Manufacturing and measurement of freeform optics

A comprehensive analysis of literature pertaining to surface texture metrology for metal additive manufacturing has been performed. This review paper structures the results of this analysis into sections that address specific areas of interest: industrial domain; additive manufacturing processes and materials; types of surface investigated; surface measurement technology and surface texture characterisation. Each section reports on how frequently specific techniques, processes or materials have been utilised and discusses how and why they are employed. Based on these results, possible optimisation of methods and reporting is suggested and the areas that may have significant potential for future research are highlighted.

Surface texture metrology for metal additive manufacturing: a review

By synergistically combining additive and subtractive processes within a single workstation, the relative merits of each process may be harnessed. This facilitates the manufacture of internal, overhanging and high aspect ratio features with desirable geometric accuracy and surface characteristics. The ability to work, measure and then rework material enables the reincarnation and repair of damaged, high-value components. These techniques present significant opportunities to improve material utilisation, part complexity and quality management in functional parts. The number of single platform workstations for hybrid additive and subtractive processes (WHASPs) is increasing. Many of these integrate additive directed energy deposition (DED) with subtractive CNC machining within a highly mobile multi-axis machine tool. Advanced numerical control (NC), and computer aided design (CAD), manufacture (CAM) and inspection (CAI) help to govern the process. This research reviews and critically discusses salient published literature relating to the development of WHASPs, and identifies future avenues for research and development. It reports on state-of-the-art WHASP systems, identifying key traits and research gaps. Finally, a future vision for WHASPs and other hybrid machine tools is presented based upon emerging trends and future opportunities within this research area.

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Hybrid additive and subtractive machine tools – Research and industrial developments

This is the second part of the paper ‘Paradigm shifts in surface metrology’. In part I, the three historical paradigm shifts in surface metrology were brought together, and the subsequent evolution resulting from the shifts discussed. The historical philosophy highlighted the fact that the paradigm shifts must be robust and flexible, meaning that surface metrology must allow for full control of surface manufacture and provide an understanding of the surface functional performance. Part II presents the current paradigm shift as a ‘stepping stone’, building on the above historical context. Aspects of surface geometry will also have to cater for surfaces derived from disruptive application, i.e. structured and freeform surfaces are identified candidates. The current shift is presented in three aspects: from profile to areal characterization; from stochastic to structured surfaces; and from simple geometries to complex freeform geometries, all spanning the millimetre to sub-nanometre scales. In this paradigm shift, the scale of surface texture is beginning to approach some of the geometrical features in micro/nano electro-mechanical systems devices and is becoming one of the most important functionality indicators. Part II will contextualize the current shifts in the discipline of surface metrology, and cement surface metrology in place in the ultra precision and nanotechnology age.

https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2007.1873

Paradigm shifts in surface metrology. Part II. The current shift

Surfaces in Precision Engineering, Microengineering and Nanotechnology

Super-smooth finishing of diamond turned hard X-ray molding dies by combined fluid jet and bonnet polishing

High Energy Fluid Jet Machining (HEFJet-Mach): From scientific and technological advances to niche industrial applications

Dynamic multiphase modeling and optimization of fluid jet polishing process

Compliant grinding and polishing refers to a class of fine material processing methods relying on one or more system element being compliant with the workpiece surface in a controllable and reversible manner, thus being distinct from conventional rigid wheel grinding and polishing. The resulting surface adaptability greatly facilitates the ultra-precision machining of freeform surfaces, with a level of accuracy and productivity difficult to achieve with conventional rigid processing systems. Aiming for a comprehensive review of signal advances on this topic in the last decades, this paper introduces a multi-level compliance categorization system to sort between distinctive processes. For each category, various perspectives are explored that pertain to principles, methodologies, and physical properties such as material removal and surface integrity. Finally, relative merits are analyzed, together with a discussion of the outlook and future trends.

Compliant grinding and polishing: A review

The Precessions™ process polishes complex surfaces from the ground state preserving the ground-in form, and subsequently rectifies measured form errors. Our first paper introduced the technology and focused on the novel tooling. In this paper we describe the unique CNC machine tools and how they operate in polishing and correcting form. Experimental results demonstrate both the ‘2D’ and ‘2½D’ form-correction modes, as applied to aspheres with rotationally-symmetric target-form.

Anthony Beaucamp

Papers

Super-smooth finishing of diamond turned hard X-ray molding dies by combined fluid jet and bonnet polishing

High Energy Fluid Jet Machining (HEFJet-Mach): From scientific and technological advances to niche industrial applications

Dynamic multiphase modeling and optimization of fluid jet polishing process

Compliant grinding and polishing: A review

Use of the ‘Precessions’™ process for prepolishing and correcting 2D & 2½D form