Product Code: ICA11_M1206

Micro-sculpting of Diffractive Scales on Metal Surfaces for Optical Position Encoders, the 'YAGboss' Process
Authors:
S. Giet, Heriot-Watt University; Edinburgh Scotland
M. Ardron, Renishaw plc; Edinburgh
F. Albri, Heriot Watt University; Edinburgh
M.D. Kidd, Renishaw plc; Edinburgh
R.R.J. Maier, Heriot Watt University; Edinburgh
J.D. Shephard, Heriot Watt University; Edinburgh
N.J. Weston, Renishaw plc; Edinburgh
D.P. Hand, Heriot Watt University; Edinburgh
Presented at ICALEO 2011

YAGboss, a process named after the UV YAG laser used to emboss fine features on metals, relies on a combination of surface and bulk effects to texture surfaces and achieve repeatable sub-micron features. Surface tension effects, also known as Marangoni flows, are a combination of laser-induced temperature gradients across the radiated area and temperature-dependent diffusion and chemical reactions occurring during irradiation at the surface of the material. Bulk effects comprise buoyancy, convection and thermal currents that take place below the surface. Both phenomena add up to form surface textures: indeed, they are responsible for the local movements of the molten material before it re-solidifies. In this paper, we describe and explain the influence of the laser, optical and cover gas parameters in the formation of micro-sculpted features with respect to the substrate composition. In addition, we present how YAGboss is applied as a single-step and reliable industrial manufacturing technique to create sinusoidal surface diffraction gratings (8µm period, 200±20nm deep features) with high repeatability. We show how these gratings are integrated in Optical Position Encoders (OPEs), and how they fit the quality requirements of demanding high accuracy position feedback devices. The use of diffractive scales YAGbossed on stainless steel and integrated in commercially available OPEs is discussed.