Laser milling: Pulse duration effects on surface integrity

Abstract

Laser milling of engineering materials is a viable alternative to conventional methods for machining complex microcomponents. The laser source employed to perform such microstructuring has a direct impact on achievable surface integrity. At the same time, the trade-offs between high removal rates and the resulting surface integrity should be taken into account when selecting the most appropriate ablation regime for performing laser milling. In this paper the effects of pulse duration on surface quality and material microstructure are investigated when ablating a material commonly used for manufacturing microtooling inserts. For both micro-and nanosecond laser regimes, it was estimated that the heat-affected zone on the processed surface is within 50 mm. When performing ultra-short pulsed laser ablation, the effects of heat transfer are not as evident as they are after processing with longer laser pulse durations. Although some heat is dissipated into the bulk when working in pico-and femtosecond regimes it is not sufficient to trigger significant structural changes.

A new process chain for producing bulk metallic glass replication masters with micro- and nano-scale features

“…Laser micromilling as a technology for manufacturing replication masters has attracted research (Dobrev, Dimov, & Thomas, 2006;Petkov, Dimov, Minev, & Pham, 2008; and industrial interest (M. Knowles, Kearsley, & Karnakis, 2007). Laser milling can be used to structure parts in a wide range of materials directly from CAD data via a layer by-layer machining strategy (Pham, Dimov, Ji, Petkov, & Dobrev, 2004).…”

Recent advances in micro- and nano-machining technologies

“…An accurate control of the laser parameters combined with the optimization of the scan pattern is the key to achieving high-quality laser micromilling. Petkov et al [79] proposed two major material removal mechanisms based on laser pulse length (i.e., ultrashort pulses and long pulses) in laser micro-milling. Ultrashort pulses refer to femtosecond and picosecond pulses, whereas long pulses comprise nanosecond and longer pulses.…”

Material micromachining using a pulsed fiber laser platform with fine temporal nanosecond pulse shaping capability

“…Compared to laser polishing, [12] this approach offers the additional advantage of completing the laser micro-milling process with pulses of shorter duration resulting in a decreased HAZ. Consequently, the integrity of the grain microstructure of the material is better preserved, [1] since layers of the thermally modified material of the large HAZ created at longer pulse duration are removed by this two-step process. Nevertheless, the agility of INO MOPA fiber laser allows the implementation of proper conditions for laser polishing in cases where deemed appropriate.…”

“…Such a laser process does not suffer from the problems related to tool wear or breakage, and the laser beam can be focussed to small dimensions in the 1-10 µm range, allowing for the production of micro-features. [1] In industrial laser milling, the material removal rate, which depends on scan speed, laser pulse energy and/or power, and pulse repetition rate directly determines the laser process throughput and the production rate, but also the quality of the laser-machined surfaces. [2] Sharp edges, smooth surfaces, minimum heat affected zone (HAZ), minimum recast and splatter are desirable characteristics.…”