Surface shape development of the pitch lap under the loading of the conditioner in continuous polishing process

Abstract

Continuous polishing using the pitch lap is a key process in finishing large flat optical elements. The optical elements’ surface figure is primarily dependent on the surface shape of the pitch lap, which is controlled by a large‐size conditioner. However, underlying fundamentals of the process control is not yet clear, and it remains empirical and nondeterministic to date. In this study, a novel analysis model is proposed for exploring the surface shape development of the pitch lap under the conditioner loading. The analysis model divides the polishing time into a series of segments, in which the shape variation of the pitch lap due to viscoelastic creep is derived from the pressure distribution at the conditioner‐lap contact interface. Further, a contact model of the lap and conditioner is built to obtain the pressure distribution at the interface, and a novel creep model is proposed for the viscoelastic behavior of the pitch lap under the pressure. The analysis model combined with the contact and viscoelastic models can be used to explore the pitch lap shape development under various conditions and hence reveal the underlying fundamentals of controlling the lap shape by the conditioner.

Formation and changing principle of the dynamic shape of the pitch polishing lap under the loading conditioner in continuous polishing

“…to control the surface shape of the pitch lap by adjusting the conditioner's radial position on the pitch lap. The control principal has been thought that when the conditioner is moved outward, the contact pressure of the pitch lap increases in the outer zone but decreases in the inner zone, leading the surface shape of the pitch lap changes convexly, vice versa [13] .…”

“…It consists of two springs and two dashpots where a pair of spring and dashpot connected in parallel can be considered as a Kelvin submodel. That is, the Burgers Model is composed of three components including a spring, a dashpot and a Kelvin submodel connected in series [13,20] . The spring represents the recoverable elastic set of the creep, the Kelvin submodel represents the recovery viscous set, and the dashpot stands for the permanent viscous set.…”

Research on High‐Efficiency Curved Surface Polishing with Even Distribution of Slurry Based on Dielectrophoresis

“…In the domains of optics, aerospace, and semiconductors, surface roughness demands have surged to the nanometer level. [ 1–6 ] This aim can be met through ultra‐precision polishing. However, the surface curvature makes it difficult for the existing polishing methods to achieve uniform surface removal, which requires a lot of detection and correction during processing.…”