Direct selective laser sintering (SLS) is a layered manufacturing technique that can produce fully dense, functional components in high performance metals. In this review paper, a first step is taken towards identifying and understanding some of the important physical mechanisms in direct SLS. This study not only provides an insight into phenomena observed during direct SLS processing of a variety of metallic materials but also helps in selecting those materials that are most amenable to direct SLS processing. The physical mechanisms discussed include oxidation, non‐equilibrium wetting, epitaxial solidification, metal vaporization, and oxide purification. Understanding these mechanisms is crucial for the design of direct SLS machines, process development, and process control.

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C O 2 laser micromachining provides a flexible and low-cost means for the rapid prototyping and manufacturing of miniaturized polymer systems such as polymethyl methacrylate (PMMA) microfluidic chip devices. In this paper, the relationships between the process variables (profile and depth of laser-ablated channels) and the process parameters (laser power and scanning velocity) are investigated. In contrast with the fabrication of 100–500μm wide channels reported in previous work, we focus on the fabrication of narrower channels using low laser power which can reduce the cost of the fabrication system and low scanning speeds. In this work, the laser power used for channel fabrication ranged from 0.45to1.35W and the scanning speeds ranged from 2to14mm∕s. The width of fabricated channels ranged from 44to240μm and their depths ranged from 22to130μm. Physical models were developed for predicting the depth and the profile of laser-ablated channels. The profile model incorporates the threshold fluence for CO2 laser ablation of PMMA to account for the partial ablation across the beam diameter. Our models are in excellent agreement with experimental results, with a maximum deviation of approximately 5%.