1,721,640 research outputs found
Depth monitoring during laser ablation of ceramic coatings with self-mixing interferometry
No full textIn this paper self-mixing interferometry for measuring ablation depth during laser
percussion drilling of TiAlN coating is studied. The accuracy of self-mixing interferometry
measurements was investigated in a large processing range producing blind holes with
depths below and beyond the average coating thickness. The self-mixing measurements
were compared to a conventional measurement device based on focus variation
microscopy to evaluate the measurement error. The self-mixing signal defects as well as
measurement error classes were defined. The results depict that the measurement error
was independent from the processing condition and for 76% of cases it was below the
intrinsic resolution of the device (λ/2=0.393 μm)
Submerged laser microcutting of Mg alloys with ns pulsed green laser for biodegradable stents
Get PDFRemote cutting of Li-ion battery electrodes with infrared and green ns-pulsed fibre lasers
Get PDF"Thin sheet anode and cathode materials made in
composite structures constitute some of the most important
components of a Li-ion battery. These materials are currently
cut by punching technology, which shows degrading behaviour
as the tool wears out. A viable option for Li-ion battery
electrode manufacturing is the use of remote laser cutting.
However, the operation requires fulfilling both productivity
and quality aspects to substitute the conventional production
method. One of the most critical aspects in quality is the
clearance width, which is defined as the extent of the exposed
middle layer of the sandwich at the laser cut kerf. This work
investigates the quality aspects of laser cutting of Li-ion
electrodes when a green fibre laser source (λ=532 nm, τ=
1 ns) is used rather than the more traditional infrared (IR) fibre
laser source (λ=1,064 nm, τ=250 ns). The processing conditions
were investigated to reveal the technological feasibility
zones. Clearance width was studied within the technological
feasibility zones for all the material-laser combinations.
Results showed that high productivity criterion is met by the
IR system, since cutting speed could reach 30 m/min with
54Waverage laser power on both anode and cathode. On the
other hand, the green laser provided clearance width below
20 μm. In the best case, the clearance on anode could be
eliminated with the green laser system. Although the maximum
cutting speed was 4.5 m/min, upscaling of green laser
power can provide required productivity.
Microcutting of multi-layer foils with IR and green ns-pulsed fibre lasers for Li-Ion batteries
Get PDFLi-Ion batteries are crucial components in mobile devices that range from cellular phones to electrical vehicles. With the increasing demand in the market for these devices, manufacturers are required to reduce production cycle times. The main components of the Li-Ion batteries are anode and cathode foils, which are cut in required forms by punching. These materials consist of Cu sheets sandwiched between graphite layers for anode, and Al sheets sandwiched between Li metal oxide layers for cathode. In punching, the process quality degrades in time due to tool wear. This eventually causes machine down times for tool repair or change, which can increase the whole process cycle time drastically. Laser remote cutting based on ablation can be adequate solution to substitute the current technology, if the cutting edge quality and productivity can be matched to punching. This paper investigates laser microcutting of Li-Ion battery anode and cathode thin foils with ns-pulsed fibre lasers. These laser sources are cost effective and provide industrially robust operation. Two systems operating with 1 μm and 0.5 μm wavelength and 250 ns and 1 ns pulse durations respectively were compared. The cut kerfs were evaluated in terms of clearance, which is defined as the extent of the exposed middle layer of the sandwich (i.e. Cu or Al) at the laser cut kerf
A comparative study of femtosecond and nanosecond laser microcutting of AZ31 magnesium alloy stents
No full textMulti-material selective laser melting of Fe/Al-12Si components
Get PDFIn this work, a multi-material selective laser melting (SLM) prototype system is demonstrated with the capability of mixing two metallic powders at different compositions on demand. The flexible system can operate for in-situ alloying of different elements as well as producing composite materials. In this preliminary work, Fe/Al-12Si component manufacturing is demonstrated. Initially, pure Fe and Al-12Si powders are studied separately. At a second phase the 55/45 volumetric ratio of Fe/Al-12Si mixture is processed. Finally, deposition of parts composed of Fe, Fe/Al-12Si, and Al-12Si layers is carried out demonstrating the feasibility of the powder-bed fusion based additive manufacturing method for multi-material manufacturing
Micromachining with ns-pulsed fibre lasers: materials, applications and sectors
No full text"In today’s industrial micromachining applications lasers play a fundamental role. As a highly
flexible, versatile and non-contact tool lasers enable high precision machining on polymers,
metals, semi-conductors and ceramics. The introduction of commercial fibre lasers in the
market during the last decade resulted in a larger diffusion of lasers in the industry due to
their stability and ease of operation. Micromachining operations also benefited from the use
of solid state highly efficient lasers. This work gives an outlook on some of the key materials,
sectors and applications concerning pulsed fibre laser micromachining.
Micro laser metal wire deposition for additive manufacturing of thin-walled structures
Get PDFIn this work, the micro laser metal wire deposition (ÂμLMWD) process is studied as an additive manufacturing process for manufacturing thin walled structures with high aspect ratio. The developed ÂμLMWD system consisted of a flash-pumped Nd:YAG laser source operating with ms-long pulses and an in-house developed wire feeding system. Processing conditions were investigated for single and multi-layer deposition in terms of geometry, microhardness and material use efficiency. Thin-walled structures with aspect ratio up to 20 were manufactured successfully, where layer width was between 700 and 800 Âμm. In multi-layer deposition conditions, the material use efficiency was observed to be close to 100%. The microhardness over the build direction was homogenous. The results show that the ÂμLMWD process yields geometrical resolution close to powder-bed additive manufacturing processes, while maintaining the benefits of using wire feedstock
Manufacturing and characterisation of a wettability controlled microvalve with darkness/UV actuation
No full textA contactless microvalve actuation method through UV irradiation and darkness application was developed, based on the control of the capillary pressures created in microchannels. This paper reports the design and the manufacturing phases, along with the demonstration of the concept and characterization of a manufactured prototype. To realize the wettability
microvalve with UV/darkness actuation concept, commercially pure titanium sheet was microdrilled with a pulsed fiber laser system, then chemical etching was applied to remove spatter created during the laser process and finally anodic oxidation was employed to functionalize the microchannel surfaces with TiO2 nanotubes. The alternate application of UV and darkness
allows commuting between hydrophobic and hydrophilic states of the nanotubular surface. Two aims have driven the manufacturing parameters investigation: i) to reach contact angle values towards the extremes in the hydrophobic and hydrophilic regions, ii) to obtain smallest hole diameters possible. A prototype microvalve was in the end realized and tested. The
concept was validated, as switching from off to on, and on to off phases were achieved. The break pressure was measured and compared to the theoretical value. Finally the temporal behaviour of the wetting change under the UV irradiation as a function of contact angle was evaluated
Evolution of Laser Ablation Plume Measured by Self-Mixing Interferometry
No full textLaser ablation is the basis of most of the laser micromachining processes. Depending on the pulse duration, wavelength, intensity of the beam, as well as the material type, material removal may occur in the form of vaporization, melt expulsion, or direct sublimation. Most commonly material removal is accompanied by a plume formation. The characteristics of the plume can be analyzed to assess the ablation performance. Non-invasive optical methods for the purpose can be further exploited in industrial laser micromachining applications, if opportunely designed and implemented. This work uses an interferometric approach to investigate the optical path changes induced by the ablation plume formed during the laser percussion drilling of different metallic and ceramic materials. A self-mixing interferometer is installed inline to a laser micromachining setup composed of a ns-pulsed green fiber laser
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