Three-Point Spindle Mount for Low Non-Repetitive Runout
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Solution Overview
Problem
High-precision rotational systems, such as those used in X-ray or electron diffraction, face challenges in minimizing radial and axial displacements to maintain sample alignment within the beam path, as existing technologies allow for unacceptable deviations that impede system performance.
Innovation Solution
A rotational device with a spindle assembly and sockets having multiple contact points, utilizing hardened materials and elastic mechanisms to minimize displacements, and employing linear stages for precise adjustments and real-time corrections to maintain sample alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional rotational mechanisms are used, then rotation can be achieved, but radial and axial displacements exceed acceptable tolerances for high precision applications
Solution Approach 1:
The rotational mechanism is segmented into multiple independent components: a first socket with three contact points, a second socket with three contact points, and a spindle assembly with convex surfaces. Each component is precisely manufactured and assembled to achieve sub-micron runout tolerances through cumulative precision rather than requiring a single complex precision component.
Solution Approach 2:
The contact points on the sockets and convex surfaces on the spindle are engineered with specific local geometric properties (spheroidal shapes with controlled radii of curvature) to ensure point contact and minimize runout. The local quality of these contact surfaces directly determines the precision of rotation.
2Measurement precision
If precision is increased to sub-micron levels, then sample alignment is maintained, but sensitivity to dimensional variations and contaminants increases
Solution Approach 1:
The design incorporates inherent mechanical cushioning through the elastic deformation capability of the socket and spindle contact surfaces. This cushioning effect absorbs and compensates for minor dimensional variations and contaminants before they can significantly impact sample position, providing robustness against harmful factors while maintaining precision.
Solution Approach 2:
The precisely engineered contact surfaces act as intermediaries between the drive mechanism and the sample holder. These intermediary surfaces filter out dimensional variations and contaminants through their controlled elastic deformation, protecting the sample position from harmful factors while transmitting the necessary rotational motion.
3Manufacturing precision
If repetitive runout is compensated using precision linear stages, then radial displacement can be corrected, but non-repetitive runout remains uncorrected
Solution Approach 1:
The rotational mechanism is designed to be self-correcting for non-repetitive runout through its inherent mechanical properties. The elastic deformation of the contact surfaces and the geometric constraints of the three-point contact configuration automatically compensate for non-repetitive errors without requiring external sensing or correction systems, making the system self-sufficient in maintaining precision.
Data Source
AI summary
A rotational device provides rotation of a location of interest about a rotational axis and includes first and second sockets each having three contact points distributed about the rotational axis. The contact points of each socket may be on convex surfaces and a spindle assembly is held between the sockets, which face each other along the rotational axis. The spindle assembly has a first convex surface centered about the rotational axis that contacts the contact points of the first socket, and a second convex surface that contacts the contact points of the second socket. The spindle assembly also has a drive shaft aligned with the rotational axis. Linear stages may be used to provide adjustment in one or more mutually perpendicular directions. An alternative embodiment uses a spindle assembly with two curved contact surfaces that contact respective curved surfaces that are adjacent to the rotational axis rather than aligned therewith.