Additively manufactured flexure for astronomy instrumentation

Abstract

Additive Manufacturing (AM) has several potential advantages for astronomical instrumentation: particularly the ability to create custom parts with optimised geometries that cannot be produced with traditional manufacturing. The goal of the EU H2020 funded OPTICON (Optical Infrared Coordination Network for Astronomy; grant agreement 730890) A2IM (Additive Astronomy Integrated-component Manufacturing; PI H. Schnetler) project completed in June 2021, was to develop prototypes demonstrating these benefits. This paper presents the design and additive manufacture of a piezoelectric stack actuator driven, monolithic flexure for the active array of the Freeform Active Mirror Experiment (FAME). Flexure geometry had previously proved difficult to repeatedly produce and AM was considered as a potential solution. Two AM processes were used: powder bed fusion where metal powder is bonded using a laser, and binder jetting where powder is bonded using a polymer adhesive. A topology optimised, flexure hinged frame was designed based on the minimum feature size of each AM machine. This geometry was produced in Aluminium (AlSi10Mg), Titanium (Ti64Al4V) and Stainless Steel 316L. Porosity is a known issue with AM and Hot Isostatic Pressing (HIP): a post process whereby parts are subject to increased temperature and pressure was identified as a way of reducing this, thereby increasing the predictability of flexure behaviour and suitability for vacuum applications. Conformity of AM parts to their original geometry was assessed using external dimensional metrology. X-ray Computed Tomography (XCT) was used to identify internal porosity.

Development of a modular system to provide confidence in porosity analysis of additively manufactured components using x-ray computed tomography

“…The flexure was designed to hold a piezoelectric actuator and to impart an amplified displacement normal to the actuator displacement. The motivation to use AM to create the flexure was to explore the fidelity of AM to recreate the thin flexure hinges (0.3 mm) [33]. To accommodate the reference pin, which has three rows of hole diameters (30 µm, 50 µm, 90 µm and 120 µm), a hole is machined in the AM part, as shown in figure 1.…”

Understanding the role of additive manufacturing in the development of astronomical hardware

“…15 Unlike the metal counterparts, AM ceramic mirrors have been created using a variety of AM categories, fused deposition modelling 16 (FDM; filament), stereolithography 15 (SLA; liquid resin) and binder jetting 17 (powder + a binding agent). Beyond lightweight AM mirrors, there have been a number of investigations into AM for optical housings, 18,19 opto-mechanical structures 20 and compliant mechanisms [21][22][23] for astronomy or space-based applications.…”