth fluctuations in single-mode fiber laser welds

October 28, 2009

Single mode fiber lasers are sensitive to penetration spiking power modulation and beam rotation can minimize this effect

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