Dual-tool multiplexing model of parallel computer controlled optical surfacing

Abstract

Fabrication of large optics is a time-consuming process and requires a vast investment in manpower and financial resources. Increasing the material removal rate of polishing tools and minimizing dwell time are two common ways of reducing the processing time. Indeed, the polishing efficiency can be further improved if multiple tools are used at the same time. In this Letter, we propose a dual-tool deterministic polishing model, which multiplexes the dwell time and optimizes the run parameters of two polishing tools simultaneously. The run velocities of the two tools are coordinated by boundary conditions with a velocity adjustment algorithm, and the corresponding polishing paths are studied. We demonstrate this model with a simulation of polishing one segment of the Giant Magellan Telescope, where, with the proposed dual-tool multiplexing, the processing time of an ø8.4 m mirror has been reduced by 50.54% compared with that using two tools in a sequential schedule.

Generalized large optics fabrication multiplexing

“…The efficiency of the optics manufacturing process can be significantly improved with multiple fabrication tools by adopting a simultaneous CCOS multiplexing process [8] based on the mathematical dwell time treatment and multiplexing framework described by Ke et al [12]. The 8.4 m class large polishing machine (LPM) at the Richard F. Caris Mirror Lab, University of Arizona, consists of two tools with different sizes, as shown in Figure 1 (left).…”

“…In the dual-tool multiplexed case, Tool 1 is selected as the primary tool so that the run parameters of Tool 2 (i.e., dwell time and velocity) are adjusted and synchronized with the primary tool [12]. The dwell time calculated for each tool is synched in real-time.…”

“…The dwell time calculated for each tool is synched in real-time. Specifically, the velocity adjustment algorithm [12] has adjusted the velocities for Tool 1 and Tool 2 to be within their respective maximum speed. Also, appropriate tool paths for the multi-tool scenario are carefully studied.…”

“…Increasing the material (e.g., glass, ceramics, SiC mirror substrates) removal rate and minimizing dwell time have been the two common approaches for reducing the overall processing time [8][9][10][11]. As an innovative breakthrough, we introduced the concept that the CCOS efficiency can be improved when multiple tools are multiplexed [12]. This helps reduce the fabrication process time while gradually correcting the surface using multiple tools simultaneously to enhance the quality of the surface.…”

Advances in optical engineering for future telescopes

“…For example, polishing each segment of the Giant Magellan Telescope (GMT) to the specified accuracy consumed about one year. Modern precision optical surfaces are manufactured with Computer Controlled Optical Surfacing (CCOS) processes 5−7 , such as small-tool polishing 5,7 , bonnet polishing 8 , magnetorheological finishing, ion beam figuring 9,10 , etc. With these systems, there are two main categories of methods for improving polishing efficiency: increasing the material removal rate and minimizing the total dwell time.…”