Melt ejection during laser drilling of metals

Voisey, K.T.; Kudesia, S S; Rodden, W S O; Hand, Duncan Paul; Jones, Julian D. C.; Clyne, T.W.

doi:10.1016/s0921-5093(03)00155-2

Cited by 87 publications

(34 citation statements)

References 16 publications

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“…Of interest to this study, is the laser drilling of holes which are micrometres in diameter, through different metals that measure millimetres in thickness -this is similar to the process which is used to drill cooling holes in turbine blades [2,3] . These holes are typically drilled using laser pulses with length of the order of milliseconds; where material removal is dominated by melt ejection [2][3][4] . In this process, absorption of the laser beam by the top surface of the material generates a melt pool; continued laser irradiation then leads to further heating and vaporization of the surface.…”

Section: Introductionmentioning

confidence: 99%

Application of high speed filming techniques to the study of rearwards melt ejection in laser drilling

Jones

Hann

Voisey

et al. 2017

Journal of Laser Applications

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Melt ejection is the dominant material removal mechanism in long, ms, pulse laser drilling of metals, a process with applications such as the drilling of cooling holes in turbine blades. Droplets of molten material are ejected through the entrance hole and, after breakthrough, through the exit hole. High speed filming is used to study the ejected material in order to better understand how this debris may interact with material in the immediate vicinity of the drilled hole. Existing studies have quantified various aspects of melt ejection, however they usually focus on ejection through the entrance hole. This work concentrates on rear melt ejection and is relevant to issues such as rear wall impingement. A 2kW IPG 200S fibre laser is used to drill mild steel. High speed filming is combined with image analysis to characterise the rearward-ejected material. Particle size and velocity data is presented as a function of drilling parameters. It is concluded that high speed filming combined with image analysis and proper consideration of process limitations and optimisation strategies can be a powerful tool in understanding resultant debris distributions.

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Section: Introductionmentioning

confidence: 99%

Application of high speed filming techniques to the study of rearwards melt ejection in laser drilling

Jones

Hann

Voisey

et al. 2017

Journal of Laser Applications

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“…With a laser wavelength of 1064 nm, the maximum material removal rate obtained was about 1 µm per pulse. Voisey et al studied single pulse drilling with a millisecond-pulsed Nd:YAG laser [21]. They determined particle size distribution, the angle of trajectory, molten layer thickness, and the temporal variation of melt ejection.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Laser-Engraved Hole Properties between Cold-Rolled and Laser Additive Manufactured Stainless Steel Sheets

et al. 2017

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Laser drilling and laser engraving are common manufacturing processes that are found in many applications. With the continuous progress of additive manufacturing (3D printing), these processes can now be applied to the materials used in 3D printing. However, there is a lack of knowledge about how these new materials behave when processed or machined. In this study, sheets of 316L stainless steel produced by both the traditional cold rolling method and by powder bed fusion (PBF) were laser drilled by a nanosecond pulsed fiber laser. Results were then analyzed to find out whether there are measurable differences in laser processing parts that are produced by either PBF (3D printing) or traditional steel parts. Hole diameters, the widths of burn effects, material removal rates, and hole tapers were measured and compared. Additionally, differences in microstructures of the samples were also analyzed and compared. Results show negligible differences in terms of material processing efficiency. The only significant differences were that the PBF sample had a wider burn effect, and had some defects in the microstructure that were more closely analyzed. The defects were found to be shallow recesses in the material. Some of the defects were deep within the material, at the end and start points of the laser lines, and some were close to the surfaces of the sample.

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“…Both methods generate a hole by ejecting molten material back through the hole entrance until breakthrough (Figure 3), after which molten material can exit through the bottom of the hole [1]. Some vaporisation occurs, and the recoil pressure generated can aid expulsion of molten material.…”

Section: Introductionmentioning

confidence: 99%

“…Some vaporisation occurs, and the recoil pressure generated can aid expulsion of molten material. Both processes usually result in resolidified material lining the hole [1] and the generation of heat affected zones [2] and surface spatter [3]. However, laser drilling is usually carried out using pulsed lasers, whereas continuous wave irradiation is often used for piercing.…”

Section: Introductionmentioning

confidence: 99%

Fibre laser piercing of mild steel – The effects of power intensity, gas type and pressure

Hashemzadeh

Powell

Voisey

2014

Optics and Lasers in Engineering

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Laser piercing is used to generate a starting point for laser cutting. The pierced hole is normally larger than the kerf width, which means that it cannot lie on the cut line. An experimental program investigating the piercing process as a function of laser and assist gas parameters is presented. An Nd:YAG fibre laser with a maximum power of 2 kW was used in continuous wave mode to pierce holes in 2 mm thick mild steel. Oxygen and nitrogen were used as assist gases, with pressures ranging from 0.3 to 12 bar. The sizes, geometries and piercing time of the holes produced have been analysed. The pierced hole size decreases with increasing gas pressure and increasing laser power. Oxygen assist gas produced larger diameter holes than nitrogen. A new technique is presented which produces pierced holes no larger than the kerf with and would allow the pierced hole to lie on the cut line of the finished product -allowing better material usage. This uses an inclined jet of nitrogen when piercing prior to oxygen assisted cutting.

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Melt ejection during laser drilling of metals

Cited by 87 publications

References 16 publications

Application of high speed filming techniques to the study of rearwards melt ejection in laser drilling

Application of high speed filming techniques to the study of rearwards melt ejection in laser drilling

Comparison of Laser-Engraved Hole Properties between Cold-Rolled and Laser Additive Manufactured Stainless Steel Sheets

Fibre laser piercing of mild steel – The effects of power intensity, gas type and pressure

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