Space Telescope Optical Shells via Metal Spinning and Diamond Turning
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Solution Overview
Problem
Current methods for manufacturing optical elements, such as grazing incidence optics for telescopes, face challenges including high costs, precision issues, and fragility in glass shell production, and difficulties with large-diameter mirrors in nickel electroforming, leading to long production times and limited angular resolution.
Innovation Solution
A process involving metal spinning of an aluminum alloy sheet to create axially symmetric shells, followed by diamond spinning, nickel plating, and precision polishing to produce lightweight, precise optical elements, which can be assembled into complete optics with reduced costs and risk of breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If monolithic glass shells are used to produce optical elements, then manufacturing precision and azimuthal symmetry are improved, but the process becomes costly, time-consuming, and fragile with limited mechanical strength
Solution Approach 1:
The patent changes the material parameter from glass to aluminum alloy, transforming the manufacturing approach from precision glassblowing to metal forming processes. This allows achieving optical precision through controlled deformation and finishing processes while avoiding the fragility and complexity of glass shell production
Solution Approach 2:
The patent uses a mandrel as a template to copy the desired optical shape onto the aluminum alloy blank. The mandrel defines the parabolic and hyperbolic surfaces, and the aluminum blank is formed to match this template, enabling precise replication of optical surfaces without the complexity of direct glass forming
2Ease of manufacture
If nickel electroforming is used to produce mirrors, then a complete mirror can be produced in one piece, but the process is limited to small diameters (maximum 70 cm) and achieves limited angular resolution
Solution Approach 1:
The patent changes the material from nickel to aluminum alloy, which has lower density and allows for larger structural dimensions. This enables production of mirrors with diameters exceeding 70 cm while maintaining structural integrity and optical performance
Solution Approach 2:
The patent divides the mirror into multiple annular segments that can be produced separately and then assembled. This segmentation allows each segment to be manufactured within feasible size limits while the complete mirror achieves large diameter, and the segmentation facilitates quality control and assembly
3Manufacturing precision
If glass shells are used for optical elements, then optical quality is improved, but procurement time increases and mechanical strength is limited by safety factors
Solution Approach 1:
The patent changes the material from glass to aluminum alloy, which has superior mechanical strength properties. This allows thinner wall thicknesses to be used while maintaining structural integrity, reducing procurement time and enabling faster production cycles without compromising optical quality
4Ease of manufacture
If a single metallic piece is used to produce mirrors, then a complete mirror is obtained, but production cost increases, working time extends, and material uniformity cannot be verified until the end of processing
Solution Approach 1:
The patent divides the mirror into multiple annular segments that can be produced separately through casting or forging, then assembled. This allows intermediate quality checks of each segment, reduces total working time by enabling parallel production, and maintains structural completeness while improving manufacturing efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process enables the production of optical elements with improved precision, reduced costs, and faster production times, while avoiding the fragility and high costs associated with traditional methods, allowing for the creation of high-performance optics with enhanced angular resolution.
Implementation Method 1
The blank initially undergoes a step known as metal spinning, in which the blank is axially blocked between a shaped matrix, defining the shape to be obtained, mounted on the mandrel of a lathe and a counter-head. The mandrel is made to rotate and consequently rotates the matrix/blank/counter-head assembly. During the rotation, the blank is deformed by means of a tool which acts on the face of the blank opposite the matrix and is moved parallel to a generatrix of the matrix, so as to deform the blank and cause it to adhere progressively to an outer surface of the matrix, reproducing the shape thereof.
Implementation Method 2
The optical surface of the shell then undergoes a step of being coated with electroless nickel or with another material deposited by a chemical or physical process in order to form a coating layer on the optical surface.
Implementation Method 3
The shell subsequently undergoes a step known as diamond spinning, in which a diamond tool is brought into contact with the optical surface of the shell, which is machined at very high precision.
Data Source
AI summary
A process for manufacturing an optical element comprising a first step of spinning a circular sheet of a first metallic material for it to adhere to a rotating matrix and form a shell; a second step of assembling the shell on a temporary support; and at least a third step of diamond turning the shell by means of a diamond tool to obtain an optical surface.