Interlaced Laser Beam Scanning: A Method Enabling an Increase in the Throughput of Ultrafast Laser Machining of Borosilicate Glass

Abstract

We provide experimental evidence that the laser beam scanning strategy has a significant influence on material removal rate in the ultrafast laser machining of glass. A comparative study of two laser beam scanning methods, (i) bidirectional sequential scanning method (SM) and (ii) bidirectional interlaced scanning method (IM), is presented for micromachining 1.1-mm-thick borosilicate glass plates (Borofloat® 33). Material removal rate and surface roughness are measured for a range of pulse energies, overlaps, and repetition frequencies. With a pulse overlap of ≤90%, IM can provide double the ablation depth and double the removal rate in comparison to SM, whilst maintaining very similar surface roughness. In both cases, the root-mean-square (RMS) surface roughness (Sq) was in the range of 1 μm to 2.5 μm. For a 95% pulse overlap, the difference was more pronounced, with IM providing up to four times the ablation depth of SM; however, this is at the cost of a significant increase in surface roughness (Sq values >5 μm). The increased ablation depths and removal rates with IM are attributed to a layer-by-layer material removal process, providing more efficient ejection of glass particles and, hence, reduced shielding of the machined area. IM also has smaller local angles of incidence of the laser beam that potentially can lead to a better coupling efficiency of the laser beam with the material.

Maskless, rapid manufacturing of glass microfluidic devices using a picosecond pulsed laser

“…The mean depth (D) and surface roughness (S a ) of the patterns generated using the 515 nm wavelength were observed to depend on many laser machining parameters, such as the laser spot size (2ω), pulse energy (E P ), pulse repetition frequency (PRF), scan velocity (v), hatch distance (ΔH), and number of laser passes. Also the laser beam scanning strategy may have a significant impact on these two surface parameters (D and S a ), as recently reported in Micromachines 54 . In general, too high PRF value, too low v, or too small ΔH may result in the generation of highly irregular surfaces that can contain thin glass fibres and glass particles partially fused to the surface.…”

“…The laser uses TruTops PFO software that enables the generation of various microfluidic patterns by raster scanning the laser beam. This scanning method was described in our other publication 54 . In TruTops PFO software the laser machining parameters, such as pulse energy (E P ), laser beam scan speed (v) and the number of laser passes (N), can be defined for each line and polyline.…”

Process Optimization for 100 W Nanosecond Pulsed Fiber Laser Engraving of 316L Grade Stainless Steel

“…and 79.8 μm to identify an optimized value for further studies. More details of this method of machining are presented in our previous work [19]. ).…”

“…For glass, the authors of [19,22] suggest that the IM increases laser coupling efficiency as a result of the smaller angle of incidence of the laser beam. This results from the perpendicular beam interaction to the surface in the case of IM as opposed to the SM, where the beam is incident on the wall of the previously machined groove.…”

“…Again, although the use of the single-line machining experiments for investigating parametric influence during laser interactions is well established [11,18], the "scaling up" of findings from single lines to the more industrially relevant area engraving has not been reported. This scale-up introduces a further key parameter set, namely, the laser beam scanning strategy, including interlacing, which has been reported as an effective process route for the machining of borosilicate glass [19], and more complex scanning patterns, such as halftone printing angles, that have been shown to provide a good surface polishing effect [20].…”