Laser based micro texturing of freeform surfaces of implants using a Stewart platform

Abstract

Pulsed laser-based micro-texturing induces topographical and chemical modifications on surfaces that yield beneficial properties such as anti-microbial effect, micro-hydrodynamic bearing, and surface hardening. These properties find a multitude of applications in surface treatment and tribology. However, laser texturing of free form surfaces is a cost and effort-intensive process, specifically medical implants or ergonomically designed tools/devices. Such components often require numerically controlled 3 or 5 axes machines and sophisticated computer-aided manufacturing (CAM) software for precise tool movement. In this manuscript, the authors have designed, fabricated, and validated a jerk-free, cost-effective Stewart platform that works in tandem with an existing laser machining setup. A microcontroller and stepper motor based linear actuators were used to orient and translate the six degrees-of-freedom (DoF) platform. A customized computer program helped maneuver the workpieces (medical implants) for the micro texturing of the 3D surface profiles. As laser irradiation demands a time-invariant focal length for effective ablation, the platform maintains the focal length from the galvo-scanner of the laser machine to the workpiece while maneuvering the workpiece throughout the texture trajectory. To estimate the smoothness of the platform during motion, vibrational parameters were also measured and analyzed. Such cost-effective platforms may find applications in free form texturing in non-contact mode of machining as well as in metrology. Texturing was performed successfully on implants freeform surface with an average diameter of ~35–40 μm and depth of ~15–20 μm.