Optical testing cryogenic thermal vacuum facility

The construction of a turnkey cryogenic vacuum test facility was recently completed. The facility will be used to measure and record the surface profile of large diameter and 540 kg optics under simulated space conditions. The vacuum test chamber is a vertical stainless steel cylinder with a 3.5 diameter and a 7 m tangent length. The chamber was designed to maximize optical testing quality by minimizing the vibrations between the laser interferometer and the test specimen. This was accomplished by designing the chamber for a high natural frequency and vibration isolating the chamber. An optical test specimen is mounted on a movable presentation stage. During thermal vacuum testing, the specimen may be positioned to + or - 0.00025 cm accuracy with a fine adjustment mechanism. The chamber is evacuated by a close coupled Roots-type blower and rotary vane pump package and two cryopumps. The chamber is equipped with an optically dense gaseous nitrogen cooled thermal shroud. The thermal shroud is used to cool or warm the optical test specimen at a controlled rate. A control system is provided to automatically evacuate the chamber and cooldown the test specimen to the selected control temperature

Design of ultraprecision machine tools with application to manufacturing of miniature and micro components

Currently the underlying necessities for predictability, producibility and productivity remain big issues in ultraprecision machining of miniature/microproducts. The demand on rapid and economic fabrication of miniature/microproducts with complex shapes has also made new challenges for ultraprecision machine tool design. In this paper the design for an ultraprecision machine tool is introduced by describing its key machine elements and machine tool design procedures. The focus is on the review and assessment of the state-of-the-art ultraprecision machining tools. It also illustrates the application promise of miniature/microproducts. The trends on machine tool development, tooling, workpiece material and machining processes are pointed out

A dynamics-driven approach to precision machines design for micro-manufacturing and its implementation perspectives

Precision machines are essential elements in fabricating high quality micro products or micro features and directly affect the machining accuracy, repeatability and efficiency. There are a number of literatures on the design of industrial machine elements and a couple of precision machines commercially available. However, few researchers have systematically addressed the design of precision machines from the dynamics point of view. In this paper, the design issues of precision machines are presented with particular emphasis on the dynamics aspects as the major factors affecting the performance of the precision machines and machining processes. This paper begins with a brief review of the design principles of precision machines with emphasis on machining dynamics. Then design processes of precision machines are discussed, and followed by a practical modelling and simulation approaches. Two case studies are provided including the design and analysis of a fast tool servo system and a 5-axis bench-top micro-milling machine respectively. The design and analysis used in the two case studies are formulated based on the design methodology and guidelines

Inherent Problems in Designing Two-Failure Tolerant Electromechanical Actuators

An electromechanical ac-powered rotary actuated four-bar linkage system for rotating the Shuttle/Centaur deployment adapter is described. The essential features of the deployment adapter rotation system (DARS) are increased reliability for mission success and maximum practical hazard control for safety. The requirements, concept development, hardware configuration, quality assurance provisions, and techniques used to meet two-fault tolerance requirements are highlighted. The rationale used to achieve a degree of safety equivalent of that of two-failure tolerance is presented. Conditions that make this approach acceptable, including single failure point components with regard to redundancy versus credibility of failure modes, are also discussed

In-situ defect detection systems for R2R flexible PV films

The atomic layer deposition technique (ALD) is used to apply a thin (40-100 nm thick) barrier coating of Al2O3 on polymer substrates for flexible PV cells, to minimise and control the degradation caused by water vapour ingress. However, defects appearing on the film surfaces during the Al2O3 ALD growth have been seen to be highly significant in deterioration of the PV module efficiency and lifespan [1]. In order to improve the process yield and product efficiency, it is desirable to develop an inspection system that can detect transparent barrier film defects in the production line during film processing. Off-line detection of defects in transparent PV barrier films is difficult and time consuming. Consequently, implementing an accurate in-situ defects inspection system in the production environment is even more challenging, since the requirements on positioning, fast measurement, long term stability and robustness against environmental disturbance are demanding. For in-situ R2R defects inspection systems the following conditions need to be satisfied by the inspection tools. Firstly the measurement must be fast and have no physical contact with the inspected film surface. Secondly the measurement system must be robust against the environmental disturbance inspection. Finally the system should have sub-micrometre lateral resolution and nanometre vertical resolution in order to be able to distinguish defects on the film surface. Optical interferometry techniques have the potentially to be used as a solution for such application. However they are extremely sensitive to environmental noise such as mechanical vibration, air turbulence and temperature drift. George [2] reported that a single shot interferometry system “FlexCam” developed by 4D Technology being used currently to detect defects for PV barrier films manufactured by R2R technology. It is robust against environmental disturbances; but it has a limited vertical range, which is restricted by the phase ambiguity of the phase shift interferometry. This vertical measurement range (a few hundreds nanometres) is far less than the normal vertical range of defects (a few micrometres up to a few tens micrometres). It is not possible to detect the majority of defects in the R2R flexible PV barrier films

Methods of Parallel Voxel Manipulation for 3D Digital Printing

A novel digital printing concept is explored for desktop fabrication of multimaterial objects with arbitrary 3D geometry. Digital objects are composed of many discrete, self-aligning voxels instead of continuous (analog) deposition techniques. Overall accuracy is determined by the individual voxels instead of the printer, and digital properties such as perfect replication and error correction are physically meaningful. The key challenge in digital printing is massively parallel, deterministic voxel manipulation. To quickly print millions of voxels while keeping errors low, we propose a parallel manufacturing process that exploits electrostatic forces to place an entire 2D pattern of voxels concurrently. Using a custom charged print head, we demonstrate selective 1.5mm voxel pick-up within a larger, self-aligned layer. We expect the principle to scale to million voxel layers using currently available technology.Mechanical Engineerin

Study of tooling concepts for manufacturing operations in space Final report

Mechanical linkage device for manufacturing operations with orbital workshop

A spaceborne optical interferometer: The JPL CSI mission focus

The JPL Control Structure Interaction (CSI) program is part of the larger NASA-wide CSI program. Within this larger context, the JPL CSI program will emphasize technology for systems that demand micron or sub-micron level control, so-called Micro-Precision Controlled Structures (u-PCS). The development of such technology will make it practical to fly missions with large optical or large precision antenna systems. In keeping with the focused nature of the desired technology, the JPL approach is to identify a focus mission, develop the focus mission CSI system design to a preliminary level, and then use this design to drive out requirements for CSI technology development in the design and analysis, ground test bed, and flight experiment areas

The design and description of a 300-1200 angstrom stellar spectrograph

Design of 300 to 1200 angstrom stellar spectrograp