Investigation of the Capabilities of Transverse Magnetic Field Controlled Laser-Induced Plasma Micro-Machining

Laser-induced plasma micro-machining (LIPMM) has proven a number of advantages in micro-machining due to reduced thermal defects, smaller heat-Affected zones, and larger aspect ratios when compared with conventional laser ablation. The present work explores the use of external magnetic fields to further enhance process outcomes in LIPMM. Specifically, machining characteristics and outcomes including plasma intensity, attainable aspect ratios, and surface quality will be explored through a theoretical and experimental study in different classes of materials in a transverse magnetic field controlled LIPMM. First, process improvement mechanisms are illustrated in terms of plasma confinement and laser absorption in transverse magnetic fields. A magnetic field redistribution analysis is performed to reveal the differences in the achievable enhancements in machining characteristics in terms of material characteristics. Second, a set of single-factor experiments is conducted to investigate the effects of the strength and direction of the magnetic field on machining capabilities in magnetic and nonmagnetic materials (410, 304 stainless steels and silicon). The experimental results show that plasma intensity and aspect ratios can be significantly increased in the presence of transverse magnetic fields. The greatest influence on machining capability is achieved in a magnetic material. In this case, plasma intensity and aspect ratios were increased by about 176% and 160%, respectively, when compared with other materials with a magnetic field strength of 0.1 T and a magnetic field direction parallel to the processing direction. Finally, the morphology and cross-section profiles of micro-channels have been measured for verifying the impact on the surface quality of transverse magnetically controlled LIPMM.