Effects of laser mode and scanning direction on melt pool shape

Farooq, K.; Kar, Aravinda

doi:10.1063/1.370145

Cited by 11 publications

(3 citation statements)

References 17 publications

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“…It can be concluded from Figure 1 that, beyond 1 min of irradiation, the radius of the spheroidal areas affected tends to be independent of irradiation time. The growth As mentioned above, the area affected by femtosecond laser pulses is spheroidal in shape 24,36 and is shown as Φ in Figure 9. Point O is the focal point of the femtosecond laser.…”

Section: Discussionmentioning

confidence: 95%

Microstructure of the Crystals Generated in Borate Glass Irradiated by Femtosecond Laser Pulses

Yu¹,

Chen²,

Lu³

et al. 2006

Crystal Growth & Design

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Section: Discussionmentioning

confidence: 95%

Microstructure of the Crystals Generated in Borate Glass Irradiated by Femtosecond Laser Pulses

Yu¹,

Chen²,

Lu³

et al. 2006

Crystal Growth & Design

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“…The techniques using beam reflection, refraction and diffraction are developed. Simple beam stops have been used to change a laser beam shape and use it on surface coating (Steen, 1978), and a resonator has also produced a more uniform beam profile, although the actual distribution contained spikes at the corners (Farooq and Kar, 1999). This distribution was applied to steel during laser welding and compared with a Gaussian beam, the generated molten pool had a slightly flatter floor from the transverse direction.…”

Section: Introductionmentioning

confidence: 99%

Selective laser melting using holographic beam manipulation: influence of polypropylene molecular weight

Haworth

Tyrer

Zhou

2018

RPJ

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Purpose-There is a requirement to match selective laser melting (SLM) technologies to a wider range of polymeric materials, since the existing market for SLM powders is dominated by polyamide PA12. Drivers include the tailoring of physical properties to individual applications, or cost reduction. Polypropylene (PP) currently has limited use in SLM, so the potential use of PP materials of varying molecular weight (Mw) is explored here. Design / methodology / approach-PP polymers of differing molecular weight were characterised using a range of analytical techniques, including DSC, thermogravimetric analysis (TGA), rotational rheometry and real-time hot-stage (optical) microscopy. Findings-The techniques are sufficiently sensitive to distinguish molecular weight effects, notably in terms of material viscosity. The stable sintering region for SLM has been defined clearly. Some success was achieved in melting parts using some grades of PP, including higher molecular weight grades, which potentially offer improved mechanical performance. Research limitations / implications-The range of techniques (DSC, OIT and TGA) form an effective analytical package with which to consider new polymeric materials for SLM. Practical implications-High-MW PP polymers, in tape or powder form, have potential use in SLM processes, providing scope to enhance part properties in future. Originality / value-This is believed to be the first in-depth study noting the influence of PP molecular weight on important physical performance in a proprietary SLM process, using holographic beam manipulation (HBM).

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“…These include square beams produced using complex and expensive lens arrays or using a series of beam stops or masks. 15 Farooq and Kar 16 experimented with a resonator to produce a more uniform irradiance distribution. In practice, the actual distribution created was equivalent to four spikes at the corners, which produced a near rectangular beam print.…”

Section: Introductionmentioning

confidence: 99%

Laser weld pool management through diffractive holographic optics

Kell

Tyrer

Higginson

et al. 2012

Materials Science and Technology

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Conduction laser welding involves initiating a melt pool by exposure to high power laser induced light and controlled thermal conduction. Existing welding techniques generally provide enough energy to join the component but have no real control over the melt pool. This process can invariably lead to overheating in adjacent areas or even the melt pool itself, often causing unavoidable effects, such as ‘burn through’. The present work presents a procedure in which a desired melt pool shape is conceived, and a bespoke beam irradiance distribution is designed to match. The beam is shaped not by conventional lenses but by a diffractive holographic optical element (DHOE). The DHOE utilises holography to wholly create highly complex three-dimensional energy distributions through constructive and destructive interference. This technique allows novel beam irradiance distributions to be applied to conduction mode laser welding, with the melt pool transverse profile being shaped to a specific design. Holographic conduction laser welding has been shown to be successful and represents a significant step forward in the industry, as demonstrated in this case in both mild and stainless steels. The fusion zone is shown to be particularly influenced by the shape of the illuminating laser beam profile, and many of the welds demonstrate a highly novel weld profile because of this. The use of a bespoke beam irradiance distribution allows control of the heat flow to the workpiece, and this allows greater control over material migration due to surface tension effects. Many of the welds demonstrate unique surface solidification patterns directly linked to the beam profile used. The DHOE also presents a number of additional advantages, such as an increased usable depth of field, allowing for less stringent set-up tolerances. Comprehensive metallography has been performed on samples of these welds through the use of optical microscopy, electron microscopy, electron backscatter diffraction and energy dispersive (X-ray) spectroscopy. These techniques offer in depth analysis of crystal size, shape, orientation and phase. By incorporating DHOEs into a laser welding process, not only does the melt pool shape become controllable, but also the crystal growth is highly influenced. Many of the undesirable attributes of a conventional laser weld are reduced by using a beam distribution created by a DHOE, bringing the microstructure of the weld pool closer to that of the parent material.

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Effects of laser mode and scanning direction on melt pool shape

Cited by 11 publications

References 17 publications

Microstructure of the Crystals Generated in Borate Glass Irradiated by Femtosecond Laser Pulses

Microstructure of the Crystals Generated in Borate Glass Irradiated by Femtosecond Laser Pulses

Selective laser melting using holographic beam manipulation: influence of polypropylene molecular weight

Laser weld pool management through diffractive holographic optics

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