Dimensionally Stable Calibration Device Using Composite Sheets
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Solution Overview
Problem
Conventional long calibration devices experience errors due to deflection caused by gravity and temperature sensitivity, especially when orientation changes from vertical to horizontal, which affects precision measurements.
Innovation Solution
A lightweight, rigid calibration device design using thin sheets separated by a filler or air gap, with high shear strength glue, and a central core with low thermal expansion, along with trihedral mounts and thermally stable materials to maintain dimensional stability and prevent wrinkling, combined with a robust frame and elastic coating to minimize stress and thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the long calibration device is made heavy and rigid to reduce deflection under gravity, then measurement precision is improved, but the device becomes difficult to position and handle
Solution Approach 1:
The calibration device uses a composite structure combining aluminum alloy sheets with foam core material. The aluminum sheets provide rigidity and dimensional stability to resist gravitational deflection, while the lightweight foam core reduces overall weight, enabling a single technician to position and handle the device easily.
2Measurement precision
If structural sheets are added below the central shaft to reduce deflection, then measurement precision is improved, but the device bulkiness doubles
Solution Approach 1:
Instead of adding bulky structural sheets, the invention uses thin aluminum alloy sheets (0.030 to 0.060 inches thick) that provide sufficient structural support through their high strength-to-thickness ratio. The sheets are spaced apart by the foam core, creating a rigid yet lightweight structure that maintains precision without increasing bulkiness.
3Stability of the object's composition
If the calibration device uses conventional rigid structure to maintain dimensional stability, then rigidity is improved, but temperature sensitivity increases
Solution Approach 1:
The invention selects aluminum alloy as the sheet material specifically for its low coefficient of thermal expansion, which minimizes dimensional changes with temperature variations. This parameter selection allows the device to maintain dimensional stability across different temperatures without requiring active temperature control or compensation mechanisms.
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
The design ensures minimal deflection and thermal expansion, maintaining precision across orientations and temperatures, enabling accurate high-precision measurements without bulkiness or increased material usage.
Implementation Method 1
The central core may be coated with a thin layer of rubber like elastomer. This elastic coating allows the outside structural frame, with its relatively high rate of thermal expansion and contraction, to move without causing any stresses in the low expanding and contracting central core.
Implementation Method 2
The large shear area of these thin sheets is at right angles to the bending moment caused by the force of gravity acting on the device, as it is moved to the various positions all the way from vertical to horizontal.
Data Source
AI summary
A calibration device provides a lightweight rigid support for a long arm. The rigid support includes thin flat sheets separated by a light weight filler. The filler prevents wrinkling or rippling of the flat sheets. Three ball trihedral nest kinematic mounts may be attached to opposite ends of the long arm for precise mounting of retro-reflectors for optical calibration, or precision spheres may be attached to the opposite ends of the long tube to obtain a mechanical calibration standard.